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Metal structure fatigue crack expansion life prediction method based on Taylor perturbation series method

A technology of fatigue crack growth and perturbation series, applied in the direction of electrical digital data processing, special data processing applications, instruments, etc., can solve the problems of errors in initial crack measurement results, manufacturing errors, etc.

Inactive Publication Date: 2016-10-26
BEIHANG UNIV
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Problems solved by technology

[0004] Using the Paris formula to calculate the fatigue crack growth, the initial crack length of the structure must first be determined. However, in the actual engineering structure, due to the accuracy of the measuring equipment, there are often errors in the measurement results of the initial crack. At the same time, in the fatigue test, the prefabricated crack There will also be manufacturing errors in the test piece

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  • Metal structure fatigue crack expansion life prediction method based on Taylor perturbation series method
  • Metal structure fatigue crack expansion life prediction method based on Taylor perturbation series method
  • Metal structure fatigue crack expansion life prediction method based on Taylor perturbation series method

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[0093] In order to understand more fully the characteristics of this invention and its applicability to engineering practice, the present invention uses image 3 The shown 475-T761 aerospace aluminum alloy center crack (MT) specimen was taken as an example to verify the crack growth fatigue life prediction. The MT sample is 75mm wide and 2.5mm thick, with a central crack, such as image 3 shown. The frequency of the applied load is 10Hz, and the length of the prefabricated half-crack is a 0 = 4mm, due to manufacturing errors, the actual initial half-crack length is a 0 =4.06mm, the half-crack length a and the corresponding number of load cycles N are shown in Table 1.

[0094] Table 1a-N test data points

[0095]

[0096] According to formula (5), calculate the tangent slope of each discrete point, and through regression analysis, the parameter value in the crack propagation equation (4) is obtained: Q=3.9547×10 -8 , b=3.3794. The initial half-crack length is a(0)=4.0...

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Abstract

The invention discloses a metal structure fatigue crack expansion life prediction method based on Taylor perturbation series method, and the method comprises the steps of first describing fatigue crack expansion process of the metal structure by employing Paris formula; conducting integration to the Paris formula to obtain an integration-formed crack expansion equation; and conducting Taylor expansion to the crack expansion equation. Then considering apparatus measuring error and structure manufacturing error to make an initial crack length contain a small disturbance; expressing the solution of the crack expansion equation and the initial crack length in perturbation grades by introducing a small parameter Epsilon; determining the perturbation grades according to an nominal value of the initial crack length and the disturbance so as to get the value of each coefficient at an initial time; obtaining a crack expansion perturbation equation in combination with the Taylor expansion of the crack expansion equation based on parameter perturbation theory; then solving the perturbation equation to obtain a fatigue crack expansion length perturbation grades solution; calculating load cycle times when a critical crack length is reached; and taking the load cycle times as a predicted value of the metal structure fatigue crack expansion life.

Description

technical field [0001] The invention relates to the technical field of metal structure fatigue life prediction, in particular to a metal structure fatigue crack growth life prediction method based on the Taylor perturbation series method. Background technique [0002] Fatigue damage is a phenomenon of low-stress brittle fracture of materials or structures under alternating cyclic loads, especially in engineering structures such as aircraft, ships, automobiles, and bridges. Therefore, the problem of fatigue crack growth has been widely concerned, and it is also an important aspect of engineering research. the key of. The expansion of cracks under the action of fatigue load often leads to the instability and fracture of the structure, resulting in huge losses. Therefore, the study of fatigue crack growth characteristics has an important role and significance for the fatigue check and life evaluation of engineering structures. After decades of development, it has been recogni...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50
CPCG06F30/17
Inventor 邱志平朱静静王晓军吕峥王磊王鹏博蒋文婷
Owner BEIHANG UNIV
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