JP2013015367A - Method and device for estimating relative superiority of internally originated flaking life of rolling contact metal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the relative superiority or inferiority of the internal origin type peeling life of a metal material having high shear fatigue strength that comes into rolling contact with a rolling bearing steel or the like from the result of a short-term torsional fatigue test. Provided are a method, an estimation device, and an estimation system for a relative superiority or inferiority of a starting-type peel life.
A method for estimating relative superiority or inferiority includes a test process (S1), a shear fatigue life determination process (S2), and a relative superiority / inferiority estimation process (S3). In the test process (S1), the relationship between the shear stress amplitude of the metal material and the number of loads is obtained by an ultrasonic torsional fatigue test. In the shear fatigue life determination process (S2), the shear fatigue life in the time strength region is determined from the relationship between the shear stress amplitude and the number of loads. In the relative superiority or inferiority estimation process (S3), it is presumed that the determined metal material having an excellent shear fatigue life is excellent in the relative superiority of the internal origin type peeling life.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a method and an apparatus for estimating the relative superiority or inferiority of an internal origin type peeling life of a rolling contact metal material. The present invention relates to a method and an apparatus for estimating the relative superiority or inferiority of an internal starting type peeling life of a machine element, and a bearing material selection method using this estimation method.

It is thought that the internal origin type delamination of rolling bearings is caused by the occurrence and propagation of cracks by repeated alternating shear stress (almost both swings) with the maximum amplitude inside the surface layer. In the case of a tensile compression fatigue test (axial load fatigue test, rotary bending fatigue test), it is customary to set the fatigue strength at 10 ⁷ times as the fatigue limit. On the other hand, in the case of rolling bearings with good lubrication conditions, even if a considerably high load is applied, the internal starting type separation does not occur at a load frequency of about 10 ⁷ times. There are torsional fatigue test as a test for fatigue fracture at a shear stress (e.g., Non-Patent Document 1), load the frequency of the hydraulic servo type torsional fatigue test is at most 10 Hz, for example, to reach ¹⁰⁹ times the load number It takes more than 3 years and evaluation is impossible.
Conventionally, in order to evaluate the internal origin-type peel life within a finite time, the maximum contact surface pressure of 5 GPa or more, which greatly exceeds the actual use conditions, has been evaluated. In the prior art, a maximum contact surface pressure of 5.88 GPa is given (for example, Patent Document 1). Even in that case, the internal origin type peeling life (for example, 10% life or 50% life) is on the order of 10 ⁷ to 10 ⁸ times.

Japanese Patent No. 4459240

Morimoto Hiroo and Matsubara Yukio, Tribology Conference Proceedings, (Tokyo 2007-5), 145-146.

  Rolling bearings are effective for improving efficiency and reliability if a rapid torsional fatigue test is performed for each supplier of materials used, lots, and the like to estimate the relative superiority or inferiority of the internal origin-type peel life. However, in the prior art, as described above, the torsional fatigue test requires a long period of time, and it is practically impossible to estimate the relative superiority or inferiority of the internal origin type peeling life of the material used.

  The object of the present invention is to provide a rolling contact metal that can estimate the relative inferiority of the internal origin type peeling life of a metal material having high shear fatigue strength that is in rolling contact with rolling bearing steel or the like from the results of a short-term torsional fatigue test. An object is to provide a method, an estimation device, and an estimation system for a relative superiority or inferiority of an internal origin type peeling life of a material.

The method of estimating the relative superiority of the internal origin type peeling life of the rolling contact metal material of the present invention is a method of estimating the relative superiority of the internal origin type peeling life of the metal material in rolling contact,
A test process (S1) for determining the relationship between the shear stress amplitude of metal material and the number of loads by an ultrasonic torsional fatigue test;
A shear fatigue life determination process (S2) for determining a shear fatigue life in a time strength region from the relationship between the obtained shear stress amplitude and the number of loads, according to a predetermined standard,
Relative superiority / inferiority estimation process (S3) in which the metal material having an excellent shear fatigue life determined in the shear fatigue life determination process (S2) estimates that the internal origin type peeling life is excellent in relative superiority.
including.
The ultrasonic torsional fatigue test is preferably a full-twisted torsional fatigue test that gives torsional vibration in which the torsion in the normal rotation direction and the reverse rotation direction is symmetric with respect to the test piece. The metal material may be a rolling bearing steel used as a bearing ring or rolling element of a rolling bearing.

The above-mentioned “relative superiority / inferiority of internal origin-type peeling life” means that the internal origin-type peeling life is relatively higher than the metal material to be compared among a plurality of metal materials, even if the internal origin-type peeling life is not indicated as a numerical value. Say whether is good for long or inferior or short. The metal material to be compared is arbitrarily determined.
The “specified standard” used in the process of determining the shear fatigue life is, for example, a curve obtained by fitting the relationship between the shear stress amplitude of the test result and the number of loads to the established theoretical curve indicating the shear fatigue characteristics. The shear fatigue life is determined from the curve. Specifically, it is possible to use an SN diagram (fracture probability 50%) 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 for Materials. . The SN diagram may be obtained by applying not only to the fatigue limit type broken line model but also to a continuously decreasing curve model. The shear fatigue life may be the life that intersects the above curve at any shear stress amplitude. To compare the relative merits of shear fatigue life from high to low shear fatigue strength in a unified manner, the shear stress amplitude However, it is preferable to obtain the shear fatigue life at 700 MPa or more and 800 MPa or less.
The “time strength region” in the process of determining the shear fatigue life refers to an oblique portion of the SN diagram of FIG. 1C, that is, a finite life region.

  According to the method of the present invention, since the fatigue test is performed by the ultrasonic torsional fatigue test, an extremely high-speed load is possible, and the relationship between the shear stress amplitude and the number of loads up to the ultra-long life region of the metal material can be obtained in a short time. it can. From the relationship thus obtained, the shear fatigue life at an arbitrary shear stress amplitude is determined. In the relative superiority or inferiority estimation process, it can be estimated that the metal material having the excellent shear fatigue life is superior in the relative superiority of the internal origin type peeling life.

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. On the other hand, there has been little research on ultrasonic torsional fatigue tests to evaluate fatigue characteristics due to shear stress at high speed, and the materials evaluated so far have a maximum shear stress amplitude (full swing) of 250 MPa or less. It is a mild steel or aluminum alloy that undergoes fatigue failure. On the other hand, the fatigue limit surface pressure of the rolling bearing defined in ISO-281: 2007, which is the standard of the dynamic load rating and rated life of the rolling bearing, is 1500 MPa. The maximum alternating shear stress amplitude acting on τ ₀ = 375 MPa. Therefore, an ultrasonic torsion tester that can be evaluated with a maximum shear stress amplitude of 375 MPa or more is required, but there is no example of an ultrasonic torsion tester that can be evaluated with such a large maximum shear stress amplitude. Therefore, the present invention has been made by the idea of developing an ultrasonic torsion tester.

