Method for investigating fatigue crack expansion

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

Inactive Publication Date: 2006-11-29
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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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
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Embodiment Construction

[0022] The method for fatigue crack propagation test of the present invention comprises the following steps:

[0023] 1) will be the test piece, e.g. figure 1 The shown crankshaft 1 is mounted on a resonant loading mechanism consisting 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 every certain time interval, such as 50,000 times or 100,000 times. The frequency sweep test is to obtain the resonance frequency of the vibration system under the condition of forced vibration. The method is to apply excitation of different frequencies and record the response acceleration value of the system under the excitation of each frequency. That is to get the data sequence {ω i , a i | i＝1，2，3...}, the measured sequence is drawn on the graph, and the sweep frequency graph can be obtained, image 3 An example of some time sweep plots is given. As the number of test cycles increases, the sw...

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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 fatigue test of mechanical parts. Background technique [0002] Fatigue failure of mechanical components is a major form of failure. According to various statistical data, the proportion is about 80% to 95%. Therefore, the problem of fatigue failure is a key area of ​​mechanical reliability research. Fatigue failure is a very complex problem. There are many factors affecting fatigue strength, and most of the influencing factors cannot be given 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 failure from different observation angles. Among them, the rate curve of fatigue crack growth has achieved good results in the fatigue reliability estimation of many practical engi...

Claims

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Application Information

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