由裂纹嘴位移确定双悬臂梁试样应力强度因子的权函数解法

双悬臂梁(DCB)试样在材料的损伤容限性能评价,特别是应力腐蚀开裂门槛值(K_ISCC)测定中有重要应用。由于该试样几何的特殊性,一般采用与试样端部(裂纹嘴)有一定距离的特定位置裂纹面位移加载方式,然而该加载点的位移测量不但费时而且精度低,位移测量最方便和准确的位置是在DCB试样的裂纹嘴。通过对一种参考载荷条件的有限元计算,应用边缘裂纹的经典权函数解法,推导出DCB试样的权函数解析解,并与复变函数泰勒级数展开的权函数解法作了比较验证。在此基础上根据特定加载点的位移反算出相应位置均布应力加载下的应力强度因子,进而建立DCB试样在特定位置的裂纹面位移加载条件下的应力强度因子与裂纹嘴位移之间的关系式,为采用这种试样的材料损伤容限性能评价,特别是K_ISCC的高精度自动化测定奠定了基础。

Weight function method of determining double cantilever beam specimen stress intensity factor by crack mouth displacement

Double cantilever beam(DCB) specimen has important applications in materials' damage tolerance properties evaluation, especially for experimental determination of the stress corrosion cracking threshold(K_ISCC). Because of the particular specimen geometry, crack surface displacement loading at a specific position which is a certain distance away from the specimen edge(crack mouth) is commonly used. However, displacement measurement at the loading position is not only time-consuming but also inaccurate. For the DCB specimen, the most convenient and accurate displacement measurement location is at the crack mouth. In this paper, through finite element calculations for a reference load case and by using the classical weight function method for the edge crack geometry, analytical weight function for the DCB specimen is developed. Comparisons and verification have been conducted using the complex variable function Taylor series expansion weight function. Furthermore, from the specific loading point displacement, stress intensity factor for uniform stress loading at the corresponding crack surface location is obtained by inverse calculation. An analytical expression between the stress intensity factor and the crack mouth displacement is derived for DCB specimen subjected to the crack surface displacement loading at specific position. Thus, a solid foundation is laid for the evaluation of materials' damage tolerance properties using the DCB specimen, especially for K_ISCC measurement automation with high accuracy.