表面塑性损伤的描述及其细观机理分析

DESCRIPTION OF SURFACE PLASTIC DAMAGE AND ANALYSIS OF ITS MESO\|MECHANISM

对ＬＹ１２ＣＺ铝合金板件单向拉伸状态下表面塑性损伤的细观演变过程进行了定量、定性对比观测，并选用和定义了表面损伤变量ＤＡ、Ｄ（Ｌ）和Ｄ（Ｒａ），以及整体损伤变量Ｄ（Ｅ），对材料表面的损伤演变规律进行了描述，并与材料整体的损伤进行了比较。结果表明：表面塑性损伤的细观机理与材料内部的基本一致，是微空穴的形核、长大与汇合为宏观裂纹的过程，汇合方向只与外载的方向有关；三表面损伤变量中，Ｄ（Ａ） 、Ｄ（Ｒａ）随ε的增大呈幂函数增大，Ｄ（Ｌ）则是先平稳变化，最后迅速增大；三变量间互相关，且Ｄ（Ｌ）较Ｄ（Ａ）对材料损伤变化更为敏感；表面损伤较整体损伤的变化稍有滞后。

A detailed quantitative and qualitative contrast observation was investigated for Meso\|process of surface plastic damage of LY12CZ aluminum plate under Uni\|stretch .Meso\|damage variables D()、D() and D(a) were defined to describe the development of surface material damage.Also, damage variables D() was defined to describe the damage of the whole material. The processes of surface damage and whole damage were compared with each other. The results showed: the meso\|mechanism of surface damage was basically similar to that of inner damage of material,that is the damage process of nucleation,growing and combination of the cavities.The combination direction was determined by the direction of loading.Of three surface variables, D( )、 D(a) rose with the increase of ε according to the power functions, D() changed smoothly first,and near to the end,then it changed violently.The three variables were correlated with each other and D() was more sensitive to the change of material damage than D() .In addition,by comparison,the evolvement of the surface damage lagged behind the inner material damage.