JP5718690B2 - Method and apparatus for evaluating shear fatigue characteristics of rolling contact metal materials - Google Patents

Description

  The present invention relates to a method and apparatus for evaluating shear fatigue characteristics of a rolling contact metal material, for example, a method and apparatus for quickly evaluating the shear fatigue characteristics of a high strength metal material for rolling bearings such as bearing steel.

There are hydraulic servo type torsional fatigue testing machines and Schenck type torsional fatigue testing machines for evaluating shear fatigue characteristics, but the load frequency is about 10 Hz at the maximum for the former and about 30 Hz for the latter. It takes a lot of time to evaluate the shear fatigue characteristics up to the ultra-long life region.
The most commonly used high-strength metal material for rolling bearings is JIS-SUJ2, a high-carbon chromium bearing steel that is heated to a temperature above the A1 transformation point (approximately 850 ° C) in a reducing atmosphere. It is quenched from a low temperature and tempered at a relatively low temperature (about 180 ° C), resulting in a hardness of about 750HV. The most commonly used high-strength metal material for power transmission shafts is steel containing about 0.4 mass% carbon and containing hardenability enhancing elements (Mn, B, etc.). After tempering, it is tempered at a low temperature (about 150 ° C), and the hardness becomes about 650HV.

In the case of rolling bearings, internal origin-type debonding that occurs at the end of its life under good lubrication conditions is a process in which cracks are generated and propagated by repeated alternating shear stress (approximately double swing) with the maximum amplitude inside the surface layer. It is thought to follow. In the case of a tensile compression fatigue test (axial load fatigue test, rotary bending fatigue test), it is customary to set the normal stress amplitude at 10 ⁷ times to the fatigue limit σ _W0 . On the other hand, in the case of a rolling bearing, even if a considerably high contact load is applied, the internal origin type separation does not occur at a load frequency of about 10 ⁷ times. For example, it takes more than 3 years to reach 10 ⁹ load cycles with a hydraulic servo torsional fatigue tester with a load frequency of 10 Hz. Therefore, it is practically impossible to obtain the shear fatigue characteristics up to the ultra-long life range.

  Instead, it is inevitably included in rolling bearing steel, and non-metallic inclusions, which are a source of stress concentration due to structural discontinuity, are included in an arbitrary volume because it is considered as the starting point of internal starting type separation. A method for estimating the maximum size of non-metallic inclusions by extreme statistical analysis has been devised, and a method has been adopted in which the maximum size of non-metallic inclusions is used as an index of steel quality (for example, Patent Documents 1 to 4). ).

JP 2004-251898 A JP 2005-105363 A JP 2006-128865 A JP 2006-349698 A

Yukio Fujii, Kikuo Maeda, Akio Otsuka, NTN Technical Review, 69 (2001) 53-60. Wy. Murakami, Sea. Sakae, S. Y. Murakami, C. Sakae and S. Hamada, Engineering Against Fatigue, Univ. Of Sheffield, UK, (1997), 473p. Material Society of Japan, Revised Material Strength Science, Material Society of Japan, Kyoto, (2006), 94p.

The mode of fatigue crack propagation at the surface of the rolling contact surface prior to internal origin type delamination is considered to be mode II. As a method of estimating the fatigue limit surface pressure from the maximum size of the non-metallic inclusions, there is a concept described in the consideration of Non-Patent Document 1. As shown in FIG. 13 of Non-Patent Document 1, when the Hertz contact pressure moves, a circle having a diameter 2a at a depth b / 2 (b is the minor axis radius of the contact ellipse) at which the alternating shear stress amplitude is approximately maximized. It is considered that a plate crack exists. Think of this crack as the diameter of the largest inclusion. In Non-Patent Document 1, an original mode II fatigue crack growth experiment is performed, and the lower limit value of the stress intensity factor at which fatigue crack growth does not occur is determined as ΔK _IIth = 3 MPa√m. In FIG. 14 of Non-Patent Document 1, in the case of ΔK _IIth = 3 MPa√m, it is assumed that the coefficient of friction between the crack surfaces is 0.5, and the critical pressure on whether or not the maximum contact surface pressure and fatigue crack progress. The relationship of the crack diameter 2a is shown. For example, when 2a = 50 μm, the fatigue limit surface pressure is estimated to be P _maxlim = 2.5 GPa. However, in this method, the coefficient of friction between the crack surfaces is unknown and must be assumed to be a certain value. Non-Patent Document 2 also conducted an original mode II fatigue crack growth experiment and found that the lower limit value of the stress intensity factor at which fatigue crack growth does not occur is ΔK _IIth = 13 MPa√m. _Very different from ΔK _IIth .

  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.

Shear fatigue properties evaluation method of the first invention in this inventions is the shear fatigue property of the metal material in rolling contact, a method of testing is evaluated 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, Using control means for providing control input,
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are those that resonate with the torsional vibration of the front amplitude expansion horn,
Drive the torsional vibration converter in the frequency range of the ultrasonic region, resonate the amplitude expanding horn and the test piece, and perform a test for shear fatigue failure of the test piece ,
The shape of the amplitude expanding horn is an exponential function type in which the tip side that becomes the mounting portion of the test piece becomes thin,
Using the relationship between the shear stress amplitude and the load count obtained by testing, and evaluating the shear fatigue property of the metallic material.
The amplifier may be capable of controlling the output size and on / off by external input.
In this specification, the “frequency range of the ultrasonic region” refers to a frequency region of sound waves of 16000 Hz or higher in a broad sense.

According to this method, an extremely high-speed ultrasonic torsional fatigue testing machine in which the excitation frequency is in the ultrasonic range is performed. Therefore, the required number of loads can be reached in a short time to evaluate the shear fatigue characteristics of the metal material in rolling contact. Shear fatigue characteristics 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. In addition, since a test that actually causes shear fatigue failure is performed, the shear fatigue characteristics can be obtained with higher accuracy than the conventional method in which the maximum size of the 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.
It should be noted that the stress governing the fatigue fracture of the material is either normal stress or shear stress. Several years have passed since the ultrasonic axial load fatigue tester (full swing) was put on the market to evaluate fatigue characteristics due to normal stress at high speed. In contrast, 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 makes it possible to realize a rapid evaluation of shear fatigue characteristics by applying a torsional vibration with an excitation frequency in the ultrasonic region to a metal material that is in rolling contact under such a technical level. Is.

