A forming method named powder cavity flexible forming was proposed. It is a forming technology which uses powder medium instead of rigid punch or die to form sheet metals. Cup shells were successfully obtained by this...A forming method named powder cavity flexible forming was proposed. It is a forming technology which uses powder medium instead of rigid punch or die to form sheet metals. Cup shells were successfully obtained by this technology. The theoretical calculation equation of forming load was obtained through mechanical analysis and the stress state in cup shells was analyzed by finite element simulation. The results show that powder cavity flexible forming technology can improve the forming limit of sheet metal. Compared with rigid die forming process, the thickness reduction in the punch fillet area significantly decreases and the drawing ratio increases from 1.8 to 2.2. The thinning compressive stress in the bottom of cup shell emerges, which makes the bottom of the cup shell in three-dimensional stress state and the stress in punch fillet region decrease due to powder reaction force, which can effectively inhibit the sever thinning of the sheet and prevent the generation of fracture defects.展开更多
In this study, based on the classical Archard adhesion wear theory, a three-dimensional finite element model was established, with the aim of simulating the failure process of self-lubricating spherical plain bearings...In this study, based on the classical Archard adhesion wear theory, a three-dimensional finite element model was established, with the aim of simulating the failure process of self-lubricating spherical plain bearings in the swinging wear condition. The results show that the self-lubricating spherical plain bearings go through two different stages during the wear process, namely, initial wear stage and stable wear stage. Because the large contact points wear out during the initial wear stage, the maximum contact pressure decreases as the test period increases. The relatively larger wear depth region shows elliptical distribution, and the maximum distribution appears in the central contact area. The wear depth reaches 0.974 mm after swinging 25,000 times. PTFE fibers, which possess a good friction performance but poor abrasion resistance, abundantly exist on the friction surfaces of the fabric liner. Consequently, the friction torque during the initial wear stage is slightly smaller than the friction torque during the stable wear stage; however, the wear rate during the initial wear stage is high. The reliability and effectiveness of the finite element model are verified by experiment. The developed finite element model can be used for the analysis of the wear mechanisms of bearings and the prediction of the service life of bearings.展开更多
基金Project(E2017203046)supported by the Natural Science Foundation of Hebei Province,China
文摘A forming method named powder cavity flexible forming was proposed. It is a forming technology which uses powder medium instead of rigid punch or die to form sheet metals. Cup shells were successfully obtained by this technology. The theoretical calculation equation of forming load was obtained through mechanical analysis and the stress state in cup shells was analyzed by finite element simulation. The results show that powder cavity flexible forming technology can improve the forming limit of sheet metal. Compared with rigid die forming process, the thickness reduction in the punch fillet area significantly decreases and the drawing ratio increases from 1.8 to 2.2. The thinning compressive stress in the bottom of cup shell emerges, which makes the bottom of the cup shell in three-dimensional stress state and the stress in punch fillet region decrease due to powder reaction force, which can effectively inhibit the sever thinning of the sheet and prevent the generation of fracture defects.
文摘In this study, based on the classical Archard adhesion wear theory, a three-dimensional finite element model was established, with the aim of simulating the failure process of self-lubricating spherical plain bearings in the swinging wear condition. The results show that the self-lubricating spherical plain bearings go through two different stages during the wear process, namely, initial wear stage and stable wear stage. Because the large contact points wear out during the initial wear stage, the maximum contact pressure decreases as the test period increases. The relatively larger wear depth region shows elliptical distribution, and the maximum distribution appears in the central contact area. The wear depth reaches 0.974 mm after swinging 25,000 times. PTFE fibers, which possess a good friction performance but poor abrasion resistance, abundantly exist on the friction surfaces of the fabric liner. Consequently, the friction torque during the initial wear stage is slightly smaller than the friction torque during the stable wear stage; however, the wear rate during the initial wear stage is high. The reliability and effectiveness of the finite element model are verified by experiment. The developed finite element model can be used for the analysis of the wear mechanisms of bearings and the prediction of the service life of bearings.