  In the method of the present invention, in the test process, the ultrasonic torsional fatigue test is performed a plurality of times to obtain a plurality of relationships between the shear stress amplitude of the metal material and the number of loads, and in the shear fatigue life determination process, the plurality of times A PSN diagram having an arbitrary failure probability may be obtained from the relationship between the shear stress amplitude obtained during the test process and the number of loads, and the shear fatigue life may be determined from the PSN diagram.

  In the method of the present invention, the ultrasonic torsional fatigue test includes, for example, a torsional vibration converter that generates a torsional vibration that rotates forward and backward around a rotation center axis when AC power is applied, and a test piece concentrically at the tip. A mounting portion to which the torsional vibration converter is attached at the base end, and an amplitude expanding horn for expanding the amplitude of the torsional vibration of the torsional vibration converter applied to the base end. The shape and size resonate with the vibration of the amplitude-amplifying horn driven by the torsional vibration converter, the shearing fatigue is generated by driving the torsional vibration converter at a frequency in the ultrasonic region and resonating the test piece with the vibration of the amplitude-amplifying horn. Do by destroying.

In the method of the present invention, in the test process, the test piece may be forcibly air-cooled in order to suppress heat generation of the metal material test piece in the ultrasonic torsional fatigue test. Moreover, in order to suppress the heat generation of the test piece, the load and the pause may be alternately repeated. In the test process, a continuous load may be applied in a low load region where heat generation of the test piece of the metal material does not become a problem in the ultrasonic torsional fatigue test. You may use the amplitude expansion horn whose magnification rate which is a ratio with respect to the twist angle of the large diameter side end surface with respect to the twist angle of the small diameter side end surface is 43 times or more.
In the present invention, an ultrasonic torsional fatigue test capable of applying a load at high speed is used. For example, an ultrasonic torsional fatigue test with an extremely high excitation frequency of 20000 Hz is performed. As a result, if the vibration is continuously applied, the load number reaches 10 ⁹ times in just half a day. However, when the sample is continuously vibrated with a somewhat high shear stress amplitude, the test piece generates heat, and it is impossible to obtain a precise relationship between the shear stress amplitude and the number of loads. Therefore, it is preferable to forcibly air-cool the test piece. If the heat generation of the test piece is not sufficiently suppressed by forced air cooling alone, it is preferable to alternately repeat excitation and pause. Although the actual load frequency is reduced by resting, if an ultrasonic torsional fatigue tester with an excitation frequency of 20000 Hz is used, the suspension time is about 2000 Hz even if the suspension time is about 10 times the excitation time. Reach 10 ⁹ loads in the day.

  The method for selecting a rolling bearing material according to the present invention is such that the shear fatigue life in the time strength region determined by the method of estimating the relative superiority or inferiority of the internal origin type peeling life of any one of the above-described configurations of the present invention is determined. The metal material as described above is used as a material for a bearing ring or rolling element of a rolling bearing.

  According to the method for estimating the relative superiority of the internal origin type peeling life of the present invention, the shear fatigue life in the time strength region of the metal material for rolling bearing can be accurately determined from the result of the short-time fatigue test. Therefore, the shear fatigue life in the time strength region can be adopted as one of the test items of the material used for the bearing ring or rolling element of the rolling bearing. By using only a material having a shear fatigue life in a time strength region determined by an actual fatigue test that is equal to or greater than a predetermined shear fatigue life as a bearing material, it greatly helps to improve the reliability of the rolling bearing. In addition, what is necessary is just to set "the defined shear fatigue life" used as a criterion suitably according to the objective. Moreover, estimation of the relative superiority or inferiority of the internal origin-type peel life is performed, for example, for each lot of material, for each purchased amount, for each purchaser, or the like.

The apparatus for estimating the relative superiority of the internal origin type peeling life of the rolling contact metal material in this invention is an apparatus for determining the shear fatigue life in order to estimate the relative superiority of the internal origin type peeling life of the metal material in rolling contact,
An input means 22 for storing the relationship between the shear stress amplitude of the metal material and the number of loadings in a predetermined storage area by a complete double-sided ultrasonic torsional fatigue test;
A shear fatigue life determining means 23 for determining a shear fatigue life in a time strength region from the relationship between the stored shear stress amplitude and the number of loads, according to a predetermined standard;
Is provided.
The metal material may be a rolling bearing steel used as a bearing ring or rolling element of a rolling bearing. The input means 22 uses, for example, an input device that performs manual input such as a keyboard, a reading device for a recording medium, a communication network, and the like, for example, a file that summarizes the relationship between the shear stress amplitude of the metal material and the number of loads. It is a means for memorize | storing so that a predetermined | prescribed storage area or its memory | storage location can be specified for later calculation.

According to the apparatus of the present invention, the ultrasonic torsional fatigue test capable of extremely high speed load can be used as described for the method of the present invention, and the shear stress amplitude and load frequency of the rolling bearing steel can be measured in a short period of time. By obtaining the relationship, the shear fatigue life in the time strength region can be determined with high accuracy.
The shear stress amplitude in the shear fatigue life determining means 23 is, for example, 700 MPa or more and 800 MPa or less.

  In the present invention device, the input means 22 has a function of storing the relationship between the shear stress amplitude of the metal material and the number of loads obtained in each ultrasonic torsional fatigue test in a plurality of times in a predetermined storage area, The shear fatigue life determining means 23 obtains a PSN diagram having an arbitrary fracture probability from the relationship between the shear stress amplitude and the number of loads in the plurality of tests, and from this PSN diagram, It may determine the fatigue life.

The system for estimating the relative superiority of the internal origin type peeling life of a rolling contact metal material according to the present invention is an ultrasonic torsional fatigue testing machine main body that performs a complete double swing ultrasonic torsional fatigue test on a test piece 1 of a metal material in rolling contact. 3, a testing machine control device 4 for controlling the ultrasonic torsional fatigue testing machine main body 3 in accordance with input test conditions, and a relative superiority / inferiority estimation device 5 for the internal origin type peeling life of any of the above-described configurations of the present invention. It is a system equipped with.
In this system as well, the ultrasonic torsional fatigue test capable of extremely high-speed loading can be used as described for the method of the present invention, and the shear stress amplitude and the number of loads of rolling bearing steel can be measured in a short period of time. By obtaining the relationship, the shear fatigue life in the time strength region can be determined with high accuracy.

