高精度数字梯度敏感法测量PMMA板的转角场

用数字梯度敏感法(DGS)测量聚甲基丙烯酸甲酯(PMMA)板的应力梯度(偏转角)。首先,利用数字图像相关方法(DIC)测量了PMMA板在三点弯曲作用下应力集中区域的全场位移,再根据光弹效应建立PMMA板的应力梯度与光线穿过透明件后的偏转角之间的关系,得到PMMA板的转角场。将直接测得的转角场与解析值进行对比,发现存在误差。这是由于试验中不可避免地存在面内刚体平移及离面位移,导致试验中得到的转角场产生误差。通过补偿区域法消除上述影响因素,并讨论了面内刚体平移和离面位移对试验的影响。最后,与解析值对比,结果表明,通过补偿区域法降低了测量误差,得到高精度的转角场。x和y方向转角场的平均相对误差分别为4.90%和5.89%。

Measuring angular deflections of PMMA by high-precision digital gradient sensing method

Stress gradient (angle deflection) of polymethyl methacrylate (PMMA) plate is measured by digital gradient sensing method(DGS). DGS first uses the digital image correlation method (DIC) to measure the full field displacements in the region of stress concentration of PMMA plate under the three-point bending. Then, angular deflection of light rays can be linked to stress gradients of PMMA plate according to the photo-elastic effect, and the angular deflections of PMMA plate can be further obtained. The angle deflections that are measured directly are compared with the analysis data, and errors are found. Because the in-plane motion of the rigid body and the out-of-plane motion exist unavoidably in the test, so the error of the angle deflections appears. After removing the above influencing factors by compensation regional method, we discuss the influence of the in-plane motion of the rigid body and the out-of-plane motion on the test. Finally compared with the analytic value, the results show that the compensation regional method reduces the measurement error, and the high-precision angular deflections are obtained. The average relative error of angular deflections in the x and y directions are 4.90% and 5.89%, respectively.