Uniform amplitude full-strain-life curve test method for metal material

Abstract

The invention relates to a uniform amplitude full-strain-life curve test method for a metal material, and the method comprises the following steps of 1, performing processing and surface treatment ona sample; 2, performing a short-life fatigue test, and using an extensometer for strain control when the cycle life is less than 100,000 times, wherein the test frequency is 0.1Hz to 1Hz; 3, testing the cycle life under different strain amplitudes with a total strain amplitude greater than three per thousand, and controlling the test with the strain amplitudes, wherein the frequency is 0.1Hz and 1Hz; 4, determining a strain amplitude corresponding to the transition point of short-life fatigue to long-life fatigue in the range of one to three per thousand of the total strain amplitude; 5, performing long-life fatigue test, using the extensometer for strain control in the first stage within 50,000 times, wherein the test frequency is 10Hz to 25Hz, and selecting the stress amplitude corresponding to the cycle of 50,000 times as the stress control amplitude of the second stage; and 6, fitting the total strain-life formula. The full strain-life curve of the metal material can be obtained bythe method provided by the invention.

Description

technical field [0001] The invention relates to the technical field of testing the mechanical properties of metal materials, in particular to a testing method for the full strain-life curve, ie, the ε-N curve, with the loading ratio of the metal material being -1. Background technique [0002] With the change of the design concept of structural parts, more and more customers request to provide the full strain-life curve of metal materials when designing. The curve includes high-cycle fatigue characteristics under low stress and small strain and low-cycle fatigue characteristics under high stress and large strain, which unifies the high-cycle fatigue and low-cycle fatigue properties of the material, and is characterized by the strain-life curve. The traditional strain-life curve is mainly used to describe the low-cycle fatigue behavior of materials under high stress and large strain, and the high-cycle fatigue behavior of low stress is described by the stress-life curve. [...

AI Technical Summary

Problems solved by technology

The technical difficulties of the full strain-life curve test of metal materials are as follows: 1) In the test process, short-life fatigue with large strain and long-life fatigue with small strain are designed. How to accurately select different test control methods for the two stages is a key technical point and difficulty

2) Based on the consideration of the test cycle and test methods, it is currently impossible to completely use strain control for long-life fatigue tests. Strain control fatigue tests have low frequency, long time, and very low efficiency.

3) The fatigue performance of metal materials has a frequency effect, and a frequency range that has little influence on the fatigue performance test results has not yet been defined; 4) The strain range corresponding to the short-life and long-life turning points of the material has not yet been defined

5) For different test control methods, the original strain-life curve data processing method will be changed

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