Papers by Keyword: Micro-Mechanical Modeling

Abstract: In the present study the crack initiation and propagation is investigated in the ductile-brittle transition region by means of a microscopic model. In particular, the particles in the process zone in front of the crack tip are resolved discretely in finite element simulations. The competing mechanisms of particle debonding and possible subsequent void growth as well as particle breakage and cleavage of the metallic matrix are incorporated explicitly in the micromechanical model by means of a cohesive zone. This approach accounts for the complex interactions of the mechanisms and allows to simulate all stages of crack initiation and propagation at all relevant temperatures.

Abstract: The viscoplastic behavior of the fiber-reinforced metal matrix composites under the thermomechanical loading is discussed in this study. The theories of micro-mechanics with the concepts of average stress and strain are adopted and developed to integrate matrix, coating and fiber properties for predicting the stress-strain response. It is reduced to a set of the ordinary differential equations of one order that can be resolved by the numerical solution algorithms based on the classical fourth order Runge-Kutta method.

Abstract: The influences of stress triaxiality on ductile fracture have been emphasized to explain the geometry independent fracture resistance characteristics of specimens and structures during past two decades. For the estimation of this material behavior, two-parameter global approach and local approach can be used as case by case manner. Recently, the interests for the local approach and micro-mechanical damage model are increased again due to progress of computational environments. In this paper, the applicability of the local approach has been assessed through a series of finite element analyses incorporating both modified GTN model and Rousselier model. The ductile crack growth behaviors are examined to guarantee the transferability on different sizes and geometries of C(T) specimens and SE(T) specimens. The material fitting constants are determined from calibration of tensile tests and numerical analyses results, and used to simulate the fracture behaviors of typical specimens. Then, a comparison is drawn between the numerically estimated crack resistance curves and experimentally determined ones. The comparison results show a good agreement and the two damage models are regarded as promising solutions for ductile crack growth simulation.