双剪统一屈服准则中的材料屈服极限和滑移面方向分析

Research on the yield limits and slip directions of the twin-shear unified yield criterion

对双剪统一屈服准则所表征的材料屈服极限和滑移面方向特性作了分析。结果表明,在描述材料的屈服极限方面,双剪统一屈服准则能够较好地反映中间主应力的影响,如中间主应力可提高材料的屈服极限,且屈服极限的提高具有区间性。但在描述材料屈服时的滑移面方向方面,虽然双剪统一屈服准则也能反映中间主应力的影响,但由于该准则是由两个表达式及相应的应力状态限制条件组成,当材料的实际应力状态同时满足这两个表达式的边界限制条件时,存在双重滑移角现象,并且滑移面的方向在该应力状态下会产生突变。由此可见,双剪统一屈服准则尚不能很好地描述材料屈服时的滑移特性。

Two aspects of the yield limits and the slip directions for materials in the twin-shear unified yield criterion are analyzed in this paper.The results show that on the yield limits of the materials,the criterion can express the influences of the intermediate principal stress on promoting the values of yield limits and such promotions varied in intervals with the intermediate principal stress.But on the slip directions for materials when yielding,although the effects of the intermediate principal stress can also be boundary restrictions of the two equations in the twin-shear unified yield criterion simultaneously.Such stress states make the slip directions varied abruptly.So it is summarized that the twin-shear unified yield criterion could not give a proper descriptions to the slip characteristics for the materials when yielding.