WO2011115101A1 - 転がり接触金属材料のせん断疲労特性の評価方法、それを用いた疲労限面圧の推定方法および装置 - Google Patents
転がり接触金属材料のせん断疲労特性の評価方法、それを用いた疲労限面圧の推定方法および装置 Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
- G01N3/34—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces generated by mechanical means, e.g. hammer blows
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0005—Repeated or cyclic
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0021—Torsional
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0658—Indicating or recording means; Sensing means using acoustic or ultrasonic detectors
Definitions
- the present invention relates to a method for evaluating shear fatigue characteristics of a rolling contact metal material, a method for estimating fatigue limit surface pressure using the method, and an apparatus, for example, shear fatigue of a high-strength metal material for rolling bearings such as steel for bearings.
- the present invention relates to a method and apparatus for quickly evaluating characteristics.
- the most commonly used high-strength metal material for rolling bearings is the high-carbon chromium bearing steel JIS-SUJ2, which is heated to a temperature above the A1 transformation point (approximately 850 ° C) in a reducing atmosphere. And hardened to a temperature of about 750 HV.
- non-metallic inclusions contained in an arbitrary volume are considered from the idea that non-metallic inclusions that are inevitably contained in steel and are structurally discontinuous, and that cause non-metallic inclusions as the source of stress concentration, will be the origin of internal-origin separation.
- a method of estimating the maximum size of an object by extreme value statistical analysis has been devised, and a method has been adopted in which the maximum size of a nonmetallic inclusion is used as an index of steel quality (for example, Patent Documents 1 to 4).
- Patent Document 5 a test for rapidly accelerating and decelerating the rolling bearing
- Patent Document 6 a test for operating the rolling bearing while spraying salt water
- Patent Document 8 a test for rolling bearing operation with a constant current
- Patent Document 9 Ultrasonic axial load fatigue test capable of very high vertical load after hydrogen charging (completely A hydrogen resistance evaluation method (Patent Document 9) that causes fatigue before hydrogen is not dissipated has been devised.
- the cathode axial hydrogen charge was applied to the bearing steel SUJ2 test piece for a certain time after changing the current density, and as a result of conducting an ultrasonic axial load fatigue test, the fatigue at 10 7 times as the amount of diffusible hydrogen increased. It has also been reported that the strength decreases and there is a linear relationship between them (see Non-Patent Document 6). This means that the amount of diffusible hydrogen is a governing factor of fatigue strength reduction, and suggests that the original hydrogen resistance evaluation by controlling the amount of invading hydrogen is necessary as the first step.
- An object of the present invention is to provide a method and an apparatus capable of quickly and accurately evaluating the shear fatigue characteristics of a metal material in rolling contact with a test.
- the method for evaluating the shear fatigue strength of a rolling contact metal material includes a test process for determining the relationship between the shear stress amplitude of a metal material and the number of loads by an ultrasonic torsional fatigue test, and the obtained shear stress amplitude and the number of loads. From the relationship, a shear fatigue strength determination process for determining the shear fatigue strength ⁇ 1im in the ultra-long life region according to a predetermined standard is included.
- shear fatigue strength in the ultralong life region is synonymous with “shear fatigue limit”, but in this specification, it will be described as “shear fatigue strength in the ultralong life region”.
- the “specified standard” used in the process of determining the shear fatigue strength is, for example, a curve obtained by fitting the relationship between the shear stress amplitude and the number of loadings of the test result to the established theoretical curve indicating the shear fatigue strength.
- the shear fatigue strength is determined from the curve.
- the SN diagram fatigue strength diagram with 50% fracture probability
- the SN diagram may be obtained by applying not only to the fatigue limit type broken line model but also to a continuously decreasing curve model. However, in that case, ⁇ 1im needs to be defined as “a value on the SN diagram at 10 10 times”, for example.
- an extremely high-speed ultrasonic torsional fatigue test in which the excitation frequency is in the ultrasonic range is performed. Fatigue properties can be evaluated quickly. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 9 times in just half a day. In addition, since a test that actually causes shear fatigue failure is performed, the shear fatigue characteristics can be obtained with higher accuracy than in the conventional method in which the maximum size of non-metallic inclusions is used as an index of steel quality.
- the stress governing the fatigue fracture of a material is either normal stress or shear stress.
- the ultrasonic axial load fatigue tester full swing
- ultrasonic torsional fatigue tests for evaluating shear fatigue properties at high speed have hardly been studied, and the materials evaluated so far have a maximum shear stress amplitude (full swing) of 250 MPa or less. It is mild steel or aluminum alloy that undergoes fatigue failure.
- the present invention causes a shear fatigue failure by applying a torsional vibration having an excitation frequency in the ultrasonic region to a metal material used as a bearing ring or a rolling element of a rolling bearing, thereby providing rapid shear fatigue characteristics. It is possible to realize the evaluation.
- the ultrasonic torsional fatigue test is preferably a full-twisted torsional fatigue test that gives torsional vibration in which the torsion in the normal rotation direction and the reverse rotation direction is symmetrical to the test piece.
- the metal material may be a rolling bearing steel used as a bearing ring or rolling element of a rolling bearing.
- the ultrasonic torsional fatigue test is performed a plurality of times to obtain a plurality of relationships between the shear stress amplitude of the metal material and the number of loads, and in the shear fatigue strength determination process, the plurality of times A PSN diagram having an arbitrary failure probability is obtained from the relationship between the shear stress amplitude obtained during the test process and the number of loadings, and the shear fatigue strength ⁇ 1im in the ultra-long life region is obtained from this PSN diagram. You may make it decide.
- the size effect that appears in fatigue tests with the above stress gradient is brought about by a mechanical factor called stress gradient and a statistical factor that increases or decreases the volume (dangerous volume) subjected to a large load. From the viewpoint of statistical factors, a plurality of evaluations may be performed at a plurality of stress levels to obtain a PSN diagram.
- a value of 85% of the shear fatigue strength in the ultralong life region determined from the PSN diagram is used in the process of calculating the fatigue limit surface pressure. It is good also as a value of fatigue strength (tau) 1im .
- the value of 85% of the shear fatigue strength in the ultralong life region determined from the PSN diagram, and the value obtained by further 80% being the fatigue limit surface pressure is preferable to set the value of the shear fatigue strength ⁇ 1im used in the calculation process.
- the ultrasonic torsional fatigue test is performed a plurality of times in the test process to obtain a plurality of relationships between the shear stress amplitude of the metal material and the number of loads,
- a PSN diagram having an arbitrary fracture probability is obtained from the relationship between the shear stress amplitude obtained in the plurality of test processes and the number of loads, and from this PSN diagram.
- the fracture probability correction which is a correction for determining the shear fatigue strength ⁇ 1im in the ultra-long life region, and the value of 85% with respect to the shear fatigue strength determined according to the determined criteria in the shear fatigue strength determination process, and overestimation correction is a correction to the value of the shear fatigue strength tau HM used in the fatigue limit contact pressure calculation process, the ultra-long life region decided by the shear fatigue strength determination process 80% of the value for the kick shear fatigue strength, of the three correction with correction at a size effect correction to a value of shear fatigue strength tau HM used in the fatigue limit contact pressure calculation process, any two or more correction Fatigue fatigue strength ⁇ 1im obtained by combining the above may be regarded as an absolute value.
- the shear fatigue strength can be safely estimated, and the fatigue limit surface pressure can be estimated more safely.
- an ultrasonic torsional fatigue test capable of applying a load at high speed.
- an ultrasonic torsional fatigue test with an extremely high excitation frequency of 20000 Hz is performed.
- the test piece generates heat, and it is impossible to obtain a precise relationship between the shear stress amplitude and the number of loads. Therefore, it is preferable to forcibly air-cool the test piece. If the heat generation of the test piece is not sufficiently suppressed by forced air cooling alone, it is preferable to alternately repeat vibration and pause.
- the suspension time is about 2000 Hz even if the suspension time is about 10 times the excitation time. If there is a week, the load count reaches 10 9 times.
- the ultrasonic torsional fatigue test includes, for example, a torsional vibration converter that generates a torsional vibration that rotates in the forward and reverse directions around the rotation center axis when AC power is applied, and a test piece concentrically at the tip.
- the shape and dimensions resonate with the vibration of the amplitude expanding horn driven by the torsional vibration converter, and the vibration converter is driven at a frequency in the ultrasonic region to resonate the test piece with the vibration of the amplitude expanding horn to cause shear fatigue destruction.
- the amplifier may be capable of controlling the output size and on / off by external input.
- the “frequency range of the ultrasonic region” refers to a frequency region of sound waves of 16000 Hz or higher in a broad sense.
- the lower limit value of the frequency for driving the torsional vibration converter is (20000 ⁇ 500 + ⁇ ) Hz
- the upper limit value is (20000 + 500) Hz
- ⁇ is a margin value for the property change during the test of the test piece and is 200 Hz or less. good.
- the margin value may be 200 Hz.
- the amplitude expansion horn is resonated with the vibration of the torsional vibration converter.
- the amplitude expanding horn preferably has a circular cross-sectional shape, and a vertical cross-sectional shape of a portion excluding the base end portion is a tapered shape. By adopting this shape, amplitude expansion is effectively performed.
- the test piece has a dumbbell shape including a cylindrical shoulder portion at both ends, and a middle thin portion in which a cross-sectional shape along the axial direction follows the shoulder portions on both sides is an arc curve. .
- the shape is the dumbbell shape, shear fatigue failure is likely to occur at the thinned portion.
- the test piece needs to resonate, and accordingly, the shape and dimensions of each part must be designed appropriately.
- the length of the shoulder portion of the test piece is L 1
- the half chord length which is half the length of the thinned portion is L 2
- the radius of the shoulder portion is R 2
- the minimum radius of the thinned portion is R.
- the radius of the circular arc curve is R (all are m, R is determined from R 1 , R 2 , L 2 ), the resonance frequency is f (unit is Hz), Young's modulus E (unit is Pa), Poisson's ratio ⁇ (dimensionless), density ⁇ (unit: kg / m 3 ),
- the L 2 , R 1 , and R 2 are set to arbitrary values, the resonance frequency f is set to an arbitrary value in a frequency range of 20000 ⁇ 500 Hz that can be driven by the vibration converter, and the following equations (1) to (6) are used.
- a test piece having the shoulder length L 1 obtained as the theoretical solution and the dimensions L 2 , R 1 , R 2 , and R of the respective parts used for the calculation of the solution may be prepared and tested. There may not be. In that case, a plurality of test piece shape models in which L 1 obtained as the above theoretical solution is slightly shortened are created, and for each of these shape models, measured physical property values of metal materials having E, ⁇ , and ⁇ as test pieces.
- the analytical solution L 1N that torsionally resonates at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis, and test pieces having the dimensions L 2 , R 1 , R 2 , R, and L 1N are created. And used for testing. By setting the shape and dimensions of such a test piece, resonance of the test piece occurs.
- the rated output of the torsional vibration converter is 300 W, and the volume excluding the male screw part attached to the tip of the vibration magnifying horn of the test piece and the center hole part on the end face of the non-attachment part necessary for processing the test piece is 1.2 ⁇ It may be 10 ⁇ 6 m 3 or less.
- the torsion angle of the end face of the test piece is 0.01 rad
- the maximum shearing stress that acts on the surface may be 520 MPa or more.
- the resonance frequency f is in the range of 20000 ⁇ 500 Hz, and the maximum output of the torsional vibration converter is 300 W
- the weight excluding the mounting protrusion composed of the male screw portion for mounting the test piece to the amplitude expansion horn It is preferable to be 9.36 g or less. Resonance instability may occur even if the shape and size of the test piece can resonate. As a result of the study, it was found that the resonance instability greatly affects the weight of the specimen.
- the output of the amplifier is 90%
- the measured value of the torsion angle of the test piece is 0.018 rad or more
- free torsional resonance by finite element analysis is achieved. It is preferable that the maximum shear stress acting on the surface of the minimum diameter portion of the test piece when the torsion angle of the end face obtained by eigenvalue analysis of 0.018 rad is 951 MPa or more.
- the shear fatigue characteristics of the metal material under hydrogen penetration can be evaluated by the ultrasonic torsion fatigue test.
- a torsional fatigue test in which an ultrasonic torsional vibration in which the excitation frequency is in the ultrasonic range is applied to the test piece, and thus a torsional fatigue test in which an extremely high load is repeatedly applied can be performed. Therefore, before the charged hydrogen is dissipated, the test specimen of the metal material to be evaluated is subjected to shear fatigue, and the shear fatigue characteristics under hydrogen intrusion can be evaluated reasonably and quickly. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 7 times in just 9 minutes.
- the hydrogen charging may be performed by cathodic electrolytic charging of hydrogen.
- a dilute sulfuric acid aqueous solution may be used for this cathodic electrolytic charge.
- thiourea may be added to the dilute sulfuric acid aqueous solution as a catalyst poison.
- the amount of thiourea added is preferably 1.4 g / L as the upper limit.
- an aqueous sodium chloride solution may be used for the cathodic electrolytic charging.
- ammonium thiocyanate may be added as a catalyst poison to the aqueous sodium chloride solution in order to increase the hydrogen charging efficiency.
- the addition amount of ammonium thiocyanate is preferably 3 g / L.
- an aqueous sodium hydroxide solution may be used for the cathodic electrolytic charging.
- sodium sulfide nonahydrate may be added as a catalyst poison to the aqueous sodium hydroxide solution in order to increase the hydrogen charge efficiency.