It is preferable that the torsional vibration generated by the torsional vibration converter is a complete swing that is a vibration in which the forward rotation direction and the reverse rotation direction are symmetric.
The lower limit value of the frequency for driving the torsional vibration converter is (20000-500 + α) Hz, the upper limit value is (20000 + 500) Hz, where α is a margin value for property change during the test of the test piece, and is 200 Hz or less, Also good. In this way, when the lower limit value of the frequency is (20000−500 + α) Hz and the upper limit value is (20000 + 500) Hz and the torsional vibration converter is tested at the maximum possible output, resonance instability can be prevented.
When the lower limit value and the upper limit value of the frequency are the frequency, the margin value may be 200 Hz. Further, when performing a test for causing the test piece to resonate with the vibration of the amplitude expansion horn to cause shear fatigue destruction, it is preferable that the amplitude expansion horn is resonated with the vibration of the torsional vibration converter. In this case, 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 material of the amplitude expanding horn may be a titanium alloy.
The titanium alloy that is the material of the amplitude expanding horn may contain at least 6% Al and 3% Mo.
The Rockwell C hardness of the titanium alloy that is the material of the amplitude expanding horn may be 35 or more .
The shear fatigue property evaluation method of the second invention in this invention is a method for testing and evaluating the shear fatigue property of a metal material in rolling contact 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, A control means for providing a control input, and the shape and size of the amplitude expanding horn is set to a shape and size that resonates with torsional vibration generated by driving the torsional vibration converter, and the shape and size of the test piece is set to expand the amplitude. The shape and dimensions resonate with the torsional vibration of the horn, and the torsional vibration converter is driven in the ultrasonic frequency range, The test piece is resonated and the test piece is subjected to a shear fatigue fracture test.The amplitude expanding horn has a circular cross-sectional shape, and a vertical cross-sectional shape of a portion excluding the base end portion is a tapered shape. The material of the amplitude expansion horn is a titanium alloy, and the Rockwell C hardness of the titanium alloy that is the material of the amplitude expansion horn is 35 or more,
Before SL amplitude expansion horn, for its mounting portion mounted from the center of the end surface of the proximal end portion to the torsional vibration converter projects, and the tip the amplitude larger horn shape model except the female threaded portion for attaching the test piece, the physical properties The torsion angle of the end face on the small diameter side obtained by eigenvalue analysis of free torsional resonance by finite element analysis, where E = 1.16 × 10 ¹¹ Pa, ν = 0.27, and ρ = 4460 kg / m ³ magnification, which is the ratio twist angle of the large diameter side end face is not less 43 times or more, when the torsional angle of the tip of 0.018Rad, the maximum shear stress acting on the tapered section surface that follows Do 180 MPa.

In this invention, it is preferable that the said test piece is a dumbbell shape which consists of the cylindrical shoulder part of both ends, and the cross-sectional shape along an axial direction following the shoulder part of these both sides becomes a circular curve. When 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.
In order to design and manufacture a test piece having an appropriate shape and size capable of resonating, the following method is preferable.
The length of the shoulder portion of the test piece is L ₁ , the half chord length that is half the length of the thinned portion is L ₂ , the radius of the shoulder portion is R ₂ , and the minimum radius of the thinned portion is R ₁ , the radius of the 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 ν (dimensionless), density ρ (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. determined the length of the shoulder portion of the test piece at a resonant frequency f is torsional resonance of L ₁ as the theoretical solution, the L2, R1, R2, R and a plurality of specimen geometry model the L1 that Motoma' slightly shortened as theoretical solution Create
For these shape models, E, ν, and ρ are measured physical property values of a metal material, and an analytical solution L1N that undergoes torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis. Test pieces having the dimensions L2, R1, R2, R, and L1N are prepared and used for the test.

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 above parts used for the calculation of the solution may be prepared and tested. There may not be.
In that case, a plurality of specimen shape models with slightly shortened L1 obtained as the above theoretical solution are created,
For each of these shape models, an analytical solution L1N for torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis using E, ν, and ρ as measured physical property values. , Test pieces having dimensions of L2, R1, R2, R, and L1N are prepared and used for the test.
By setting the shape and dimensions of such a test piece, resonance of the test piece occurs.

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、
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動拡大ホーン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穴部を除いた体積が１．２×１０ ^-6 ｍ ³ 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穴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。 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 of 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 .
According to a third aspect of the present invention, there is provided a method for evaluating a shear fatigue property of a metal material that is in rolling contact with 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, Using control means for providing control input,
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are the shapes and dimensions that resonate with the torsional vibration of the amplitude-amplifying horn,
Drive the torsional vibration converter in the frequency range of the ultrasonic region, resonate the amplitude expanding horn and the test piece, and perform a test for shear fatigue failure of the test piece,
Using the relationship between the shear stress amplitude obtained by the test and the number of loads, the shear fatigue property of the metal material is evaluated,
The test piece is a dumbbell shape having a cylindrical shoulder portion at both ends, and a thinned portion in which the cross-sectional shape along the axial direction follows the shoulder portions on both sides is an arc curve,
The length of the shoulder is L1, the half chord length which is half the length of the thinned portion is L2, the radius of the shoulder is R3, the minimum radius of the thinned portion is R1, and the radius of the arc curve Is R (unit is m, R is determined from R1, R2, and L3), resonance frequency is f (unit is Hz), Young's modulus E (unit is Pa), Poisson's ratio ν (dimensionless), density ρ (Unit: kg / m ³ )
L2, R1, R2 are set to arbitrary values, the resonance frequency f is set to an arbitrary value in the frequency range 20000 ± 500 Hz that can be driven by the vibration converter, and the resonance frequency f is expressed by the following equations (1) to (6). The theoretical length of the shoulder length L1 at which the test piece resonates is obtained.

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,
For these shape models, E, ν, and ρ are measured physical property values of a metal material, and an analytical solution L1N that undergoes torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis. Test pieces having the dimensions of L2, R1, R2, R, L1N were prepared and used for the test.
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 of the end face of the non-attachment part necessary for processing the test piece is 1.2 × 10 ^-6 m ³ or less,
When the end surface twisting angle before the SL test piece of 0.01 rad, the male screw portion attached to the distal end of said amplitude expansion horn, and specimen test piece shape model except the center hole of the opposite mounting end surface required for processing per When the physical properties are E = 2.04 × 10 ¹¹ Pa, ν = 0.29, ρ = 7800 kg / m ³ , the surface of the minimum diameter part of the specimen obtained by eigenvalue analysis of free torsional resonance by finite element analysis the maximum shear stress acting on the that Do equal to or greater than 520MPa.

In the present invention, when the test is performed using the test pieces having the dimensions L ₁ , L ₂ , R ₂ , R ₁ , and R obtained by the eigenvalue analysis of the free torsional resonance by the finite element analysis as described above, When the 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 projection consisting of the male thread for mounting the test piece on the amplitude expansion horn is 9 .36 g or less is preferable.
Resonance instability may occur even if the shape and size of the test piece can resonate. As a result of the research, it was found that the resonance instability greatly affects the weight of the specimen. In addition, when a test piece having the above shape and size is used and a test is performed with an excitation frequency of 20000 ± 500 Hz and a maximum output of the torsional vibration converter of 300 W, if the weight of the test piece is 9.36 g or less, resonance instability occurs. It was confirmed that it did not occur.

  In addition, when the test piece weight is 9.36 g or less as described above, the output of the amplifier is 90% and the measured value of the torsion angle of the test piece is 0.018 rad or more, and 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 part 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.

In the method of the present invention, the test piece may be forcibly air-cooled in order to suppress the temperature rise of the test piece. Further, in order to suppress the temperature rise of the test piece, the torsional vibration load on the test piece and the pause by the torsional vibration converter may be alternately repeated. In the low load region where the heat generation of the test piece does not become a problem with respect to the test result, a continuous load may be applied, thereby enabling a quick test.
When the sample is continuously vibrated with a somewhat high shear stress amplitude, the test piece generates heat. 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 excitation and pause. It becomes smaller substantially the load frequency by pauses, real load frequencies downtime as 10 times the vibration time is still fast and about 2000 Hz, the load count of 10 ⁹ times Some 1 week To reach.

In the method of the present invention, a value of 85% with respect to the shear fatigue strength in the ultralong life region, which is obtained from the relationship between the number of loads obtained by the test and the shear stress amplitude, is used for the evaluation of the shear fatigue characteristics. It is good also as shear fatigue strength (tau) _{w0 in} . This is because in the ultrasonic torsional fatigue test, when the volume subjected to a large load (dangerous volume) is substantially equal to the conventional fatigue test, the shear fatigue strength tends to be evaluated higher.

