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Method for investigating fatigue crack expansion

A technology of fatigue crack propagation and fatigue testing, which is applied in the direction of testing the ductility of materials, and can solve problems such as difficulty in implementation.

Inactive Publication Date: 2008-12-03
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For many actual parts, such as engine crankshafts, these methods are difficult to implement due to the complexity of its structure and the special location and shape of cracks.

Method used

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  • Method for investigating fatigue crack expansion
  • Method for investigating fatigue crack expansion
  • Method for investigating fatigue crack expansion

Examples

Experimental program
Comparison scheme
Effect test

Embodiment Construction

[0022] The fatigue crack growth test method of the present invention includes the following steps:

[0023] 1) The pieces to be tested, for example figure 1 The crankshaft 1 shown is mounted on a resonant loading mechanism composed of an active arm 2, a passive arm 3 and an eccentric vibration exciter 4.

[0024] 2) Load the fatigue test, and perform a frequency sweep test at a certain interval of time, such as 50,000 times or 100,000 times. The frequency sweep test is to obtain the resonance frequency of the vibration system under forced vibration conditions. The method is to apply excitations of different frequencies and record the response acceleration value of the system under each frequency excitation. Get the data sequence {ω 1 , Α i | i＝1，2，3... }, plot the measured sequence on the graph to get the frequency sweep graph, image 3 An example of a frequency sweep graph at some moments is given. With the increase of the number of test cycles, the left shift of the frequency s...

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Abstract

The invention discloses a fatigue crack extension testing method, making a sweeping test in the fatigue test course and obtaining the variation condition of vibration response of the test system varies with test piece crack extension on the forced vibration condition; using a numeric method to make sweeping data fitting and obtaining variation curve of resonant frequency with number of circulating times; after the test piece is broken, according to actually observed crack size and shape, prefabricating crack of a CAD model and making finite model analysis and obtaining a curve of resonant angular frequency of the system against test piece size, using the curve and able to obtain dynamic extension rule of test piece crack and then obtaining its curve of variation rate; and finally combining with calculation of stress strength factor range Delta K, and able to obtain a curve of crack extension rate.

Description

Technical field [0001] The invention relates to a crack propagation test method applied to the fatigue test of mechanical parts. Background technique [0002] The fatigue failure of mechanical components is a main form of failure. In summary from various statistical data, the proportion is about 80%-95%. Therefore, the problem of fatigue failure is an important area of ​​mechanical reliability research. Fatigue failure is a very complex problem. There are many factors that affect fatigue strength, and most of the influencing factors are currently unable to give a strict physical mechanism explanation, and it is difficult to give a more thorough quantitative description mathematically. [0003] In a large number of production practices, people have gradually formed some engineering approximate description methods of fatigue damage from different observation angles. Among them, the fatigue crack growth rate curve has achieved good results in the fatigue reliability estimation of ma...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/28
Inventor 俞小莉周迅沈瑜铭
Owner ZHEJIANG UNIV