JP2010014473A - Detection method of detecting temporal change generated when contact fatigue damage is generated - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that data obtained by comparing signals output from a component in which damage is generated in advance and a component without damage are used as an index indicating the occurrence of contact fatigue damage, because it takes time to detect the change point, i.e. a signal indicating the change, generated in the component at the moment of the occurrence of contact fatigue damage in the component having a contact part regarding power transmission of a motor vehicle or the like. <P>SOLUTION: After hydrogen is charged into the component, rolling contact fatigue test is performed with conditions similar to the actual use conditions of the component, and the temporal change of the signal arising from the component is detected. Thus, the change point, i.e. the signal indicating the change, generated in the component at the moment of the occurrence of contact fatigue damage is precisely detected more efficiently in a shorter time than in a case in which hydrogen is not charged into the component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a detection method for detecting a state in which contact fatigue damage occurs over time, and more specifically, it occurs with the occurrence of contact fatigue damage in a part having a contact site related to power transmission or the like. The present invention relates to a detection method for detecting a signal representing a change in physical quantity with high accuracy.

  Parts having contact parts related to power transmission of automobiles, for example, rolling bearings, constant velocity universal joints, gears, ball screws, linear guides, etc., are repeatedly contacted by running or turning of the automobile when continuously used. As a result, contact fatigue damage can occur, which can lead to malfunction. Recently, in particular, there has been an increasing demand for reduction in fuel consumption of automobiles, and in order to meet this demand, parts have been reduced in size and weight. With the reduction in size and weight, the torque transmitted by the component is relatively increased, so that the load applied to the component is increased, and the component is used under more severe conditions. As a result, the frequency of contact fatigue damage is increasing. Therefore, it is important to improve resistance in order to suppress contact fatigue damage.

  In order to improve the resistance for suppressing contact fatigue damage, for example, a design change or a material change is performed. In order to verify the effectiveness of the results of design changes and material changes in detail, the prototypes of parts that have undergone design changes and material changes are continuously used under actual usage conditions, and contact fatigue damage Therefore, it is necessary to detect with high accuracy a signal representing a change that occurs in a part at the moment when the damage occurs, that is, a change in physical quantity. The signal data representing the change at the moment when damage occurs, thus detected, contains a lot of useful information related to, for example, how damage occurs and the life of parts. For this reason, the data of this signal can be used as an index indicating that the contact fatigue damage has occurred in the subsequent contact fatigue damage test.

Conventionally, various methods for diagnosing contact fatigue damage have been proposed. For example, in Japanese Patent Application Laid-Open No. 2007-285874 (Patent Document 1), a sound or vibration when the outer ring raceway surface of a double-row tapered roller bearing has been subjected to defects under actual use conditions is disclosed. A method of detecting the presence or absence of a defect by detecting a signal and comparing it with a signal when a double-row tapered roller bearing having no defect is used under actual use conditions is disclosed.
JP 2007-285874 A

  The conventional diagnostic method described above does not detect a signal representing a change at the moment when damage occurs. Therefore, usefulness such as the amount of information included in the detected signal is inferior to a signal representing a change at the moment when damage occurs. In other words, conventional detection methods that compare vibration signals between parts that have been previously defective and parts that do not have defects are insufficient, and it is possible to detect signals that represent changes at the moment when the parts are damaged. It is considered important. However, when used under actual usage conditions, it takes a long time to cause contact fatigue damage. For this reason, it takes a long time to detect a signal representing a change at the moment when contact fatigue damage occurs.

The present invention has been made in view of the above-described problems. The purpose is to generate contact fatigue damage at a moment when the contact fatigue damage occurs in a short time by using a part that has a contact part related to power transmission under conditions close to actual use conditions. Another object of the present invention is to provide a detection method for detecting a signal representing a change with high accuracy.

  The detection method in the present invention is a detection method for detecting a change over time that occurs when contact fatigue damage occurs in a bench test of a steel part. The detection method includes a step of charging a steel part with hydrogen and a step of detecting a signal output in a process in which the steel part charged with hydrogen generates contact fatigue damage.