- the amount of sodium sulfide nonahydrate added is preferably 1 g / L.
- the hydrogen may be immersed in an aqueous solution for charging.
- hydrogen may be charged by dipping in an aqueous solution of ammonium thiocyanate.
- concentration of the ammonium thiocyanate aqueous solution is preferably 20 mass%.
- An apparatus for estimating shear fatigue characteristics of a rolling contact metal material of the present invention includes an input means for storing a relationship between the shear stress amplitude of a metal material and the number of loads obtained by an ultrasonic torsion fatigue test in a predetermined storage area; Shear fatigue strength determination means for determining the shear fatigue strength ⁇ 1im in the ultra-long life region from the stored relationship between the shear stress amplitude and the number of loadings according to a predetermined standard.
- the metal material may be rolling bearing steel or rolling bearing steel that serves as a rolling element.
- the input means uses a manual input device such as a keyboard, a recording medium reading device, a communication network, etc., for example, a file summarizing the relationship between the shear stress amplitude of the metal material and the number of loads, It is a means for memorize
- This estimation device has a torsional vibration converter that generates a torsional vibration that rotates forward and backward around the rotation center axis when AC power is applied, and a mounting portion that attaches a test piece concentrically to the distal end.
- the torsional vibration converter is fixed to the torsional vibration converter, the amplitude expansion horn that expands the torsion angle of the torsional vibration converter applied to the base end, an oscillator, and an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter
- Control and data collection means for collecting data including the control input to the amplifier and collecting the excitation frequency under test, the state of the amplifier, and the number of loads, and the shape and dimensions of the amplitude expansion horn
- the shape and dimensions of the specimen resonate with the torsional vibration caused by the drive of the torsional vibration converter. Shape resonates in a dimension, the torsional vibration converter is driven at a frequency range in the ultrasonic range, said to resonate the amplitude expansion horn
- the lower limit value of the frequency range for driving the torsional vibration converter is (2000 ⁇ 500 + ⁇ ) Hz, and the upper limit value is (2000 + 500) Hz, where ⁇ is a margin value for property change during the test of the test piece and is 200 Hz or less. Also good.
- the generated torsional vibration is a complete double swing in which the normal rotation direction and the reverse rotation direction are symmetrical.
- the said amplitude expansion horn resonates with the vibration by the excitation frequency during the test of a torsional vibration converter.
- the amplitude expanding horn preferably has a circular cross-sectional shape, and a vertical cross-sectional shape of a portion excluding the base end portion is a tapered shape represented by an exponential function. By adopting this shape, amplitude expansion is effectively performed.
- the method for estimating the fatigue limit surface pressure of a rolling contact metal material is a method for estimating the fatigue limit surface pressure using the evaluation method of the present invention, and further comprises an object manufactured from the metal material and the object.
- the maximum alternating shear stress amplitude ⁇ 0 acting inside the surface layer of the metal material object determined from the shape and size of the surfaces in contact with each other of the rolling contact object and the load giving the contact surface pressure was determined by the evaluation method.
- Fatigue with the maximum contact surface pressure Pmax when the load equal to the shear fatigue strength ⁇ 1im is applied is determined by a predetermined calculation formula, and the maximum contact surface pressure Pmax is an estimated value of the fatigue limit surface pressure Pmax1im. Including the process of calculating the surface pressure.
- Non-Patent Document 3 describes a “defined calculation formula” used in the fatigue limit surface pressure calculation process.
- Rolling bearings are effective in improving reliability if the fatigue limit surface pressure can be estimated by conducting a torsional fatigue test at the supplier or lot of the material used.
- the torsional fatigue test requires a long time, and it is impossible to estimate the fatigue limit surface pressure of the material used. For this reason, there was no idea of adopting fatigue limit surface pressure as one of the test items for bearing materials.
- the apparatus for estimating the fatigue limit surface pressure of a rolling contact metal material according to the present invention is an apparatus for estimating the fatigue limit surface pressure using the estimation apparatus according to the present invention, and further includes an object manufactured from the metal material and the object
- the maximum alternating shear stress amplitude ⁇ 0 acting inside the surface of the object of the metal material determined from the shape and size of the surfaces in contact with each other and the load that gives the contact surface pressure is the shear fatigue strength.
- a fatigue limit surface obtained by calculating a maximum contact surface pressure P max when the load equal to ⁇ 1im is applied by a predetermined calculation formula, and using the maximum contact surface pressure P max as an estimated value of the fatigue limit surface pressure P max 1im. It has pressure calculation means.
- the ultrasonic torsional fatigue test capable of applying an extremely high speed load can be used and the shear stress of rolling bearing steel can be achieved in a short period of time, similar to the method for estimating the fatigue limit surface pressure.
- the relationship between the amplitude and the number of loads can be obtained, and the fatigue limit surface pressure P max 1im can be accurately estimated.
- (D) is a sectional view of the object and the object in contact with it are made of a metal material to be tested.
- It is a block diagram of the estimation system of the shear fatigue characteristic.
- It is a conceptual diagram of the test machine control device and the fatigue limit surface pressure estimation device in the shear fatigue characteristic estimation system.
- It is a block diagram which shows the conceptual structure of the estimation apparatus of a shear fatigue characteristic.
- It is a front view of the main body of an ultrasonic torsional fatigue testing machine. It is a schematic diagram of a test piece. It is a front view of a test piece.
- FIG. 6 is a graph showing an axial distribution of torsion angle ⁇ and surface shear stress ⁇ (when end surface torsion angle ⁇ end is 0.01 rad). It is a microscope picture which shows the test piece shoulder part cylindrical surface lower end at the time of stationary. It is a microscope picture which shows the test piece shoulder part cylindrical surface lower end at the time of vibration. It is explanatory drawing which shows the relationship between the range 2a of FIG. 10, and end surface twist angle
- FIG. 16 is a graph showing a PSN diagram (broken line) with a fracture probability of 10% and an original SN diagram (solid line) determined from the relationship of FIG. 15.
- (A) is a figure which shows the heat pattern of the induction hardening of the raw material of S53C
- (B) is a figure which shows the heat pattern of the tempering of the raw material.
- (A) is a front view of a test piece schematically showing an induction hardening pattern
- (B) is a side view of the test piece. It is a figure which shows the shear fatigue characteristic of the test piece of S53C induction hardening.
- It is explanatory drawing which combined the front view of the testing machine main body in the shear fatigue characteristic evaluation apparatus used for the shear fatigue characteristic evaluation method which concerns on 2nd Embodiment of this invention, and the block diagram of the control system. It is a block diagram which shows the conceptual structure of the same shear fatigue characteristic evaluation apparatus.
- FIG. 1 It is a schematic flowchart of the evaluation method. It is a graph which shows a time-dependent change of the relative hydrogen concentration of a test piece minimum diameter part.
- FIG. 43 is a PSN diagram with a destruction probability of 10% obtained from the relationship of FIG. It is explanatory drawing which shows an example of the method of carrying out the cathode electrolytic charge of hydrogen. It is a figure which shows the shear fatigue characteristic of a test piece.
- the evaluation method of the shear fatigue property of the rolling contact metal material is a method of estimating the shear fatigue strength ⁇ 1im of the metal material in contact with the rolling, and as shown in FIG. Including a fatigue strength determination step (S2).
- the fatigue limit surface pressure estimation method further including (S3) will be described.
- the “metal material in contact with rolling” is, for example, a metal material that becomes a race or a rolling element of a rolling bearing.
- the metal material include Japanese Industrial Standards; JIS SUJ2, SCr420, M50, M50NiL, SNCM420, SUJ3, SCr420, S53C, and SUS440C.
- SUJ2 corresponds to SAE52100 in the US AISI standard.
- the test process (S1) is a process for obtaining the relationship between the shear stress amplitude of the metal material and the number of loads by a complete double-sided ultrasonic torsional fatigue test.
- an ultrasonic torsional fatigue testing machine 2 that applies a complete double-sided ultrasonic torsional vibration to the metal material test piece 1 shown in FIG.
- the ultrasonic torsional fatigue tester 2 uses an extremely high-speed ultrasonic torsional fatigue test (complete double swing) with an excitation frequency of 20000 Hz. This ultrasonic torsional fatigue testing machine 2 cannot be used as it is, and has various improvements.
- the shear fatigue strength ⁇ 1im in the ultra-long life region is determined according to a predetermined standard from the relationship between the shear stress amplitude and the number of loads obtained in the test process (S1).
- the above-mentioned “shear fatigue strength in the ultra-long life region” refers to the “shear fatigue limit”, but in this specification, it will be described as “shear fatigue strength in the ultra-long life region”.
- the above-mentioned “defined standard” in the shear fatigue strength determination process (S2) is, for example, a curve obtained by fitting the relationship between the shear stress amplitude of the test results and the number of loads to an established theoretical curve indicating the shear fatigue strength.
- the shear fatigue strength is determined from the curve.
- the SN diagram fatigue strength diagram with 50% fracture probability
- the SN diagram may be obtained by applying not only to the fatigue limit type broken line model but also to a continuously decreasing curve model. However, in that case, it is necessary to define, for example, “ ⁇ 1im is a value on the SN diagram at 10 10 times”.
- the fatigue limit type polyline model of JSMS-SD-6-02 a metal material fatigue reliability evaluation standard of the Japan Society of Materials Science, is applied to the following equation and regressed.
- ⁇ ⁇ Alog 10 N + B (N ⁇ N W )
- ⁇ E (N ⁇ N W )
- A, B, E, and Nw are constants.
- the average value of the rupture data stress minimum value ⁇ f min and the censored data stress maximum value ⁇ r max lower than this is defined as the fatigue limit (see FIG. 21).
- the probability fatigue characteristic is evaluated by evaluating a plurality of test pieces with a plurality of stress amplitudes and obtaining a PSN diagram at a certain fracture probability (see Non-Patent Document 5). However, it takes a lot of man-hours and time to obtain the PSN diagram.
- JSMS-SD-6-04 a method for obtaining a PSN diagram at an arbitrary fracture probability from an SN diagram is proposed. As shown in FIG. 22, it is assumed that the strength distribution in an arbitrary fatigue life follows a normal distribution and that the standard deviation ⁇ is constant.
- the obtained SN diagram is a fatigue strength curve with a fracture probability of 50%.
- the damage data of the time-strength part (inclined straight line part), and in the continuous decline type curve model, the damage data of the whole range are targeted.
- FIG. 23 is an example of a continuously decreasing curve model. Translate individual failure data along a straight line or curve to any fatigue life and determine the standard deviation as they are normally distributed. For example, assuming that the obtained standard deviation is s, a PSN diagram having a fracture probability of 10% is obtained by translating a fatigue strength curve with a fracture probability of 50% downward by 1.282s.
- the dimensions of the contact dimensions of the object M1 made of the metal material (FIG. (D)) and the surfaces of the object M2 that are in rolling contact with the object M2 are in contact with each other (
- the load is applied such that the maximum alternating shear stress amplitude ⁇ 0 acting inside the surface layer of the object M1 of the metallic material determined from the shape and dimensions) and the load that gives the contact surface pressure is equal to the shear fatigue strength ⁇ 1im
- the maximum contact surface pressure P max is determined by a predetermined calculation formula, and this maximum contact surface pressure P max is used as an estimated value of the fatigue limit surface pressure P max 1im .
- the metal material is a rolling bearing steel
- the object M1 manufactured from the metal material is a race or a rolling element of a rolling bearing. This rolling bearing may be a ball bearing or a roller bearing.
- the proportional constant of ⁇ 0 and P max when b / a ⁇ 0 is shown in FIG. It is shown in 5.14.
- the fatigue test is performed by an ultrasonic torsional fatigue test, an extremely high speed load is possible, and the relationship between the shear stress amplitude of the metal material and the number of loads can be obtained in a short time. From the relationship thus obtained, the shear fatigue strength ⁇ 1im in the ultra-long life region is determined, and the maximum alternating shear stress amplitude ⁇ 0 acting on the inside of the surface layer is equal to the shear fatigue strength ⁇ 1im from the contact dimension specifications of the metal material.
- P max when the load acts as a fatigue limit surface pressure P max HM, it is possible to precisely estimate the fatigue limit surface pressure P max HM from the results of the torsional fatigue test. For this reason, when estimating the fatigue limit surface pressure P max 1im of the rolling bearing steel, which is a material having a strong shear fatigue strength ⁇ 1im , the effect that only a short test is required is more effectively exhibited.
- the relationship between the shear stress amplitude of the rolling bearing steel and the number of loads is determined in a short period of time by an ultrasonic torsional fatigue test with an extremely high vibration frequency of 20000 Hz and a very high speed.
- the shear fatigue strength (or shear fatigue limit) ⁇ 1im in the long-life region is determined, and a load is applied in which the alternating shear stress amplitude ⁇ 0 acting inside the surface layer is equal to the shear fatigue strength ⁇ 1im from the contact dimension specifications of the rolling bearing.
- the maximum contact surface pressure P max is estimated as the fatigue limit surface pressure P max 1im . For example, if the vibration continuous pressurization at 20000 Hz, and reaches the slight load times at 109 half day or so.
- test piece 1 since the test piece 1 generates heat when continuously vibrated with a somewhat high shear stress amplitude, the test piece 1 needs to be cooled and forced air cooling is performed. If the heat generation of the test piece 1 is not sufficiently suppressed by forced air cooling alone, vibration and pause are alternately repeated. Although the actual load frequency is reduced by pausing, if the testing machine 2 has an excitation frequency of 20000 Hz, even if the pause time is set to about 10 times the excitation time, it is still about 2000 Hz, which is one week. For example, the load count reaches 10 9 times.