In the method of the present invention, a value of 80% relative to the shear fatigue strength in the ultralong life region obtained from the relationship between the number of loads obtained by the test and the shear stress amplitude is used for evaluating the shear fatigue properties. It is good also as shear fatigue strength (tau) _{w0 in} . When torsional vibration is applied to the test piece, a stress gradient is generated so that the stress of each part in the cross section of the test piece is the lowest at the center and the maximum at the outer peripheral surface. For this reason, the value of 80% with respect to the shear fatigue strength in the ultra-long life region, which is obtained from the relationship between the number of loads obtained by the test and the shear stress amplitude, is an appropriate value for use in evaluating the shear fatigue characteristics.

In the method of the present invention, a PSN diagram having an arbitrary failure probability is obtained from the relationship between the shear stress amplitude obtained by the test and the number of loads, and in the super long life region in the PSN diagram. The shear fatigue strength may be the shear fatigue strength τ _w0 in the ultra-long life region for use in the evaluation of shear fatigue characteristics.

In the method of the present invention, in order to safely estimate the shear fatigue strength in the ultra-long life region, from the relationship between the shear stress amplitude obtained by the test and the number of loads, a PSN diagram of an arbitrary fracture probability is obtained, Fracture probability correction, which is correction for setting the shear fatigue strength in the _ultralong life region to be used as the shear fatigue strength τ _{w0 in the ultralong} life region in order to use the shear fatigue strength in the ultralong life region from the PSN diagram for evaluation of shear fatigue characteristics, obtained from the relationship between the shear stress amplitude and the load times obtained by the test, the value of 85% relative to the shear fatigue strength in ultra long life region, for use in the evaluation of shear fatigue properties, shear fatigue strength in ultra long life region tau _w0 80% of the shear fatigue strength in the ultra-long life region obtained from the relationship between the overestimation correction that is The value obtained by combining any two or more corrections with the dimensional effect correction, which is the correction for setting the shear fatigue strength τ _w0 in the ultra-long life region to use the value of The shear fatigue strength τ _w0 in the ultra-long life region for use in the evaluation of fatigue characteristics may be used. As a result, the shear fatigue strength in the ultra-long life region can be more safely estimated.

The apparatus for evaluating shear fatigue characteristics of the present invention is an apparatus for testing and evaluating the shear fatigue characteristics of a metal material that is in rolling contact with a test piece made of the metal material. A torsional vibration converter that generates a torsional vibration that rotates forward and backward about an axis, and a mounting portion that attaches a test piece concentrically to the distal end; fixed to the torsional vibration converter at the proximal end; and provided to the proximal end An amplitude-enlarging horn that expands the torsion angle of the torsional vibration converter, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, an input for the control to the amplifier, and an addition during the test Control / data collection means for collecting data including vibration frequency, the state of the amplifier, and the number of loads, and the shape and dimensions of the amplitude magnifying horn The shape and size of the specimen resonate with torsional vibration due to the drive of the dynamic converter, and the shape and size of the test piece are the shape and size that resonate with torsional vibration of the amplitude-enhancing horn. Driven in a range, the amplitude expanding horn and the test piece are caused to resonate, and the test piece is subjected to shear fatigue fracture, and the shape of the amplitude expanding horn is an index where the tip side that becomes the mounting portion of the test piece becomes narrower and said that it is a function type.
By using the shear fatigue characteristic evaluation apparatus of this configuration, the above-described shear fatigue characteristic evaluation method of the present invention can be implemented.

  The lower limit value of the frequency range for driving the torsional vibration converter is (2000−500 + α) Hz, and the upper limit value is (2000 + 500) Hz, where α is a margin value for property change during the test of the test piece and is 200 Hz or less. Also good.

  In the torsional vibration converter, it is preferable that the generated torsional vibration is a complete double swing in which the normal rotation direction and the reverse rotation direction are symmetrical. Moreover, it is preferable that the said amplitude expansion horn resonates with the vibration by the excitation frequency during the test of a torsional vibration converter. In this case, 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.

A shear fatigue property evaluation apparatus according to a second aspect of the present invention is an apparatus for testing and evaluating the shear fatigue property of a metal material in rolling contact with a test piece made of the metal material,
It has 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 part that attaches a test piece concentrically to the distal end. An amplitude-amplifying horn that expands the torsion angle of the torsional vibration converter fixed to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies the output to the torsional vibration converter, and the control to the amplifier And a control / data collection means for collecting data including the excitation frequency under test, the state of the amplifier, and the number of loads.
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are shapes and dimensions that resonate with torsional vibration of the amplitude-amplifying horn,
The torsional vibration converter is driven in the frequency range of the ultrasonic region, the amplitude expanding horn and the test piece are resonated, and the test piece is subjected to shear fatigue fracture,
Before SL amplitude expansion horn, for its mounting portion mounted from the center of the end surface of the proximal end portion to the torsional vibration converter projects, and the tip the amplitude larger horn shape model except the female threaded portion for attaching the test piece, the physical properties The torsion angle of the end face on the small diameter side obtained by eigenvalue analysis of free torsional resonance by finite element analysis, where E = 1.16 × 10 ¹¹ 1Pa, ν = 0.27, and ρ = 4460 kg / m ³ magnification, which is the ratio twist angle of the large diameter side end face is not less 43 times or more, when the torsional angle of the tip of 0.018Rad, the maximum shear stress acting on the tapered section surface that follows Do 180 MPa.

  In the shear fatigue characteristic evaluation apparatus of the present invention, a test piece cooling means for forcibly air-cooling the test piece may be provided. In the shear fatigue characteristic evaluation apparatus according to the present invention, the control / data collection unit includes an intermittent oscillation control unit that controls intermittent oscillation that causes the torsional vibration converter to alternately repeat generation and pause of torsional vibration. It is also possible to switch between intermittent oscillation and continuous oscillation. Due to the forced air cooling and intermittent oscillation, temperature rise due to heat generation of the test piece can be prevented, and appropriate evaluation can be performed.

In the shear fatigue characteristic evaluation apparatus according to the present invention, the control / data collection means includes a test condition setting unit for setting a test condition including a condition for driving the torsional vibration converter and a condition for collecting the data according to an input, A test control unit that drives the torsional vibration converter and collects the data according to the test conditions set in the test condition setting unit may be included.
In this way, the test conditions including the torsional vibration converter drive conditions and data collection conditions can be set by input, and control can be performed so that the test is performed under the set test conditions. Appropriate tests and evaluations.

The shear fatigue property evaluation method of the present invention is a method for testing and evaluating the shear fatigue property of a metal material that is in rolling contact with a test piece made of the metal material. The torsional vibration converter that generates torsional vibration that rotates forward and backward around the axis, and the vibration applied to the proximal end that is fixed to the torsional vibration converter at the proximal end with a mounting part for concentrically attaching the test piece to the distal end Using an amplitude expansion horn that expands the amplitude of the torsional vibration of the converter, an oscillator, an amplifier that amplifies the output of this oscillator and applies it to the torsional vibration converter, and a control means that gives the input of the control to the amplifier, The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter, and the shape and dimensions of the test piece are The shape and dimensions resonate with the torsional vibration of the amplitude expanding horn, the vibration converter is driven in the frequency range of the ultrasonic region, and the test is performed by causing the amplitude expanding horn and the test piece to resonate and causing the test piece to shear fatigue. performed, the shape of the amplitude expansion horn, said an exponential function type tip side becomes narrower as the attachment portion of the test piece, by using the relationship between the shear stress amplitude and the load count obtained by testing, the metallic material In order to evaluate the shear fatigue characteristics of the metal, the shear fatigue characteristics of the metal material in rolling contact can be evaluated quickly and accurately by a test.