  Specifically, steel parts made of the same material as parts that have contact parts related to power transmission of automobiles, such as rolling bearings, constant velocity universal joints, gears, ball screws, linear guides, etc. Prepare as test parts. Then, hydrogen is contained (charged with hydrogen) in the steel part as the test part. By including hydrogen in the steel part before using the steel part in this way, the material of the part deteriorates due to the influence of hydrogen, so contact fatigue damage can occur in a short time in a bench test. it can. In addition, the steel parts are continuously used under actual use conditions. During continuous use, it detects and records changes over time in signals such as sound and temperature output from steel parts. Then, since a signal representing a change in the part, that is, a change in physical quantity, is output at the moment when the steel part causes contact fatigue damage, the signal representing this change can be detected with high accuracy.

  According to the detection method of the present invention, electrolysis can be performed in a method of charging a steel part with hydrogen. For example, there is a method of performing electrolysis in a solution obtained by adding thiourea as a catalyst poison to a dilute sulfuric acid aqueous solution. Alternatively, for example, electrolysis may be performed in a solution obtained by adding ammonium thiocyanate as a catalyst poison to a sodium chloride aqueous solution. Electrolysis may be performed in a solution obtained by adding sodium sulfide nonahydrate as a catalyst poison to an aqueous sodium hydroxide solution. By performing the electrolysis, the steel parts can be charged with hydrogen.

  In the detection method of the present invention, in the step of charging the steel part with hydrogen, instead of electrolysis, for example, a method of charging the steel part with hydrogen by immersing in an aqueous solution of ammonium thiocyanate may be used. Good. By using this method, it is possible to charge steel parts with hydrogen more easily and cheaply than the method of performing electrolysis.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to raise | generate contact fatigue damage in a short time, the signal showing the change which generate | occur | produces in the moment when the said contact fatigue damage occurs can be detected with high precision.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each embodiment, portions having the same function are denoted by the same reference numerals, and the description thereof will not be repeated unless particularly necessary.

FIG. 1 is a flowchart showing the steps of the detection method in the embodiment of the present invention. The present invention relates to parts having contact parts related to power transmission of automobiles, such as rolling bearings, constant velocity universal joints, gears, ball screws, linear guides, etc., by receiving repeated contact when the parts are continuously used. The present invention provides a method for detecting a signal (change in the occurrence state of contact fatigue damage with time), which is generated at the moment when contact fatigue damage occurs, with high accuracy. The outline of the process will be described below. First, as shown in FIG. 1, a process of preparing test parts (S10) is performed. Specifically, steel parts made of the same material as parts that have contact parts related to power transmission of automobiles, such as rolling bearings, constant velocity universal joints, gears, ball screws, linear guides, etc. This is a step of preparing as a test part for performing a bench test. The shape of the test part is appropriately determined according to the test method.

  Next, a step of charging hydrogen (S20) is performed. Specifically, it is a step of charging hydrogen, for example, by performing electrolysis on the test part prepared in step (S10).

  And the process (S30) to continue using is implemented. Specifically, for test parts charged with hydrogen under the same conditions as those described above, for example, rolling bearings, constant velocity universal joints, gears, ball screws, linear guides, etc. It is a process to give a load. By performing the signal detection step (S31) while performing this continuous use, the time-dependent change in signals such as sound and temperature output from the steel parts during continuous use A step of detecting and recording the error is performed. Then, since the material of the test part which is a steel part charged with hydrogen is deteriorated due to the influence of hydrogen, contact fatigue damage can be caused in the test part in a shorter time than usual. In addition, by charging hydrogen, contact fatigue damage can be caused in a shorter time than usual, but the manner of damage is not different from the normal case. Therefore, by charging with hydrogen, it is possible to accurately reproduce a signal representing a change that is output at the moment when the test component causes contact fatigue damage in a shorter time than usual.

  In addition, a process (S20) and a process (S21) may be started simultaneously, and a process (S21) may be started after a fixed time passes after starting a process (S20). Alternatively, depending on the detection method, the step (S20) and the step (S21) may be repeated a plurality of times. Further, by performing the step (S31) while performing the step (S30), it is possible to detect the signal representing the change output at the moment when the test part generates the contact fatigue damage with high accuracy. Hereinafter, each process described above will be described in more detail.

