复合挤压时的杆部表面裂纹分析

李淼泉; 吴诗惇; 唐才荣

复合挤压时的杆部表面裂纹分析

西北工业大学锻压教研室

基金项目: 国家自然科学基金资助项目

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出版历程
- 收稿日期: 1989-05-04
- 刊出日期: 1990-08-15

Analysis of Surface Crack on Forward Extruding Bar during Axisymmetric Cup-Bar Combined Extrusion Process

Northwest Polytechnical University, Xi'an

摘要

摘要: 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(ε_f,ε_b)组合、坯料相对余厚(T/R₀)、摩擦因数m值以及模具工作带相对长度(l_f/R₀,l_b/R₀)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.

Abstract: In this paper, the kinematically admissible velocity field with surface crack on forward extruding bar is put forward during the axisymmetric cup-bar combined extrusion process, in accordance with the results of model experiments.On the basis of velocity field, the necessary condition for surface crack formation on the forward extruding bar is derived, with the help of upper bound theorem and the minimum energy principle. Meanwhile, the relationships between surface crack formation and combination of reduction in area for the part of forward and backward extursions (ε_b,ε_f) relative residual thickness of billet (T/R₀),frictional factor (m) or relative land length of ram and chamber (l_b|R₀,l_f|R₀) are calculated during the extrusion process. Therefore, whether the surface crack on forward exturding bar occurs can be predicted before extruding the lower-plasticity metals for axisymmetric cup-bar combined extrusion process.The analytical results agree very well with experimental results of aluminium alloy LY12 (ASTM 2024) and LC4 (ASTM 7075).

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参考文献(12)

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