Abstract Unidirectional tensile tests of PMMA square hole specimens result in mixed mode crack initiation at the square hole corners, highlighted by inclined cracks with respect to the V-notch bisector. Generalized stress intensity factors (GSIF) of the opening and shear modes at a V-notch are derived experimentally in a direct manner from digital image correlation (DIC) displacement and strain fields by means of a path independent integral. With increasing square hole side, the opening mode GSIF increases whereas the shear mode one decreases so that the mode mixity globally decreases, together with the crack deflection with respect to the V-notch bisector. GSIFs predictions obtained by means of finite element calculations are in good agreement with those determined experimentally.

中文翻译：

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从全场测量中实验确定广义应力强度因子

摘要 PMMA 方孔试样的单向拉伸试验导致方孔角部产生混合模式裂纹，以相对于 V 型缺口平分线的倾斜裂纹突出。V 型缺口处的张开和剪切模式的广义应力强度因子 (GSIF) 是通过与路径无关的积分以直接方式从数字图像相关 (DIC) 位移和应变场中导出的。随着方孔边长的增加，开口模式 GSIF 增加，而剪切模式 1 减小，因此模式混合度整体降低，裂纹偏转相对于 V 型缺口平分线。通过有限元计算获得的 GSIF 预测与实验确定的预测非常一致。