  In the step of preparing a test part (S10), as described above, a steel part formed of the same material as a part having a contact part related to power transmission of an automobile is prepared as a test part. However, it is preferable to use a material that deteriorates when charged with hydrogen. For example, JIS-SUJ2, JIS-SCr420, JIS-S53C, etc. are used as materials for test parts, and it is submerged, carburized, or induction-hardened. Apply.

  FIG. 2 is a schematic diagram showing the shape of the test part in the embodiment of the present invention. Consider a case where the test parts used in the bench test of the present invention are made of, for example, a material constituting a ball as a rolling element located between an outer ring and an inner ring of a rolling bearing used for an automobile wheel. . In this case, since the balls are repeatedly contacted according to driving conditions such as traveling and turning of the automobile, it is preferable to perform a test so that the test components are subjected to the same load. Therefore, it is preferable that the shape of the test part has the shape of a test piece used for a test capable of performing such repeated contact. Therefore, a part having a configuration as shown in FIG. 2 is prepared as a test part. That is, as shown in FIG. 2, for example, a cylindrical and hollow test part 2 having a larger radius than the cylindrical test part 1 is fitted to the outside of the long axis of the cylindrical test part 1. . As shown in FIG. 3 to be described below, two identical parts are prepared by fitting a hollow test part 2 to a cylindrical test part 1 and one side is a driving side test part 3 and the other side is the other side. Is a driven-side test part 4.

FIG. 3 is a schematic view showing a state in which the test parts on the driving side and the driven side are driven by rotation while being in contact with each other. In order to allow the two drive side test parts 3 and the driven side test parts 4 that have been prepared to always come into contact with each other when rotated about the major axis direction as shown in FIG. The outer peripheral surfaces of the hollow test components 2 of the test component 3 and the driven test component 4 are brought into contact with each other. Then, the radial outer surface of the hollow test component 2 of the driving side test component 3 and the radial outer surface of the hollow test component 2 of the driven side test component 4 are always brought into contact with each other. Can do.

  As for the size of the test parts described above, the drive side test part 3 and the driven side test part 4 have a circular radius of 20 mm, for example, which forms the bottom surface of the cylindrical test part 1, and are for hollow test use. What is necessary is just to prepare so that the radius of the circular outer side which makes the bottom face of the component 2 may be set to 60 mm.

  Next, a step of charging hydrogen (S20) is performed. As described above, this is a step of charging hydrogen by, for example, performing electrolysis on the test component prepared in step (S10). FIG. 4 is a schematic view showing a state in which hydrogen is charged to the test component by electrolysis. As shown in FIG. 4, a vessel such as a beaker for scientific experiments is filled with a solution, and an anode and a cathode are prepared inside the solution. For example, a platinum electrode is used for the anode, and a hollow test component 2 of the drive side test component 3 is used for the cathode, for example. When the test as described above is performed, the hollow test components 2 are in contact with each other, and therefore it is preferable to charge the hollow test components 2 with hydrogen. Hydrogen may be charged only to the hollow test part 2 of the drive side test part 3, or hydrogen may be charged to both the drive side test part 3 and the driven side test part 4. May be.

  As the solution 5 that fills the container of FIG. 4, for example, a solution obtained by adding thiourea to a dilute sulfuric acid aqueous solution is used. In this case, the concentration of dilute sulfuric acid is preferably adjusted to a concentration of about 0.05 mol / L, more specifically 0.04 mol / L or more and 0.06 mol / L or less. When an acidic aqueous solution is used in this way, the efficiency of charging the hollow test component 2 with hydrogen is improved. Thiourea is a catalyst poison and is used to increase the efficiency of hydrogen charging. In order to maximize the efficiency of hydrogen charging, the concentration of thiourea added is preferably 1.2 g / L or more and 1.4 g / L or less. The catalyst poison is a catalytic action that lowers the activation energy in the process of atomic hydrogen adsorbing on the surface of the steel forming the hollow test part 2 and entering the steel during hydrogen charging. It is a substance that you have. The reason why the lower limit of the thiourea concentration range is set to 1.2 g / L is that the efficiency is lowered if the concentration is lower than that. The reason why the upper limit of the thiourea concentration range is set to 1.4 g / L is that the efficiency does not increase even if the concentration is increased beyond that.

