Assessment of shear fatigue property of rolling contact metal material and estimation of fatigue limit maximum contact pressure using same assessment

Patent metadata

Field	Value
Publication number	US-9234826-B2
Application number	US-201113634412-A
Country	US
Kind code	B2
Filing date	Mar 15, 2011
Priority date	Mar 16, 2010
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A method of assessing the shear fatigue property of a metallic material that undergoes a rolling contact includes a testing step for determining the relation between the shear stress amplitude of a rolling contact metallic material and the number of loading by means of an ultrasonic torsional fatigue test, and a shear fatigue strength determining step for determining the shear fatigue strength τlim within the ultra long life regime from the relation between the shear stress amplitude and the number of loadings, which relation has been determined during the test step, in accordance with a predetermined standard. It is a completely reversed torsional fatigue test, in which torsional vibrations, respective torsions in the positive rotational direction and reversed rotational direction of which are symmetrical relative to each other, are applied to a test piece.

First claim

What is claimed is:

1. A method of assessing a shear fatigue property of a metallic material that undergoes a rolling contact using a torsional vibration converter for generating torsional vibrations, which will become positive and reversed rotations about the axis of rotation when an electric alternating power is applied, an amplitude amplifying horn having a tip end, provided with a mounting portion to which a metallic material is fitted coaxially and also having a base end that is fixed to the torsional vibration converter, and operable to amplify the amplitude of the torsional vibration of the vibration converter applied to the base end, an oscillator, an amplifier for amplifying an output of the oscillator and then applying the output to the torsional vibration converter, and a control unit for applying an input of the control to the amplifier, which method comprises:
a testing step of determining a relation between a shear stress amplitude of the metallic material and the number of loadings by means of an ultrasonic torsional fatigue test; and
a shear fatigue strength determining step of determining a shear fatigue strength τ lim within an ultra long life regime from the determined relation between the shear stress amplitude and the number of loadings in accordance with a predetermined standard.

2. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which the ultrasonic torsional fatigue test is chosen to be a completely reversed torsional fatigue test, in which torsions in respective directions of positive and reversed rotations relative to the test piece are symmetrical to each other.

3. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which the metallic material is a rolling contact metallic material, which is a rolling bearing steel and which becomes a bearing ring and/or a rolling element of a rolling bearing assembly.

4. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which the predetermined standards used during the shear fatigue strength determining step for determining the shear fatigue strength τ lim within the ultra long life regime is a treatment of determining a curve, in which the relation between the shear stress amplitude and the number of loadings, as a test result, is applied to a fatigue limit line model descriptive of the shear fatigue strength, and then determining the shear fatigue strength from such curve.

5. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which the predetermined standards used during the shear fatigue strength determining step for determining the shear fatigue strength τ lim within the ultra long life regime is a treatment of determining a curve, in which the relation between the shear stress amplitude and the number of loadings, as a test result, is applied to a continuously decreasing type curve model descriptive of the shear fatigue strength, and then determining the shear fatigue strength from such curve.

6. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which during the test step, a plurality of the ultrasonic torsional fatigue tests are carried out to determine a plurality of relations between the shear stress amplitude of the metallic material and the number of loadings and, during the shear fatigue strength determining step, a P-S-N diagram of an arbitrarily chosen fracture probability is determined from the relation between the shear stress amplitude and the number of loadings, determined during the plurality of the test steps, and from this P-S-N diagram the shear fatigue strength τ lim within the ultra long life regime is determined.

7. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 , in which a value determined by combining two or more of the following corrections (a), (b) and (c) is rendered to be the shear fatigue strength τ lim within the ultra long life regime for use in evaluating the shear fatigue property:
(a) a fracture probability correction to obtain an arbitrary chosen P-S-N diagram descriptive of an arbitrary fracture probability, which diagram is determined from the relation between the shear stress amplitude and the number of loadings, obtained through the test, and to render the shear fatigue strength within the ultra long life regime to be the shear fatigue strength τ lim within the ultra long life regime for use in evaluating the shear fatigue strength;
(b) an excessive evaluation correction to render the value of 85% relative to the shear fatigue strength within the ultra long life regime, that is determined from the relation between the shear stress amplitude and the number of loadings, obtained through the test, to be the shear fatigue strength τ lim within the ultra long life regime for use in evaluating the shear fatigue strength;
(c) a dimensional effect correction to render the value of 80% relative to the shear fatigue strength within the ultra long life regime, that is determined from the relation between the shear stress amplitude and the number of loadings, obtained through the test, to be the shear fatigue strength τ lim within the ultra long life regime for use in evaluating the shear fatigue strength.

8. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 1 ,
wherein the shape and the dimensions of the amplitude amplifying horn are chosen to be the shape and the dimensions enough to resonate with the torsional vibrations resulting from the drive of the torsional vibration converter;
the shape and the dimensions of the test piece are chosen to be the shape and the dimensions enough to resonate with the torsional vibrations of the amplitude amplifying horn;
a test is conducted to cause a shear fatigue fracture in the test piece by driving the vibration converter at a frequency region within the ultrasonic wave region and causing the amplitude amplifying horn and the test pieces to resonate; and
using the relation between the number of loadings and the shear stress amplitude, obtained from the test, the shear fatigue property of the metallic material is evaluated.

9. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 8 , in which the amplifier is such that the magnitude of an output thereof and the ON or OFF state thereof are controllable in response to an input from the outside.

10. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 8 , in which the lowermost limit value of the frequency, at which the torsional vibration converter is driven, is chosen to be (20,000−500+α) Hz and the uppermost limit value thereof is (20,000+500+α) Hz, where α represents a spare value relative to a change in property of the test piece during the test and α is not higher than 200 Hz.

11. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 8 , in which the amplitude amplifying horn has a transverse sectional shape which is round and the longitudinal sectional shape except for a base end portion is of a tapered shape.

12. The method of assessing the shear fatigue property of the rolling contact metallic material as claimed in claim 8 , in which the test piece is of a dumbbell shape including cylindrical shoulder portions at opposite ends thereof and a narrowed interm

Assignees

• Matsubara Yukio
• Sakanaka Noriaki
• Ishii Hitoshi
• Ntn Toyo Bearing Co Ltd

Inventors

• Matsubara Yukio
• Sakanaka Noriaki
• Ishii Hitoshi

Classifications

• G01N2203/0025

  Shearing · CPC title

• G01N2203/0021

  Torsional · CPC title

• G01N2203/0658

  using acoustic or ultrasonic detectors · CPC title

• G01N3/34 Primary

  generated by mechanical means, e.g. hammer blows · CPC title

• G01N2203/0005

  Repeated or cyclic · CPC title