Abstract: The objective of #x0201c;mechanism investigation of out-of-plane tearing on light metal (wall thickness less than or equal to 10mm)#x0201d; is to provide the theoretical foundation for shredding and recovery processing of end-of-life vehicles and household appliances. The research and analysis on the shredding process of light metal indicates that the mode #x02162; crack contributes mostly in the shredding process. The material used is simplified as an ideal elastic-plastic model based on the phenomenon that the stress-strain curves of a tensile test have an identical variable trend with the ideal elastic-plastic material. The variable trend of load-displacement curves obtained by a trousers tearing test shows that a greater load is required at a crack initiation stage, comparing with a propagation stage. The study on the process of out-of-plane tearing has found that the crack tip plastic zone expands gradually under loading, when the plastic zone reaches the maximum size, the crack begins to propagate as the loading 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 a greater load is required at the crack initiation stage.