  By the way, when hydrogen is charged in the acidic aqueous solution as described above, the surface of the hollow test component 2 is covered with a thin corrosion product, so that after hydrogen is charged, the surface of the hollow test component 2 is rewrapped. It is preferable to improve the surface roughness.

  Instead of using the acidic aqueous solution described above for performing electrolysis, for example, a sodium chloride aqueous solution may be used. In this case, it is preferable to adjust the concentration of sodium chloride to a concentration of about 3% by mass, more specifically 2% by mass to 4% by mass. When using a sodium chloride aqueous solution, for example, ammonium thiocyanate can be used as a catalyst poison used to increase the efficiency of hydrogen charging. In order to maximize the efficiency of hydrogen charging, the concentration at which ammonium thiocyanate is added is preferably 2.5 g / L or more and 3 g / L or less. The reason why the lower limit of the ammonium thiocyanate concentration range is set to 2.5 g / L is that if the concentration is lower than that, the efficiency decreases. Moreover, the reason why the upper limit of the ammonium thiocyanate concentration range is 3 g / L is that the efficiency does not increase even if the concentration is increased. Further, the concentration range of ammonium thiocyanate is more preferably 2.8 g / L or more and 3.0 g / L or less. In this way, it is possible to obtain an effect that more stable hydrogen charging can be performed.

When hydrogen is charged in an aqueous sodium chloride solution, the surface of the hollow test part 2 may be covered with a thin corrosion product. Therefore, after hydrogen is charged, the surface of the hollow test part 2 is re-wrapped. It is further preferable to improve the surface roughness.

  Further, an alkaline aqueous solution, for example, a sodium hydroxide aqueous solution can be used for the electrolysis. In this case, it is preferable to adjust the concentration of sodium hydroxide to about 1 mol / L, more specifically to a concentration of 0.8 mol / L to 1.2 mol / L. In the case of using an aqueous sodium hydroxide solution, for example, sodium sulfide nonahydrate can be used as the catalyst poison used to increase the efficiency of hydrogen charging. In order to maximize the efficiency of hydrogen charging, the concentration of sodium sulfide nonahydrate added is preferably 0.8 g / L or more and 1 g / L or less. The reason why the lower limit of the concentration range of sodium sulfide nonahydrate is set to 0.8 g / L is that if the concentration is lower than that, the efficiency decreases. The reason why the upper limit of the concentration range of sodium sulfide nonahydrate is set to 1 g / L is that the efficiency is not improved even if the concentration is increased. When electrolysis is performed using an alkaline aqueous sodium hydroxide solution, no corrosion product is generated on the surface of the hollow test component 2 after charging with hydrogen.

  Further, for example, as a method of charging the hollow test component 2 with hydrogen, there is a method not using electrolysis. FIG. 5 is a schematic view showing a state in which hydrogen is charged to a test component by being immersed in an aqueous solution. As shown in FIG. 5, for example, there is a method in which the hollow test part 2 is simply immersed in the aqueous solution 6. Specifically, an aqueous solution of ammonium thiocyanate is used as the aqueous solution 6. By immersing the hollow test component 2 in this aqueous ammonium thiocyanate solution, the hollow test component 2 is charged with hydrogen. At that time, the concentration of ammonium thiocyanate in the ammonium thiocyanate aqueous solution is preferably 5% by mass or more and 20% by mass or less. In this way, hydrogen can be charged by simply immersing in an aqueous solution without using electrolysis. By using this method, the hollow test component 2 can be charged with hydrogen more easily and cheaply than the method of performing electrolysis. The reason why the lower limit of the ammonium thiocyanate concentration is set to 5% by mass is that if it is less than that, the amount of hydrogen necessary for causing contact fatigue damage in a short time is not charged. The upper limit of the ammonium thiocyanate concentration is 20% by mass because the concentration of charged hydrogen is saturated at 20% by mass.

