• CN:11-2187/TH
  • ISSN:0577-6686

›› 2008, Vol. 44 ›› Issue (1): 222-226.

• 论文 • 上一篇    下一篇

等通道转角挤压下变形体长度对应力的影响及开裂判据分析

许晓静;张雪峰;刘桂玲;程晓农   

  1. 江苏大学先进成形技术研究所
  • 发布日期:2008-01-15

Work-piece Length of the Effect on Stress and Analysis of Cracking-criterion Under Equal Channel Angular Pressing

XU Xiaojing;ZHANG Xuefeng;LIU Guiling;CHENG Xiaonong   

  1. Institute of Advanced Forming Technology, Jiangsu University
  • Published:2008-01-15

摘要: 利用有限元软件ANSYS对2024铝合金等通道转角挤压((Equal-channel angular pressing,ECAP)过程进行计算模拟,得到等效正应力(Von Mises应力)、切应力随变形体长度及下行位移的变化,结合ECAP试验,研究ECAP形变开裂的判据。结果表明,无论变形体长度及下行位移如何变化,等效正应力都小于材料的抗拉强度,而切应力则随着变形体长度的降低总体上呈下降趋势,当变形体的长度小于某一临界值时,计算模拟表明最大切应力小于材料的抗剪强度,样品开裂倾向大幅降低,二者相当吻合。研究结果不仅说明“最大切应力不大于材料抗剪强度”可以作为材料ECAP形变过程中不出现开裂现象的判据,而且也为材料的ECAP加工提供理性研究思路,即先实测材料的应力-应变曲线,然后基于上述判据对模具结构、材料预处理工艺及样品尺寸等进行优化设计。

关键词: 等通道转角挤压, 断裂分析, 应力, 有限元模拟

Abstract: Finite-element method (FEM) and experimental investigation of 2024 Al subjected to equal-channel angular pressing (ECAP) has been carried out. The maximum equivalent normal stress and the maximum shear stress at an optionally given displacement of ECAP have been obtained through FEM for various given initial length of ECAP samples. The cracking criterion for the materials subjected to ECAP is further discussed with the help of experimental investigation. It is observed that at all given displacement of ECAP, the maximum equivalent normal stress is always less than the ultimate tensile strength of materials for all ECAPed samples with various initial length, while the maximum shear stress is always present at the angular channel zone of ECAP die, and its value decreases with the decrease of initial length of ECAPed samples. When the used initial length is small enough, the computed maximum shear stress becomes less than the shear strength of the materials, which is in very good agreement with the experimental observation that the frequency of sample cracking is decreased greatly. It is concluded that the non-cracking criterion of the materials subjected to ECAP could be expressed as “the maximum shear stress is less than the shear strength of materials”. It is also suggested that a rational research should be involved in the actual measurement of stress-strain curve and the optimization in the configuration of ECAP die, the technology of materials pretreatment and the length of samples based on the above-motioned non-cracking criterion.

Key words: Equal-channel angular pressing, Finite-element method, Fracture analysis, Stress

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