杆—杆型复合挤压时剩余坯料的中部开裂

Central Cracking in Billet Remainder during Bar-Bar Combined Extrusion

在杆杆型复合挤压时,如果坯料原始高度不大或剩余高度较小,则可能在剩余坯料的中部出现开裂。本文利用上限法,通过建立带中部开裂缺陷的运动学容许速度场,并利用最小能量原理,确定了中部开裂的产生条件。变形程度增加,可以使得这种缺陷产生的临界相对余厚减小。实验表明,理论结果与实验结果相当一致。

Cracks may occur in the centre of the remainder of a billet during bar- bar combined extrusion if the original height or the remaining height of the billet is short.In this paper,the upper bound method is used to determine the conditions for the formation of central cracking by establishing a kinem- atically admissible velocity field with crack defects and utilizing the minim- um energy principle.The experimental results showed that the increase of de- formation will cause the critical relative thickness of a billet to dcrease,and that the theoretical analysis is in good agreement with the experimental resu- lts.