  By charging the hollow test part 2 with hydrogen, the hollow test part 2 can be turned into a hollow test part 2 in a shorter time than the normal case in which hydrogen is not charged due to the effect of containing hydrogen. Can cause contact fatigue damage. Since the material of the hollow test component 2 is deteriorated due to the charged hydrogen, contact fatigue damage can be caused in a shorter time than usual. In addition, by charging hydrogen, contact fatigue damage can be caused in a shorter time than usual, but the manner of damage is not different from the normal case. Therefore, by charging with hydrogen, it is possible to accurately reproduce a signal representing a change that is output at the moment when the test component causes contact fatigue damage in a shorter time than usual.

  As described above, when the step of charging hydrogen (S20) is completed, the step of continuous use (S30) is performed. That is, first, as shown in FIG. 3, for example, a cylindrical and hollow test part 2 is prepared by fitting it on the outside of the long axis of the cylindrical test part 1. Then, as shown in FIG. 3, the driving-side test component 3 and the driven-side test component 4 are arranged such that the outer surfaces in the radial direction of the hollow test components 2 are in contact with each other. At this time, only the hollow test part 2 constituting the drive side test part 3 may be charged with hydrogen, but both the drive side test part 3 and the driven side test part 4 are hollow. Alternatively, a hydrogen-charged test component 2 may be used.

  Then, the drive side test component 3 and the driven side test component 4 are rotated in the direction indicated by the arrow in FIG. Then, the hollow test parts 2 of the drive side test part 3 and the driven side test part 4 are continuously brought into contact with each other by rotation. As described above, these hollow test components 2 are formed of the same material as the components having contact portions related to power transmission of the automobile. For this reason, the situation in which the hollow test components 2 are continuously in contact with each other by rotation is, for example, that a ball as a rolling element located between an outer ring and an inner ring of a rolling bearing used for an automobile wheel is an automobile. The situation is similar to the situation of repeated contact according to the driving situation such as traveling and turning. By continuing the above state, the hollow test components 2 are continuously brought into contact with each other.

  While performing the continuous use step (S30) as described above, the signal detection step (S31) is performed. Specifically, it is a process of detecting and recording a change over time of a signal such as sound or temperature output from the hollow test component 2 while continuously using and receiving contact. .

  Since test parts are used, for example, temperature, vibration, sound, acoustic emission, or the like can be used as a signal for detecting a change with time. Here, the temperature signal is a signal obtained by monitoring the temperature of the surface of the hollow test component 2. The vibration signal is, for example, a signal indicating acceleration, speed, displacement, etc. of the hollow test component 2 that is continuously in contact with rotation. The sound signal is a sound wave signal generated by the hollow test component 2 that is continuously in contact with rotation. In addition, acoustic emission is an elastic wave (vibration, sound wave) that is generated due to fracture such as generation and progress of material cracks. For example, an earthquake is considered to be a global acoustic emission.

  FIG. 6 is a schematic diagram showing a situation where a temperature signal of a hollow test part is detected. For example, in order to detect a change over time in the temperature signal of the surface of the hollow test component 2, a radiation thermometer 7 is installed in the vicinity of the hollow test component 2 as shown in FIG. 6. Then, while the hollow test components 2 are continuously brought into contact with each other in the step of continuous use (S30), the radiation thermometer 7 detects a change in the temperature signal of the surface of the hollow test component 2 with time. Record. At this time, it is preferable to apply a black paint to the surface of the hollow test component 2 for detecting the surface temperature in order to increase the emissivity because of the use of the radiation thermometer. When contact fatigue damage occurs on the surface of the hollow test component 2, the surface temperature changes, so from the change point and temperature, the moment of contact fatigue damage occurs, and further Signals before and after the occurrence time can be detected with high accuracy. Further, in the step of charging hydrogen (S20), the hollow test component 2 is charged with hydrogen (contained), and due to the deterioration of the material of the component, it is shorter than the normal case where hydrogen is not charged. Contact fatigue damage can occur in the hollow test part 2 over time. Therefore, it is possible to easily detect and record the time-dependent change in the output signal such as the above-described temperature for the entire time from the start of the test to the occurrence of contact fatigue damage. As a means for detecting a temperature signal, instead of the illustrated radiation thermometer 7, for example, a thermocouple is installed in the vicinity of the contact portion between the hollow test components 2 to detect the temperature signal. A method may be used.