The apparatus for evaluating shear fatigue characteristics of the present invention is an apparatus for testing and evaluating the shear fatigue characteristics of a metal material that is in rolling contact with a test piece made of the metal material. A torsional vibration converter that generates a torsional vibration that rotates forward and backward about an axis, and a mounting portion that attaches a test piece concentrically to the distal end; fixed to the torsional vibration converter at the proximal end; and provided to the proximal end An amplitude-enlarging horn that expands the torsion angle of the torsional vibration converter, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, an input for the control to the amplifier, and an addition during the test Control / data collection means for collecting data including vibration frequency, the state of the amplifier, and the number of loads, and the shape and dimensions of the amplitude magnifying horn The shape and size of the specimen resonate with torsional vibration due to the drive of the dynamic converter, and the shape and size of the test piece are the shape and size that resonate with torsional vibration of the amplitude-enhancing horn. Driven in a range, the amplitude expanding horn and the test piece are caused to resonate, and the test piece is subjected to shear fatigue fracture, and the shape of the amplitude expanding horn is an index where the tip side that becomes the mounting portion of the test piece becomes narrower because the is functional, shear fatigue properties of the metallic material to be rolling contact, it can be rapidly and accurately evaluated by tests.

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 one 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. It is a schematic diagram of a test piece. It is a front view of a test piece. It is a graph which shows axial direction distribution of torsion angle (theta) and the surface shear stress (tau) (when the torsion angle (theta) _{end of an} end surface 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. 7, and end surface torsion angle (theta) _end . It is a graph which shows the relationship between amplifier output P and end surface twist angle | corner (theta) _end . It is the microscope picture of the example of the test piece which carried out torsional fatigue destruction, and explanatory drawing of the whole test piece. It is a front view of the test piece evaluated with a hydraulic servo type torsional fatigue testing machine. It is a graph which shows the relationship between the shear stress amplitude obtained by the ultrasonic torsional fatigue test and the number of loads, and the SN diagram (solid line). 13 is a graph showing a P-S-N diagram (broken line) with a fracture probability of 10% and an original S-N diagram (solid line) determined from the relationship of FIG. It is explanatory drawing which shows the example of a test condition input screen of a shear fatigue characteristic evaluation apparatus. It is a flowchart of an initialization process. It is a flowchart of the input process of test conditions. It is a flowchart of a test preparation process. 5 is a flowchart of details of a test process.

  An embodiment of the present invention will be described with reference to the drawings. In this embodiment, an example of a shear fatigue property evaluation apparatus used for a method for evaluating a shear fatigue property of a metal material in rolling contact is shown. This shear fatigue characteristic evaluation apparatus includes a testing machine main body 10 having a torsional vibration converter 7 and an amplitude expanding horn 8, an oscillator 4, an amplifier 5, and a control / data collection means 3. 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. Examples of this metal material include Japanese Industrial Standards; bearing steels such as JIS SUJ2 and SCr420, M50, M50NiL, SNCM420, SUJ3, SCr420, S53C, and SUS440C. SUJ2 corresponds to SAE52100 in the US AISI standard.

  The testing machine main body 10 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 of the torsional vibration converter 7. 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 10 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.

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
The amplitude expanding horn 8 is formed in a tapered shape and has a mounting portion including a female screw hole for attaching a test piece concentrically to a distal end surface, and is fixed to a torsional vibration converter at a 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 4 includes 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 5 is an electronic device that amplifies the output of the oscillator 4 and applies AC power having a frequency in the ultrasonic region to the torsional vibration converter 7. The amplifier 5 is assumed to be capable of controlling the output magnitude and on / off of the AC power by an external input. The maximum output of the amplifier 5 is 300 W in this embodiment.

  The control / data collection means 3 gives the amplifier 5 control inputs such as the magnitude and on / off of the output, and data including the excitation frequency under test, the state of the output of the amplifier 5 and the number of loads. Means for collecting from the amplifier 5. In addition to the above, the control / data collection unit 3 has a function of controlling the test piece cooling unit 9. The control / data collection means 3 includes a computer such as a personal computer and a program (not shown) to be executed by the computer. The control / data collection means 3 displays an input device 11 such as a keyboard and a mouse and an image of a liquid crystal display device on a screen. A screen display device 12 is connected or provided as part of the computer.

The control / data collection means 3 includes the respective units 13 to 18 whose blocks are conceptually shown in FIG. That is, the control / data collection unit 3 includes a test condition setting unit 13, a test condition / collection data storage unit 14, and a test control unit 15.
When a test condition including a condition for driving the torsional vibration converter 8 and a condition for collecting data is input from the input device 11, the test condition setting unit 13 stores data in the test condition / collected data storage unit 14, that is, It is means for setting as a control condition. Specifically, the test condition setting unit 13 is a means for displaying the input screen shown in FIG. 14 on the screen display device 12 and performing the processing shown in the flowchart in FIG.

  The test control unit 15 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 13. The test control unit 15 includes a basic control unit 16, a continuous oscillation control unit 17, and an intermittent oscillation control unit 18. The test control unit 15 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 17, the means for performing the processing of steps R14 to R24 is the intermittent oscillation control unit 18, and the means for performing the processing of the remaining steps is basically. It is the control unit 16.

  The shear fatigue characteristic evaluation method of this embodiment will be described. 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 + α) Hz. However, α is a margin value for property change during the test of the test piece, and may be 200 Hz or less. Various data are collected during this test, and the shear fatigue characteristics of the metal material are evaluated using the relationship between the obtained shear stress amplitude and the number of loads. 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. As a reference example, the high-strength metal material for the power transmission shaft is, for example, steel containing about 0.4 mass% carbon and adding a hardenability improving element (Mn, B, etc.).

According to this shear fatigue property evaluation method, 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 the conventional method in which the maximum size of the 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 specific contents of this shear fatigue property evaluation method and evaluation apparatus will be described below. 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.

A device for the amplitude expansion horn 8 will be described. 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. In addition, a male screw portion, which is a mounting portion for fixing to the torsional vibration converter, protrudes from the center of the large-diameter end face of the amplitude-enhancing horn, and a female screw 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. As a result of actually measuring Young's modulus E, Poisson's ratio ν, and density ρ, they were E = 1.16 × 10 ¹¹ Pa, ν = 0.27, and ρ = 4460 kg / m ³ , respectively. Using the FEM analysis software (Marc Mentat 2008 r1) (registered trademark), eigenvalue analysis of free torsional resonance was performed using the above E 1, ν, and ρ as physical property values. As a result, the enlargement ratio (ratio of the small-diameter side torsion angle to the large-diameter side torsion angle) was 25.8 times.

FIG. 3 shows a schematic diagram of the test piece 1. The test piece 1 has a dumbbell shape including cylindrical shoulder portions 1a and 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 and 1a on both sides. . 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).
In designing the test piece, an arbitrary half chord length L ₂ , a shoulder radius R ₂ , a minimum radius R ₁ are given (all are in m), a resonance frequency is f (unit is Hz), and Young's modulus E ( (Unit: Pa), Poisson's ratio ν (dimensionless), density ρ (unit: kg / m ³ ) (Measured values for standard heat-treated bearing steel SUJ2 are E = 2.04 × 10 ¹¹ Pa, ν = 0.29, ρ = 7800 kg / The shoulder length L ₁ (unit: m) as a theoretical solution was obtained by substituting it into the following equations (1) to (6) together with m ³ ). R is obtained from R ₁ , R ₂ and L ₂ .

