Analysis of Crack Growth Behavior in A Polymeric Strip using Photo-Viscoelastic Method

为了准确地分析粘弹性材料中裂纹运动尖端周围的应力和应变场，不仅需要开发方便实用的计算机辅助算法，而且需要开发处理海量图像数据的技术。1)在本研究中，我们开发了一种方便的算法用于积分条纹的计算机辅助应力分析。本文提出了一种简便易行的分析CT型试件从平面应变到平面应力状态的应力强度因子KI随镜片厚度变化的方法，该系统配有改进的散射光弹性装置。对于K_&lt；III&gt；，我们也可以成功地以同样的方式进行精确的测量。2)本研究提出了一种函数逼近方法，以克服分析裂纹尖端和载荷等奇点附近的应力分布的困难。折叠的Data…利用Goursat应力函数的一般形式，可以很好地重建奇点附近更多的光弹性条纹图，其未知参数由非线性优化逼近技术确定。作为典型算例，将该方法应用于I型裂纹试件，成功地得到了作为未知参数之一的应力强度因子。3)考虑材料随时间变化的力学行为，将位移速率改变为裂纹扩展长度的几个阶跃，研究了裂纹扩展行为的变化。考虑材料的分子结构和纠缠结构，研究了J‘_i(T)随时间的变化和断口表面粗糙度的变化，讨论了宏观和微观断裂机制之间的关系。在此基础上，提出了一种新的亚微观尺度下的裂纹扩展机制模型，用以描述这些材料中裂纹扩展的时间和温度相关行为。较少

In order to perform accurate analysis of stress and strain field around a moving tip of crack particalarly in viscoelastic materials, it should be emphasized that not only convenient and useful computer-aided algorithms but also techniques for handling image data of tremendous amounts have to be developed.1) In this study, we developed a convenient algorithm for computer-aided stress analysis of the integrated fringe. The authors proposed a convenient technique to analyze the variation of the stress intensity factor K_I of CT type specimen from plane strain to plane stress state over the thickness of spesimen using a system with the improved devices of the Scattered Light Photoelasticity. Regarding to K_<III>, we can also be successful for accurate measurement in the same manner.2) This study is concerned with a proposal of the functional approximation method to overcome the difficulty in analysis stress distribution near a singular point such as a crack tip and loading. Collapsed data … More of photoelastic fringe pattern in the neighborhood of a singular point will be well reconstructed, using a general form of Goursat stress functions, unknown parameters of which are determined by a nonlinear optimizing approximation technique. And, as an typical example, the stress intensity factor determined as one of the unknown parameters is successfully obtained by applying this method to a Mode I type cracked specimen.3) Taking the time dependent mechanical behavior of the material into consideration, variation of crack growth behavior after changing displacement rate as several steps in length of crack growth is studied. Time dependent J'_I(t) and change in fracture surface roughness are investigated to proceed discussions on relationship between macro- and microscopic mechanisms of fracture taking molecular and entanglement structures of the material into consideration. Then, a new model of crack growth mechanism in sub-micro scale dimension is proposed to describe the time and temperature dependent behavior of crack growth in these materials. Less