FIG. 7 is a schematic diagram showing a situation in which a sound signal generated by a hollow test component is detected. For example, in order to detect a change over time of a sound signal generated by the hollow test component 2, as shown in FIG. 7, an ultrasonic microphone 8 is installed as a sound collector. Then, in the step of continuous use (S30), while the hollow test components 2 are continuously in contact with each other, the ultrasonic microphone 8 detects a time-dependent change in the sound signal generated by the hollow test components 2. Record. At this time, for example, a recording monitor (storage device) (not shown) is preferably connected to the ultrasonic microphone 8. When contact fatigue damage occurs on the surface of the hollow test component 2, the sound generated by the surface changes, so contact fatigue damage occurs such as the change point and the frequency and amplitude of the changed sound wave. Instantaneous signals can be detected with high accuracy. Also, in this case, the hollow test component 2 is charged (contained) with hydrogen, and contact fatigue damage is caused to the hollow test component 2 in a shorter time than usual due to the deterioration of the material of the component. Can wake up. If the frequency of the sound detected at the time of occurrence of contact fatigue damage can be detected depending on the material or configuration of the hollow test component 2, a microphone having a lower upper limit frequency that can be measured than the ultrasonic microphone 8 is used. May be.

  In addition to these, in order to detect the acceleration and velocity signals as the vibration signals described above, for example, a sensor such as an acceleration pickup or a velocity pickup is provided on the surface of the spindle that supports the cylindrical test component 1. To detect acceleration and speed signals. Further, when detecting an acoustic emission (AE) signal, an AE pickup is attached to detect the signal.

  By using the detection method described above, if a rolling contact fatigue test is performed on a test part containing hydrogen by charging hydrogen, a normal test part that does not charge hydrogen is used. Contact fatigue damage can occur in a shorter time than when the rolling contact fatigue test is performed. For this reason, it is possible to detect changes over time in signals such as sound, vibration and temperature during the rolling contact fatigue test. Can be detected continuously and accurately including before and after the moment when contact fatigue damage occurs. This will be specifically described in Example 1 below.

  A rolling contact fatigue test that actually generates contact fatigue damage on the test part was performed according to the procedure of the flowchart shown in FIG. 1 described above. First, as a step (S10), a two-cylindrical test part as shown in FIG. 3 was prepared. Both the driving side test part 3 and the driven side test part 4 have a circular radius forming the bottom surface of the cylindrical test part 1 of 20 mm, and the circular outer radius forming the bottom surface of the hollow test part 2 is 60 mm. Prepared to be. JIS-SUJ2 was used as a material constituting the driving side test part 3 and the driven side test part 4. Moreover, as heat processing with respect to the drive side test component 3 and the driven side test component 4, it heat-processed at 850 degreeC for 40 minutes, Then, it hardened | quenched and then performed tempering at 180 degreeC for 2 hours.

And as a process (S20), the hollow test part 2 of the drive side test part 3 was installed in the cathode of the equipment which performs the electrolysis shown in FIG. Solution 5 is electrolyzed at a current density of 1 mA / cm ² for 20 hours using a 0.05 mol / L sulfuric acid aqueous solution with 1.4 g / L of thiourea added as a catalyst poison. Thus, hydrogen was contained in the hollow test part 2. Immediately thereafter, the hollow test component 2 is subjected to a lapping process to reduce the surface roughness, and a thin corrosion product covering the surface of the hollow test component 2 is obtained by immersing in an acidic aqueous solution for a long time. The removal process was performed.

