镍基单晶板非晶轴方向复合型裂纹尖端塑性区

Plastic Zone at Mixed Mode Non-Crystal Axial Crack Tip in 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。通过对Hill屈服准则进行修正,给出一考虑拉剪应力耦合的修正Hill屈服准则。应用修正Hill屈服准则对镍基单晶合金板中、非晶轴方向Ⅰ/Ⅱ复合型裂纹尖端的塑性区进行了分析。在平面应力和平面应变状态下,得到Ⅰ/Ⅱ复合型裂纹尖端塑性区的解析解。讨论了拉剪应力耦合、应力比及裂纹面与材料晶轴间夹角对裂尖塑性区的影响。结果表明,考虑拉剪应力耦合时的裂纹尖端塑性区比不考虑拉剪耦合时的小,拉剪应力耦合对平面应力状态下的裂尖塑性区影响比对平面应变状态下的影响大。无论是平面应力状态还是平面应变状态,Ⅰ/Ⅱ复合型裂纹应力比对裂纹尖端塑性区形状均不产生明显影响,但对塑性区范围的影响较大。裂纹面与材料晶轴间的夹角对裂尖塑性区的形状影响较大。

Crack tip plastic zone was very significant to analyze crack propagation. A modified Hill yield criterion with considering tension-shear stress coupling was given by modifying the classical Hill yield cri- terion . The plastic zones at the tip of I / ]I mixed mode non- crystal axial crack in nickel-based single crystal plate were analyzed by using this modified Hill yield criterion. The analytical solutions of polar ra- dius of crack tip plastic zones were derived respectively in the plane stress condition and in the plane strain condition. The influences of tension-shear stress coupling, stress ratio of [ /II mixed mode crack and the angle between the crack plane and material crystal axis on crack tip plastic zones were discussed. The results obtained showed that crack tip plastic zone obtained when considering tension-shear stress coupling was a little smaller than the plastic zone obtained under the condition of omittion of tension-shear coupling and the effect of tension-shear stress coupling on the plastic zone in the plane stress condition was larger than that in plane strain condition. In this two kinds of plane problem, the stress ratio of I / II mixed mode crack had less effect on the shape of plastic zone and had obvious effects on the dimension of plastic zone. The angle between the crack plane and material crystal axis had more effect on the shape of the crack tip plastic zone.