Information and System Modelling in the Problems of the Fracture Mechanics

Abstract

The fracture mechanics is successfully used to study the crack appearance and proliferation under certain conditions. However, analytical solutions currently exist only for simple cracks. The complex cracks (inclined, branched, etc.) can only be solved using the numerical methods.

Thanks to the constantly developing computer technologies, the engineers and scientists have already received the opportunity to analyze the strength, the deflected mode of a structure with or without cracks, without resorting to creating the models that are equivalent to the data, but only working in the analysis engineering systems. The method using mathematical models instead of the experimental stands is very promising from the point of view of the automation and acceleration of engineering calculations. This method is economical in terms of the material and labour costs.

In the ANSYS, a similar 3D geometric model of a hollow thick-walled cylinder with a semi-elliptical surface crack was simulated, a finite-element mesh is built, and the necessary loads are applied. It should also be noted that in the 3D modelling it is necessary to shift the units of the finite element at the crack tip. Consequently, there is a need to develop a method for the automated process for generating a finite element mesh at the crack tip for three-dimensional objects.

As a result of the calculation, the maps of the shift distribution and equivalent stresses according to the IV theory of strength, as well as the distribution of stress intensity factors (SIF) along the crack front are obtained. The SIF values obtained in the ANSYS were presented in the form of graphs of the SIF dependence on the number of the crack front unit.

Based on the simulation results, it can be concluded that these types of defects depend on the tensile stresses. The internal pressure, material specifications, the wall thickness and the cylinder bore have the greatest influence on the tensile stresses. The results of this work can become the basis for studying the parameters of the fracture mechanics for the prefabricated welded structures of the cylindrical high-pressure vessels, as well as in problems where it is necessary to take into account the elastoplastic behaviour of the material. On the basis of the proposed research method, the additional factors, affected the considered issues of the strength calculations of the dynamic deflected mode of the automobile parts, can be identified.