  The estimation method, estimation apparatus, and estimation system for the internal origin-type peel life of rolling contact metal materials according to the present invention determine the relationship between the shear stress amplitude of metal materials and the number of loads by an ultrasonic torsional fatigue test. The ultrasonic torsional fatigue test capable of various loads can be used, and even for metal materials with high fatigue strength such as rolling bearing steel, the relationship between the shear stress amplitude and the number of loads is obtained in a short period of time, and the time strength The shear fatigue life in the region can be determined with high accuracy. It can be presumed that the metal material with the excellent shear fatigue life is excellent in the relative superiority of the internal origin-type peel life, and from the results of the short-term torsional fatigue test, the steel for rolling bearings, etc. It is possible to estimate the relative superiority or inferiority of the internal origin type peeling life of a metal material having a high shear fatigue strength in contact with rolling.

  In the method for selecting a rolling bearing material according to the present invention, the relative superiority or inferiority of the shear fatigue life estimated by the method for estimating the relative superiority or inferiority of the shear fatigue life of any of the above-described configurations of the present invention is equal to or greater than the predetermined shear fatigue life. Since the metal material is used as the material for the bearing ring or rolling element of the rolling bearing, the reliability of the rolling bearing can be improved by adopting test items that were not previously conceived.

(A) is a flowchart showing a method for estimating the relative superiority or inferiority of the internal origin type peeling life according to one embodiment of the present invention, (B) is a schematic diagram of an estimation system for the relative superiority or inferiority of the internal origin type peeling life, (C) These are explanatory drawing which shows a SN diagram and a shear fatigue life. It is a block diagram of the estimation system of the relative superiority of the internal origin type | mold peeling life. It is a conceptual diagram of a testing machine controller and an internal origin type peeling life relative superiority estimation device in the internal origin type peeling life relative quality estimation system. It is a block diagram which shows the conceptual structure of the estimation apparatus of the relative dominance of an internal origin type | mold peeling life. It is a front view of the main body of an ultrasonic torsional fatigue testing machine. It is a schematic diagram of a test piece. It is a front view of a test piece. It is a graph which shows axial direction distribution of torsion angle (theta) and surface shear stress (tau) (when 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. 10, and end surface twist angle | corner (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 graph which shows the relationship between the shear stress amplitude obtained by the ultrasonic torsional fatigue test, and the number of loads, the SN diagram (solid line), and the PSN diagram (broken line) having a fracture probability of 10% obtained therefrom. Explanation of distribution of alternating shear stress τ _yz and normal stress σ _{z in} the depth direction (y: circumferential direction, z: depth direction) when P _max = 1500 MPa acts in the line contact state FIG. It is the microscope picture of the circumferential cross section which shows the micro crack parallel to the surface seen around the depth where the absolute value of an alternating shear stress becomes the maximum. It is explanatory drawing which shows the example of a test condition input screen of the control apparatus of an ultrasonic torsional fatigue testing machine. 5 is a flowchart of details of a test process. It is a schematic diagram of the fatigue test result regarding how to determine the fatigue limit type broken line SN diagram. It is a schematic diagram which shows that the intensity distribution in arbitrary load frequency | counts follows a normal distribution, and a standard deviation is the same. This is a method for obtaining a PSN diagram (in the case of a continuous decline type curve model, the destruction probability is 10%). (A) is a figure which shows the heat pattern of the induction hardening of S53C raw material, (B) is a figure which shows the heat pattern of the tempering of the same material. (A) is a front view of a test piece schematically showing an induction hardening pattern, and (B) is a side view of the test piece. It is a figure which shows the shear fatigue characteristic of the test piece of SUJ2 submerged hardening, M50NiL carburization, and S53C induction hardening. It is a schematic diagram of a rolling fatigue life tester. It is a figure which shows the relationship of the internal origin type | mold peeling life and shear fatigue life of SUJ2 submerged hardening, M50NiL carburizing, and S53C induction hardening.

  An embodiment of the present invention will be described with reference to the drawings. The following description also includes an explanation of a method for selecting a rolling bearing material. The method for estimating the relative superiority of the internal origin type peeling life of the rolling contact metal material is a method for estimating the relative superiority of the internal origin type peeling life of the metal material in rolling contact, as shown in FIG. The metal material having an excellent shear fatigue life determined in the test process (S1), the shear fatigue life determination process (S2), and the shear fatigue life determination process (S2) has a relative superiority or inferiority in the internal origin type peeling life. And a relative superiority / inferiority estimation process (S3) for estimating that it is excellent. The metal material is, for example, rolling bearing steel used as a bearing ring or rolling element of a rolling bearing, but in addition to this, it can be generally applied to metal materials used for machine elements that are in rolling contact.

  The test process (S1) is a process of obtaining the relationship between the shear stress amplitude of the metal material and the number of loads by a complete double-sided ultrasonic torsional fatigue test. In this test, an ultrasonic torsional fatigue testing machine 2 that applies a complete double-sided ultrasonic torsional vibration to the metal material test piece 1 shown in FIG. The ultrasonic torsional fatigue tester 2 uses an extremely high-speed ultrasonic torsional fatigue test (complete double swing) with an excitation frequency of 20000 Hz. This ultrasonic torsional fatigue testing machine 2 cannot be used as it is, and has various improvements.

  In the shear fatigue life determination process (S2), the shear fatigue life in the time strength region is determined according to a predetermined standard from the relationship between the shear stress amplitude and the number of loads obtained in the test process (S1). The above-mentioned “specified standard” in the shear fatigue life determination process (S2) is, for example, a curve obtained by fitting the relationship between the shear stress amplitude of the test results and the number of loads to an established theoretical curve indicating the shear fatigue strength. And the shear fatigue strength is determined from the curve. Specifically, the SN diagram (fracture probability 50%) obtained by applying to the fatigue limit type broken line model of JSMS-SD-6-02 of the Japan Society of Materials Fatigue Reliability Evaluation Standard (figure (C )) Can be used. The SN diagram may be obtained by applying not only to the fatigue limit type broken line model but also to a continuously decreasing curve model. The shear fatigue life may be a life intersecting with the above curve in the time strength region, but in order to relatively compare the superiority and inferiority of the shear fatigue life from high to low shear fatigue strength, the shear stress amplitude is 700 MPa. The shear fatigue life at 800 MPa or less is preferably obtained.