Here, when L ₂ = 0.0070 m, R ₂ = 0.0060 m and R ₁ = 0.0030 m are substituted into the equations (1) to (6) together with the above f, E, ν, and ρ, L ₁ = 0.01012 m Become. However, when the test piece 1 with L ₁ = 0.01012 m was manufactured from the standard hardened and tempered bearing steel SUJ2 (see Table 1 for alloy components), it did not resonate. Therefore, using the finite element method (FEM) analysis software (Marc Mentat 2008 r1) (registered trademark), eigenvalue analysis of free torsional resonance was performed using the above E, ν, and ρ as physical properties. As a result, the frequency of torsional resonance at L ₁ = 0.01012 m was f = 19076 Hz, which was outside the range of 20000 ± 500 Hz that is the excitation frequency range of the torsional vibration converter 7. The L ₁ to torsional resonance at f = 20000 Hz results obtained in the analysis was the L ₁ = 0.00915m. When the test piece 1 with L ₁ = 0.00915 m was manufactured, it resonated around 20000 Hz. As a result of evaluation by intermittent operation (vibration time: 110 msec, pause time: 1100 msec) in which vibration and pause are alternately performed at room temperature in the air at an amplifier output of 100%, the load was broken on the order of 10 ⁷ times. Although high-strength metallic materials could be subjected to shear fatigue failure, higher efficiency is required in order to cause shear fatigue failure in a lower cycle region. The breaking mode will be described later (see FIG. 10).

In order to increase the torsional amplitude of the amplitude expanding horn 8, 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 so as to resonate around 20000 Hz. The material of the high efficiency amplitude expansion horn is a titanium alloy. As a result of actually measuring Young's modulus E, Poisson's ratio ν, and density ρ, they were E = 1.16 × 10 ¹¹ Pa, ν = 0.27, and ρ = 4460 kg / m ³ , respectively. Using the FEM analysis software (Marc Mentat 2008 r1) (registered trademark), eigenvalue analysis of free torsional resonance was performed using the above E 1, ν, and ρ as physical property values. As a result, the enlargement ratio (ratio of the small-diameter side torsion angle to the large-diameter side torsion angle) was 43.1 times. Therefore, the high-efficiency amplitude expansion horn is improved by 67% in comparison with the standard amplitude expansion horn. However, when the test piece 1 made of SUJ2 with the above dimensions was attached at room temperature and the output of the amplifier 5 was 50%, and the evaluation was started under the above-mentioned intermittent operation conditions, the phenomenon that resonance became unstable soon occurred. It was.

In order to prevent the resonance instability phenomenon from occurring, the shape of the test piece 1 was reviewed. The theoretical solution of the maximum shear stress amplitude τ _max acting on the surface of the minimum diameter part of the specimen is given by Eq. (7).

Here, R ₁ , L ₁ , and L ₂ are the minimum radius, shoulder length, and half chord length of the test piece 1 (the unit is m). g, α, k, and β are obtained by the above-described equations (1), (3), (4), and (5), respectively. θ _end is an end surface torsion angle of the test piece 1 described later (unit: rad). At the same end surface twist angle θ _end , the maximum shear stress τ _max acting on the test piece minimum diameter portion generally increases as the test piece increases and decreases as the test piece decreases. Here, the test piece shape is changed by the high-efficiency amplitude-expanding horn 8 in which the torsion angle enlargement ratio (ratio of the small-diameter side torsion angle to the large-diameter side torsion angle) is improved 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.
(1) The test piece is enlarged and a large maximum shear stress τ _max is applied to the surface of the minimum diameter part of the test piece even with a small amplifier output.
(2) As described above, the high-efficiency amplitude-enlarging horn has a 67% improvement in the torsion angle expansion rate compared to the standard product. When the specimen is made smaller, the maximum shear stress τ _max acting on the surface of the smallest diameter part of the specimen
Is smaller, but the test piece is smaller.

Under the two guidelines, specimens A to E in Table 2 were manufactured using the bearing steel SUJ2 in Table 1. 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 in accordance with the guideline (1), and the τ _max ratio (to A) at the same end face torsion angle is increased, and the weight ratio (to A) is also increased. On the other hand, 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 τ _max ratio (vs. A) is reduced and the weight ratio (vs. A) is also reduced. The shoulder length L ₁ in Table 2 is not the theoretical solution obtained by the above equation (6), but is obtained by the eigenvalue analysis of the free torsional resonance by FEM as described above so as to cause the torsional resonance at 20000 Hz. Value.

Each 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. As a result, the test piece B along the guideline (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%. On the other hand, the test piece D along the pointer (2) had a resonance instability phenomenon at an amplifier output of 80%. In the test piece E, resonance instability did not occur until the amplifier output reached 90%. At an amplifier output of 90%, shear fatigue failure occurred in a low cycle range where the number of loads was on the order of 10 ⁵ times. 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.

  As described above, the weight excluding the screw portion fixed to the amplitude-amplifying horn 8 of the test piece A is 21.7 g. On the other hand, the weight of the test piece E excluding the threaded portion is 9.36 g. In addition, in order to improve the grinding accuracy on the free end (on the opposite thread side) of the actual test piece, it is necessary to provide a center hole by turning, and the weight excluding the mounting projection is slightly lighter than 9.36 g. Become.

FIG. 4 shows a test piece drawing drawn based on the dimensions of the test piece E in Table 2 (unit: mm). FIG. 5 shows the torsion angle θ and the surface shear stress τ obtained by eigenvalue analysis of free torsional resonance using the specimen model of FIG. FIG. 5 shows the case where the _end surface twist angle θ _end is 0.01 rad, and the maximum shear stress τ _max acting on the surface of the minimum diameter portion of the test piece at this time is 526.18 MPa. That is, in the category of linear elasticity, the relationship between the torsion angle θ _{end of the end} surface and the maximum shear stress τ _max acting on the surface of the minimum diameter portion of the test piece is expressed by equation (8). However, the unit of τ _max is MPa, and the unit of θ _end is rad.
τ _max = 52618θ _end (8)

Using the three specimens made of standard hardened and tempered bearing steel SUJ2 (see Table 1 for alloy components) with the shape shown in FIG. 4, the end face twist angle θ _end (rad) was measured while changing the amplifier output P (%). . The specimen hardness was 722HV. A photograph of the lower end of the shoulder of the test piece during vibration was taken with a digital microscope (Keyence VHX-900) at 200x magnification. Prior to that, emery polishing (# 500, # 2000) and diamond wrapping (particle diameter: 1 μm) were applied to the shoulder of the test piece with a drilling machine to obtain a mirror surface state. After the test piece 1 was attached to the high-efficiency amplitude-enlarging horn 8, a color check developer was applied to the shoulder.

FIG. 6 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. 6, attention is paid to the behavior of the part with an arrow. The amplifier output P was changed from 10% to 90% in 5% increments, and shaken for 1 second, during which time a photo was taken at a shutter speed of 1/15 sec. FIG. 7 is a photograph taken at the time of vibration at P = 50%, and a range 2a is a locus of a point of interest in FIG. From the range 2a measured by changing the amplifier output P (%), the end surface torsion angle θ _end was obtained as shown in FIG. As a result, as shown in FIG. 9, almost the same linear relationship was observed between P and θ _end in all three test pieces, and equation (9) was obtained as a regression line. From the equation (9), θ _end = 0.018 rad when P = 90%. From the equations (8) and (9), the relationship between the amplifier output P and the maximum shear stress τ _max acting on the surface of the minimum diameter portion of the test piece is as shown in the equation (10). From equation (10), P = 90% and τ _max = 951 MPa, and it is sufficiently expected that torsional fatigue can be given to a high-strength metal material.