- the fatigue limit surface pressure of rolling bearings defined in ISO-281: 2007, which is the standard of dynamic load rating and rated life of rolling bearings is 1500 MPa.
- the maximum alternating shear stress amplitude acting on ⁇ 0 375 MPa. Therefore, an ultrasonic torsional fatigue testing machine that can be evaluated with a maximum shear stress amplitude of 375 MPa or more is required, but there is no example of an ultrasonic fatigue torsion testing machine that can be evaluated with such a large maximum shearing stress amplitude.
- the present invention develops an ultrasonic torsion tester and determines the maximum contact surface pressure P max when a load is applied in which the maximum alternating shear stress amplitude ⁇ 0 acting inside the surface layer is equal to the shear fatigue strength ⁇ 1im. This is based on a comprehensive idea with the knowledge that the fatigue limit surface pressure P max can be estimated as 1 im .
- FIG. 2 shows a conceptual configuration of a shear fatigue property estimation system used in the evaluation method and a fatigue limit surface pressure estimation system used in the fatigue limit surface pressure estimation method including the system.
- the fatigue limit surface pressure estimation system will be mainly described, and the shear fatigue property estimation system will be described only with respect to the fatigue limit surface pressure estimation system.
- This estimation system includes an ultrasonic torsional fatigue testing machine 2 and a fatigue limit surface pressure estimation device 5 that performs the processes of the shear fatigue strength determination process (S2) and the fatigue limit surface pressure calculation process (S3) in FIG. Is done.
- the ultrasonic torsional fatigue testing machine 2 is composed of a testing machine body 3 and a testing machine control device 4.
- the testing machine main body 3 is attached to a torsional vibration converter 7 installed on the upper part of the frame 6 with an amplitude-amplifying horn 8 projecting downward, and a test piece 1 is detachably attached to the tip thereof, and The sound wave vibration is expanded and transmitted to the test piece 1 as vibration in the forward / reverse rotation direction around the axis of the amplitude expansion horn 8.
- the testing machine control device 4 includes a computer 10 and a testing machine control program 11 that can be executed by the computer 10.
- the computer 10 is a desktop personal computer or the like, and includes a central processing unit 12, storage means 13 such as a memory, and an input / output interface 14.
- the tester control program 11 is stored in the storage means 13, and the remaining storage area of the storage means 13 becomes a data storage area 13a or a work area.
- an input device 15 such as a keyboard and a mouse
- a display device such as a liquid crystal display device and an output device 16 such as a printer are provided as a part of the computer 10 or connected to the computer 10. ing.
- the tester control device 4 is a device that controls the torsional vibration converter 7 of the tester main body 3, and a control output is given from the input / output interface 14 to the vibration converter 7 via the amplifier 17.
- the test machine control device 4 performs the following processing according to the test machine control program 11.
- a display device serving as an output device 16 displays a screen prompting input of test conditions (output, intermittent operation or continuous operation, test end condition, data collection condition, etc.).
- test condition is input from the input device 15 and a test start command is input, the tester body 3 is driven and controlled according to the input condition. Note that the value of the maximum shear stress amplitude is converted and displayed with respect to the input output P by the equation (9) described later.
- the fatigue limit surface pressure estimation device 5 includes a computer 10 and a fatigue limit surface pressure estimation program 19 executable by the computer 10.
- the computer 10 may be the same as or different from the computer constituting the tester control device 4, and includes a central processing unit 12, storage means 13 such as a memory, and an input / output interface 14. .
- the input device 15 and the output device 16 are provided as a part of the computer 10 or connected to the computer 10.
- FIG. 3 shows an example in which the tester control program 11 and the fatigue limit surface pressure estimation program 19 are stored in the same computer 10 and used as a tester control device / fatigue limit surface pressure estimation device 29.
- the fatigue limit surface pressure estimation device 5 is configured by the computer 10 and the fatigue limit surface pressure estimation program 11 and each means shown in a conceptual configuration in FIG.
- the fatigue limit surface pressure estimation device 5 is a device for estimating the fatigue limit surface pressure P max 1im of a metal material that is in rolling contact, and includes an input means 22, a shear fatigue strength determination means 23, and a fatigue limit surface pressure calculation means. 24, and storage means 13 and output means 28 are configured.
- the apparatus excluding the fatigue limit surface pressure calculating means 24 is an apparatus for estimating shear fatigue characteristics.
- the input means 22 is a means for storing the relationship between the shear stress amplitude of the metal material and the number of loads obtained by a complete double swing ultrasonic torsional fatigue test in a storage area defined by the storage means 13.
- the input means 22 is a file that summarizes the relationship between the shear stress amplitude of the metal material and the number of loads, for example, using an input device for manual input such as a keyboard, a reading device for a recording medium, a communication network, etc. Is stored so that a predetermined storage area or its storage location can be specified for later calculation.
- the shear fatigue strength determining means 23 is means for determining the shear fatigue strength ⁇ 1im in the ultra-long life region according to a predetermined standard from the relationship between the shear stress amplitude stored in the storage region and the number of loads.
- the specific processing content performed by the shear fatigue strength determination means 23 is as described for the shear fatigue strength determination process (S2) of FIG.
- the fatigue limit surface pressure calculating means 24 is determined by the shape and size of the surfaces of the object M1 made of the metal material and the object M2 that is in rolling contact with the object M1 and the load that gives the contact surface pressure.
- the maximum alternating shear stress amplitude ⁇ 0 acting inside the surface layer of the object M1 of the metal material is obtained by a predetermined calculation formula for the maximum contact surface pressure P max when the load is applied which is equal to the shear fatigue strength ⁇ 1im.
- the maximum contact surface pressure P max is a means for setting the estimated value of the fatigue limit surface pressure P max 1im .
- the specific processing performed by the fatigue limit surface pressure calculating means 24 is as described for the fatigue limit surface pressure calculation process (S3) of FIG.
- This ultrasonic torsional fatigue testing machine 2 is designed as a complete double swing ultrasonic torsional fatigue testing machine that gives shear fatigue to rolling bearing steel at an extremely high speed.
- the excitation frequency range of the torsional vibration converter 7 is 20000 ⁇ 500 Hz. Note that while there are various types of longitudinal vibration converters used in the ultrasonic axial load fatigue test, commercially available torsional vibration converters have only low output, and it is virtually impossible to make them yourself. It was. Therefore, it is necessary to optimize the shapes of the amplitude expanding horn 8 and the test piece 1 to give torsional fatigue to the high-strength rolling bearing steel.
- the amplitude expansion horn 8 is of an exponential function type, and the diameter of the large-diameter side end face fixed to the torsional vibration converter 7 is 38 mm, and the diameter of the small-diameter side end face fixing the test piece 1 is 13 mm.
- the amplitude magnifying horn 8 is designed to resonate in the vicinity of 20000 Hz with as large an enlargement ratio as possible (ratio of the small-diameter side torsion angle to the large-diameter side torsion angle). ⁇ Adjusted.
- the large-diameter end face of the amplitude expanding horn 8 is provided with a male thread portion protruding in the axial direction for fixing to the torsional vibration converter, and the small-diameter end face is provided with a female thread for fixing the test piece. ing.
- the material of the amplitude expanding horn 8 is a titanium alloy.
- FIG. 6 shows a schematic diagram of the test piece.
- One end of the actual test piece 1 is provided with a male screw portion for fixing to the tip of the amplitude expanding horn 8.
- a test piece 1 is composed of cylindrical shoulder portions 1a, 1a at both ends, and a thinned portion 1b whose cross-sectional shape along the axial direction is an arc curve 1ba following the shoulder portions 1a, 1a on both sides. Dumbbell shape.
- the shape and dimensions of the test piece 1 are as follows: the length L 1 of the shoulder portion 1a, the half chord length L 2 that is half the length of the thinned portion 1b, the radius R 2 of the shoulder portion 1a, and the thinned portion 1b.
- the minimum radius R 1 and the radius of the arc curve 1ba are determined by R (both units are m).
- the arc radius R is obtained from R 1 , R 2 and L 2 .
- L 2 0.0065 m
- R 2 0.0045 m
- R 1 0.002 m
- FIG. 8 shows the torsion angle ⁇ and the surface shear stress ⁇ obtained by eigenvalue analysis of free torsional resonance using the test piece model of FIG.
- FIG. 9 is a photograph at rest, where there are places where the developer is not applied. The behavior at the time of vibration was observed in the uncoated areas. In the case of FIG. 9, attention is paid to the behavior of the part with an arrow.
- the manufactured ultrasonic torsional fatigue tester 2 controls the amplifier 17 with the tester control device 4 configured by the personal computer 10 and the tester control program 11 described above with reference to FIG.
- FIG. 19 shows a screen for inputting test conditions of the ultrasonic torsional fatigue testing machine 2.
- FIG. 20 is a detailed flowchart of the test process. In the test process, according to the input test conditions, control of amplifier output, control for selecting continuous oscillation or intermittent oscillation, information acquisition (frequency and amplifier) as shown in FIG. (Acquisition of status), control of the end of the test, and the like are performed.
- the fact that the resonance frequency is displayed as 19.97 mm in the measurement preparation column indicates that the test piece resonated at 19.97 kHz with an output of 10%, which is almost equal to the target 20000 Hz.
- this tester control device 4 when an amplifier output is input in the column of measurement conditions, it is converted into the maximum shear stress amplitude from the straight line slope and intercept of equation (9) input in advance on the initial setting screen. In the same column, select either continuous operation where vibration is continued or intermittent operation where vibration and pause are alternately repeated.
- FIG. 13 shows an example of a test piece subjected to torsional fatigue failure. It shows that an axial shear crack occurred, grew to a certain length, then shifted to a tensile mold and deviated obliquely.
- the bearing steel SUJ2 which was standard hardened and tempered in a normal temperature atmosphere, was evaluated by intermittent operation in which vibration and pause were alternately repeated. Regardless of the magnitude of the maximum shear stress amplitude, the vibration time was consistently 110 msec and the rest time was 1100 msec. The test piece is the same lot as that used for the measurement of the torsion angle of the end face. The test was aborted if no damage occurred up to 10 10 times.
- FIG. 15 shows the relationship between the shear stress amplitude obtained by the ultrasonic torsional fatigue test and the number of loads.
- the solid line in Fig. 15 is the SN diagram (fatigue strength diagram with 50% fracture probability) obtained by fitting to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials Science.
- a torsional fatigue test piece (standard quenching) using the bearing steel SUJ2 in Table 1 as a raw material and providing a thin part with the same minimum diameter of 4 mm as the ultrasonic torsional fatigue test piece in a parallel part with a diameter of 10 mm as shown in FIG. (Temperature unit in the figure is mm).
- the reason why the thinned portion is provided is to make the dangerous volumes substantially equal.
- the reason for changing R is to make the stress concentration factor uniform.
- emery polishing # 500, # 2000
- diamond wrapping particle size 1 ⁇ m
- the torsional fatigue test was performed with a hydraulic servo type torsional fatigue tester with a complete swing and a load frequency of 10 Hz. As a result, a white circle plot in FIG. 15 was obtained, and the time strength of the hydraulic servo torsional fatigue test result was about 15% lower than that of the ultrasonic torsional fatigue test result.
- the shear stress is maximum on the specimen surface and zero on the shaft core. That is, a fatigue test with a stress gradient.
- the tensile compression fatigue test it is known that in the axial load fatigue test, the vertical stress in the cross section of the smooth portion is uniform and shows a constant fatigue limit regardless of the diameter of the smooth portion.
- the rotating bending fatigue test having a stress gradient it is known that the fatigue limit decreases as the diameter of the smooth portion increases, and a dimensional effect that gradually approaches the fatigue limit in the axial load fatigue test is known.
- a stress gradient a mechanical factor that increases or decreases the volume subjected to a large load (dangerous volume).
- a PSN diagram may be obtained by evaluating multiple lines at multiple stress levels.
- the metal material fatigue reliability evaluation standard JSMS-SD-6-02 of the Japan Society of Materials was used to determine the shear fatigue limit ⁇ 1im in FIG. It has a function to obtain a PSN diagram with a small number of data.
- FIG. 16 is a PSN diagram (broken line in FIG. 16) with a fracture probability of 10% obtained thereby, and the 10% shear fatigue limit was 500 MPa.
- 500 ⁇ 0.85 425 MPa (dotted line in FIG. 16).
- 425 ⁇ 0.8 340 MPa (the chain line in FIG. 16).
- This value is the safest estimate of ⁇ 1im .
- ⁇ 1im 340 MPa, which is equal to the maximum alternating shear stress amplitude ⁇ 0
- the appropriate failure probability is set to 10%.
- a reasonable failure probability should be considered by comparing the dangerous volume of the ultrasonic torsional fatigue test piece with the dangerous volume of the actual rolling bearing.
- the relationship between the shear stress amplitude of the rolling bearing steel and the number of loads is obtained by the ultrasonic torsional fatigue test (complete swinging), and then the shear fatigue strength (or shear fatigue limit) ⁇ 1im in the ultralong life region is obtained .
- Determine the maximum contact surface pressure P max when a load is applied in which the maximum alternating shear stress amplitude ⁇ 0 acting on the inside of the surface layer is equal to the shear fatigue strength ⁇ 1im from the contact dimension specifications of the rolling bearing, and the fatigue limit surface pressure P max The method of estimating as 1 im was shown.
- the coordinates are made dimensionless by the uniaxial radius b of the contact ellipse.
