Study On The Tearing Mechanism Of Light Metal

With the rapid development of our economic and society, the motor vehicles are driving into our family quickly while all kinds of the household appliances have become the daily products. How to realize the process of recycling end-of-life vehicles and household appliances with efficiency, low-consumption and pollution-free in the near future has become one of the most important problems.The most efficient method to dispose the end-of-life vehicles and household appliances is to shred all of them, and light metal material is one of their main parts. In order to conduct more thorough research on the shredding mechanism of the light metal, impact crushing test, the tensile test and out-of-plane tearing test for three trousers have been done based on the analysis for shredding process of the light metal. Research and analysis on the results of tests indicates that the mode Ⅲ out-of-plane tearing contributes mostly in the shredding process of light metal and the tearing process should be divided into three stages:Crack initiation, propagation and fracture. The material used is simplified as an ideal elastic-plastic model based on the phenomenon that the stress-strain curves of tensile test have the same change trend with the ideal elastic-plastic material. The change trend of the load-displacement curves obtained by trousers tearing test shows that greater load is required at the crack initiation stage than the propagation stage, which indicates that the tearing process of light metal have to break through a critical state.Study on the process of out-of-plane tearing has found that the crack tip elastic plastic zone expands gradually under load, when the plastic zone reaches the maximum size, the equilibrium state of crack tip elastic plastic zone is disturbed and the crack begins to propagate as load increasing, meanwhile the plastic-zone moves ahead gradually until fracture. The solution to the crack tip field indicates that singularity exists in the crack tip stress-strain fields, and the singularity is weaker at the stage of propagation than that of the crack initiation stage, namely, the stress-strain concentration level of the crack initiation stage is much higher than that of the propagation stage, which means that greater load is required at the crack initiation stage, and the result is agreeable with the one of tearing test. The tearing work for crack propagating has been calculated based on the tearing process investigation of light metal.The tearing process simulation of light metal is performed by explicit element code LS-DYNA, and the simulation result agrees with that of tearing test and theoretical research.