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Obtaining Method of Conversion Coefficient k Value of Two-stage Loading Fast Fatigue Test

A fatigue test and conversion factor technology, applied in the direction of applying repeated force/pulsation force to test the strength of materials, etc., can solve the problem of long test time

Active Publication Date: 2015-11-25
CHINA FIRST AUTOMOBILE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Due to the material characteristics, the life under low load is often dozens of times longer than under high load, resulting in the need to obtain single-stage low-load σ 2 The lifetime N corresponding to any reliability α 2α The test time required is too long

Method used

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  • Obtaining Method of Conversion Coefficient k Value of Two-stage Loading Fast Fatigue Test
  • Obtaining Method of Conversion Coefficient k Value of Two-stage Loading Fast Fatigue Test
  • Obtaining Method of Conversion Coefficient k Value of Two-stage Loading Fast Fatigue Test

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] Such as figure 1 As shown, the tension and compression fatigue life of 40Cr steel, the K value is obtained as follows:

[0030] step one

[0031] Single-stage high-load σ for the sample 1 = 550MPa symmetrical tension-compression fatigue test, get the fatigue life corresponding to each reliability α under this load.

[0032]

[0033] step two

[0034] Determining the first-stage single-stage high-load σ in the two-stage loading rapid fatigue test 1 =550MPa fatigue test pre-cycle times n, in order to speed up the progress of the whole test, n should be as large as possible, but n should be less than N 1，0.999 =10436. Take n=8000 times.

[0035] step three

[0036] A group of metal samples to be tested are subjected to the first-stage single-stage high-load σ 1 =550MPa fatigue test, fixed cycle 8000 times;

[0037] step four

[0038] For the single-stage high load σ after the first stage 1 =550MPa, the sample after 8000 cycles is subjected to the second-stage...

Embodiment 2

[0059] Obtaining the bending fatigue conversion factor of 40Cr steel and the application of the two-stage loading rapid fatigue test method, the steps are the same as in Example 1, and the process is omitted.

Embodiment 3

[0061] The steps for obtaining the bending fatigue conversion factor of 45# steel and the application of the two-stage loading rapid fatigue test method are the same as in Example 1, and the process is omitted.

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Abstract

The invention relates to a method for acquiring secondary loading rapid fatigue test conversion coefficient K value. The method comprises the following steps: determining the precycling times n of a first stage of single-stage high load; carrying out secondary of single-stage low load fatigue test after a to-be-tested metal sample recycles for n times regularly under single-stage high load, thereby obtaining the residual fatigue service life of the to-be-tested metal sample; calculating the fatigue test service life false calculated value corresponding to single-stage low load and random reliability of the to-be-tested metal material; calculating the two-stage load rapid fatigue test conversion coefficient K. In the future, the conversion coefficient K value can be utilized for rapidly obtaining the fatigue service life corresponding to high-precision single-stage low load and random reliability range of 50%-99.9% by the secondary load rapid fatigue test under the condition of the fatigue service life corresponding to the known single-stage high load and random reliability. The method provided by the invention can be applied to the fatigue test of various mechanical common metal materials.

Description

technical field [0001] The invention belongs to the technical field of fatigue tests of commonly used metal materials, and relates to a method for obtaining a conversion coefficient K value of a two-stage loading rapid fatigue test. Background technique [0002] The conventional P-S-N test method is to obtain the fatigue life distribution based on the fatigue life samples under a certain single-stage load. According to the fatigue life distribution, the fatigue life corresponding to any reliability α (ranging from 50% to 99.9%, the same below) under this level of load is obtained. The test sequence is carried out step by step according to the load from high to low. [0003] Due to material characteristics, the life at low load is often dozens of times longer than at high load, resulting in the need to obtain a single-stage low-load σ 2 The lifetime N corresponding to any reliability α 2α The required test time is too long. Contents of the invention [0004] The technic...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/32
Inventor 王文阁霍福祥
Owner CHINA FIRST AUTOMOBILE