- the alternating shear stress ⁇ yz has a maximum absolute value at the depth of the dotted line.
- FIG. 18 shows a microcrack parallel to the surface seen near the depth at which the absolute value of the alternating shear stress is maximized when the rolling fatigue test was stopped before peeling occurred and the circumferential cross section was observed. .
- the driving force developed parallel to the surface is considered as alternating shear stress.
- the crack growth mode is mode II type (in-plane shear type).
- mode II in-plane shear type
- FIG. 17 since the normal stress ⁇ z in the direction perpendicular to the crack surface is compression, there is no mode I type (tensile type), and ⁇ z interferes between the crack surfaces, so mode II Acts to prevent progress.
- the compressive stress perpendicular to the crack surface does not act on the mode II crack (shear crack in FIG. 13) generated and propagated in the ultrasonic torsional fatigue test. Therefore, it can be said that the fatigue limit surface pressure P max1im estimated from the shear fatigue strength ⁇ 1im in the ultralong life region obtained by the ultrasonic torsional fatigue test gives a value lower than the actual value and a value on the safe side.
- the method for selecting a rolling bearing material according to this embodiment is a method in which a metal material having a shear fatigue characteristic value evaluated by the characteristic evaluation method of the rolling bearing material having the above-described configuration is equal to or greater than a predetermined shear fatigue characteristic value, It is used as a material for a ring or rolling element.
- the shear fatigue characteristic of a metal material for a rolling bearing can be accurately estimated from the result of a short-time fatigue test. Therefore, the shear fatigue characteristics can be adopted as one of the test items of the material used for the bearing ring or rolling element of the rolling bearing.
- the use of only a material having a shear fatigue characteristic value obtained through an actual fatigue test that is equal to or greater than a predetermined shear fatigue characteristic value as a bearing material greatly helps to improve the reliability of the rolling bearing.
- Adopting shear fatigue properties as one of the test items of the materials used has conventionally required many years of testing, and was too far from the actual situation, but this method can be put to practical use, By adopting it, it can be used to improve the reliability of the bearing.
- the shear fatigue characteristic value used as a criterion suitably according to the objective.
- the shear fatigue characteristic value is estimated, for example, for each lot of material, for each purchased amount, for each supplier, and the like.
- the method for selecting a rolling bearing material of this embodiment is such that the fatigue limit surface pressure estimated by the fatigue limit surface pressure estimation method of any one of the above configurations is equal to or greater than a predetermined fatigue limit surface pressure. It is also possible to use a metal material as a material for a bearing ring or rolling element of a rolling bearing.
- the adoption of fatigue limit surface pressure as one of the test items for the materials used has been difficult for the past because it took many years to test and was far from the actual situation, but according to this method of selecting rolling bearing materials, This can be used to improve bearing reliability.
- the “predetermined fatigue limit surface pressure” that serves as a judgment criterion may be set appropriately according to the purpose, etc., and the fatigue limit surface pressure may be estimated, for example, for each lot of material or for each purchased amount. This is done every time.
- Example 1> Fatigue limit surface pressure P max 1im of a metal material used as a bearing ring or rolling element of a rolling bearing used under a condition in which only a stress within the elastic limit acts is estimated.
- the above-mentioned “under the condition that only the stress within the elastic limit acts” refers to the condition under which the stress and strain acting on the metal material return to “0” after the load is applied to the metal material and the load is removed. .
- bearing steel for bearings
- Various types of steel for bearings are conceivable as a metal material used as a bearing ring or rolling element of a rolling bearing used under the condition that only the stress within the elastic limit acts.
- Representative bearing steels include Japanese Industrial Standards; abbreviations JIS SUJ2, SCr420, and the like.
- SUJ2 corresponds to SAE52100 in the US AISI standard.
- Example 1 (1) "SUJ2 standard” in which SUJ2 material was subjected to quenching and tempering heat treatment, (2) “SUJ2 carbonitriding” in which SUJ2 material was subjected to carbonitriding and quenching and tempering heat treatment, (3 ) Shear fatigue characteristics of each specimen of “SCr420 carburized”, which was carburized and quenched and tempered on the SCr420 material, was determined by ultrasonic torsional fatigue test (both swings), and fatigue limit surface pressure was estimated from this shear fatigue characteristics did. The test piece shown in FIG. 7 was used as each test piece.
- Table 2 shows the alloy components of the SUJ2 material used for the test pieces.
- the following specimens (1) and (2) were manufactured by sequentially turning the SUJ2 material shown in Table 2 above, turning, heat treatment, and grinding.
- the heat treatment of the “SUJ2 standard” specimen is a so-called soaking quenching and tempering (heating: 830 ° C. ⁇ 80 min, RX gas atmosphere ⁇ oil quenching ⁇ tempering: 180 ° C. ⁇ 180 min) that quenches the entire SUJ2 material. .
- soaking quenching and tempering heat treatment: 830 ° C. ⁇ 80 min
- For the “SUJ2 carbonitriding” test piece carbonitriding and tempering and tempering of SUJ2 material (heating: 850 ° C.
- the RX gas atmosphere is an atmospheric gas mainly composed of CO, H 2 , and N 2 that is obtained by mixing air into a hydrocarbon gas such as butane and methane, and then filling the catalyst and heating at a high temperature.
- Table 3 shows the alloy components of the SCr420 material used for the test pieces.
- the test specimen (3) was manufactured by sequentially turning, heat-treating and grinding the SCr420 material shown in Table 3 above. (3) For “SCr420 carburized” specimens, carburizing and tempering (carburization: 920 ° C. ⁇ 4 h, RX gas atmosphere, carbon potential maintained at 1.2 ⁇ diffusion 920 ° C. ⁇ 3 h, RX gas atmosphere ⁇ oil quenching ⁇ Tempering: 180 ° C. ⁇ 120 min).
- FIG. 24 is a diagram showing the shear fatigue characteristics of the “SUJ2 standard” test piece.
- the solid line in the figure is the SN diagram obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials, and the shear fatigue limit ⁇ w0 is 577 MPa. became.
- fracture probability correction fracture probability 10%
- size effect correction size effect correction
- overestimation correction were performed to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 4 shows an estimation result of the fatigue limit surface pressure P max 1im .
- FIG. 25 is a diagram showing the shear fatigue characteristics of the “SUJ2 carbonitriding” test piece.
- the solid line in the figure is an SN diagram obtained in the same manner as in FIG. 24, and the shear fatigue limit ⁇ w0 is 524 MPa.
- fracture probability correction fracture probability 10%
- size effect correction size effect correction
- overestimation correction were performed to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 5 shows an estimation result of the fatigue limit surface pressure P max 1im .
- FIG. 26 is a diagram showing the shear fatigue characteristics of the “SCr420 carburized” test piece.
- the solid line in the figure is an SN diagram obtained in the same manner as in FIG. 24, and the shear fatigue limit ⁇ w0 is 500 MPa.
- fracture probability correction fracture probability 10%
- size effect correction size effect correction
- overestimation correction were performed to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 6 shows an estimation result of the fatigue limit surface pressure P max 1im .
- Rolling bearings that are used under conditions where only a macroscopic elastic stress is applied, that is, a rolling bearing that is applied only under the elastic limit, is considered to have a semi-permanent bearing life. Therefore, obtaining the maximum contact surface pressure at which internal origin-type separation does not occur by testing is important in selecting the materials for the bearing rings and rolling elements or in determining the use conditions of the bearing.
- the rolling bearing steel used under the condition that only the stress within the elastic limit acts can be subjected to an extremely high speed load by performing the fatigue test by an ultrasonic torsional fatigue test.
- the relationship between the shear stress amplitude and the number of loads of each rolling bearing steel can be obtained in half a day to one week. From this relationship, the fatigue limit surface pressure P max 1im can be accurately estimated. Therefore, the fatigue limit surface pressure can be adopted as one of the test items of the material used for the bearing ring or rolling element of the rolling bearing used under the condition that only the stress within the elastic limit acts.
- Example 2 Fatigue limit surface pressure P max 1im of a metal material used as a bearing ring or rolling element of a rolling bearing for an aircraft is estimated.
- This rolling bearing is used, for example, as a bearing that supports a main shaft of an aircraft engine turbine.
- the “for aircraft” includes space use.
- Examples of the metal material include M50 and M50NiL.
- the shear fatigue characteristics of each test piece are obtained using a test piece obtained by heat-treating the M50 material and a test piece obtained by heat-treating the M50NiL material, and the fatigue limit surface pressure is determined from the shear fatigue characteristics. Estimated. The test piece shown in FIG. 7 was used as each test piece.
- Table 7 shows the alloy components of the M50 material and M50NiL material used for the test pieces.
- Specimens were manufactured by sequentially turning, heat-treating and grinding the M50 materials shown in Table 7 above.
- the heat treatment in this case is so-called quenching, sub-zero treatment, tempering (heating: 850 ° C. ⁇ 80 min + 1090 ° C. ⁇ 20 min, vacuum ⁇ steaming oil quenching ⁇ sub-zero treatment: ⁇ 60 ° C. ⁇ 90 min ⁇ quenching) Return: 450 ° C. ⁇ 60 min + 550 ° C. ⁇ 180 min.
- the M50NiL material shown in Table 7 was sequentially turned, heat treated, and ground to produce a test piece.
- the heat treatment in this case is carburizing quenching, intermediate annealing, quenching, sub-zero treatment, tempering (carburization: 960 ° C. ⁇ 15 h, RX gas atmosphere, carbon potential maintained at 1.2 ⁇ diffusion: 960 ° C. ⁇ 74 h, RX gas atmosphere ⁇ Intermediate annealing: 650 ° C. ⁇ 6 h ⁇ heating: 850 ° C. ⁇ 40 min + 1090 ° C. ⁇ 25 min, vacuum ⁇ oil quenching ⁇ subzero treatment: ⁇ 80 ° C. ⁇ 180 min ⁇ tempering: 450 ° C. ⁇ 60 min + 550 ° C. ⁇ 180 min.
- FIG. 27 is a diagram showing the shear fatigue characteristics of the M50 test piece.
- the solid line in the figure is an SN diagram obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials, and the shear fatigue limit ⁇ w0 is 551 MPa. became.
- fracture probability correction fracture probability 10%
- size effect correction size effect correction
- overestimation correction were performed to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 8 shows an estimation result of the fatigue limit surface pressure P max 1im .
- the solid line in the figure of the M50NiL carburized specimen is an SN diagram obtained by fitting to the fatigue limit type broken line model of the JSMS-SD-6-02 metal material fatigue reliability evaluation standard of the Japan Society of Materials.
- the shear fatigue limit ⁇ w0 was 678 MPa.
- Fracture probability correction (fracture probability 10%), size effect correction, and overestimation correction were performed on the shear fatigue limit ⁇ w0 to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 9 shows an estimation result of the fatigue limit surface pressure P max 1im .
- Aircraft machine parts are required to have high reliability compared to general industrial machine parts.
- a metal material that is used as a bearing ring or rolling element of a rolling bearing for an aircraft can be subjected to an extremely high speed load by performing a fatigue test by an ultrasonic torsional fatigue test.
- the relationship between the shear stress amplitude of each metal material and the number of loadings can be obtained in half a day to one week). From this relationship, the fatigue limit surface pressure P max 1im can be accurately estimated. Therefore, fatigue limit surface pressure can be adopted as one of the test items of materials used for bearing rings or rolling elements of rolling bearings for aircraft.
- ⁇ Embodiment 3> Fatigue limit surface pressure P max 1im of a metal material used as a race or rolling element of a rolling bearing for a railway vehicle is estimated.
- the rolling bearing of the railway vehicle is a bearing that supports an axle of the railway vehicle, for example.
- the metal material include SNCM420, SUJ2, SUJ3, and SCr420.
- Example 3 the shear fatigue property of each test piece was obtained using a test piece obtained by heat-treating the SNCM420 material and a test piece obtained by heat-treating the SUJ3 material, and the fatigue limit surface pressure was determined from this shear fatigue property. Estimated. The test piece shown in FIG. 7 was used as each test piece.
- Table 10 shows the alloy components of the SNCM420 material and SUJ3 material used for the test pieces.
- the SNCM420 material shown in Table 10 above was sequentially turned, heat treated, and ground to produce test pieces.
- Heat treatment in this case is carburizing quenching, secondary quenching, tempering (carburization: 920 ° C. ⁇ 4 h, RX gas atmosphere, carbon potential is maintained at 1.2 ⁇ diffusion: 920 ° C. ⁇ 3 h, RX gas atmosphere ⁇ heating: 800 ° C. ⁇ 70 min ⁇ oil quenching ⁇ tempering: 180 ° C. ⁇ 120 min).
- the SUJ3 material shown in Table 7 above was sequentially turned, heat-treated, and then ground by grinding to produce test pieces.
- the heat treatment in this case is so-called quenching and tempering (heating: 810 ° C. ⁇ 80 min ⁇ oil quenching ⁇ tempering: 180 ° C. ⁇ 180 min) in which the entire SUJ3 material is quenched.
- FIG. 29 is a diagram showing shear fatigue characteristics of a test piece of SNCM420 carburized.
- the solid line in the figure is an SN diagram obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials, and the shear fatigue limit ⁇ w0 is 526 MPa. became.
- fracture probability correction fracture probability 10%
- size effect correction size effect correction
- overestimation correction were performed to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 11 shows an estimation result of the fatigue limit surface pressure P max 1im .
- FIG. 30 is a diagram showing shear fatigue characteristics of SUJ3 test pieces.
