Fatigue life prediction method based on fatigue crack propagation

Abstract

The invention discloses a fatigue life prediction method based on fatigue crack propagation, and belongs to the technical field of fatigue life prediction. The method comprises the steps of pretreatment, iterative solution and crack propagation which can be completed by means of SESAM, ABAQUS and FRANC 3D platforms respectively, and the specific steps comprise S1 model modeling, S2 hydrodynamic analysis, S3 structural strength analysis, S4 three-dimensional crack propagation area modeling, S5 crack insertion and grid updating, S6 fatigue characteristic characterization, S7 incremental calculation judgment, S8 termination condition verification and S9 service life statistics. According to the method, the fatigue performance of the structure is represented through stress intensity factor transfer function calculation; the concept of equivalent damage accumulation rate is introduced for the first time and is successfully applied to simplification of irregular waves; inheritance and transmission of the internal stress state of the structure in the process from hydrodynamic force to structural strength and even crack propagation are achieved; based on a sub-model and multi-scale model technology, coupling analysis of a real-scale structure and a crack propagation region is successfully carried out.

Description

technical field [0001] The invention belongs to the technical field of fatigue life prediction, in particular to a fatigue life prediction method based on fatigue crack growth. Background technique [0002] For marine structures in service, the continuous and uninterrupted wave force will cause the structure to be under alternating loads for a long time, which will inevitably lead to the occurrence and deterioration of fatigue. With the enlargement of marine structures and the widespread use of high-strength steel in construction, fatigue damage has become increasingly prominent, and has gradually been recognized as one of the most important failure modes by inspectors of classification societies of various countries. The existence and growth of fatigue cracks are usually extremely destructive, which may lead to a decrease in fatigue strength and load-carrying capacity, and even pose a great risk to the integrity and stability of the structure. Although the fatigue performa...

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Problems solved by technology

The introduction and development of the S-N curve method has played a very positive role in the improvement of traditional structural types and the reduction of accident rates, but its inherent theoretical defects have greatly limited its further application potential, such as:

[0004] (1) The S-N curve method is not suitable for the assessment of the remaining life of the aging structure with existing defects;

[0005] (2) Since there is no unified failure criterion, the prediction results are highly discrete;

[0006] (3) The effects of loading sequence and material properties cannot be taken into account;

[0007] (4) Can not be accurately predicted based on the crack propagation path and crack morphology

Coupling analysis between models of different magnitudes is also a huge challenge for the application of fracture mechanics

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