用相移法全自动绘制主应力迹线

Automatic Constructing Isostatics with Phase Shifting Method

光弹性试验可以得到两种有用的参数条纹:等倾线和等差线。等差线包含主应力差的信息,利用等倾线可以得知模型上各点的主应力方向。然而工程上更需要这样一种曲线,其上每一点的切线与法线方向为该点两个主应力的方向,主应力迹线正是这样一种很直观、实用的曲线。主应力迹线只与主应力方向有关,而与主应力大小无关。利用等倾线可以通过作图法将主应力迹线描绘出来。传统都是用手动绘制主应力迹线,本文提出了新的图像处理方法,结合等倾线相移技术实现了主应力方向的全场确定,从而实现了主应力迹线的全自动绘制。实验证明用相移法全自动绘制主应力迹线在工程上非常有用。

Using photoelasticity,isochromatic and isoclinic fringepatterns can be generated in a model specimen with an appliedload.The isochromatic fringes are related to the difference betweenthe two principal stresses and the isoclinics give the directionof the principal stresses of any point in the model.However,a more useful representation is the isostatic or stress trajectorydiagram where the principal stresses are tangent or normal to theisostatic lines at each point.Since the isoclinic patterns identifythe direction of the principal stresses,therefore the isostatic diagramcan be constructed directly from the composite isoclinicpattern.Usually this method is done by hand and involves sometedious curve fitting techniques.This paper propose a new imageprocessing method which combined with phase shifting method can construct isostatics.From the results of abundant experiments,the method is proved to be practically effective.