- the solid line in the figure is an SN diagram obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials, and the shear fatigue limit ⁇ w0 is 547 MPa. became. Fracture probability correction (fracture probability 10%), size effect correction, and overestimation correction were performed on the shear fatigue limit ⁇ w0 to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 12 shows an estimation result of the fatigue limit surface pressure P max 1im .
- a metal material that is used as a rolling ring or rolling element of a rolling bearing for a railway vehicle can be subjected to an extremely high speed load by performing a fatigue test using an ultrasonic torsional fatigue test, and can be performed in a short time (for example, The relationship between the shear stress amplitude of each metal material and the number of loadings can be obtained in half a day to one week. From this relationship, the fatigue limit surface pressure P max 1im can be accurately estimated. Therefore, the fatigue limit surface pressure can be adopted as one of the test items of the material used for the bearing ring or rolling element of the rolling bearing for the railway vehicle.
- the inner ring (hub ring) outboard raceway and the outer ring fixed to the knuckle are induction-hardened in S53C material, and the inner ring inboard raceway and rolling elements are made of SUJ2 material. Steel that has been subjected to heat treatment of quenching and tempering is applied. As described above, in Example 4, the shear fatigue characteristics of the test piece obtained by heat-treating the S53C material were obtained, and the fatigue limit surface pressure was estimated from the shear fatigue characteristics. The test piece shown in FIG. 7 was used as each test piece.
- Table 13 shows the alloy components of the S53C material used for the test pieces.
- FIG. 31A is a diagram showing a heat pattern of induction hardening of the S53C material
- FIG. 31B is a diagram showing a heat pattern of tempering the material.
- FIG. 32A is a front view of a test piece schematically showing an induction hardening pattern
- FIG. 32B is a side view of the test piece.
- the hatched portion in FIG. 32A is a schematic induction hardening pattern.
- the minimum diameter portion ⁇ dmin ( ⁇ dmin is 4 mm) is fully cured.
- the burning escape width W (four corners) is 3 mm or less. You may burn out to the end face.
- the old ⁇ grain size of the minimum diameter portion ⁇ dmin is set to about # 8.
- FIG. 33 is a diagram showing shear fatigue characteristics of a test piece of S53C induction hardening.
- the solid line in the figure is an SN diagram obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02, a metal material fatigue reliability evaluation standard of the Japan Society of Materials, and the shear fatigue limit ⁇ w0 is 442 MPa. became. Fracture probability correction (fracture probability 10%), size effect correction, and overestimation correction were performed on the shear fatigue limit ⁇ w0 to determine the fatigue limit surface pressure P max 1im in the line contact state.
- Table 14 shows an estimation result of the fatigue limit surface pressure P max 1im .
- the fatigue test is performed by the ultrasonic torsional fatigue test for the metal material used as the bearing ring or rolling element of the rolling bearing, which is a bearing for a vehicle wheel.
- the relationship between the shear stress amplitude of each metal material and the number of loadings can be obtained in time (for example, half day to one week). From this relationship, the fatigue limit surface pressure P max 1im can be accurately estimated. Therefore, fatigue limit surface pressure can be adopted as one of the test items of the material used for the bearing ring or rolling element of a rolling bearing that is a bearing for a vehicle wheel.
- FIGS. A second embodiment of the present invention will be described with reference to FIGS.
- This shear fatigue characteristic evaluation apparatus includes a testing machine main body 3A having a torsional vibration converter 7 and an amplitude expanding horn 8, an oscillator 20, an amplifier 17, and a control / data collection unit 4A.
- the control / data collection means 4A corresponds to the testing machine control device 4 of the first embodiment.
- the testing machine main body 3A is attached to a torsional vibration converter 7 installed on the upper part of the frame 6 with an amplitude-amplifying horn 8 projecting downward, and a test piece 1 is detachably attached to the tip thereof.
- the sound wave vibration is expanded and transmitted to the test piece 1 as vibration in the forward and reverse rotation directions around the axis O of the amplitude expansion horn 8.
- the test machine main body 3 ⁇ / b> A has a test piece air cooling means 9 that performs forced air cooling of the test piece 1.
- the test piece air cooling means 9 includes, for example, a nozzle or the like that is connected to a compressed air generation source (not shown) such as a blower by a pipe and blows air against the test piece 1, and is an electromagnetic valve (not shown) or By switching on and off the compressed air generation source, it is possible to switch between blowing air and stopping blowing.
- a compressed air generation source such as a blower by a pipe and blows air against the test piece 1
- an electromagnetic valve not shown
- the torsional vibration converter 7 is a device that generates torsional vibration that rotates in the forward and reverse directions around the rotation center axis O at the frequency of the alternating current power when two-phase alternating current power is applied.
- the AC power supplied to the torsional vibration converter 7 is a positive / negative symmetrical AC power such as a sine wave, and the generated torsional vibration is a complete double swing, that is, a vibration in which the positive rotation direction and the reverse rotation direction are symmetric.
- the amplitude-amplifying horn 8 is formed in a tapered shape and has a mounting portion composed of a female screw hole for attaching a test piece concentrically to the distal end surface, and is fixed to the torsional vibration converter at the proximal end.
- the amplitude expansion horn 8 sets the amplitude of the torsional vibration of the vibration converter 7 applied to the base end to an amplitude expanded at the distal end.
- the material of the amplitude expanding horn 8 is, for example, a titanium alloy.
- the oscillator 20 is composed of an electronic device that generates a voltage signal having a frequency in the ultrasonic region that is a frequency at which the amplitude expanding horn 8 is vibrated.
- the oscillator 4 has a fixed frequency or an adjustable frequency within an oscillation frequency of, for example, ⁇ 500 Hz.
- the amplifier 17 is an electronic device that amplifies the output of the oscillator 20 and applies AC power having a frequency in the ultrasonic region to the torsional vibration converter 7.
- the amplifier 17 is assumed to be capable of controlling the magnitude of the output of the AC power and on / off by input from the outside.
- the maximum output of the amplifier 17 is 300 W in this embodiment.
- the control / data collection means 4A gives the amplifier 17 control inputs such as the output magnitude and on / off, and also includes data including the excitation frequency under test, the state of the output of the amplifier 17 and the number of loads. Means for collecting from the amplifier 17. In addition to the above, the control / data collection unit 4A has a function of controlling the test piece cooling unit 9.
- the control / data collection means 4A includes a computer such as a personal computer and a program (not shown) to be executed by the computer.
- the control / data collection unit 4A displays an input device 15A such as a keyboard and a mouse and an image of a liquid crystal display device on the screen.
- a screen display device 18 is connected or provided as part of the computer.
- the control / data collection unit 4A includes a test condition setting unit 21, a test condition / collection data storage unit 13A, and a test control unit 12A.
- the test condition / collected data storage unit 13A and the test control unit 12A correspond to the storage unit 13 and the central processing unit 12 of the first embodiment, respectively.
- the test condition setting unit 21 stores the data in the test condition / collected data storage unit 13A, that is, It is means for setting as a control condition.
- the test condition setting unit 21 is a means for displaying the input screen shown in FIG. 19 on the screen display device 18 and performing the processing shown in the flowchart in FIG.
- the test control unit 12A is means for driving the torsional vibration converter 8 and collecting the data in accordance with the test conditions set by the test condition setting unit 21.
- the test control unit 12A includes a basic control unit 25, a continuous oscillation control unit 26, and an intermittent oscillation control unit 27.
- the test control unit 12A is means for performing the processing shown in the flowchart in FIG.
- the means for performing the processing of steps R8 to R13 in the figure is the continuous oscillation control unit 26, the means for performing the processing of steps R14 to R24 is the intermittent oscillation control unit 27, and the means for performing the processing of the remaining steps is basically. It is the control unit 25.
- This evaluation method is a method for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact using the test piece 1 made of the metal material, using the shear fatigue characteristic evaluation apparatus shown in FIG.
- the shape and size are made to resonate with the vibration of the amplitude expanding horn 8 driven by the torsional vibration converter 7, and the vibration converter 7 is driven at an ultrasonic frequency (in this example, 20000 ⁇ 500 Hz), A test is performed in which the specimen 1 is resonated with the vibration of the amplitude expanding horn 8 to cause shear fatigue fracture.
- the lower limit value of the frequency range for driving the torsional vibration converter 7 may be (2000 ⁇ 500 + ⁇ ) Hz.
- ⁇ is a margin value for property change during the test of the test piece, and may be 200 Hz or less.
- the metal material is, for example, bearing steel such as high carbon chromium bearing steel (JIS-SUJ2) as a high-strength metal material for rolling bearings.
- an extremely high speed ultrasonic torsional fatigue testing machine in which the excitation frequency is in the ultrasonic range is performed. Therefore, in order to evaluate the shear fatigue property of a metal material in rolling contact, it is necessary in a short time. The number of loads can be reached, and shear fatigue characteristics can be evaluated quickly. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 9 times in just half a day. In addition, since a test that actually causes shear fatigue failure is performed, the shear fatigue characteristics can be obtained with higher accuracy than in the conventional method in which the maximum size of non-metallic inclusions is used as an index of steel quality. Since the test piece resonates, shear fatigue failure can be efficiently generated with a small amount of energy input.
- the torsional vibration converter 7 that is commercially available and can be controlled by the amplifier is only one model in the examined range, and there was no room for selection. Therefore, the shape of the amplitude expanding horn 8 and the test piece 1 was optimized and optimized. Shear fatigue was applied to high-strength metal materials.
- the standard amplitude expansion horn (exponential function type) sold together with the commercially available torsional vibration converter 7 has a diameter of the large-diameter side end face fixed to the torsional vibration converter 7 of 38 mm and a diameter of the small-diameter side end face fixing the test piece 1. Is 15 mm.
- This amplitude expansion horn is designed and adjusted to resonate around 20000 Hz.
- a male threaded portion which is a mounting part for fixing to the torsional vibration converter, protrudes from the center of the large diameter end face of the amplitude expanding horn, and a female thread for fixing the test piece to the small diameter end face.
- the attachment part which consists of a screw is vacated.
- the material of the amplitude expanding horn 8 is a titanium alloy.
- FEM analysis software Marc Mentat 2008 r1 (registered trademark)
- eigenvalue analysis of free torsional resonance was performed using the above E, ⁇ , and ⁇ as physical property values.
- the enlargement ratio ratio of the small-diameter side torsion angle to the large-diameter side torsion angle
- test piece 1 The shape of the test piece 1 is the same as that shown in FIG. 6 of the first embodiment.
- L 2 0.0070 m
- R 2 0.0060 m
- R 1 0.0030 m
- the eigenvalue analysis of free torsional resonance was performed using the finite element method (FEM) analysis software (Marc Mentat 2008 r1) (registered trademark) with the above E, ⁇ , and ⁇ as physical properties.
- FEM finite element method
- the amplitude expanding horn 8 having a diameter of 38 mm on the end face on the large diameter side and a diameter of 13 mm on the end face on the small diameter side was manufactured.
- the high-efficiency amplitude expansion horn (exponential function type) is designed and adjusted to resonate around 20000 Hz.
- the material of the high efficiency amplitude expansion horn is a titanium alloy.
- R 1 , L 1 , and L 2 are the minimum radius, shoulder length, and half chord length of the test piece 1 as described above (all units are m 2).
- g, ⁇ , k, and ⁇ are obtained by the above-described equations (1), (3), (4), and (5), respectively.
- ⁇ end is the torsion angle of the end face of the test piece 1 (unit: rad).
- the maximum shear stress ⁇ max acting on the test piece minimum diameter portion generally increases as the test piece increases and decreases as the test piece decreases.
- the above-described high-efficiency amplitude-expanding horn 8 with improved torsion angle expansion ratio changes the shape of the test piece to cause a resonance instability phenomenon.
- the following two plans were considered as guidelines for causing the test specimen 1 to undergo shear fatigue failure without any failure.
- the test piece is enlarged and a large maximum shear stress ⁇ max is applied to the surface of the test piece minimum diameter portion even with a small amplifier output.
- the high-efficiency amplitude-enlarging horn has a 67% increase in the torsion angle expansion rate compared to the standard product.
- the maximum shear stress ⁇ max acting on the surface of the test piece minimum diameter portion is reduced, but the test piece is made smaller.
- test pieces A to E in Table 15 were manufactured using the bearing steel SUJ2 in Table 1 described above.
- the test piece A has the above-mentioned initial shape, and the weight excluding the mounting protrusion composed of the screw portion fixed to the amplitude expanding horn 8 is 21.7 g.
- the test pieces B and C are obtained by enlarging the test piece along the pointer (1), and the ⁇ max ratio (vs. A) at the same end face twist angle is increased, and the weight ratio (vs. A) is also increased.
- the test pieces D and E are obtained by reducing the test piece along the guideline (2). At the same end face twist angle, the ⁇ max ratio (vs. A) is reduced and the weight ratio (vs.
- the shoulder length L 1 in Table 15 is not the theoretical solution obtained by the above equation (6), but is obtained by the eigenvalue analysis of free torsional resonance by FEM as described above so as to cause torsional resonance at 20000 Hz. Value.
- test piece 1 was attached to the high-efficiency amplitude-expanding horn 8 and evaluated in the above-mentioned intermittent operation conditions in a room temperature atmosphere.
- the test piece B along the pointer (1) had a resonance instability phenomenon at an amplifier output of 50%.
- the test piece C did not even resonate even when the amplifier output was 10%.
- the test piece D along the pointer (2) had a resonance instability phenomenon at an amplifier output of 80%.