ここで、Ａ、Ｂ、Ｄは定数である。
疲労強度、疲労寿命にはバラツキがある。本来、確率疲労特性は、複数の応力振幅で複数個の試験片を評価し、ある破壊確率におけるＰ−Ｓ−Ｎ線図を求めて評価する。しかしながら、Ｐ−Ｓ−Ｎ線図を求めるには多大な工数と時間を要する。金属材料疲労信頼性評価標準ＪＳＭＳ−ＳＤ−６−０２では、Ｓ−Ｎ線図から任意の破壊確率におけるＰ−Ｓ−Ｎ線図を求める方法が提案されている。それは、図２０のように、任意の疲労寿命における強度分布は正規分布に従い、その標準偏差σは一定と仮定する。得られたＳ−Ｎ線図を破壊確率５０％の疲労強度曲線とする。疲労限度型折れ線モデルでは時間強度部（傾斜直線部）の破損データ、連続低下型曲線モデルは全範囲の破損データを対象とする。図２１は連続低下型曲線モデルの例である。直線または曲線に沿って個々の破損データを任意の疲労寿命に平行移動し、それらが正規分布するとして標準偏差を求める。例えば、得られた標準偏差をｓとすると、破壊確率５０％の疲労強度曲線を１．２８２ｓだけ下に平行移動したものが破壊確率１０％のＰ−Ｓ−Ｎ線図となる。 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, regresses by applying the following equation.
σ = −Alog ₁₀ N + B (N <N _W )
σ = E (N ≧ N _W )
Here, A, B, E, and _Nw are constants. The fatigue limit (E in the above equation) is estimated as follows when there is one or more censored data at a load count of N = 5 × 10 ⁶ or more. An average value of the fracture data stress minimum value σ _{f min} and the censored data stress maximum value σ _{r max} lower than this is defined as the fatigue limit (see FIG. 19). If censored data exists at the same stress level as σ _{f min} and there is no censored data at a stress level lower than this, this σ _{f min} is used as the fatigue limit. After determining the fatigue limit in this way, this value is fixed and other parameters in the above equation are estimated from only the fracture data.
The continuously decreasing curve model is regressed by applying the following equation which is a basic equation of Stromeyer.

Here, A, B, and D are constants.
There are variations in fatigue strength and fatigue life. Originally, the probability fatigue characteristic is evaluated by evaluating a plurality of test pieces with a plurality of stress amplitudes and obtaining a PSN diagram at a certain fracture probability. However, it takes a lot of man-hours and time to obtain the PSN diagram. In the metal material fatigue reliability evaluation standard JSMS-SD-6-02, a method for obtaining a PSN diagram at an arbitrary fracture probability from an SN diagram is proposed. As shown in FIG. 20, it is assumed that the strength distribution in an arbitrary fatigue life follows a normal distribution and that the standard deviation σ is constant. Let the obtained SN diagram be a fatigue strength curve with a fracture probability of 50%. In the fatigue limit type broken line model, the damage data of the time-strength part (inclined straight line part), and in the continuous decline type curve model, the damage data of the whole range are targeted. FIG. 21 is an example of a continuously decreasing curve model. Translate individual failure data along a straight line or curve to any fatigue life and determine the standard deviation as they are normally distributed. For example, when the obtained standard deviation is s, a P-S-N diagram with a fracture probability of 10% is obtained by translating a fatigue strength curve with a fracture probability of 50% downward by 1.282s.

  According to the estimation method of this embodiment, since the fatigue test is performed by an ultrasonic torsional fatigue test, an extremely high-speed load is possible, and the relationship between the shear stress amplitude of the metal material and the number of loads can be obtained in a short time. The shear fatigue life is determined from the relationship thus obtained. And, for example, based on the correlation shown in FIG. 26, it can be estimated that the metal material having the determined shear fatigue life is excellent in relative superiority of the internal origin type peeling life, and the result of the torsional fatigue test. Therefore, it is possible to accurately estimate the relative superiority of the internal origin type peeling life. For this reason, when estimating the relative superiority or inferiority of the internal origin type peeling life of the rolling bearing steel, which is a material having a strong shear fatigue life, the effect that only a short test is required is more effectively exhibited. .

In this embodiment, as described above, the relationship between the shear stress amplitude of the rolling bearing steel and the number of loads is determined in a short period of time by an ultrasonic torsional fatigue test with an extremely high excitation frequency of 20000 Hz and a very high speed. The shear fatigue life in the strength region is determined, and the relative superiority or inferiority of the internal origin type peel life is estimated. For example, if the vibration continuous pressurization at 20000 Hz, and reaches the slight load times at ¹⁰⁹ half day or so. However, since the test piece 1 generates heat when continuously vibrated with a somewhat high shear stress amplitude, the test piece 1 needs to be cooled and forced air cooling is performed. If the heat generation of the test piece 1 is not sufficiently suppressed by forced air cooling alone, vibration and pause are alternately repeated. Although the actual load frequency is reduced by resting, if the tester 2 has an excitation frequency of 20000 Hz, it is still about 2000 Hz even if the stop time is about 10 times the excitation time, and it is still over 6 days. 10 The number of loads reaches ⁹ times.

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. On the other hand, there has been little research on ultrasonic torsional fatigue tests to evaluate fatigue characteristics due to shear stress at high speed, and materials evaluated so far have a maximum shear stress amplitude (full swing) of 250 MPa or less. It is a mild steel or aluminum alloy that undergoes fatigue failure. On the other hand, the fatigue limit surface pressure of the rolling bearing defined in ISO-281: 2007, which is the standard of the dynamic load rating and rated life of the rolling bearing, is 1500 MPa. The maximum alternating shear stress amplitude acting on τ ₀ = 375 MPa. Therefore, an ultrasonic torsion tester that can be evaluated with a maximum shear stress amplitude of 375 MPa or more is required, but there is no example of an ultrasonic torsion tester that can be evaluated with such a large maximum shear stress amplitude. Therefore, the present invention has been made by the idea of developing an ultrasonic torsion tester.

The method for selecting a rolling bearing material of this embodiment is a metal material having a shear fatigue life estimated by a method for estimating the relative superiority or inferiority of the internal origin type peeling life of any one of the above-described structures, which is equal to or greater than a predetermined shear fatigue life. It is used as a material for a bearing ring or rolling element of a rolling bearing.
According to the method for estimating the relative superiority of the internal origin type peeling life of this embodiment, the shear fatigue life in the time strength region of the metal material for rolling bearing can be determined with high accuracy from the result of the short-time fatigue test. Therefore, the shear fatigue life in the time strength region can be adopted as one of the test items of the material used for the bearing ring or rolling element of the rolling bearing. By using only a material whose shear fatigue life in the time strength region obtained by actual fatigue tests is equal to or greater than a predetermined shear fatigue life as a bearing material, it greatly helps to improve the reliability of the rolling bearing. In addition, what is necessary is just to set "the defined shear fatigue life" used as a criterion suitably according to the objective. Moreover, estimation of the relative superiority or inferiority of the internal origin-type peel life is performed, for example, for each lot of material, for each purchased amount, for each purchaser, or the like.

