Damage prediction for magnesium matrix composites formed by
liquid-solid extrusion process based on finite element simulation
liquid-solid extrusion process based on finite element simulation
(1. School of Mechatronic Engineering, Northwestern Polytechnical University, Xi’an 710072, China;
2. Key Laboratory of Contemporary Design and integrated Manufacturing Technology, Ministry of Education,
Northwestern Polytechnical University, Xi’an 710072, China)
2. Key Laboratory of Contemporary Design and integrated Manufacturing Technology, Ministry of Education,
Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness cracks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature criterion and Cockcroft & Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively. A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of Csf/AZ91D composites. It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending. The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement. In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur. The maximum damage values increase with increasing extrusion speed or extrusion temperature. Theoretical results obtained by the DeformTM-2D simulation agree well with the experiments.
Key words: magnesium matrix composite; liquid-solid extrusion; hot shortness cracks; surface cracks; finite element method