  The manufactured testing machine main body 10 controls the amplifier 5 by the control / data collecting means 3 including the personal computer described above with reference to FIGS. FIG. 14 shows a screen for inputting test conditions of the ultrasonic torsional fatigue testing machine 2. FIG. 15 is a flowchart of the initial setting process, FIG. 16 is a flowchart of the test condition input process, and FIG. 17 is a flowchart of the test preparation process. FIG. 18 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, etc.

In the example of the input screen in FIG. 14, the resonance frequency of 19.97 is displayed in the measurement preparation column, indicating that the test piece resonated at 19.97 kHz with an amplifier output of 10%, which is almost equal to the target 20000 Hz. . When the amplifier output is entered in the measurement condition input field, the maximum shear stress amplitude τ _max acting on the surface of the test minimum diameter is calculated from the slope and intercept of the straight line of equation (10) entered in advance on the initial setting screen. (The conversion process is performed by the test condition setting unit 13 (FIG. 2)). In the same column, select either continuous operation for continuous vibration or intermittent operation for alternately repeating vibration and pause.

  When a crack occurs and grows to a certain size, the resonance frequency of the test piece 1 decreases. The reason why 50.00 is entered in the frequency fluctuation range in the same column is to stop the test because the fatigue failure occurs when the resonance frequency is lowered by 50 Hz or more from the time of the test. This value is variable, and an appropriate value should be input according to the test piece material. FIG. 10 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.

In the air at normal temperature, the test piece used for the measurement of the torsion angle of the end face and the same lot were evaluated by intermittent operation in which vibration and rest 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. Prior to the evaluation, emery polishing (# 500, # 2000) and diamond wrapping (particle diameter: 1 μm) were applied to the test piece joints. The test was terminated if no damage occurred ¹⁰ times.

FIG. 12 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. 12 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. Yes, the shear fatigue limit was τ _W0 = 564 MPa.

The torsional fatigue test piece (standard quenching) using the bearing steel SUJ2 of 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 the 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 torsional fatigue test piece in FIG. 11 has R = 11.4 mm, whereas the ultrasonic torsional fatigue test piece has R = 9.7 mm. The reason for changing R is to make the stress concentration factor uniform. Prior to the torsional fatigue test, emery polishing (# 500, # 2000) and diamond wrapping (particle size 1 μm) were applied to the thinned portion for the purpose of eliminating the influence of the surface roughness. 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. 12 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, 479 MPa (dotted line in FIG. 12), which is 85% of the shear fatigue limit of 564 MPa, is defined as τ _WO .

  In the torsional fatigue test, the shear stress is maximum on the specimen surface and zero on the shaft core. That is, a fatigue test with a stress gradient. Here, in 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. On the other hand, in 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. There is a report that the three steel types having different tensile strengths were subjected to an axial load fatigue test and a rotating bending fatigue test in which the diameter of the smooth part was variously changed, and the respective fatigue limits were obtained (see Non-Patent Document 3). According to this, regardless of the steel type, the fatigue limit in the axial load fatigue test is about 80% of the fatigue limit in the rotating bending fatigue test with a smooth part diameter of 4 mm.

In the tensile and compression fatigue test, the fatigue limit in the axial load fatigue test without a stress gradient is the safety standard, but in the torsional fatigue test, the stress gradient is maintained no matter how large the diameter of the smooth part is. not exist. As long as it has a stress gradient, dimensional effects are unavoidable even in torsional fatigue tests. Therefore, it is assumed that the standard of the tensile compression fatigue test can be applied as it is to the torsional fatigue test. That is, since the minimum diameter of the ultrasonic torsional fatigue test piece is 4 mm, 383 (dotted line in FIG. 12) which is 80% of the shear fatigue limit of 479 MPa corrected for overestimation of the ultrasonic torsional fatigue test is τ _WO . .

The size effect that appears in the fatigue test with the above stress gradient is brought about by a mechanical factor called a stress gradient and a statistical factor that increases or decreases the volume subjected to a large load (dangerous volume). From the viewpoint of statistical factors, a PSN diagram may be obtained by evaluating multiple lines at multiple stress levels. However, it will often be difficult to implement due to time constraints. 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 τ _W0 in FIG. It has a function to obtain a PSN diagram with a small number of data.

FIG. 13 is a PSN diagram (broken line in FIG. 13) with a fracture probability of 10% obtained thereby, and the 10% shear fatigue limit was 500 MPa. When overestimation correction of the ultrasonic torsional fatigue test is performed on the value, 500 × 0.85 = 425 MPa (dotted line in FIG. 13). Further, when the above-described dimensional effect correction is performed, 425 × 0.8 = 340 MPa (a chain line in FIG. 13). This value is the safest estimate of τ _lim . Here, the appropriate fracture probability is set to 10%, but the critical volume of the ultrasonic torsional fatigue test specimen and the critical volume of the actual part are compared, and an appropriate fracture probability may be considered.

The control / data collection means 3 of FIGS. 1 and 2 will be described together with FIGS. 14 to 18. The test condition setting unit 13 in FIG. 2 causes the screen display device 12 to display the test condition input screen shown in FIG. In this input screen, 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 13 stores the test condition information input on the input screen of FIG. 14 in the test condition / collected data storage unit 14 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 13 in FIG. 2 displays an initial setting input screen on the screen display device 12 in addition to the input screen in FIG. 14, and the voltage output by the amplifier 5 as shown in the flowchart in FIG. Prompts the input of values and physical quantities, and the input of shear amplitude stress coefficient, initializes voltages and physical quantities with the input values, and records them 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. In the following explanation of each item, “controller (PC)” refers to the control / data collection means 3.
Amplitude IN: Amplifier output amplitude This is the amplifier output amplitude, and the controller (PC) instructs 0-100% from -10V to + 10V.
Amplitude OUT: Voltage output proportional to the actual amplifier output amplitude. 0-100% is indicated from 0V to + 10V by the controller (PC).
Ultrasonic power: A voltage output proportional to the output of ultrasonic power. 0-100% is indicated from 0V to + 10V by 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: Voltage output proportional to the relative frequency output recorded in the amplifier memory. The controller (PC) indicates 19.50 to 20.50 kHz from -10V to + 10V.

  When the “oscillation start” button on the input screen of FIG. 14 is pressed, the resonance frequency is searched with 10% output. When it is confirmed that the resonance occurs, 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 15 in FIG. 2 starts the test.

  The test control unit 15 shown in FIG. 2 controls the amplifier 5 and the test piece cooling means 9 and collects data from the amplifier 5 according to the test conditions input as described above and stored in the test file. Briefly, after the start of the test (R1), the amplitude output is determined (R3), the test condition of continuous operation or intermittent operation is determined (R4), and in the case of continuous operation, the processing of steps R5 to R13 is performed. In the case of intermittent operation, steps R14 to R24 are performed. In either case, 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). When the test end condition is satisfied, the ultrasonic output is stopped (R26), and the test is ended.

