镍基单晶合金板裂纹尖端塑性区分析

Crack tip plastic zone of a nickel-based single crystal plate

裂纹尖端塑性区对研究裂纹开裂扩展具有重要意义.应用Hill屈服准则和考虑拉-剪耦合的修正Hill屈服准则,对镍基单晶合金板裂纹尖端塑性区进行了分析.得到了Ⅰ型、Ⅱ型和Ⅰ、Ⅱ复合型裂纹尖端塑性区.对镍基单晶合金板内裂纹尖端塑性区与各向同性材料板内裂纹尖端塑性区进行了比较.讨论了拉-剪耦合、Ⅰ、Ⅱ复合型裂纹复合比及温度对裂纹尖端塑性区的影响.结果表明,拉—剪耦合对裂纹尖端塑性区的尺寸有影响,760℃时影响明显.在平面应力状态下,镍基单晶合金板内裂尖塑性区尺寸随Ⅰ、Ⅱ复合型裂纹复合比的递增速度比平面应变状态下的大.温度对镍基单晶合金板裂尖塑性区有较大影响.

The crack tip plastic zone has been very significant to analysis of crack growth.In this study,crack tip plastic zones of a nickel-based single crystal plate were analyzed by using Hill yield criterion as well as a modified Hill yield criterion considering tension-shear stress coupling.The crack tip plastic zones,respectively corresponding to mode I,mode II,and mixed modes I,II,were derived.The crack tip plastic zones of the nickel-based single crystal were compared to that of isotropic material.The influences of tension-shear stress coupling,the compound ratio of mixed modes I,II,crack,and temperature on crack tip plastic zones were discussed.The results obtained show that the size of crack tip plastic zones based on Hill yield criterion is slightly different from that based on the modified Hill yield criterion for 760℃.The increase rate of crack tip plastic zones of the nickel-based single crystal increasing with a compound ratio in the plane stress condition is greater than that found in the plane strain condition,and the temperature has greater influence on crack tip plastic zones of the nickel-based single crystal.