不同距离应变片测定Ⅰ型动态应力强度因子对比试验研究

基于线弹性断裂力学理论，采用应变片法开展了冲击动荷载作用下的三点弯曲试验，探讨距扩展裂纹不同距离的应变片测定Ⅰ型应力强度因子的差异。当应变片与扩展裂纹成特定锐角和钝角时，采用与裂纹扩展速度和应变片的位置相关的二项式表征裂纹尖端附近应变场，并结合理论解析和试验实测的应变与裂纹扩展时间曲线，推导得到了应力强度因子计算公式。同时，采用动焦散线试验对比分析应变片法测定的动态应力强度因子值。结果表明，应变片在裂纹尖端附近合理区域内，测定的裂纹尖端动态应力强度因子值与动焦散线试验结果吻合较好;明确了不同距离对测定Ⅰ型裂纹应力强度因子的影响，随着应变片粘贴距离变大，测定的动态应力强度因子值与动焦散线法相差增大。研究结果为进一步应用应变片法研究岩石类材料的断裂性能提供了试验基础。

Comparative experimental study on the measurement of type-Ⅰ dynamic stress intensity factor using different distance strain gages

Based on the linear elastic fracture mechanics theory,the difference of the measurement of type-Ⅰ dynamic stress intensity factor (DSIF) using different distance strain gages was analyzed.The three-point bending tests under impact loading were performed using strain gage method.When the orientation angles between stain gage and crack track were at specific acute and obtuse,the strain field in the vicinity of crack tip can be described by a two-parameter formula,which was related with the crack velocity and distance between strain gage and crack.Combining the strain-time curves of analytical solation and experimental test,an equation for calculating the value of DSIF was derived.The detailed comparisons and discussions of the values of DSIF obtained by simultaneous strain gage and dynamic caustics tests were presented.The results showed that there was an excellent agreement in the values of DSIF between strain gage and dynamic caustics tests when the strain gage was placed within the valid locations.The tests analysis indicated that the difference of DSIF between strain gage and dynamic caustics methods increased with the increase of distance between strain gage and crack.The results provide an experimental basis for a further application of strain gage method in the research of fracture properties of rock-like materials.