QUANTITATIVE MICROMECHANISTIC STRESS AND DEFORMATION ANALYSIS OF ENVIRONMENTAL CRAZES IN CRACKED POLYMERS BY USING THE SHADOW-OPTICAL-METHOD OF CAUSTICS

本文研究了聚甲基丙烯酸甲酯（pmma）裂纹前甲醇裂纹的实验应力和变形分析。结论如下：1。研究表明，利用焦散，即阴影光学图形，可以评估裂纹层周围的应力和变形分布。在拉伸作用下，裂纹阴影模式的变化与面外变形的变化相对应。已经证实，裂纹尖端存在应力集中，这意味着使用dugdale模型进行断裂力学研究有其局限性。弹性近似是允许的试样从甲醇中去除到空气和干燥的裂纹尖端变形。在这种情况下，裂纹层的应力分布与kramer等人用全息干涉测量得到的结果吻合得很好。环境热的增长速度与阴影图案的直径有相关性。建立了沿裂纹层的应力分布模型，并在此基础上进行了预测阴影图案的计算机模拟。通过与实验结果的拟合，可以对裂纹尖端和裂纹尖端的应力等参数进行评估。研究了应力光学常数随裂纹板周围环境液体折射率的变化规律。已经证明，这种液体的光学效应是不可忽视的。从poly ?的裂纹尖端得到了反射焦散图。这使得评价延展性聚合物的韧性成为可能。

THIS STUDY IS CONCERNED WITH EXPERIMENTAL STRESS AND DEFORMATION ANALYSIS OF A METHANOL CRAZE AHEAD OF A PMMA CRACK. THE FOLLOWINGS ARE CONCLUDED.1. IT HAS BEEN SHOWN THAT EVALUATION OF STRESS AND DEFORMATION DISTRIBUTION AROUND THE CRAZE LAYER IS POSSIBLE BY THE USE OF CAUSTICS, I.E., SHADOW OPTICAL PATTERNS.2. CHANGE OF THE SHADOW PATTERN OF A CRAZE-CRACK UNDER TENSION CORRESPONDS WELL TO THE CHANGE OF OUT-OF-PLANE DEFORMATION THERE.3. IT HAS BEEN CONFIRMED THAT THERE EXISTS A STRESS CONCENTRATION AT THE CRAZE TIP, WHICH MEANS THAT USE OF THE DUGDALE MODEL HAS ITS LIMITATION FOR FRACTURE MECHANICS STUDY.4. ELASTIC APPROXIMATION IS ALLOWABLE FOR THE CRACK TIP DEFORMATION OF A SPECIMEN REMOVED FROM METHANOL TO AIR AND DRIED. THE STRESS DISTRIBUTION OF THE CRAZE LAYER IN THIS CASE AGREED WELL WITH THE RESULT OBTAINED BY KRAMER ET AL USING THE HOLOGRAPHIC INTERFEROMETRY.5. THE GROWTH RATE OF THE ENVIRONMENTAL CRAZE HAS A CORRELATION WITH THE DIAMETER OF THE SHADOW PATTERN.6. THE STRESS DISTRIBUTION ALONG A CRAZE LAYER HAS BEEN MODELLED, BASED ON WHICH COMPUTER SIMULATION WAS MADE FOR PREDICTING SHADOW PATTERNS. FROM THE PATTERN FITTING WITH THE ONE OBTAINED FROM EXPERIMENTS, PARAMETERS SUCH AS STRESS AT CRACK-AND CRAZE TIPS COULD BE EVALUATED.7. THE STRESS-OPTICAL CONSTANT WAS STUDIED AS A FUNCTION OF REFRACTIVE INDICES OF ENVIRONMENTAL LIQUIDS SURROUNDING A CRACKED PLATE UNDER TENSION. IT HAS BEEN SHOWN THAT THE OPTICAL EFFECT OF THE LIQUIDS IS NOT NEGLIGIBLE.8. REFLECTED CAUSTIC PATTERNS HAVE BEEN OBTAINED FROM A CRACK TIP OF POLY?.IER ALLOYS, WHICH HAS DE POSSIBLE TO EVALUATE TOUGHNESS OF THE DUCTILE POLYMERS.