约束条件下界面纯铝层裂尖应力场的数值分析

对强度错配约束条件下LY12／Al／LY12四点弯曲试样界面纯铝层内裂纹前端进行了弹塑性大变形平面应变应力场数值分析。结果表明：在小范围屈服条件下随着中间纯铝层厚度的降低，其峰值载荷呈线性增加；强界面的约束使得其塑性变形由类似单金属纺锤形转变为平行于界面的纵向发展，该趋势随其厚度降低而越来越明显；裂尖三轴应力约束及最大拉应力水平随载荷增加或纯铝层厚度降低而升高，且均随归一化J积分增加沿一特定的路径变化．当界面对纯铝层塑性变形约束明显增加时，高的三轴约束将诱发微裂纹和孔洞的萌生，同时伴随着中间纯铝层的脆化甚至局部解理。

Numerical Analysis of the Crack-Tip Stress Field in Pure Aluminum Sheet Constrained by Interfaces

Elastic-plastic large deformation finite element (FE) analysis was conducted on the crack-tip stress field of pure Al sheet in LY12/A1/LY12 sandwich specimen with a strength mismatch and fatigue pre-crack under plane strain condition. The results show that, in the condition of small scale yielding (SSY), the peak value of loadings linearly increases with decreasing pure Al sheet thickness. Plastic deformation zone in Al sheet constrained by interfaces will spread along the crack-tip ligament parallel to the two interfaces instead of a spindle-like in a constraint-free metal, and this tendency becomes more remarkable with decreasing pure Al thickness. The maximum triaxial constraint and the tensile stress continue to rise with either increasing load or decreasing pure Al thickness. The high triaxial constraint in the Al sheet results in cavitations and micro-cracks as well as brittleness even local cleavage of pure Al sheet.