- resonance instability did not occur until the amplifier output reached 90%.
- shear fatigue failure occurred in a low cycle range of the order of 10 5 times of loading. From the above, it was found that the specimen weight is strongly related to the resonance instability phenomenon. This is considered to be because the maximum output of the torsional vibration converter 7 is as low as 300 W. It was decided to adopt E as an evaluation specimen.
- the weight excluding the screw portion fixed to the amplitude expanding horn 8 of the test piece A is 21.7 g.
- the weight of the test piece E excluding the screw portion is 9.36 g.
- the weight excluding the mounting protrusion is slightly less than 9.36 g. Become.
- This test piece E is the same as the test piece 1 of the first embodiment, and the shape, dimensions and evaluation results of this test piece E are as shown in FIGS. 7 to 16 of the first embodiment.
- the control / data collection means 4A shown in FIGS. 34 and 35 will be described together with FIGS. 19 and 20 and FIGS. 36 to 38.
- the test condition setting unit 21 in FIG. 35 causes the screen display device 18 to display the same test condition input screen as in the first embodiment shown in FIG.
- the input field for the material name of the specimen material, the input field for the comment, and the input field for the amplifier output which is a condition for driving the torsional vibration converter 7, a selection input for selecting between intermittent operation and continuous operation Field, input field for one excitation time and pause time in the case of intermittent operation, input field for test end condition (number of loads to end test, and frequency fluctuation range), and initial cycle as data acquisition condition, end Cycle and cycle interval input fields are displayed, and a file name input field is displayed.
- the test condition setting unit 21 stores the test condition information input on the input screen of FIG. 19 in the test condition / collected data storage unit 13A as one test file, and gives the input file name.
- the input procedure is performed, for example, in the order shown in the flowchart in FIG.
- the test condition setting unit 21 in FIG. 35 displays an initial setting input screen on the screen display device 18 in addition to the input screen in FIG. 19, and as shown in the flowchart in FIG. Input of physical quantity and input of shear amplitude stress coefficient are prompted, voltage and physical quantity are initially set with the inputted value, and recorded in the test file or the like.
- the “physical quantity” mentioned here is a quantity such as the next amplitude IN, amplitude OUT, ultrasonic power, frequency, memory frequency, and the like.
- controller (PC)” refers to the control / data collection means 4A.
- Amplitude IN Amplifier output amplitude This is the amplifier output amplitude.
- the controller (PC) instructs 0 to 100% at -10V to + 10V.
- Amplitude OUT Voltage output proportional to the actual amplifier output amplitude.
- the controller (PC) indicates 0 to 100% from 0V to + 10V.
- Ultrasonic power A voltage output proportional to the output of ultrasonic power. 0-100% is indicated by 0V to + 10V on the controller (PC).
- Frequency A voltage output proportional to the output of the amplifier operating frequency.
- the controller (PC) instructs 19.50 to 20.50kHz from -10V to + 10V.
- Memory frequency A voltage output proportional to the output of the relative frequency recorded in the amplifier memory.
- the controller (PC) indicates 19.50 to 20.50 kHz from -10V to + 10V.
- the resonance frequency is searched with 10% output (see FIG. 38).
- the screen shifts to the screen of the “test information” tab, and when the “test start” button is pressed, a start command is given, and the test control unit 12A in FIG. 35 starts the test.
- the test control unit 12A in FIG. 35 controls the amplifier 17 and the test piece cooling means 9 according to the test conditions input and stored as described above, and collects data from the amplifier 17.
- the amplitude output is determined (R3)
- the test condition of continuous operation or intermittent operation is determined (R4)
- the processes of steps R5 to R13 are performed, and in the case of intermittent operation, the processes of steps R14 to R24 are performed.
- the excitation frequency and the output state of the amplifier are collected (R6, R18), and the test file is updated with the collected data (R12, R22).
- the test end condition is satisfied, the ultrasonic output is stopped (R26), and the test is ended.
- the method for selecting a rolling bearing material according to this embodiment is a method in which a metal material having a shear fatigue characteristic value evaluated by the characteristic evaluation method of the rolling bearing material having the above-described configuration is equal to or greater than a predetermined shear fatigue characteristic value, It is used as a material for a ring or rolling element. This also has the same effect as the first embodiment.
- this rolling contact / torsion load acting metal material has a shear fatigue property evaluation method under the penetration of hydrogen before performing an ultrasonic torsional fatigue test using the test apparatus of FIG. 39 (B).
- the second embodiment is the same as the second embodiment in that it includes a hydrogen charging process (step S1 in FIG. 40) for charging the metal specimen 1 with hydrogen.
- step S1 in FIG. 40 the hydrogen charging process for charging the metal specimen 1 with hydrogen.
- the hydrogen charging means 30 in FIG. 39A is means for charging the test piece 1 with hydrogen by any of the following methods.
- it is a means for cathodic electrolytic charging of hydrogen or a means for charging by immersing hydrogen in an aqueous solution.
- cathodic electrolytic hydrogen charging is performed by immersing a platinum electrode 34 and a test piece 33 in an electrolyte solution 32 in a container 31, and applying a voltage with the test piece 33 being negative and the electrode 34 being positive. Do that.
- These hydrogen charges will be specifically described later.
- Other configurations are the same as those of the second embodiment.
- an ultrasonic torsional fatigue test is performed in which an ultrasonic torsional vibration in which the excitation frequency is in the ultrasonic range is applied to the test piece. Therefore, a torsional fatigue test in which an extremely high load is repeatedly applied can be performed. Therefore, before the charged hydrogen is dissipated, the test specimen of the metal material to be evaluated is subjected to shear fatigue, and the shear fatigue characteristics under hydrogen intrusion can be evaluated reasonably and quickly. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 7 times in only 8.3 min. Since the test piece resonates, shear fatigue failure can be efficiently generated with a small amount of energy input.
- the specimens made of bearing steel SUJ2 that was standard hardened and tempered at room temperature and under hydrogen intrusion were evaluated by intermittent operation in which vibration and pause were alternately repeated.
- Emery polishing # 500, # 2000
- diamond wrapping particle size: 1 ⁇ m
- the vibration time was consistently 110 msec and the rest time was 1100 msec.
- the test piece is the same lot as that used for the measurement of the torsion angle of the end face. The test was aborted if no damage occurred up to 10 8 times.
- the electrolyte was a 0.05 mol / L dilute sulfuric acid aqueous solution with 1.4 g / L thiourea added. Current density was 0.2 mA / cm 2.
- This hydrogen charge condition about 3.5 mass-ppm of diffusible hydrogen enters.
- diamond wrapping particle size: 1 ⁇ m
- FIG. 41 shows the change with time of the relative hydrogen concentration in the minimum diameter portion of the test piece calculated using the above diffusion coefficient. It shows that the core is almost saturated in 20 hours. This is the basis for setting the hydrogen charge time to just 20 hours.
- FIG. 42 shows the relationship between the shear stress amplitude with and without hydrogen charge and the number of loads obtained in the ultrasonic torsional fatigue test.
- the curve (solid line) in Fig. 42 is the SN diagram (fatigue strength line with 50% fracture probability) obtained by applying the continuous degradation type curve model of the JSMS-SD-6-02 metal materials fatigue reliability evaluation standard of the Japan Society of Materials Science. Figure).
- the shear fatigue strength at 10 7 times was 789 MPa without hydrogen charge and 559 MPa with hydrogen charge, and the shear fatigue strength clearly decreased under hydrogen penetration.
- a torsional fatigue test piece (standard quenching and tempering) as shown in FIG. 14 is manufactured as in the first embodiment, and the same conditions as in the first embodiment.
- a torsional fatigue test was conducted. As a result, a black triangle plot in FIG. 42 was obtained, and the time strength of the hydraulic servo torsional fatigue test result was about 15% lower than that of the ultrasonic torsional fatigue test result.
- the ultrasonic torsional fatigue test tends to be evaluated with higher shear fatigue strength than the conventional torsional fatigue test. Therefore, 671 MPa and 475 MPa, which are 85% of the shear fatigue limit of 789 MPa and 559 MPa in 10 7 times with and without hydrogen charge, respectively, may be used as a standard when discussing in absolute values.
- the standard of the tensile compression fatigue test is applied as it is, and 631 MPa and 447 MPa which are 80% of the shear fatigue limit of 789 MPa and 559 MPa at 10 7 times with and without hydrogen charge, respectively. Can also be used as a guide when discussing absolute values.
- the metal material fatigue reliability evaluation standard JSMS-SD-6-02 of the Japan Society for Materials is used to determine the shear fatigue strength at 10 7 times in FIG. It has a function to obtain a PSN diagram with a small number of data.
- FIG. 43 is a PSN diagram (broken line) with a fracture probability of 10% obtained thereby, and the 10% shear fatigue limit at 10 7 times with and without hydrogen charge was 736 and 512 MPa, respectively. It may be used as a guide when discussing them in absolute values.
- the ultrasonic torsional fatigue test should be corrected to evaluate the shear fatigue strength higher than the conventional torsional fatigue test, and the standard of the tensile compression fatigue test should be applied. It is. 50% of 626 MPa, which is 85% of 10% shear fatigue limit of 736 MPa in 10 7 times without hydrogen charge, and 80% of 626 MPa in 85% of 10% shear fatigue limit of 512 MPa in 10 7 times with hydrogen charge. 348 MPa, which is 80% of 435 MPa, may be used as a guideline for discussion.
- the method for evaluating the shear fatigue characteristics or fatigue limit surface pressure of the rolling contact metal material has been described. However, these evaluation methods can be applied to materials other than the rolling contact metal material.
- application examples of the present invention will be described. In this application example, a high-strength metal material for a power transmission shaft is used instead of the rolling contact metal material, and other configurations are the same as those in the second embodiment.
- the load frequency is about 10 Hz at the maximum in the former and about 30 Hz in the latter, and the load is high. It takes a lot of time to evaluate the torsional fatigue characteristics up to the number of times.
- the most commonly used high-strength metal material for power transmission shafts is the carbon steel JIS-S40C base with an increased amount of Mn, a hardenability improving element, and further B added. Then, induction hardening is performed so that the old ⁇ grain size specified in the JIS standard of the surface layer is 8 to 10, and tempering is performed at a relatively low temperature (about 150 ° C.), and the hardness becomes about 650 HV.
- the conventional torsional fatigue testing machine is a low-load frequency
- torsional fatigue characteristics of the power transmission shaft has not been evaluated only about the load times 10 6 times.
- the load times the power transmission shaft is received by the long-term use is not approximately 10 6 times, it is necessary torsional fatigue evaluation to high load times.
- the excitation frequency in the ultrasonic range, it takes a short time to evaluate the shear fatigue characteristics of the high-strength metal material for the power transmission shaft.
- the required number of loads can be reached, and the shear fatigue characteristics can be evaluated quickly. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 9 times in just half a day. Since the test piece resonates, shear fatigue failure can be efficiently generated with a small amount of energy input.
- An intermediate shaft steel of a constant velocity joint (abbreviation: CVJ) is an example of the power transmission shaft.
- CVJ constant velocity joint
- X steel with increased Mn is used for small diameter products
- Y steel with B added to S40C to increase Mn and reduce Si is used for large diameter products. It has been.
- the heat treatment conditions and shear fatigue properties of these two steel specimens X and Y are shown, respectively.
- Table 16 shows the alloy components of the steel used for the test pieces X and Y.
- the materials used for the test pieces X and Y in Table 16 were respectively turned, heat treated, and ground to produce test pieces.
- the heat treatment in this case is induction hardening and tempering.
- the induction hardening heat pattern and induction hardening pattern of the material used for the test piece are the same as those in FIGS. 31A and 31B and FIGS. 32A and 32B of the first embodiment.
- FIG. 45 is a diagram showing the shear fatigue characteristics of the test pieces X and Y.
- the solid and broken lines in the figure are SN diagrams obtained by applying the continuous degradation curve model of the JSMS-SD-6-02 metal material fatigue reliability evaluation standard of the Japan Society of Materials, showing the shear fatigue limit of both steels. ⁇ w0 was almost equal.
- an extremely high-speed ultrasonic torsional fatigue testing machine in which the excitation frequency is in the ultrasonic region can be performed in a short time. The required number of loads can be reached and the shear fatigue properties can be quickly evaluated. For example, if continuous excitation is performed at 20000 Hz, the load count reaches 10 9 times in just half a day.
- the method for estimating the shear fatigue characteristics of a high-strength metal material for a power transmission shaft which is the basic configuration of each aspect of the above application example, is a test made of the metal material for the shear fatigue characteristics of the high-strength metal material for a power transmission shaft.
- An amplitude expanding horn that has a mounting portion and is fixed to the torsional vibration converter at the proximal end and expands the amplitude of the torsional vibration of the vibration converter applied to the proximal end, an oscillator, and an output of the oscillator that amplifies the torsional vibration
- an amplifier to be applied to the vibration converter and a control means for giving the control input to the amplifier the shape and dimensions of the amplitude expanding horn are changed to those of the torsional vibration converter.
- the torsional vibration generated by the torsional vibration converter is a complete double swing that is a vibration in which the forward rotation direction and the reverse rotation direction are symmetrical.
- the lower limit value of the frequency for driving the torsional vibration converter is (20000 ⁇ 500 + ⁇ ) Hz
- the upper limit value is (20000 + 500) Hz
- ⁇ is a margin value for property change during the test of the test piece and is 200 Hz. The following is preferable.
- the material of the amplitude expanding horn is a titanium alloy.
