Method for calculating three-dimensional crack propagation fatigue life of spherical shell surface

Abstract

The invention belongs to a deep sea engineering technology and particularly relates to a spherical shell surface three-dimensional crack propagation fatigue life calculation method. The method comprises the following steps of establishing a complete spherical pressure-resistant shell initial geometric model; endowing the spherical shell model with material parameters and section attributes, dividing grids, and setting boundary and load conditions; establishing an initial crack model; endowing material parameters to the crack model, defining section attributes, dividing grids and determining the positions of the grids; importing the two models to generate a complete spherical shell finite element numerical model locally containing surface crack defects; solving an initial crack leading edgestress intensity factor value by adopting an M integral method; reading and running a fatigue life calculation model program; setting automatic crack propagation parameters; and obtaining a sphericalshell surface three-dimensional crack propagation fatigue life numerical value based on a self-defined propagation program. According to the method, finite element analysis software and fracture mechanics analysis software are combined to calculate the three-dimensional crack propagation fatigue life of the surface of the spherical shell, and applicability of the method is verified through numerical simulation.

Description

technical field [0001] The invention belongs to the technical field of deep-sea engineering, and relates to a calculation method for a pressure-resistant shell with crack defects, in particular to a calculation method for the fatigue life of three-dimensional crack propagation on the surface of a spherical pressure-resistant shell. Background technique [0002] The deep-sea submersible is an important marine engineering equipment for ocean exploration and deep-sea scientific research. The pressure hull is the key component and buoyancy unit of the submersible. It is an important part of ensuring the safety and stability of the deep-sea submersible, protecting the safety of internal personnel and equipment. As the most common basic pressure-bearing shell unit, the spherical shell has irreplaceable advantages such as good volume-to-weight ratio and bearing capacity, high strength and stability, simple structure, and convenient calculation. [0003] However, the spherical shell...

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Problems solved by technology

The traditional fracture criterion is based on two-dimensional penetrating straight cracked plate specimens. The criterion for judging structural fracture failure is the fracture toughness of structural materials with sufficient thickness under plane strain conditions. It is safe and reliable, but the result Conservative, ignoring the thickness effect, the possible influence of the three-dimensional constraints inside the structure, so that not only the low utilization rate of the material in use, but also the excess weight in the design of the structure

Moreover, the typical three-dimensional non-penetrating crack on the surface of the spherical shell is different from the standard specimen in terms of load form, material parameters, and stress state at the crack tip, and the existing model is not clear enough, with many parameters, cumbersome calculation steps, and a lack of specificity. The detailed process and calculation method description of solving the three-dimensional crack propagation fatigue life on the surface of the spherical shell

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