考虑晶粒长大效应的超塑性材料稳定性分析  

Analysis of Stability for Superplastic Material Considering Grain Growth Effect

作　　者：李跃宇[1] 刘树春[1] 

机构地区：[1]淮海工学院机械工程学院,连云港222005

出　　处：《力学季刊》2013年第4期673-679,共7页Chinese Quarterly of Mechanics

基　　金：淮海工学院2011年自然科学类校内课题(Z2011132)

摘　　要：超塑性材料具有延伸率非常高,可以成形复杂结构件等优点,已得到广泛应用.研究了考虑晶粒长大效应的超塑性材料拉伸稳定性问题.根据Hart的稳定性准则,导出了一个新的稳定性准则和临界失稳应变公式.计算结果表明:(1)临界失稳应变与4个材料常数有关.临界失稳应变随着应变速率敏感性指数m、应变硬化指数n、晶粒尺寸指数p的增大而增大;临界失稳应变随着晶粒直径比d_0/c增大而减小.应变速率敏感性指数的变化引起临界失稳应变变化最为明显;(2)当应变硬化指数为零时,临界失稳应变的解仍然有效,这就解决以往不考虑晶粒长大当应变硬化指数为零时,临界失稳应变无解的问题;(3)本文的临界失稳应变的解与已有的理论并不矛盾,晶粒尺寸保持常数的临界失稳应变解是它的一个特例,韧性材料的临界失稳应变解也是它的另一个特例.Superplastic materials have advantages like high elongation, forming complex structures easily and so on, thus they have been widely used. Tensile stability problem of superplastic material was studied considering grain growth. According to Hart＇s stability criterion, a new stability criterion and critical instable strain formula were derived. The calculation results show that, （1） critical instable strains are related to 4 material constants. Critical instable strains increase with the increase of strain rate sensitivity index m, strain hardening index n and grain size index p; critical instable strains decrease with the increase of grain diameter ratio d0 / c. The critical instable strains change most evidently because of change of the strain rate sensitivity index; （2） the solution for critical instable strains is still valid when the strain hardening index is zero. This solve a remaining problem： there is no solution when strain hardening index is zero without considering grain growth; （3） the solution in this paper for critical instable strains is not contradictory with previously existing theories. The solution of critical instable strains without considering grain growth is a special case of it. The solution of critical instable strains for ductile material is another special case of it.

关 键 词：超塑性 拉伸稳定性准则 临界失稳应变 晶粒长大 应变速率敏感性指数 应变硬化指数 

分 类 号：O344[理学—固体力学]