DESCRIPTION OF SYMBOLS 1 ... Test piece 1a ... Shoulder part 1b ... Thin part 3 ... Control and data collection means 4 ... Oscillator 5 ... Amplifier 6 ... Frame 7 ... Torsional vibration converter 8 ... Amplitude expansion horn 9 ... Test piece air cooling means 10 ... Test machine main body 13 ... Test condition setting unit 18 ... Intermittent oscillation control unit

Claims (28)

A method for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact with 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, Using control means for providing control input,
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are the shapes and dimensions that resonate with the torsional vibration of the amplitude-amplifying horn,
Drive the torsional vibration converter in the frequency range of the ultrasonic region, resonate the amplitude expanding horn and the test piece, and perform a test for shear fatigue failure of the test piece ,
The shape of the amplitude expanding horn is an exponential function type in which the tip side that becomes the mounting portion of the test piece becomes thin,
Using the relationship between the shear stress amplitude and the load count obtained by test, shear fatigue properties evaluation method of contacting the metal material in rolling, characterized in that to evaluate the shear fatigue property of the metallic material.   2. The method for evaluating a shear fatigue property of a rolling contact metal material according to claim 1, wherein the amplifier is capable of controlling the output magnitude and on / off by an external input.   3. The rolling bearing or rolling contact metal material according to claim 1, wherein the torsional vibration generated by the torsional vibration converter is a perfect double swing in which the forward rotation direction and the reverse rotation direction are symmetrical. Fatigue property evaluation method.   The lower limit value of the frequency for driving the torsional vibration converter is (20000-500 + α) Hz, the upper limit value is (20000 + 500) Hz, where α is during the test of the test piece. A method for evaluating a shear fatigue property of a rolling contact metal material, which is a margin value for property change and is 200 Hz or less.   5. The method for evaluating a shear fatigue property of a rolling contact metal material according to claim 4, wherein the margin value is 200 Hz.   6. The rolling contact metal material according to claim 1, wherein the amplitude-amplifying horn has a circular cross-sectional shape, and a vertical cross-sectional shape of a portion excluding the base end portion is a tapered shape. Shear fatigue property evaluation method.   7. The method for evaluating shear fatigue characteristics of a rolling contact metal material according to claim 6, wherein the material of the amplitude expanding horn is a titanium alloy.   8. The method for evaluating a shear fatigue property of a rolling contact metal material according to claim 7, wherein the titanium alloy, which is a material of the amplitude expanding horn, contains at least Al at least 6% and Mo at least 3%.   9. The method for evaluating a shear fatigue property of a rolling contact metal material according to claim 7 or 8, wherein the Rockwell C hardness of a titanium alloy that is a material of the amplitude expanding horn is 35 or more. A method for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact with 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, Using control means for providing control input,
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are the shapes and dimensions that resonate with the torsional vibration of the amplitude-amplifying horn,
Drive the torsional vibration converter in the frequency range of the ultrasonic region, resonate the amplitude expanding horn and the test piece, and perform a test for shear fatigue failure of the test piece,
The amplitude expanding horn has a circular cross-sectional shape, and the vertical cross-sectional shape of the portion excluding the base end portion is a tapered shape,
The material of the amplitude expansion horn is a titanium alloy, and the Rockwell C hardness of the titanium alloy that is the material of the amplitude expansion horn is 35 or more,
The amplitude expansion horn is a physical property value per amplitude expansion horn shape model excluding a mounting portion protruding from the center of the end face of the base end portion and attached to the torsional vibration converter, and a female screw portion attaching the test piece at the tip. Where E = 1.16 × 10 ¹¹ Pa, ν = 0.27, and ρ = 4460 kg / m ³ , the torsion angle of the end face on the small diameter side obtained by eigenvalue analysis of free torsional resonance by finite element analysis When the enlargement ratio, which is a ratio to the torsion angle of the large-diameter end face, is 43 times or more and the torsion angle of the tip is 0.018 rad, the maximum shear stress acting on the tapered portion surface is 180 MPa or less ,
A method for evaluating the shear fatigue property of a rolling contact metal material, wherein the shear fatigue property of the metal material is evaluated using the relationship between the shear stress amplitude and the number of loads obtained by the test . The test piece according to any one of claims 1 to 10, wherein the test piece includes cylindrical shoulder portions at both ends, and a thinned portion having a cross-sectional shape along the axial direction following the shoulder portions on both sides, which is an arc curve. Is a dumbbell shape,
The length of the shoulder is L1, the half chord length which is half the length of the thinned portion is L2, the radius of the shoulder is R3, the minimum radius of the thinned portion is R1, and the radius of the arc curve Is R (unit is m, R is determined from R1, R2, and L3), resonance frequency is f (unit is Hz), Young's modulus E (unit is Pa), Poisson's ratio ν (dimensionless), density ρ (Unit: kg / m ³ )
L2, R1, R2 are set to arbitrary values, the resonance frequency f is set to an arbitrary value in the frequency range 20000 ± 500 Hz that can be driven by the vibration converter, and the resonance frequency f is expressed by the following equations (1) to (6). The theoretical length of the shoulder length L1 at which the test piece resonates is obtained.

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,
For these shape models, E, ν, and ρ are measured physical property values of a metal material, and an analytical solution L1N that undergoes torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis. A test piece having the dimensions L2, R1, R2, R, L1N is prepared and used for the test.
A method for evaluating the shear fatigue characteristics of rolling contact metal materials. In Claim 11, 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 expansion horn of the test piece and the center hole part of the end face of the non-attachment part necessary for processing the test piece Is a method for evaluating the shear fatigue properties of rolling contact metal materials having a thickness of 1.2 × 10 ⁻⁶ m ³ or less. A method for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact with 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 part that attaches a test piece concentrically to the tip, and is fixed to the torsional vibration converter at the base end And an amplitude expansion horn that expands the amplitude of the torsional vibration of the torsional vibration converter applied to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies it to the torsional vibration converter, Using control means for providing control input,
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are the shapes and dimensions that resonate with the torsional vibration of the amplitude-amplifying horn,
Drive the torsional vibration converter in the frequency range of the ultrasonic region, resonate the amplitude expanding horn and the test piece, and perform a test for shear fatigue failure of the test piece,
Using the relationship between the shear stress amplitude obtained by the test and the number of loads, the shear fatigue property of the metal material is evaluated,
The test piece is a dumbbell shape having a cylindrical shoulder portion at both ends, and a thinned portion in which the cross-sectional shape along the axial direction follows the shoulder portions on both sides is an arc curve,
The length of the shoulder is L1, the half chord length which is half the length of the thinned portion is L2, the radius of the shoulder is R3, the minimum radius of the thinned portion is R1, and the radius of the arc curve Is R (unit is m, R is determined from R1, R2, and L3), resonance frequency is f (unit is Hz), Young's modulus E (unit is Pa), Poisson's ratio ν (dimensionless), density ρ (Unit: kg / m ³ )
L2, R1, R2 are set to arbitrary values, the resonance frequency f is set to an arbitrary value in the frequency range 20000 ± 500 Hz that can be driven by the vibration converter, and the resonance frequency f is expressed by the following equations (1) to (6). The theoretical length of the shoulder length L1 at which the test piece resonates is obtained.