  FIG. 2 shows a conceptual configuration of a system for estimating the relative superiority or inferiority of the internal origin type peeling life of the rolling contact metal material used in the estimation method. This estimation system includes an ultrasonic torsional fatigue testing machine 2 and an internal origin type peeling life estimation device 5 that performs the process of the shear fatigue life determination process (S2) of FIG.

  In FIG. 2, the ultrasonic torsional fatigue testing machine 2 includes a testing machine main body 3 and a testing machine control device 4. The testing machine main body 3 is attached to a torsional vibration converter 7 installed on the upper part of the frame 6 with an amplitude-amplifying horn 8 projecting downward, and a test piece 1 is detachably attached to the tip thereof, and The sound wave vibration is expanded and transmitted to the test piece 1 as vibration in the forward / reverse rotation direction around the axis of the amplitude expansion horn 8.

The test machine control device 4 includes a computer 10 and a test machine control program 11 that can be executed by the computer 10. The computer 10 is a desktop personal computer or the like, and includes a central processing unit 12, storage means 13 such as a memory, and an input / output interface 14. The tester control program 11 is stored in the storage means 13, and the remaining storage area of the storage means 13 becomes a data storage area 13a or a work area. In addition, an input device 15 such as a keyboard and a mouse, and a display device such as a liquid crystal display device and an output device 16 such as a printer are provided as a part of the computer 10 or connected to the computer 10. ing.
The test machine control device 4 is a device that controls the torsional vibration converter 7 of the test machine body 3, and a control output is given from the input / output interface 14 to the vibration converter 7 via the amplifier 17. The test machine control device 4 performs the following processing according to the test machine control program 11. First, as shown in an example screen in FIG. 17, a display device serving as an output device 16 displays a screen that prompts input of test conditions (output, intermittent operation or continuous operation, test end conditions, data collection conditions, etc.). When the test condition is input from the input device 15 and a test start command is input, the tester body 3 is driven and controlled according to the input condition. The value of the maximum shear stress amplitude is converted and displayed by the later-described equation (9) with respect to the input amplifier output P (%).

  In FIG. 2, the internal origin-type peeling life relative dominance estimation apparatus 5 includes a computer 10 and an internal origin-type peeling life relative dominance estimation program 19 that can be executed by the computer 10. The computer 10 may be the same as or different from the computer constituting the tester control device 4, and includes a central processing unit 12, storage means 13 such as a memory, and an input / output interface 14. . The input device 15 and the output device 16 are provided as a part of the computer 10 or connected to the computer 10. FIG. 3 shows that the tester control program 11 and the internal origin-type peel life relative dominance estimation program 19 are stored in the same computer 10 to provide a tester control device and internal origin-type peel life relative reliance superiority estimation device 9. An example is shown.

  The internal origin-type peeling life relative dominance estimation device 5 includes a computer 10 and the internal origin-type separation life relative dominance estimation program 19, which are configured by means shown in FIG. This internal origin type peeling life relative estimator 5 is a device for determining the shear fatigue life in order to estimate the internal origin type peel life relative superiority of the metal material in rolling contact, and includes an input means 22, shear fatigue. A life determining means 23 is provided, and a storage means 13 and an output means 4A are configured.

The input means 22 is a means for storing the relationship between the shear stress amplitude of the metal material and the number of loads obtained by a complete double swing ultrasonic torsional fatigue test in a predetermined storage area of the storage means 13. The input means 22 is a file that summarizes the relationship between the shear stress amplitude of the metal material and the number of loads, for example, using an input device for manual input such as a keyboard, a reading device for a recording medium, a communication network, etc. Is stored so that a predetermined storage area or its storage location can be specified for later calculation.
The shear fatigue strength determining means 23 is means for determining the shear fatigue life in the time strength region according to a predetermined standard from the relationship between the shear stress amplitude stored in the storage region and the number of loads.

  Next, the details of the ultrasonic torsional fatigue testing machine 2 and the details of the method for estimating the relative superiority or inferiority of the internal origin type peeling life will be described. This ultrasonic torsional fatigue testing machine 2 is designed as a complete double swing ultrasonic torsional fatigue testing machine that gives shear fatigue to rolling bearing steel at an extremely high speed. The excitation frequency range of the torsional vibration converter 7 is 20000 ± 500 Hz. Note that while there are various types of longitudinal vibration converters used in the ultrasonic axial load fatigue test, commercially available torsional vibration converters have only low output, and it is virtually impossible to make them yourself. It was. Therefore, it is necessary to optimize the shapes of the amplitude expanding horn 8 and the test piece 1 to give torsional fatigue to the high-strength rolling bearing steel.

The amplitude expansion horn 8 is of an exponential function type, and the diameter of the large-diameter side end face fixed to the torsional vibration converter 7 is 38 mm, and the diameter of the small-diameter side end face fixing the test piece 1 is 13 mm. It is designed and adjusted so that the enlargement ratio (ratio of the torsion angle on the small diameter side to the torsion angle on the large diameter side) is as large as possible and resonates near 20000 Hz. The large-diameter end face of the amplitude expanding horn 8 is provided with a male thread portion protruding in the axial direction for fixing to the torsional vibration converter, and the small-diameter end face is provided with a female thread for fixing the test piece. ing. The material of the amplitude expanding horn 8 is a titanium alloy. 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 was 43.1 times.

FIG. 6 shows a schematic diagram of the test piece. One end of the actual test piece 1 is provided with a male screw portion for fixing to the tip of the amplitude expanding horn 8. In FIG. 6, the test piece 1 is a dumbbell type, and is determined by a shoulder length L ₁ , a half chord length L ₂ , a shoulder radius R ₂ , a minimum radius R ₁ , and an arc radius R.

In designing the test piece 1, a half chord length L ₂ , a shoulder radius R ₂ , and a minimum radius R ₁ are appropriately given (the unit is m), a resonance frequency f (= 20000 Hz), Young's modulus E, Poisson In addition to the ratio ν and density ρ (measured values of the standard heat-treated bearing steel SUJ2 are E = 2.04 × 10 ¹¹ Pa, ν = 0.29, ρ = 7800 kg / m ³ ), the following equations (1) to (6) shoulder length L ₁ is obtained by substituting the equation (in m). The arc radius R is obtained from R ₁ , R ₂ and L ₂ .

