In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area,...In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area, therefore, needs to be compensated manually before using one step inverse approach, which causes low efficiency and in consistency with the real situation. To solve this problem, one step positive approach is proposed to simulate the sheet metal stamping process. Firstly the spatial initial solution of one step positive method is preliminarily obtained by using the mapping relationship and area coordinates, then based on the deformation theory the iterative solving is carried out in three-dimensional coordinate system by using quasi-conjugate-gradient method. During iterative process the contact judgment method is introduced to ensure that the nodes on the spatial initial solution are not separated from die surface. The predicted results of sheet metal forming process that include the shape and thickness of the stamped part can be obtained after the iterative solving process. The validity of the proposed approach is verified by comparing the predicted results obtained through the proposed approach with those obtained through the module of one step inverse approach in Autoform and the real stamped part. In one step positive method, the stamped shape of regular sheet can be calculated fast and effectively. During the iterative solution, the quasi-conjugate-gradient method is proposed to take the place of solving system of equations, and it can improve the stability and precision of the algorithm.展开更多
Now the researches concerning integral bus mainly focused on design and analysis of overall mechanical property of bus body, and paid little attention to characteristic of local structures, such as joint, plug welding...Now the researches concerning integral bus mainly focused on design and analysis of overall mechanical property of bus body, and paid little attention to characteristic of local structures, such as joint, plug welding hole, and bolt connection point, etc. So there is much blindness on the design of local connecting structure. Since integral bus body structure cancels large section longitudinal beam, and uses framework made by welding small section bars together as principal part to bear the whole load when the vehicle works, there are many joints receiving high load in the body structure, and local stress concentration can not be avoided. Under such circumstances, by adopting beam-shell mixed model based on super element technique, and selecting a joint commonly used by bus sidewall, the rule of the effect of bar joint’s welding seam spacing on joint’s local mechanical property is investigated in this paper, and the investigating results show that joints have minimum stress concentration with welding seam spacing of 8 mm. To learn whether the above rule is affected by relative bar wall thickness, many groups of bars with different relative bar wall thicknesses are studied experimentally, and the experimental results show that the joints local stress levels vary with different relative bar wall thicknesses, but the rule of the effect of bar joint’s welding seam spacing on joint’s local stress level remains the same. The research is significant for local structure design of bus joint in the future.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 51075187)
文摘In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area, therefore, needs to be compensated manually before using one step inverse approach, which causes low efficiency and in consistency with the real situation. To solve this problem, one step positive approach is proposed to simulate the sheet metal stamping process. Firstly the spatial initial solution of one step positive method is preliminarily obtained by using the mapping relationship and area coordinates, then based on the deformation theory the iterative solving is carried out in three-dimensional coordinate system by using quasi-conjugate-gradient method. During iterative process the contact judgment method is introduced to ensure that the nodes on the spatial initial solution are not separated from die surface. The predicted results of sheet metal forming process that include the shape and thickness of the stamped part can be obtained after the iterative solving process. The validity of the proposed approach is verified by comparing the predicted results obtained through the proposed approach with those obtained through the module of one step inverse approach in Autoform and the real stamped part. In one step positive method, the stamped shape of regular sheet can be calculated fast and effectively. During the iterative solution, the quasi-conjugate-gradient method is proposed to take the place of solving system of equations, and it can improve the stability and precision of the algorithm.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2006AA110104)
文摘Now the researches concerning integral bus mainly focused on design and analysis of overall mechanical property of bus body, and paid little attention to characteristic of local structures, such as joint, plug welding hole, and bolt connection point, etc. So there is much blindness on the design of local connecting structure. Since integral bus body structure cancels large section longitudinal beam, and uses framework made by welding small section bars together as principal part to bear the whole load when the vehicle works, there are many joints receiving high load in the body structure, and local stress concentration can not be avoided. Under such circumstances, by adopting beam-shell mixed model based on super element technique, and selecting a joint commonly used by bus sidewall, the rule of the effect of bar joint’s welding seam spacing on joint’s local mechanical property is investigated in this paper, and the investigating results show that joints have minimum stress concentration with welding seam spacing of 8 mm. To learn whether the above rule is affected by relative bar wall thickness, many groups of bars with different relative bar wall thicknesses are studied experimentally, and the experimental results show that the joints local stress levels vary with different relative bar wall thicknesses, but the rule of the effect of bar joint’s welding seam spacing on joint’s local stress level remains the same. The research is significant for local structure design of bus joint in the future.
