Fatigue limit rapid prediction method based on strain increment

Abstract

A fatigue limit rapid prediction method based on strain increment belongs to the field of rapid prediction of material fatigue limit. The invention discovers that under gradient stress load, the variation rule of strain capacity is very similar to the variation rule of temperature. Since the Luong method can use corresponding stable temperature rise value under gradient load to predict the fatigue limit, the strain capacity under gradient load can theoretically be used for rapid prediction of fatigue limit. The method utilizes a fatigue testing machine and an extensometer thereof (no dependence on expensive high-precision thermal infrared imager), and theoretically only uses one specimen to rapidly and economically predict a reliable fatigue limit of the material or a simple member in a day time according to variation rule of strain capacity under gradient load. The traditional lifting method and grouping method spend a few months and consume a large amount of human and financial resources, therefore the present invention has high engineering practical value and significant economic benefits.

Description

Technical field: [0001] The invention belongs to the field of rapid prediction of material fatigue limit. Background technique: [0002] At present, there is no mature theoretical model that can reveal the physical nature of the fatigue limit of materials, so it is difficult to obtain it through theoretical calculations. For strain-age hardening materials, under constant amplitude loading conditions, it is found from their S-N curves that usually more than about 10 6 A "plateau" occurs after the fatigue cycle. When the stress amplitude is lower than the platform stress, the sample can withstand infinite fatigue cycles without failure, and the platform stress is called the fatigue limit σ e (or endurance limit). However, for some materials such as high-strength steel and aluminum alloys that do not have strain age hardening, there may be no fatigue limit. With the increase of cycle times, the stress range they can withstand continues to decrease. At this time, the sample c...

AI Technical Summary

Problems solved by technology

[0017] Since the fatigue limit and static parameters have different physical meanings, these empirical prediction formulas are all based on statistical analysis of a large number of fatigue data for a specific material system, so the scope of application is narrow and the accuracy is poor

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