Here, L ₂ = 0.0065 m, R ₂ = 0.0045 m, and R ₁ = 0.002 m, which have been studied in advance so that as much shear stress as possible acts on the surface of the minimum diameter portion of the test piece, the above f, E , Ν, and ρ together with (1) to (6), L ₁ = 0.00753 m. However, when a test piece with L ₁ = 0.00753 m was manufactured using standard hardened and tempered bearing steel SUJ2, no resonance occurred. Therefore, eigenvalue analysis of free torsional resonance was performed using FEM analysis software (Marc Mentat 2008 r1) (registered trademark) with f, E, ν, and ρ as physical property values. As a result, the frequency of torsional resonance at L ₁ = 0.00753 m was 19067 Hz, which was outside the excitation frequency range of 20000 ± 500 Hz of the torsional vibration converter. Therefore, the result of obtaining the _{L 1} to torsional resonance at 20000 _Hz, became L 1 = 0.00677m. When a test piece with L ₁ = 0.00677 m was manufactured from the standard hardened and tempered bearing steel SUJ2, it resonated at around 20000 Hz. FIG. 7 shows a test piece drawing (unit: mm).
FIG. 8 shows a torsion angle θ and a surface shear stress τ obtained by eigenvalue analysis of free torsional resonance using the test piece model of FIG. FIG. 8 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 _end surface twist angle θ _end and the maximum shear stress τ _max of the surface at the minimum diameter portion of the test piece is as shown in Equation (7). However, the unit of τ _max is MPa, and θ _end is dimensionless.
τ _max = 52618θ _end (7)

Using three specimens 1 made of standard hardened and tempered bearing steel SUJ2 having the shape shown in FIG. 7, the torsion angle θ _{emd of the} end face was measured while changing the amplifier output P (%). Table 1 shows the alloy components of the specimen material. The hardness was 722HV. A SUJ2 material that has been subjected to quenching and tempering heat treatment may be referred to as a “SUJ2 standard”.

  A photograph of the lower end of the shoulder of the test piece during vibration was taken at 200 times with a digital microscope (VHX-900 manufactured by Keyence). Prior to that, emery polishing (# 500, # 2000) and diamond wrapping (1 μm) were applied to the shoulder of the test piece with a drilling machine to obtain a mirror surface state. After attaching the test piece to the testing machine, a color check developer was applied to the shoulder. FIG. 9 is a photograph at rest, where there are places where the developer is not applied. The behavior at the time of vibration was observed in the uncoated areas. In the case of FIG. 9, attention is paid to the behavior of the part with an arrow. The 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. 10 is a photograph taken during vibration with P = 50%, and the range 2a is the locus of the point of interest in FIG.

From the range 2a measured by changing the amplifier output P (%), the end surface torsion angle θ _end was determined as shown in FIG. As a result, as shown in FIG. 12, almost the same linear relationship was found between P and θ _{end in} all three test pieces 1, and the equation (8) was obtained as a regression line.

From the equations (7) and (8), the relationship between the amplifier output P and the maximum shear stress amplitude τ _max of the surface at the minimum diameter portion of the test piece is as shown in the equation (9). From equation (9), P = 90% and τ _max = 951 MPa, and it is sufficiently expected that torsional fatigue can be imparted to high-strength rolling bearing steel.

  The manufactured ultrasonic torsional fatigue tester 2 controls the amplifier 17 by the tester control device 4 configured by the personal computer 10 and the tester control program 11 described above with reference to FIG. FIG. 17 shows a screen for inputting test conditions of the ultrasonic torsional fatigue testing machine 2. 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. are performed.

  In the example of the input screen of FIG. 17, 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%. Is almost equal to According to this tester control device 4, when an amplifier output is input in the column of measurement conditions, it is converted into the maximum shear stress amplitude from the straight line slope and intercept of equation (9) input in advance on the initial setting screen. In the same column, select either continuous operation where vibration is continued or intermittent operation where vibration and pause are alternately repeated.

  When a crack occurs in the test piece 1 and grows to a certain size, the resonance frequency decreases. The reason why 50.00 is entered in the frequency fluctuation range in the same column is that the test is stopped as a result of fatigue failure 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. 13 shows an example of a test piece subjected to torsional fatigue failure. It shows that an axial shear crack occurred, grew to a certain length, then shifted to a tensile mold and deviated obliquely.

The bearing steel SUJ2 that was standard hardened and tempered in a normal temperature atmosphere was 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. The test piece is the same lot as that used for the above-mentioned end face twist angle measurement. The test was terminated if no damage occurred ¹⁰ times.

FIG. 14 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. 14 is an SN diagram (fracture probability 50%) obtained by applying to the fatigue limit type broken line model of the metal material fatigue reliability evaluation standard JSMS-SD-6-02 of the Japan Society of Materials Science. The shear fatigue life at a shear stress amplitude of 700 MPa was 5.703 × 10 ⁷ times. Note that the S—N diagram may be obtained by applying a continuous decline type curve model instead of the fatigue limit type line model.

  From the viewpoint of statistical factors, it is only necessary to perform multiple evaluations at multiple stress levels and obtain a PSN diagram. However, it will often be difficult to implement due to time constraints. In order to obtain the SN diagram of FIG. 14, the fatigue limit-type broken line model was applied using the metal material fatigue reliability evaluation standard JSMS-SD-6-02 of the Japan Society of Materials. It has a function to obtain a PSN diagram with a small number of data. The broken line in FIG. 14 is a PSN diagram with a 10% probability of destruction. Although the appropriate failure probability is 10% here, a reasonable failure probability should be considered by comparing the dangerous volume of the ultrasonic torsional fatigue test specimen with the dangerous volume of the actual rolling bearing. The intersection with the PSN diagram at an arbitrary shear stress amplitude may be the shear fatigue life.

  As described above, the relationship between the shear stress amplitude of the rolling bearing steel and the number of loads is determined by the ultrasonic torsional fatigue test (full swinging), and then the shear fatigue life in the time strength region is determined. A method for estimating superiority or inferiority is presented.

By the way, FIG. 15 shows the distribution of the alternating shear stress τ _{yz in} the circumferential cross section below the contact surface and the vertical stress σ _{z in} the depth direction when P _max = 1500 MPa acts in a line contact state (y: circumferential direction, z: depth direction). The coordinates are made dimensionless by the uniaxial radius b of the contact ellipse. The alternating shear stress τ _yz has a maximum absolute value at the depth of the dotted line. FIG. 16 shows a microcrack parallel to the surface seen near the depth at which the absolute value of the alternating shear stress is maximum when the rolling fatigue test is stopped before peeling occurs and the cross section in the circumferential direction is observed. . The driving force developed parallel to the surface is considered as alternating shear stress. In other words, the crack growth mode is mode II type (in-plane shear type). As shown in FIG. 16, since the normal stress σ _{z in the} direction perpendicular to the crack surface is compression, there is no mode I type (tensile type), and σ _z interferes between the crack surfaces, so mode II Acts to hinder progress.

  Shear fatigue life was determined by evaluating the shear fatigue properties of SUJ2 submerged quenching (quenching of the entire SUJ2 material), M50NiL carburization, and S53C induction hardening, and compared with the internally-originated peeling life.

