Damage And Failure Analysis Of Heterogeneous Materials Based On Cohesive Zone Model

Heterogeneous materials are usually composite materials which are made of different materials or composed of different phases. They are widely used in construction, machinery,electronic, aerospace and other fields, due to their high strength, temperature resistance,corrosion resistance, toughness and oxidation resistance, etc. This kind of materials is heterogeneous and its research methods are different from homogeneous materials. The numerical model of heterogeneous materials can be divided into three types, namely the macro model, the mesoscopic model and the multi-scale model. The mesoscopic model is widely adopted because it can truly reflect internal damage of the materials. To establish the numerical model which can reflect the mesoscopic structural characteristics and the damage evolution law are the premise and foundation of mesoscopic numerical researches. Many scholars at home and abroad have proposed a lot of damage models to study the heterogeneous materials. However, most of the models are too complex or have too many model parameters, so the actual engineering applications are very difficult. The cohesive zone model has become a hot research which has been used in many engineering fracture problems due to its simpleness, and accuracy. However, the use of this model to study damage and destruction of the heterogeneous material, simulating its arbitrary crack extension is still relatively rare at home and abroad, and there are many problems should be improved or to be solved.According to above problems, we adopted three different methods to establish the numerical models of the heterogeneous materials, such as concrete and solder alloy. To some extent, the methods improved the current situations. At the same time, damage and failure analysis of the heterogeneous materials based on the improved cohesive law were conducted.In order to determine cohesive model parameters, an inverse method based on kalman filter algorithm was presented, and two inverse methods were adopted to determine the cohesive law parameters. In this paper, the main research work includes the following several aspects.(1) The mesoscopic modeling methods of the heterogeneous materials were researched based on the image processing method(image method) and the random aggregate program(procedure method). The recognition efficiency and procedure of the original image method were improved, and the variety of aggregate shapes of the commonly used procedure methods was enriched. The image-procedure method coupling image method and procedure methodwas put forward, so that it could characterize the real mesos-tructure of homogeneous materials more accurately.(2) The damage and failure behaviors of the heterogeneous materials were simulated by using an improved bilinear cohesive zone model based on the user subroutine(VUEL) in ABAQUS. At the same time, an algorithm for embedding the cohesive elements automatically at the potential damage zones was put forward which was implemented by Fortran codes. It not only improved the efficiency of calculation, but also simplified the modeling procedure greatly. Finally, several typical numerical examples were given to verify the rationality and effectiveness of these proposed methods.(3) An inverse method based on Kalman Filter Algorithm was put forward, and two inverse schemes, namely the fractional optimization method and energy method were presented for the parameters identification of the improved exponential cohesive zone model.First, the interface damage behavours of Solder alloy/Cu were researched by DCB tests and SLJ tests under different load modes respectively. Then, the effectiveness of the method and its sensitivity to noise were confirmed though the pseudo-experiment data. Finally, the Mode-I and Mode-II CZM parameters were obtained by jointing fracture tests and simulations results.(4) The heterogeneous materials modeling system(HMMS) based on C programming language was developed in view of the tedious work of the heterogeneous material numerical modeling. This system has a good interactive interface whicd integrates two kinds of modeling methods and the method of implantation of cohevie elements.This system is very convenient to construct the finite element model of the heterogeneous materials.