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【答案】应助回帖
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zoe122208: 金币+30, 翻译EPI+1, ★有帮助 2013-11-10 13:54:01
The reason of B column straight-wall broken was caused by the different temperature of the flange area and the alteration of strain paths. When the size of workblank was unreasonable, workblank of the flange area at fracture risk parts would oversize. With the action of blank holder force, the size of the workblank larger, the resistance of feedstock would be greater. In the meantime, flange cooled down rapidly because it was in the positive pressure. When the temperature was below 500°C, resistance of deformation would be enhanced, hinder material flow in the middle, led to the straight wall rupture. On the other hand, because the mo(u)lding surface of mould was stepped, feedstock of workblank would glide two rounded corners during the forming process. Two more bending deflection and reverse bending deformation would happen, resulting in strain paths of straight-wall at first was deep drawing state, then plane strain state, at last in the double pull state. Complicated strain paths lead to burst occur more easily. Once sheet of the flange area was reduced, strain paths of thinning serious position was simple deep drawing state, so it could decrease the possibility of rupture.
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