- the amplitude-amplifying horn has an amplitude-amplifying horn shape excluding an attachment portion that protrudes from the center of the end face of the base end portion and is attached to the torsional vibration converter, and a female screw portion that attaches the test piece at the distal end.
- the small diameter side is obtained by eigenvalue analysis of free torsional resonance by finite element analysis.
- the maximum shear stress acting on the tapered portion surface is 180 MPa or less. It is preferable.
- the test piece is a dumbbell shape having a cylindrical shoulder portion at both ends, and a middle thin portion whose cross-sectional shape along the axial direction is an arc curve following the shoulder portions on both sides, and the shoulder
- the length of the portion is L1
- the half chord length which is half the length of the thinned portion is L2
- the radius of the shoulder portion is R3
- the minimum radius of the thinned portion is R1
- the radius of the arc curve is R.
- each unit is m, R is obtained from R1, R2, and L3
- resonance frequency is f (unit is Hz)
- Young's modulus E unit is Pa
- Poisson's ratio ⁇ dimensionless
- density ⁇ unit Is kg / m 3
- L 2 R 1, R 2 are arbitrary values
- the resonance frequency f is an arbitrary value in the frequency range 20000 ⁇ 500 Hz where the vibration converter can be driven.
- a shoulder length L 1 of the test piece at the resonance frequency f is resonant and theoretical solution
- a plurality of test piece shape models in which L1, R1, R2, R and L1 obtained as a theoretical solution are slightly shortened are created, and metal materials having E, ⁇ , and ⁇ as test pieces for these shape models.
- An analytical solution L1N that causes torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance using finite element analysis, and test pieces having dimensions of L2, R1, R2, R, and L1N are prepared. It is preferable to use it for the test.
- the apparatus for estimating the shear fatigue property of a high-strength metal material for a power transmission shaft in the above application example tests and evaluates the shear fatigue property of a high-strength metal material for a power transmission shaft using a test piece made of the metal material.
- a torsional vibration converter that generates torsional vibration that rotates forward and backward around the rotation center axis when AC power is applied, and a mounting portion for concentrically attaching a test piece to the tip.
- An amplitude expanding horn that is fixed to the torsional vibration converter at the end and expands the torsion angle of the torsional vibration converter applied to the base end, an oscillator, and an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter
- the control / data sampling means for supplying the control input to the amplifier and collecting data including the excitation frequency under test, the state of the amplifier, and the number of loads
- the shape and size of the amplitude expanding horn is a shape and size that resonates with torsional vibration by driving the torsional vibration converter
- the shape and size of the specimen is a shape that resonates with torsional vibration of the amplitude expanding horn.
- the torsional vibration converter is driven in a frequency range of an ultrasonic region, and the amplitude-amplifying horn and the test piece are resonated to cause shear fatigue fracture of the test piece.
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Abstract
Description
前記せん断疲労強度決定過程で用いる前記の「定められた基準」は、例えば、せん断疲労強度を示す確立された理論の曲線に、試験結果のせん断応力振幅と負荷回数の関係を当てはめた曲線を求め、その曲線からせん断疲労強度を求める処理とされる。具体的には、日本材料学会の金属材料疲労信頼性評価標準JSMS-SD-6-02の疲労限度型折れ線モデルにあてはめて求めたS-N線図(破壊確率50%の疲労強度線図) を用いることができる。疲労限度型折れ線モデルに限らず、連続低下型曲線モデルに当てはめてS-N線図を求めても良い。ただし、その場合は、τ1imは、例えば「1010回におけるS-N線図上の値」などとして定義する必要がある。
試験片の前記肩部の長さをL1、前記中細り部の半分の長さである半弦長さをL2、前記肩部の半径をR2、前記中細り部の最小半径をR1,前記円弧曲線の半径をR(いずれも単位はm,RはR1,R2,L2から求まる)とし、共振周波数をf(単位はHz)、ヤング率E(単位はPa),ポアソン比ν(無次元),密度ρ(単位はkg/m3)とし、
前記L2,R1,R2を任意の値とし、前記共振周波数fを前記振動コンバータが駆動可能な周波数範囲20000±500Hzの任意の値として、次式(1)~(6)により、前記共振周波数fで試験片がねじり共振する肩部の長さをL1を理論解として求め、前記L2、R1、R2、Rおよび理論解として求まったL1 を僅かに短くした複数の試験片形状モデルを作成し、
これらの形状モデルにつき、E、ν、ρを試験片とする金属材料の実測物性値とし、有限要素解析による自由ねじり共振の固有値解析により、前記共振周波数fでねじり共振する解析解L1Nを求め、前記L2、R1、R2、R、L1Nの寸法の試験片を作製して試験に用いる。
その場合、前記試験片の端面ねじり角が0.01radのとき、前記振幅拡大ホーンの先端に取り付ける雄ネジ部、および試験片加工に必要な反取付部端面のセンター孔部を除いた試験片形状モデルにつき、物性値をE=2.04×1011Pa、ν=0.29、ρ=7800kg/m3としたとき、有限要素解析による自由ねじり共振の固有値解析で求まる、試験片最小径部の表面に作用する最大せん断応力が520MPa以上となるものであっても良い。
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)
となる。
線接触とみなせる場合、前記疲労限面圧計算手段における前記定められた計算式は、例えば次式、
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)とする。
σ=-Alog10N+B(N<NW)
σ=E(N≧NW)
ここで、A、B、E、Nwは定数である。疲労限度(上式のE)は、N=5×106以上の負荷回数における打ち切りデータが1点以上存在する場合、以下のように推定する。破断データ応力最小値σf minと、これより低応力の打ち切りデータ応力最大値σr maxの平均値を疲労限度とする(図21参照)。なお、σf minと同じ応力レベルに打ち切りデータがあり、かつこれより低い応力レベルで打切りデータが存在しない場合は、このσf minを疲労限度とする。こうして疲労限度を決めた上で、この値を固定して破断データのみから上式中の他のパラメータを推定する。連続低下型曲線モデルはストロメイヤー(Stromeyer)の基礎式である次式にあてはめて回帰する。
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)
となる。接触楕円の長軸半径a、単軸半径bに対し、線接触状態はb/a=0であり、その場合、上記のようにτ0の4倍がPmaxに等しい。b/a≠0の場合のτ0とPmaxの比例定数は非特許文献3のFIG.5.14に示されている。
τmax=52618θend (7)
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)
に従って計算すれば、疲労限面圧はPmax 1im=2256MPaと推定されることになる。なお、疲労限度型折れ線モデルではなく、連続低下型曲線モデルに当てはめてS-N線図を求めてもよい。ただし、その場合、例えば「τ1imは1010回におけるS-N線図上の値」などとして定義する必要がある。
上記の「弾性限度内の応力のみ作用する条件下」とは、金属材料に負荷をかけて、負荷がなくなった後には、金属材料に作用する応力および歪みが「0」に戻る条件下を言う。
(1)「SUJ2標準」の試験片の熱処理は、SUJ2素材全体を焼入れするいわゆるずぶ焼入と焼戻し(加熱:830℃×80min,RXガス雰囲気→油焼入れ→ 焼戻し:180℃×180min)である。
(2)「SUJ2浸炭窒化」の試験片については、SUJ2素材に浸炭窒化焼入れと焼戻し(加熱:850℃×150min,RXガス雰囲気,NH3ガスを6.5L/minで添加→油焼入れ→ 焼戻し:180℃×120min)を施している。
前記RXガス雰囲気とは、ブタン、メタン等の炭化水素系ガスに空気を混合した後、触媒を充填し高温加熱してなるCO,H2,N2を主な成分とする雰囲気ガスである。
(3)「SCr420浸炭」の試験片については、浸炭焼入れと焼戻し(浸炭:920℃×4h,RXガス雰囲気,カーボンポテンシャルを1.2に保持→拡散 920℃×3h,RXガス雰囲気→油焼入れ→焼戻し:180℃×120min)を施している。
前記金属材料として、SNCM420、SUJ2、SUJ3、SCr420等が挙げられる。実施例3では、SNCM420素材に熱処理等を施した試験片と、SUJ3素材に熱処理等を施した試験片とを用いて各試験片のせん断疲労特性を求め、このせん断疲労特性から疲労限面圧を推定した。各試験片として図7に示した試験片を用いた。
第1世代の車輪用軸受では、SUJ2素材などに、焼入れと焼戻しの熱処理を施した軸受用鋼が適用されている。第2世代の車輪用軸受では、外輪(ハブ輪)はS53C素材に高周波焼入れ、内輪と転動体はSUJ2素材などに、焼入れと焼戻しの熱処理を施した鋼が適用されている。第3世代の車輪用軸受では、内輪(ハブ輪)のアウトボード側軌道と、ナックルに固定される外輪は、S53C素材に高周波焼入れ、内輪のインボード側軌道と転動体は、SUJ2素材などに、焼入れと焼戻しの熱処理を施した鋼が適用されている。以上から、この実施例4ではS53C素材に熱処理等を施した試験片のせん断疲労特性を求め、このせん断疲労特性から疲労限面圧を推定した。各試験片として図7に示した試験片を用いた。
、上記のE 、ν、ρを物性値として、自由ねじり共振の固有値解析を行った。その結果
、拡大率(小径側のねじり角の大径側のねじり角に対する比)は43.1倍になった。したがって、高効率振幅拡大ホーンは標準振幅拡大ホーンに対し、拡大率が67%向上したことになる。しかしながら、常温大気中、アンプ17の出力50%にて、上記の寸法のSUJ2製の試験片1を取り付け、上述の間欠運転条件で評価を開始したところ、間もなく共振が不安定になる現象が起きた。
(1)試験片を大きくし、小さいアンプ出力でも試験片最小径部表面に大きな最大せん断応力τmaxを作用させる。
(2)上述のように、高効率振幅拡大ホーンは標準品に対してねじり角の拡大率が67%向上した。試験片を小さくすると、試験片最小径部表面に作用する最大せん断応力τmaxは小さくなるが、試験片を小さくする。
振幅OUT:実際のアンプ出力振幅に比例した電圧出力のことで、コントローラー(PC)にて0~100%を0V~+10Vにて指示する。
超音波パワー:超音波パワーの出力に比例した電圧出力のことで、コントローラー(PC)にて0~100%を0V~+10Vにて指示する。
周波数:アンプ運転周波数の出力に比例した電圧出力のことで、コントローラー(PC)にて19.50~20.50kHzを-10V~+10Vにて指示する。
メモリ周波数:アンプメモリ内に記録されている相対周波数の出力に比例した電圧出力のことで、コントローラー(PC)にて19.50~20.50kHzを-10V~+10Vにて指示する。
動力伝達シャフトとして、等速ジョイント(略称;CVJ)の中間シャフト鋼が挙げられる。この中間シャフト鋼のうち、細径品にはMnを増量したX鋼が用いられ、大径品にはS40Cに対しBを添加し、Mnを増量し、且つ、Siを減量したY鋼が用いられている。ここでは、これら2つの鋼の試験片X,Yの熱処理条件、せん断疲労特性をそれぞれ示す。
