Structural integrity evaluation method incorporating in-plane and out-plane unified constraint

Abstract

The invention provides a structural integrity evaluation method incorporating in-plane and out-plane unified constraint. The method comprises the following steps: establishing a correlation between nominal fracture toughness of a material and a unified constraint parameter, wherein the unified constraint parameters is the ratio of the crack tip opening displacement of other samples or a to-be-evaluated structure to the crack tip opening displacement value of a reference sample under the fracture load; representing the geometric dimension and the defect dimension of the structure; determining astructure limit load and unified constraint parameters under different load ratios; constructing a failure evaluation graph of the defects; determining evaluation point coordinates under each load ratio to form a loading path line; when the fracture ratio of the coordinates of the evaluation point is calculated, substituting the constraint parameters under different load ratios into the correlation, and determining the fracture toughness related to material constraint; and performing defect safety evaluation and fracture prediction. According to the evaluation method, unified constraint parameters based on crack tip opening displacement are provided, so that in-plane constraint and out-plane constraint are unified, engineering calculation and application are facilitated, and the evaluation precision is improved.

Description

technical field [0001] The invention belongs to the technical field of structural integrity assessment, and in particular relates to a structural integrity assessment method incorporating in-plane and out-of-plane unified constraints. The method can improve the accuracy of structural integrity assessment with defects, reduce the excessive conservatism of traditional methods or eliminate non-conservatism. Background technique [0002] The current integrity assessment techniques and methods for structures with defects (such as pressure vessels, pipelines and other engineering structures and equipment) are mainly established based on traditional single-parameter fracture mechanics, using linear elastic stress intensity factor K or elastoplastic J integral A single parameter describes the strength of the stress field at the crack tip, and the fracture criterion is K≥K C or J≥J C . Material fracture toughness K C and J C Generally, deep cracks, large-size plane strain and hi...

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Problems solved by technology

In actual pressure vessels, pipelines and other structures, defects are generally surface shallow cracks with low crack tip restraint. For example, the lower limit of fracture toughness of materials measured by standard high restraint samples is used to evaluate low restraint cracks in actual structures. will produce overly conservative results; conversely, using it to assess highly restrained cracks in real structures may produce non-conservative results

[0005] British researchers proposed a unified restraint parameter based on the size of the crack tip plastic zone , but the parameter Failure at higher loads or greater plastic deformation of the crack tip

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