engleski

Modelling of Plastic Yielding Micromechanism in the Cohesive Zone around a Crack Tip in a Strain-Hardening Material

We are often faced with the problem of assessing the reliability of a structural element with a crack, which is made of a ductile material. When such a body is submitted to loading, plastified zones around the crack tips occur. Determination of the plastic zone shape and magnitude, the determination of displacements of the crack surface as well as of the crack opening is often a problem to be solved in mechanical computations by engineers. If it is assumed that a narrow yielding zone is formed around the crack tip, the Dugdale-Barenblat model of plastic yielding can be efficiently applied. This model is based on the implicit assumption that the model of the plate material is elastic-perfectly plastic, i.e. that the cohesive stress &#963 ; ; _Y in the plastic zone is constant. In this paper, we aim at creating a new and more reliable micromehanism of plastic yielding in the cohesive zone, which would better describe the real elastic-plastic state of the material around crack tips. The assumption of variable cohesive stresses &#963 ; ; _Y within the plastic zone is introduced. However, a law of distribution of stresses has not been established, and this is the most serious problem. Therefore, it is necessary to carry out an iterative procedure in order to establish a law of cohesive stresses distribution. The aim is to obtain a better micromehanical model for describing the plastic yielding around the crack tip in a plate made of strain-hardening material. The improved micromechanical model has been applied in the analysis of the elastic-plastic fracture mechanics parameters such as: the magnitude of the plastic zone around the crack tip r_p, the crack tip opening displacement &#948 ; ; _t, the displacements on the crack surface, etc. The crack, in a thin plate biaxially loaded on its edges, is straight, while the crack surface is free from loading. The loading parallel with the crack plane depends on the loading perpendicular to it. This dependence is established by using a load biaxiality factor k of the plate.

Dugdale Strip Yield Model; Variable Cohesive Stress; Strain-Hardening Material; Magnitude of the Plastic Zone; Crack Tip Opening Displacement; Analytical Methods

nije evidentirano