用双波长法和相移法确定光弹性参数

DETERMINATION OF PHOTOELASTIC PARAMETERS WITH TWO-WAVELENGTH AND PHASE SHIFTING METHODS

分别采用双波长法和相移法研究了光弹性条纹的自动分析技术。分别采用波长为630nm和532nm的激光作光源,根据在不同光场下获得的等差线条纹光强变化,可实现等差线条纹的自动定级。同时,提出了新的图像处理方法,结合等倾线相移技术实现了第一主应力方向的全场确定,再以Tardy补偿法为基础,提出了全场等差线的相移方法。该文结合经典的实验对比,详细比较分析了这两种方法的优缺点。结果表明:该文提出的新的相移方法可实现光弹性条纹的自动化分析。

The application of two-wavelength method and phase shifting for automatic analysis of fringe patterns resulted from photoelasticity was investigated. With the aid of two coherent light sources, the fringe orders of isochromatics have been determined through comparing the fractional quantities of the corresponding fringe patterns. In addition, a unique technique has been proposed to identify the orientation of the first principal stress. This technique allows extension of the phase value of the isoclinics from （0,π/2） to （-π/2, π/2） to extinguish the ambiguity of determining which orientation the first principal stress is in, which is extremely helpful for postal stress separation with shear stress differential method. With this technique, the isochromatics are the phase shifted in 8 discrete directions and then a full phase map of isochromatics has been constructed. An epoxy resin disk under diametric loading was tested with these two methods. The advantage and disadvantage of these two methods were discussed and conclusion was drawn that the proposed phase shifting method has potential to achieve automatic analysis for photoelasticity.