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本文依据实验结果拟定了轴对称杯杆型复合挤压出现杆部表面裂纹时的金属流动速度场,以此为基础,并藉助于上限原理和最小能量原理,获得了此类复合挤压时杆部表面裂纹形成的必要条件。同时,研究了此类复合挤压杆部变形开裂区与正挤,反挤部分变形程度(εf,εb)组合、坯料相对余厚(T/R_0)、摩擦因数m值以及模具工作带相对长度(l_f/R_0,l_b/R_0)的关系.从而可以估测低塑性材料在进行此类复合挤压时杆部是否形成表面裂纹.LY12和LC4材料的试验结果与本文的分析结果具有很好的一致性.
Based on the experimental results, this paper developed the metal flow velocity field in the axial symmetric cup-rod composite extrusion on the surface of the rod, and based on this, based on the principle of upper bound and the minimum energy, Necessary conditions for the formation of surface cracks. In the meantime, the combination of deformation and crack (εf, εb), the relative thickness of blank (T / R_0), the friction coefficient and the relative working length (l_f / R_0, l_b / R_0) relationship between the low plastic material can be estimated in such composite extrusion rod surface cracks are formed.LY12 and LC4 material test results and the results of this analysis has a good consistency.