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用有限元法分析了不同Ⅰ-Ⅱ复合型裂端的变形场和约束场(裂端形状改变能和应力三维度水平Rσ)分布。结果表明:复合型裂端变形为不对称的相反变形,符合钝化-锐化模型。Ⅰ-Ⅱ复合加载时裂纹尖端出现负约束区域(该区Rσ<0),当Ⅱ型分量增加,负约束区域增大,最大约束水平Rσmax降低,且绕裂纹尖端顺时针转动。Rσmax出现距裂纹尖端有一定距离处。Ⅰ-Ⅱ复合载荷下偏离原裂纹方向的裂纹在钝化区内某处危险点开始萌生,并与应力三维度最大位置处产生的空穴或孔洞聚合向前扩展。
The deformation field and the confinement field (the change of crack tip shape change energy and the three-dimensional stress level Rσ) of different Ⅰ-Ⅱ composite crack ends were analyzed by finite element method. The results show that the deformation of the composite crack tip is asymmetric and the deformation is in accordance with the passivation-sharpening model. The negative constraint region (Rσ <0) appears at the tip of the crack during the composite loading of Ⅰ-Ⅱ. When the Ⅱ component increases, the region of negative constraint increases and the maximum constraint level Rσmax decreases and turns clockwise around the crack tip. Rσmax appears at a distance from the crack tip. Cracks that deviated from the original crack direction under the composite load of I-II began to germinate at some dangerous point in the passivation zone and expanded along with the holes or holes generated at the maximum position of the three-dimensional stress.