上記応用例の各態様の基本構成となる動力伝達シャフト用の高強度金属材料のせん断疲労特性の推定方法は、動力伝達シャフト用の高強度金属材料のせん断疲労特性を、前記金属材料からなる試験片を用いて試験し評価する方法であって、交流電力が印加されることで回転中心軸回りの正逆の回転となるねじり振動を発生するねじり振動コンバータと、先端に同心に試験片を取付ける取付部を有し基端でねじり振動コンバータに固定され、基端に与えられた前記振動コンバータのねじり振動の振幅を拡大する振幅拡大ホーンと、発振器と、この発振器の出力を増幅して前記ねじり振動コンバータに印加するアンプと、このアンプに前記制御の入力を与える制御手段とを用い、前記振幅拡大ホーンの形状、寸法を、前記ねじり振動コンバータの駆動によるねじり振動に共振する形状、寸法とし、前記試験片の形状、寸法を、前記振幅拡大ホーンのねじり振動に共振する形状、寸法とし、前記振動コンバータを超音波領域の周波数範囲で駆動し、前記振幅拡大ホーンと前記試験片を共振させて、試験片をせん断疲労破壊させる試験を行い、試験により得られたせん断応力振幅と負荷回数との関係を用いて、前記金属材料のせん断疲労特性を評価する。
上記基本構成において、前記ねじり振動コンバータにより発生するねじり振動は、正回転方向と逆回転方向とが対称となる振動である完全両振りとすることが好ましい。
[応用態様2]
上記基本構成において、前記ねじり振動コンバータを駆動する周波数の下限値が(20000-500+α)Hz、上限値が(20000+500)Hz、ただしαは試験片の試験中の性状変化に対する余裕値であって200Hz以下であることが好ましい。
上記基本構成において、前記振幅拡大ホーンの材質がチタン合金であることが好ましい。
[応用態様4]
応用態様3において、前記振幅拡大ホーンは、その基端部の端面の中央から突出して前記ねじり振動コンバータへ取り付けられる取付部、および先端の前記試験片を取り付ける雌ネジ部を除いた振幅拡大ホーン形状モデルにつき、物性値をE=1.16×1011Pa、ν=0.27、ρ=4460kg/m3を物性値としたとき、有限要素解析による自由ねじり共振の固有値解析で求まる、小径側端面のねじり角の大径側端面のねじり角に対する比である拡大率が43倍以上であり、先端のねじり角が0.018radのとき、先細り部表面に作用する最大せん断応力が180MPa以下となることが好ましい。
上記基本構成において、前記試験片が、両端の円柱形状の肩部と、これら両側の肩部に続き軸方向に沿う断面形状が円弧曲線となる中細り部とでなるダンベル形であり、前記肩部の長さをL1、前記中細り部の半分の長さである半弦長さをL2、前記肩部の半径をR3、前記中細り部の最小半径をR1、前記円弧曲線の半径をR(いずれも単位はm,RはR1、R2、L3から求まる)とし、共振周波数をf(単位はHz)、ヤング率E(単位はPa),ポアソン比ν(無次元)、密度ρ(単位はkg/m3)とし、前記L2 、R1、R2を任意の値とし、前記共振周波数fを前記振動コンバータが駆動可能な周波数範囲20000±500Hzの任意の値として、次式(1)~(6)により、前記共振周波数fで試験片が共振する肩部長さL1を理論解として求め、前記L2、R1、R2、Rおよび理論解として求まったL1を僅かに短くした複数の試験片形状モデルを作成し、これらの形状モデルにつき、E、ν、ρを試験片とする金属材料の実測物性値とし、有限要素解析による自由ねじり共振の固有値解析により、前記共振周波数fでねじり共振する解析解L1Nを求め、前記L2、R1、R2、R、L1Nの寸法の試験片を作製して試験に用いることが好ましい。
上記基本構成において、試験片の発熱を抑制するために、試験片を強制空冷することが好ましい。
[応用態様7]
上記基本構成において、試験片の温度上昇を抑制するために、前記ねじり振動コンバータによる試験片に対するねじり振動の負荷と休止を交互に繰り返すことが好ましい。
1a 肩部
1b 中細り部
2 超音波ねじり疲労試験機
3、3A 超音波ねじり疲労試験機本体
4 試験機制御装置
4A 制御・データ採取手段
5 疲労限面圧の推定装置
6 フレーム
7 ねじり振動コンバータ
8 振幅拡大ホーン
9 試験片冷却手段
10 コンピュータ
11 試験機制御プログラム
17 アンプ
19 疲労限面圧推定プログラム
20 発振器
21 試験条件設定部
22 入力手段
23 せん断疲労強度決定手段
24 疲労限面圧計算手段
27 間欠発振制御部
30 水素チャージ手段
M1 金属材料で製造される物体
M2 接する物体
Claims (25)
- 転がり接触する金属材料のせん断疲労特性を評価する方法であって、
超音波ねじり疲労試験によって金属材料のせん断応力振幅と負荷回数の関係を求める試験過程と、
この求められたせん断応力振幅と負荷回数の関係から超長寿命領域におけるせん断疲労強度τ1imを、定められた基準に従って決めるせん断疲労強度決定過程と、
を含む転がり接触金属材料のせん断疲労特性の評価方法。 - 請求項1において、前記超音波ねじり疲労試験は、試験片に対して、正回転方向と逆回転方向のねじりが対称となるねじり振動を与える完全両振りのねじり疲労試験とする転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項1において、前記金属材料が、転がり軸受の軌道輪または転動体となる転がり軸受用鋼である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項1において、前記せん断疲労強度決定過程における、前記超長寿命領域におけるせん断疲労強度τ1imを決める前記定められた基準は、せん断疲労強度を示す疲労限度型折れ線モデルに、試験結果のせん断応力振幅と負荷回数の関係を当てはめた曲線を求め、その曲線からせん断疲労強度を求める処理である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項1において、前記せん断疲労強度決定過程における、前記超長寿命領域におけるせん断疲労強度τ1imを決める前記定められた基準は、せん断疲労強度を示す連続低下型曲線モデルに、試験結果のせん断応力振幅と負荷回数の関係を当てはめた曲線を求め、その曲線からせん断疲労強度を求める処理である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項1において、前記試験過程では、複数回の前記超音波ねじり疲労試験を行って、金属材料のせん断応力振幅と負荷回数の関係を複数求め、前記せん断疲労強度決定過程では、前記複数回の試験過程で求めたせん断応力振幅と負荷回数の関係から任意の破壊確率のP-S-N線図を求め、このP-S-N線図から、前記超長寿命領域におけるせん断疲労強度τ1imを決める転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項1において、
前記試験により得たせん断応力振幅と負荷回数との関係から、任意の破壊確率のP-S-N線図を求め、このP-S-N線図から超長寿命領域におけるせん断疲労強度を、せん断疲労強度の評価に用いるための、超長寿命領域におけるせん断疲労強度τlimとする補正である破壊確率補正と、
前記試験により得たせん断応力振幅と負荷回数の関係から求まる、超長寿命領域におけるせん断疲労強度に対する85%の値を、せん断疲労特性の評価に用いるための、超長寿命領域におけるせん断疲労強度τlimとする補正である過大評価補正と、
前記試験により得た負荷回数とせん断応力振幅の関係から求まる、超長寿命領域におけるせん断疲労強度に対する80%の値を、せん断疲労特性の評価に用いるための、超長寿命領域におけるせん断疲労強度τlimとする補正である寸法効果補正との、
いずれか2つ以上の補正を組み合わせて求まる値を、せん断疲労特性の評価に用いるための、超長寿命領域におけるせん断疲労強度τlimとする転がり接触金属材料のせん断疲労特性の評価方法。 - 請求項1において、
交流電力が印加されることで回転中心軸回りの正逆の回転となるねじり振動を発生するねじり振動コンバータと、先端に同心に試験片を取付ける取付部を有し基端でねじり振動コンバータに固定され、基端に与えられた前記振動コンバータのねじり振動の振幅を拡大する振幅拡大ホーンと、発振器と、この発信器の出力を増幅して前記ねじり振動コンバータに印加するアンプと、このアンプに前記制御の入力を与える制御手段とを用い、
前記振幅拡大ホーンの形状,寸法を、前記ねじり振動コンバータの駆動によるねじり振動に共振する形状,寸法とし、
前記試験片の形状,寸法を、前記振幅拡大ホーンのねじり振動に共振する形状,寸法とし、
前記振動コンバータを超音波領域の周波数範囲で駆動し、前記振幅拡大ホーンと前記試験片とを共振させて、試験片をせん断疲労破壊させる試験を行い、
試験により得られたせん断応力振幅と負荷回数との関係を用いて、前記金属材料のせん断疲労強度を評価する転がり接触金属材料のせん断疲労特性の評価方法。 - 請求項8において、前記アンプは、出力の大きさおよびオン・オフが外部からの入力により制御可能である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項8において、前記ねじり振動コンバータを駆動する周波数の下限値が(20000-500+α)Hz、上限値が(20000-500+α)Hz、ただしαは試験片の試験中の性状の変化に対する余裕値であって200Hz以下である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項8において、前記振幅拡大ホーンは、横断面形状が円形であって、基端部を除く部分の縦断面形状が、先細り形状である転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項8において、前記試験片が、両端の円柱形状の肩部と、これら両側の肩部に続き軸方向に沿う断面形状が円弧曲線となる中細り部とでなるダンベル形であり、
前記肩部の長さをL1、前記中細り部の半分の長さである半弦長さをL2、前記肩部の半径をR2、前記中細り部の最小半径をR1,前記円弧曲線の半径をR(いずれも単位はm,RはR1,R2,L2から求まる)とし、共振周波数をf(単位はHz)、ヤング率E(単位はPa),ポアソン比ν( 無次元) ,密度ρ( 単位はkg/m3)とし、
前記L2,R1,R2を任意の値とし、前記共振周波数fを前記振動コンバータが駆動可能な周波数範囲20000±500Hzの任意の値として、次式(1)~(6)により、前記共振周波数fで試験片がねじり共振する肩部の長さをL1を理論解として求め、
前記L2、R1、R2,Rおよび理論解として求まったL1を僅かに短くした複数の試験片形状モデルを作成し、
これらの形状モデルにつき、E,ν,ρを試験片とする金属材料の実測物性値とし、有限要素解析による自由ねじり共振の固有値解析により、前記共振周波数fでねじり共振する解析値LINを求め、前記L2、R1、R2、R、LINの寸法の試験片を作製して試験に用いる、
転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項12において、前記ねじり振動コンバータの定格出力を300Wとし、前記試験片の前記振幅拡大ホーン先端に取付ける雄ねじ部、および前記試験片の加工に必要な反取付部端面のセンター孔部を除いた体積が、1.2×10-6m3以下であり、
前記試験片の端面ねじり角が0.01radのとき、前記振幅拡大ホーンの先端に取り付ける雄ねじ部、および前記試験片の加工に必要な反取付部端面のセンター孔部を除いた試験片形状モデルにつき、物性値をE=2.04×1011Pa、ν=0.29、ρ=7800kg/m3としたとき、有限要素解析による自由ねじり共振固有値解析で求まる、試験片最小径部の表面に作用する最大せん断応力が520Mpa以上となる転がり接触金属材料のせん断疲労特性の評価方法。 - 請求項1において、試験片に水素チャージした後に、この試験片に前記超音波ねじり疲労試験によって、前記金属材料の水素侵入下のせん断疲労特性を評価する転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項14において、水素を陰極電解チャージする転がり接触金属材料のせん断疲労特性の評価方法。
- 請求項14において、水素を水溶液に浸漬してチャージする転がり接触金属材料のせん断疲労特性の評価方法。
- 転がり接触する金属材料のせん断疲労強度を推定する装置であって、
超音波ねじり疲労試験によって求められた金属材料のせん断応力振幅と負荷回数の関係を、定められた記憶領域に記憶させる入力手段と、
この記憶されたせん断応力振幅と負荷回数の関係から超長寿命領域におけるせん断疲労強度τ1imを、定められた基準に従って決めるせん断疲労強度決定手段と、
を備えた、転がり接触金属材料のせん断疲労特性の推定装置。 - 請求項17において、前記金属材料が、転がり軸受の軌道輪または転動体となる転がり軸受用鋼である転がり接触金属材料のせん断疲労特性の推定装置。
- 請求項17において、
交流電力が印加されることで回転中心軸回りの正逆の回転となるねじり振動を発生するねじり振動コンバータと、先端に同心に試験片を取付ける取付部を有し、基端でねじり振動コンバータに固定され、基端に与えられた前記ねじり振動コンバータのねじり角を拡大する振幅拡大ホーンと、発振器と、この発振器の出力を増幅して前記ねじり振動コンバータに印加するアンプと、このアンプに前記制御の入力を与え、かつ試験中の加振周波数、前記アンプの状態、および負荷回数を含むデータを採取する制御・データ採取手段とを備え、
前記振幅拡大ホーンの形状,寸法を、前記ねじり振動コンバータの駆動によるねじり振動に共振する形状,寸法とし、
前記試験片の形状,寸法は、前記振幅拡大ホーンのねじり振動に共振する形状,寸法であり、
前記ねじり振動コンバータを超音波領域の周波数範囲で駆動し、前記振幅拡大ホーンと前記試験片とを共振させて、試験片をせん断疲労破壊させる、
転がり接触金属材料のせん断疲労特性の推定装置。 - 請求項19において、前記ねじり振動コンバータを駆動する周波数の下限値が(20000-500+α)Hz、上限値が(20000-500+α)Hz、ただしαは試験片の試験中の性状の変化に対する余裕値であって200Hz以下である転がり接触金属材料のせん断疲労特性の推定装置。
- 請求項19において、前記ねじり振動コンバータは、発生するねじり振動が、正回転方向と逆回転方向とが対称となる振動である完全両振りである転がり接触金属材料のせん断疲労特性の推定装置。
- 請求項1の評価方法を用いて疲労限面圧を推定する方法であって、さらに、
前記金属材料で製造される物体およびこの物体に対して転がり接触する物体の互いに接触する面の形状,寸法と接触面圧を与える負荷とから決まる前記金属材料の物体の表層内部に作用する最大交番せん断応力振幅τ0が、前記評価方法によって求められたせん断疲労強度τ1imに等しくなる前記負荷が作用するときの最大接触面圧Pmaxを定められた計算式によって求め、この最大接触面圧Pmaxを疲労限面圧Pmax1imの推定値とする疲労限面圧計算過程とを含む、
転がり接触金属材料の疲労限面圧の推定方法。 - 請求項22において、前記疲労限面圧計算過程における前記定められた計算式は、次式、
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)
である転がり接触金属材料の疲労限面圧の推定方法。 - 請求項17の推定装置を用いて疲労限面圧を推定する装置であって、さらに、
前記金属材料で製造される物体およびこの物体に対して転がり接触する物体の互いに接触する面の形状,寸法と接触面圧を与える負荷とから決まる前記金属材料の物体の表層内部に作用する最大交番せん断応力振幅τ0が、前記せん断疲労強度τ1imに等しくなる前記負荷が作用するときの最大接触面圧Pmaxを定められた計算式によって求め、この最大接触面圧Pmaxを疲労限面圧Pmax 1imの推定値とする疲労限面圧計算手段と備えた、
転がり接触金属材料の疲労限面圧の推定装置。 - 請求項24において、前記疲労限面圧計算手段における前記定められた計算式は、次式、
(疲労限面圧Pmax 1im)=4×(せん断疲労強度τ1im)
である転がり接触金属材料の疲労限面圧の推定装置。
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CN102803922B (zh) | 2015-04-08 |
EP2549261A1 (en) | 2013-01-23 |
CN102803922A (zh) | 2012-11-28 |
US9234826B2 (en) | 2016-01-12 |
EP2549261A4 (en) | 2018-01-10 |
EP2549261B1 (en) | 2022-06-08 |
US20130006542A1 (en) | 2013-01-03 |
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