Table 2 shows the alloy components of the SUJ2 material used for the test pieces.

Specimens were manufactured by sequentially turning the SUJ2 material shown in Table 2 above, followed by turning → heat treatment → grinding. The heat treatment conditions are heating (830 ° C. × 80 min, RX gas atmosphere) → oil quenching → tempering (180 ° C. × 180 min). The RX gas atmosphere is an atmospheric gas mainly composed of CO, H ₂ , and N ₂ that is obtained by mixing air into a hydrocarbon gas such as butane and methane, and then filling the catalyst and heating at a high temperature.

Table 3 shows the alloy components of the M50NiL material used for the test pieces.

  The M50NiL material shown in Table 3 was sequentially turned, heat treated, and ground to produce test pieces. Heat treatment conditions are carburization / diffusion (carburization: 960 ° C. × 15 h, RX gas atmosphere, carbon potential maintained at 1.2, diffusion: 960 ° C. × 74 h, RX gas atmosphere) → oil quenching → intermediate annealing (650 ° C. × 6 h ) → Furnace cooling → Secondary heating (850 ° C. × 40 min → 1090 ° C. × 25 min, vacuum) → Oil quenching → Subzero (−80 ° C. × 180 min) → Tempering (450 ° C. × 60 min → 550 ° C. × 180 min)

Table 4 shows the alloy components of the S53C material used for the test pieces.

  S53C materials shown in Table 4 were sequentially turned, heat treated, and ground to produce test pieces. The heat treatment in this case is induction hardening and tempering. FIG. 22A is a diagram showing a heat pattern of induction hardening of the S53C material, and FIG. 22B is a diagram showing a heat pattern of tempering the material. FIG. 23A is a front view of a test piece schematically showing an induction hardening pattern, and FIG. 23B is a side view of the test piece. The hatched portion in FIG. 23A is a schematic induction hardening pattern. As shown in FIG. 23A, the minimum diameter portion φdmin (φdmin is 4 mm) is fully cured. The burning escape width W (four corners) is 3 mm or less. You may burn out to the end face. The old γ grain size of the minimum diameter portion φdmin is set to about # 8.

  FIG. 24 is a diagram showing shear fatigue characteristics of test pieces of SUJ2 submerged quenching, M50NiL carburization, and S53C induction hardening. The solid line in the figure is an SN diagram obtained by fitting to the fatigue limit type broken line model of the metal material fatigue reliability evaluation standard JSMS-SD-6-02 of the Japan Society of Materials. Table 5 shows the number of loads at the intersection with the SN diagram at a shear stress amplitude of 700 MPa as the shear fatigue life of each steel type.

  Table 6 shows the average value of 50% life obtained by Weibull analysis as a rolling fatigue life test result of SUJ2 quenching (9 lots), M50NiL carburizing (3 lots), and S53C induction hardening (2 lots).

  In the rolling fatigue life test, although it depends on the steel type, some of the test numbers have surface-origin type short life peeling. The average value of 50% life shown in Table 6 above is an average of values obtained by Weibull analysis for each lot for only the internal origin type peeling. FIG. 25 shows a schematic diagram of a rolling fatigue life tester. The test piece has a cylindrical shape with a diameter of 12 mm and a length of 22 mm, and the cylindrical surface is superfinished. Table 7 shows the test conditions.

  This rolling fatigue life tester has a drive roll 24, three guide rolls 25, and two load balls 26. Each guide roll 25 can be rotated by bearings 28, 28 fitted to a shaft 27, and the respective shaft centers are supported in parallel. The axis of the drive roll 24 is also provided parallel to the axis of the guide roll 25. On the outer peripheral surface of each guide roll 25, an annular groove 25a having an arcuate cross section for holding a load ball is formed. Three guide rolls 25 are arranged close to each other, and each load ball 26 is guided over two adjacent guide rolls 25. A test piece W is interposed between the load ball 26 and the drive roll 24, and the drive roll 24 is driven to rotate based on test conditions, whereby the test piece W rolls.

  FIG. 26 is a graph in which the horizontal axis is the average value of 50% life shown in Table 6 and the vertical axis is the shear fatigue life shown in Table 5, and a good linear correlation is observed between them. An initial crack (see FIG. 13) generated in an ultrasonic torsional fatigue test piece and an initial crack (see FIG. 16) generated in a surface layer prior to internal origin-type peeling are cracks along the direction of shear stress action. Therefore, it is said that they are equivalent. Therefore, as shown in FIG. 26, it can be said that a good linear relationship was found between the average value of 50% life and the shear fatigue life. In FIG. 26, the internal origin type peel life is 50% life obtained by Weibull analysis, but 10% life may be used instead. In FIG. 26, the shear fatigue life is set to the number of loads at the intersection with the SN diagram when the shear stress amplitude is 700 MPa. Instead, the shear fatigue life is P− with an arbitrary fracture probability in the time strength region. The number of loads at the intersection with the SN diagram may be used.

In the ultrasonic torsional fatigue test, in addition to the SUJ2 standard, M50NiL carburization and S53C induction hardening were evaluated because the M50NiL carburization was longer and the S53C induction hardening was shorter than the SUJ2 standard internal origin type peeling life. It was because I knew it. As shown in FIG. 26, in order to relatively compare the three steel types in a unified manner, as can be seen from FIG. 24, the shear stress amplitude must be 700 MPa or more and 800 MPa or less.
In the ultrasonic torsion test, the shear stress is maximum at the surface of the minimum diameter portion of the specimen and zero at the center. Therefore, as shown in FIG. 13, the initial crack occurs on the surface of the test piece minimum diameter portion. Therefore, it is possible to evaluate surface modifying materials in a broad sense such as carburizing and quenching steel (currently M50NiL carburized and the like), induction hardening steel (currently S53C induction hardening and the like) as well as continuous quenching.

  In addition, by using an ultrasonic axial load fatigue testing machine (Shimadzu Corporation USF-2000, excitation speed 20000 Hz, full swing), the axial load fatigue characteristics of various hardened steels were obtained, and the vertical fatigue life in the time strength region Internal origin-type peel life was compared, but no correlation was found.