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,
For these shape models, E, ν, and ρ are measured physical property values of a metal material, and an analytical solution L1N that undergoes torsional resonance at the resonance frequency f is obtained by eigenvalue analysis of free torsional resonance by finite element analysis. Test pieces having the dimensions of L2, R1, R2, R, L1N were prepared and used for the test.
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 of the end face of the non-attachment part necessary for processing the test piece is 1.2 × 10 ^-6 m ³ or less,
When the torsion angle of the end face of the test piece is 0.01 rad, the test piece shape model excluding the male screw part attached to the tip of the amplitude expanding horn and the center hole part of the end face of the non-attachment part necessary for processing the test piece, When the physical property values are E = 2.04 × 10 ¹¹ Pa, ν = 0.29, ρ = 7800 kg / m ³ , the surface of the minimum diameter part of the specimen is obtained by eigenvalue analysis of free torsional resonance by finite element analysis. A method for evaluating the shear fatigue characteristics of a rolling contact metal material in which the maximum shear stress to act is 520 MPa or more.   14. The method for evaluating shear fatigue characteristics of a rolling contact metal material according to claim 1, wherein the test piece is forcibly air-cooled in order to suppress a temperature rise of the test piece.   15. The shear fatigue of a rolling contact metal material according to any one of claims 1 to 14, wherein a torsional vibration load on the test piece by the torsional vibration converter and a pause are alternately repeated in order to suppress a temperature rise of the test piece. Characterization method.   14. The method for evaluating a shear fatigue property of a rolling contact metal material that is continuously loaded in a low load region in which heat generation of a test piece does not cause a problem with respect to a test result according to any one of claims 1 to 13.   The shear fatigue property evaluation method for a rolling contact metal material according to any one of claims 1 to 16, wherein the fracture is detected by a resonance frequency drop of 200 Hz or less.   18. The PSN diagram having an arbitrary failure probability is obtained from the relationship between the shear stress amplitude obtained by the test and the number of loads in any one of claims 1 to 17, and this PS— A method for evaluating the shear fatigue characteristics of a rolling contact metal material, in which the shear fatigue strength in the ultralong life region is used as the shear fatigue strength τwo in the ultralong life region in order to use the shear fatigue strength in the ultralong life region from the N diagram.   The shear fatigue property evaluation according to any one of claims 1 to 16, wherein a value of 85% with respect to the shear fatigue strength in the ultralong life region obtained from the relationship between the shear stress amplitude obtained by the test and the number of loads is obtained. A method for evaluating the shear fatigue properties of rolling contact metal materials with shear fatigue strength τwo in the ultra-long life region.   The shear fatigue property evaluation according to any one of claims 1 to 16, wherein a value of 80% with respect to the shear fatigue strength in the ultra-long life region obtained from the relationship between the number of loads obtained by the test and the shear stress amplitude is obtained. A method for evaluating the shear fatigue properties of rolling contact metal materials with shear fatigue strength τwo in the ultra-long life region.   In any one of Claims 1 thru | or 20, in order to estimate safely the shear fatigue strength in a super-long life area | region, P of arbitrary fracture probabilities is obtained from the relationship between the shear stress amplitude obtained by the said test, and the load frequency. -S-N diagram is obtained, and from this P-S-N diagram, the shear fatigue strength in the ultra-long life region is used as the shear fatigue strength τwo in the ultra-long life region for use in evaluating the shear fatigue characteristics. In order to use the value of 85% of the shear fatigue strength in the ultra-long life region obtained from the relationship between the fracture probability correction and the relationship between the shear stress amplitude obtained by the test and the number of loads, for the evaluation of the shear fatigue characteristics, Overestimation correction, which is the correction for shear fatigue strength τwo in the life region, and the super long life region obtained from the relationship between the number of loads and the shear stress amplitude obtained by the above test. Combining any two or more corrections together with the dimensional effect correction, which is a correction for setting the shear fatigue strength τwo in the ultra-long life region to use the value of 80% for the shear fatigue strength for the evaluation of the shear fatigue characteristics A method for evaluating the shear fatigue property of a rolling contact metal material, in which the obtained value is used for evaluating the shear fatigue property, with the shear fatigue strength τwo in the ultra-long life region. An apparatus for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact with a test piece made of the metal material,
It has 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 part that attaches a test piece concentrically to the distal end. An amplitude-amplifying horn that expands the torsion angle of the torsional vibration converter fixed to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies the output to the torsional vibration converter, and the control to the amplifier And a control / data collection means for collecting data including the excitation frequency under test, the state of the amplifier, and the number of loads.
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are shapes and dimensions that resonate with torsional vibration of the amplitude-amplifying horn,
The torsional vibration converter is driven in a frequency range of an ultrasonic region, the amplitude expanding horn and the test piece are resonated, and the test piece is subjected to shear fatigue failure. The shape of the amplitude expanding horn is the test piece. become the distal end side mounting portion is characterized that it is an exponential function type narrowing of the shear fatigue property evaluation apparatus of rolling contact metallic material.   23. The lower limit value of the frequency range for driving the torsional vibration converter according to claim 22 is (2000−500 + α) Hz, and the upper limit value is (2000 + 500) Hz, where α is a margin value for property change during the test of the test piece. An apparatus for evaluating shear fatigue characteristics of a rolling contact metal material having a frequency of 200 Hz or less.   24. The shear fatigue characteristic evaluation of a rolling contact metal material according to claim 22 or claim 23, wherein the torsional vibration converter generates a torsional vibration that is a perfect double swing in which a forward rotation direction and a reverse rotation direction are symmetrical. apparatus. An apparatus for testing and evaluating the shear fatigue characteristics of a metal material in rolling contact with a test piece made of the metal material,
It has 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 part that attaches a test piece concentrically to the distal end. An amplitude-amplifying horn that expands the torsion angle of the torsional vibration converter fixed to the base end, an oscillator, an amplifier that amplifies the output of the oscillator and applies the output to the torsional vibration converter, and the control to the amplifier And a control / data collection means for collecting data including the excitation frequency under test, the state of the amplifier, and the number of loads.
The shape and dimensions of the amplitude expanding horn are the shapes and dimensions that resonate with torsional vibration caused by driving the torsional vibration converter,
The shape and dimensions of the test piece are shapes and dimensions that resonate with torsional vibration of the amplitude-amplifying horn,
The torsional vibration converter is driven in the frequency range of the ultrasonic region, the amplitude expanding horn and the test piece are resonated, and the test piece is subjected to shear fatigue fracture,
The amplitude expansion horn is a physical property value per amplitude expansion horn shape model excluding a mounting portion protruding from the center of the end face of the base end portion and attached to the torsional vibration converter, and a female screw portion attaching the test piece at the tip. Where E = 1.16 × 10 ¹¹ Pa, ν = 0.27, and ρ = 4460 kg / m ³ , the torsion angle of the end face on the small diameter side obtained by eigenvalue analysis of free torsional resonance by finite element analysis When the enlargement ratio, which is the ratio to the torsion angle of the large-diameter end face, is 43 times or more and the torsion angle of the tip is 0.018 rad, the maximum shear stress acting on the tapered portion surface is 180 MPa or less. Shear fatigue property evaluation equipment.   26. The apparatus for evaluating a shear fatigue property of a rolling contact metal material according to any one of claims 22 to 25, comprising a test piece cooling means for forcibly air-cooling the test piece.   27. The intermittent oscillation control unit according to claim 22, wherein the control / data collection unit controls intermittent oscillation that causes the torsional vibration converter to alternately repeat generation and pause of torsional vibration. An apparatus for evaluating the shear fatigue characteristics of a rolling contact metal material that can be switched between intermittent oscillation and continuous oscillation.   26. The test condition setting according to claim 22, wherein the control / data collection unit sets a test condition including a condition for driving the torsional vibration converter and a condition for collecting the data according to an input. And a test control unit that drives the torsional vibration converter and collects the data in accordance with the test conditions set in the test condition setting unit.

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