  Then, a rolling contact fatigue test shown in FIG. 3 was immediately performed as a step (S30). In this test, for example, the drive side test component 3 and the driven side test component 4 are driven under conditions corresponding to the conditions under which components such as a rolling bearing, a constant velocity universal joint, a gear, a ball screw, and a linear guide are used. ing. Specifically, the maximum contact surface pressure between the driving side test component 3 and the driven side testing component 4 is 3 GPa, and the rotational speed of the driving side test component 3 in which the hollow test component 2 is charged with hydrogen is set to 3060 rpm, the number of rotations of the driven-side test component 4 was 3000 rpm. Further, VG22 oil was used as the lubricant, and the pad was supplied with oil. Here, the oil film parameter, which is the ratio of the minimum oil film thickness to the combined roughness of both contact surfaces, is about 18, and both the driving side test part 3 and the driven side test part 4 are sufficiently separated by the oil film. And good lubrication conditions.

  Then, while performing the step (S30), that is, while rotating the driving side test component 3 and the driven side testing component 4, a step of detecting a signal as a step (S31) was performed. Here, a vibration signal was detected. As a result, 9.6 hours after starting the rolling contact fatigue test as the step (S30), early peeling occurred in the hollow test part 2 of the drive side test part 3 subjected to hydrogen charge. . In the case where no hydrogen charge is performed, the time until the hollow test part 2 is damaged when the same test is performed is calculated to be 1355 hours. From the above, as described above, it can be seen that contact fatigue damage can be caused to the test component in a shorter time than usual, that is, with high efficiency due to the influence of hydrogen being charged. In such a short time, it is easy to detect and record the change over time of the vibration signal described above throughout the test time. Therefore, changes in the signal until contact fatigue damage occurs, changes in the signal at the time of occurrence of the damage, and the like can be recorded in detail. As a result, it is possible to construct a highly reliable method for detecting contact fatigue damage based on such signal changes.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is particularly excellent as a technique for detecting a change point occurring on a component at the moment when contact fatigue damage occurs, that is, a signal representing the change with high accuracy and in a short time with high efficiency.

It is a flowchart which shows the procedure of the process of the detection method in embodiment of this invention. It is the schematic which shows the shape of the test components in embodiment of this invention. It is the schematic which shows the state driven by rotation in the state which mutually contacted the test parts of the drive side and the driven side. It is the schematic which shows the state which charges the components for a test by electrolysis. It is the schematic which shows the state which charges hydrogen to the test components by immersing in aqueous solution. It is the schematic which shows the condition which detects the signal of the temperature of a hollow test component. It is the schematic which shows the condition which detects the signal of the sound which a hollow test component generates.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Cylindrical test part, 2 hollow test part, 3 driving side test part, 4 driven side test part, 5 solution, 6 aqueous solution, 7 radiation thermometer, 8 ultrasonic microphone.

Claims (9)

It is a detection method that detects changes over time that occur when contact fatigue damage occurs in a bench test of steel parts.
Charging the steel part with hydrogen;
Detecting a signal output in a process in which the steel part charged with hydrogen generates contact fatigue damage. In the process of charging the steel parts with hydrogen,
The detection method according to claim 1, wherein the steel part is charged with hydrogen by electrolysis in a solution obtained by adding thiourea as a catalyst poison to a dilute sulfuric acid aqueous solution.   The detection method according to claim 2, wherein the concentration of the thiourea in the solution is 1.2 g / L or more and 1.4 g / L or less. In the process of charging the steel parts with hydrogen,
The detection method according to claim 1, wherein the steel part is charged with hydrogen by electrolysis in a solution obtained by adding ammonium thiocyanate as a catalyst poison to an aqueous sodium chloride solution.   The detection method according to claim 4, wherein a concentration of the ammonium thiocyanate in the solution is 2.5 g / L or more and 3 g / L or less. In the process of charging the steel parts with hydrogen,
The detection method according to claim 1, wherein the steel part is charged with hydrogen by electrolysis in a solution obtained by adding sodium sulfide nonahydrate as a catalyst poison to an aqueous sodium hydroxide solution.   The detection method according to claim 6, wherein the concentration of the sodium sulfide nonahydrate in the solution is 0.8 g / L or more and 1 g / L or less. In the process of charging the steel parts with hydrogen,
The detection method according to claim 1, wherein the steel part is charged with hydrogen by being immersed in an aqueous solution of ammonium thiocyanate.   The detection method according to claim 8, wherein the concentration of ammonium thiocyanate in the solution is 5% by mass or more and 20% by mass or less.

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