Method for predicting fatigue crack expanding threshold value under different stress ratios

A fatigue crack growth and stress ratio technology, applied in the field of mechanical properties, can solve the problems of high cost, long cycle, inability to predict the threshold value of fatigue crack growth, etc., to save costs, reduce test workload, and achieve the effect of good consistency

Inactive Publication Date: 2014-04-30
TSINGHUA UNIV +1
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Problems solved by technology

However, the test results vary with the stress ratio R, and the threshold value under different stress ratio R needs to be tested, which takes a long period and high cost
[0003] Existing studies have shown that there is a certain relationship between the threshold of fatigue crack growth and the structure size ...

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  • Method for predicting fatigue crack expanding threshold value under different stress ratios
  • Method for predicting fatigue crack expanding threshold value under different stress ratios
  • Method for predicting fatigue crack expanding threshold value under different stress ratios

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Embodiment Construction

[0023] Below in conjunction with specific embodiment the present invention is described in further detail:

[0024] Step 1: According to the national standard GB / T6398-2000 "Metallic Material Fatigue Crack Growth Rate Test Method", at room temperature, the material stress ratio R 0 The fatigue crack growth threshold of the next sample is tested to obtain the relationship between the fatigue crack growth rate da / dN and the stress intensity factor amplitude ΔK, and the test data points da / dN~ΔK are required to include fatigue crack stability in the double-logarithmic coordinate system Expansion zone and near-threshold zone;

[0025] Step 2: In the log-logarithmic coordinate system, determine the fitting slopes of the data points in the fatigue crack stable growth zone and the near-threshold zone as b 0 and c 0 , and the intersection point of the two is the coordinate ((da / dN) 0 , ΔK 0 );

[0026] Step 3: According to different stress ratios, the maximum stress intensity fac...

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Abstract

The invention relates to a method for predicting a fatigue crack expanding threshold value under different stress ratios. The method comprises the steps of solving a linear fitting slope and a cross-over point of fatigue crack stable expanding area and near-threshold area data points on a log-log coordinate through the test data of the fatigue crack expanding threshold value under a known stress ratio, i.e. the relation between the fatigue crack expanding rate da/dN and a stress intensity factor range delta K, and executing the calculation under the condition that the maximal stress intensity factor Kmax is equal to delta K/R on the cross-over point of a stable expanding area and a near-threshold area under different stress ratios, so that the fatigue rack expanding threshold value of the unknown stress ratio R can be predicted, and R is more than zero. Compared with the traditional study, the method is not subjected to the limitation of the specific material, and is applicable to the material with uniform tissues and good in universality; moreover, the test workload of the threshold value can be effectively alleviated, and the cost is lowered.

Description

technical field [0001] The invention relates to the field of mechanical properties of a material with a uniform structure, in particular to a method for predicting the fatigue crack growth threshold of a material with a uniform structure under different stress ratios R (R>0). Background technique [0002] The fatigue crack growth threshold reflects the fatigue resistance of materials and is an important index to measure the high cycle fatigue performance of materials. It has important reference significance for the design of long-life and infinite-life components in engineering. However, the test results vary with the change of the stress ratio R, and it is necessary to test the threshold value under different stress ratios R, and the cycle is long and the cost is high. [0003] Existing studies have shown that there is a certain relationship between the threshold of fatigue crack growth and the structure size of the material under a certain stress ratio, and a mathematic...

Claims

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Application Information

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IPC IPC(8): G01N3/00
Inventor 蔡志鹏潘际銮李轶非孙林根杨仁杰沈红卫王朋丁玉明
Owner TSINGHUA UNIV
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