Research On Snapping With Tearing Mechanism On Light Metal Scrap Of End-of-life Vehicles

With the rapid development of Chinese economy and the improvement of people’s living standard, the vehicles and household appliances have gradually become popular consumer products. At the same time, the number of end-of-life vehicles and household appliances is increasing with each passing day. Therefore, how to effectively recycle and secondary reuse of light metal scrap on automobiles and household appliances plays an important role to promote the rapid development of cyclic economy. On the basis of a series of related research, the more in-depth experimental study of snapping with tearing (SWT) fracture process of light metal scrap and the further reveals shredding mechanism of thin metal recovery from the energy point of view have completed in this paper, which provides some certain theoretical foundation for better research of recycling scrapped automobiles and household appliances.The material was studied in this paper is from the thin metal cover of different types of vehicles, whose brand are difficult to verify and the mechanical performance parameters are unknown. Therefore, the uniaxial tensile tests have multiple conducted on metal materials which are randomly selected, then the stress-strain relationship is simplified to bilinear model and basic performance parameters of material were obtained. These results lays the foundation for the analysis investigation of subsequent SWT fracture process.In order to realistically and objectively reflect fracture situation on metal material in the pendulum crusher, according to the pendulum shredder’s working principle on light metal, the analysis result show that SWT and tearing are both main modes of shredding. Then fracture mechanics model on light metal scrap are constructed, and SWT and tearing test are respectively completed. Further studies showed that SWT mode need higher energy consumption, but the boundary condition is easy to build and large pieces of fragments are more advantageous to reduce the comprehensive energy consumption. In the test process, micro-cracks on both sides of the pre-puncture hole with tongue-shaped straight edge undergo repeatedly the process of instability, extension and stress relaxation; tongue-shaped straight edge emerges repeatedly local folding deformation, transverse and longitudinal bending in two directions happened on every specimen, and large pieces of fragments of the light metal scrap are torn off from its mother body which achieve the purpose of crushing.Through observation and analysis of multiple sets of SWT tests, the whole fracture process of light metal scrap can be divided into crack initiation, rapid crack propagation stages. The whole shredding process is accompanied by the instability initiation of Ⅰ-Ⅱ mixed crack and the rapid spread of Ⅰ-Ⅲmixed crack, and specimens have mainly generated the overall bending deformation characteristics which along the vertical direction and horizontal direction, furthermore, many times local laminating bending in reverse are happened on tongue shaped straight edge of the pre-puncture hole. According to energy analysis we know that the energy was mainly consumed by elastic-plastic bending deformation and shredding of scrap material in the whole shredding process. By establishing the SWT calculation model of the process, the local cascade bending work of tongue-shaped straight edge, the transverse overall bending work and overall longitudinal bending work are calculated respectively, eventually we get to the SWT fracture work; Investigation show the total work that external force does is mostly used for the shreeding of light metal scrap material, and the comprehensive utilization of energy is higher efficiency.SWT shredding process is simulated by nonlinear simulation software ANSYS/LS-DYNA. Through the simulation experiment confirms that specimens have mainly generated the local cascade bending of tongue-shaped straight edge, overall transverse bending and longitudinal bending deformation. Through the loading speed, cross-section of SWT tools and pre-opening shape of specimens were simulated under different conditions, the influence laws of light metal scrap shredding process are obtained. The above conclusion for automobiles and household appliances fracture processing provide theoretical basis for the research and development of crushing equipment.