单边裂纹弯曲试样的转动修正方法研究

由SEB( single edged bending)试样变形几何关系,提出断裂韧度测试中用于SEB试样J积分塑性功计算的裂纹嘴张开位移V0与加载点在加载线位移VLL的弹塑性转换公式.对SEB试样进行弹塑性有限元分析表明:试样转动中心位置受材料本构关系的影响微小,仅与裂纹长度α与试样宽度W之比有关,进而提出SEB试样转动半径R(裂纹嘴初始位置到转动中心的距离)的表达式,并对公式的有效性进行验证；应用线弹性柔度公式预测裂纹长度,可以忽略试样转动效应的影响,而刚性转动对SEB试样的J积分计算有一定影响,需采用考虑转动效应的载荷与加载线位移关系曲线来获得真实的J-△α阻力曲线.

ROTATION CORRECTION METHOD USED FOR SINGLE EDGED NOTCHED BENDING SPECIMENS

According to the geometry deformation of SEB(single edged bending) specimen,an elastic-plastic transforming formula from crack mouth opening displacement to load point displacement along loading line for a SEB specimen is given,which can be applied to plastic work computation for J integral estimation.A series of elastic-plastic finite element analyses for the SEB specimens were conducted.The results show that,there are little influences on the rotation center positions of the SEB specimens from constitutive relations of materials,and then the rotation radius of a SEB specimen which is the distance from initial location of crack mouth to rotation center is only related to the ratio of crack length a to specimen width W,therefore,a formula to describe relation between the dimensionless rotational radius R/W and the ratio a/W for a SEB specimen is proposed.At the same time,the validity of the formula was verified.The analyses indicate that the rotation effect can be ignored and the compliance equations based on linear elastic can be used to accurately predict crack length of the SEB specimen.However,the rigid rotation behavior of the SEB specimen has certain influence on J integral determination,so it is necessary to use data records of load versus loading-line crack open displacement with a consideration of rotation effect to obtain real J—Δa resistance curve.