DESCRIPTION OF SYMBOLS 1 ... Test piece 2 ... Ultrasonic torsion fatigue testing machine 3 ... Test machine main body 4 ... Test machine control apparatus 5 ... Internal origin type peeling life relative dominance estimation apparatus 7 ... Torsional vibration converter 8 ... Amplitude expansion horn 10 ... Computer 11 ... Tester control program 17 ... Amplifier 19 ... Internal origin type peeling life relative superiority / inferiority estimation program 22 ... Input means 23 ... Shear fatigue life determination means

Claims (18)

A method for estimating the relative superiority or inferiority of the internal origin type peeling life of a metal material in contact with rolling,
A test process to obtain the relationship between the shear stress amplitude of metal materials and the number of loads by ultrasonic torsional fatigue test,
A shear fatigue life determination process for determining the shear fatigue life in the time strength region from the relationship between the obtained shear stress amplitude and the number of loads, according to a predetermined standard,
Relative superiority or inferiority estimation process in which the metal material having an excellent shear fatigue life determined in this shear fatigue life determination process estimates that the internal origin type peel life is superior in relative relative inferiority,
A method for estimating the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material containing.   2. The ultrasonic torsional fatigue test according to claim 1, wherein the ultrasonic torsional fatigue test is a full-twisted torsional fatigue test that gives a torsional vibration in which the torsion in the normal rotation direction and the reverse rotation direction is symmetrical with respect to the test piece. A method for estimating the relative superiority or inferiority of the internal origin-type peel life.   3. The method for estimating relative superiority or inferiority of an internal origin type peeling life of a rolling contact metal material, wherein the metal material is a steel for a rolling bearing to be a bearing ring or a rolling element of a rolling bearing.   4. The method for estimating the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material, wherein the shear stress amplitude in the shear fatigue life determination process is 700 MPa or more and 800 MPa or less in any one of claims 1 to 3.   5. The fatigue limit type broken line model indicating the shear fatigue strength according to claim 1, wherein the predetermined criterion for determining the shear fatigue life in the time strength region in the shear fatigue life determination process is a fatigue limit type broken line model indicating shear fatigue strength. A method to estimate the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material, which is a process for obtaining the shear fatigue life in the time strength region from the curve by obtaining a curve fitting the relationship between the shear stress amplitude and the number of loads in the test results .   5. The continuous criterion curve model according to claim 1, wherein the predetermined criterion for determining the shear fatigue life in the time strength region in the shear fatigue life determination process is a continuously decreasing curve model indicating the shear fatigue strength. A method to estimate the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material, which is a process for obtaining the shear fatigue life in the time strength region from the curve by obtaining a curve fitting the relationship between the shear stress amplitude and the number of loads in the test results .   7. The method according to claim 1, wherein in the test process, the ultrasonic torsional fatigue test is performed a plurality of times to obtain a plurality of relationships between the shear stress amplitude of the metal material and the number of loads, and the shear fatigue is performed. In the life determination process, a PSN diagram having an arbitrary failure probability is obtained from the relationship between the shear stress amplitude and the number of loads obtained in the plurality of test processes, and the shear diagram is obtained from the PSN diagram. A method for estimating the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material that determines the fatigue life.   8. The ultrasonic torsional fatigue test according to claim 1, wherein the ultrasonic torsional fatigue test includes a torsional vibration converter that generates a torsional vibration that rotates forward and backward about a rotation center axis when AC power is applied. Using an amplitude expanding horn having a mounting portion for attaching a test piece concentrically at the distal end and fixed to the torsional vibration converter at the proximal end, and expanding the amplitude of the torsional vibration of the torsional vibration converter applied to the proximal end, The shape and dimensions of the test piece are those that resonate with the vibration of the amplitude-amplifying horn driven by the torsional vibration converter, the torsional vibration converter is driven at a frequency in the ultrasonic region, and the test piece is A method for estimating the relative superiority or inferiority of the internally originated flaking life of rolling contact metal materials by resonating with vibration and causing shear fatigue fracture.   9. The rolling contact metal material according to claim 1, wherein in the test process, in order to suppress heat generation of the test piece of the metal material in the ultrasonic torsional fatigue test, the test contact is subjected to forced air cooling. Of the relative superiority or inferiority of the internally-originated delamination life.   The rolling contact metal according to any one of claims 1 to 9, wherein in the test process, in order to suppress heat generation of the test piece of the metal material in the ultrasonic torsional fatigue test, a rolling contact metal that alternately repeats loading and resting. A method for estimating the relative superiority or inferiority of the internal origin-type peel life of materials   11. The rolling contact metal material according to claim 1, wherein in the test process, in the ultrasonic torsional fatigue test, heat generation of the test piece of the metal material does not become a problem. A method for estimating the relative superiority or inferiority of the starting-type peel life.   The inside of a rolling contact metal material using an amplitude expanding horn according to any one of claims 1 to 11, wherein an expansion ratio is 43 times or more, which is a ratio of a torsion angle of a small diameter side end surface to a torsion angle of a large diameter side end surface. A method for estimating the relative superiority or inferiority of the starting-type peel life.   A metal material having a shear fatigue life in a time strength region determined by the method for estimating the relative superiority or inferiority of the internally originated peeling life according to any one of claims 1 to 12, which is equal to or greater than a predetermined shear fatigue life. Is used as a material for rolling bearing races or rolling elements. An apparatus for determining the shear fatigue life in order to estimate the relative superiority or inferiority of the internal origin type peeling life of a metal material in rolling contact,
An input means for storing the relationship between the shear stress amplitude of the metal material and the number of loadings in a predetermined memory area by a complete double-sided ultrasonic torsional fatigue test;
A shear fatigue life determining means for determining a shear fatigue life in a time strength region from a relationship between the stored shear stress amplitude and the number of loads, according to a predetermined standard;
A device for estimating the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material.   15. The estimation device of relative superiority or inferiority of an internal origin type peeling life of a rolling contact metal material, wherein the metal material is a rolling bearing steel used as a bearing ring or rolling element of a rolling bearing.   16. The function according to claim 14 or 15, wherein the input means stores the relationship between the shear stress amplitude of the metal material and the number of loads obtained by a plurality of previous ultrasonic torsional fatigue tests in a predetermined storage area. The shear fatigue life determining means obtains a PSN diagram having an arbitrary fracture probability from the relationship between the shear stress amplitude and the number of loads in the plurality of tests, and from this PSN diagram An apparatus for estimating the relative superiority or inferiority of the internal origin type peeling life of a rolling contact metal material that determines the shear fatigue life.   17. The apparatus for estimating relative superiority or inferiority of an internal origin type peeling life of a rolling contact metal material, wherein the shear stress amplitude in the shear fatigue life determining means is 700 MPa or more and 800 MPa or less in any one of claims 14 to 16.   An ultrasonic torsional fatigue testing machine body that performs a complete double-sided ultrasonic torsional fatigue test on metal specimens that are in rolling contact, and a testing machine that controls the ultrasonic torsional fatigue testing machine body according to the input test conditions A system for estimating the relative superiority or inferiority of the internal origin-type delamination life of a rolling contact metal material, comprising a control device and the shear fatigue life determination device according to any one of claims 14 to 17.

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