Crack Growth Rate Prediction Method Based on Low Cycle Fatigue Performance Parameters Applicable to Negative Stress Ratio
A crack growth rate, low cycle fatigue technology, applied in electrical digital data processing, special data processing applications, instruments, etc., can solve problems such as inability to apply, insufficient consideration of crack closure effects, etc., to achieve the effect of saving time and cost.
Active Publication Date: 2019-03-01
SOUTHWEST JIAOTONG UNIV
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[0032] The model predicts the crack growth rate based on the low-cycle fatigue parameters of the material, and the obtained results fit well in the I and II areas of the growth rate curve, but it does not take into account the crack closure effect and cannot be applied to negative stress ratios. The load situation becomes a major bottleneck limiting its application
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[0077] The purpose of the present invention is to provide a method for predicting the crack growth rate based on low-cycle fatigue tests, material stress intensity factor threshold tests, and low-cycle fatigue performance parameters: the stress and strain data obtained through low-cycle fatigue tests of materials and the corresponding samples Cycle life N f , Fit the low-cycle fatigue performance parameters, obtain the threshold value of the stress intensity factor under the corresponding stress ratio of the material through the threshold value test, and substitute it into this model to calculate the crack growth rate; the detailed process includes:
[0078] (1) Material low-cycle fatigue test, obtain stress, strain data and cycle life N of the corresponding sample f The following table:
[0079] Table 1 Raw data of low cycle fatigue test
[0080]
[0081] (2) Using the low-cycle fatigue test data in Table 1, the least square method is used to fit the data, and the low-cycle fatigue ...
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The invention discloses a crack growth speed predicting method suitable for a negative stress ratio and based on a low cycle fatigue performance parameter. The low cycle fatigue parameter is obtained through fitting of low cycle fatigue test data, the low cycle fatigue parameter and different stress ratio threshold values of a material are substituted into a model formula, and the crack growth speed can be predicted. By means of the method, the defects that an existing crack growth speed predicting method based on fatigue crack growth speed test and threshold value test is high in price and long in consumed time are overcome; in addition, more importantly, the result predicted by the method better conforms to the experiment data and is more accurate; even under the condition that the negative stress ratio can be hardly predicted effectively and accurately, the prediction result of a model is quite accurate. The method has great significance in wide fatigue crack growth speed prediction and residual life prediction in aerospace, nuclear power, pipelines, high speed railways and other key major projects.
Description
Technical field [0001] The invention relates to the prediction of the fatigue crack growth rate of fracture mechanics, in particular to the prediction of the fatigue crack growth rate of advanced and important engineering structures and components and the prediction of fatigue crack life. Background technique [0002] Most engineering fractures are caused by fatigue, so the low-cycle fatigue and crack growth rate performance of metal materials has always been concerned by the safety design department. For a long time, scholars at home and abroad have conducted multi-material and multi-angle research in establishing the relationship between low-cycle fatigue behavior and crack growth rate performance of metallic materials. Based on the small-scale yield stress and strain field at the tip of the plane stress crack and the fatigue crack growth failure criterion, a prediction model for the growth rate of mode I fatigue cracks is proposed. [0003] Fatigue has always been one of the ma...
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IPC IPC(8): G06F17/50
CPCG06F30/15G06F30/17G06F2113/14G06F2119/04
Inventor 吴圣川徐忠伟张思齐蔡力勋
Owner SOUTHWEST JIAOTONG UNIV