Automated Analysis of Photoelastic Fringe Patterns

• Main Authors: Chien-Hung Lin, 林建宏
• Other Authors: Terry Yuan-Fang Chen
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/02503800895331644081

碩士 === 國立成功大學 === 機械工程研究所 === 83 === Photoelastic stress analysis is a well known and documented technique. It is usually done by using information from isoclinic and isochromatic patterns. The isoclinic gives the information of their principal stress directions and the isochromatic the infomation of differences of the principle stresses. Photoelastic stress analysis can be a long and tedious process. With the arrival of powerful personal computers and the digital image process, automated photoelastic analysis is becoming more feasible. However recent and current developments in the field of automated and computer aided photoelastic analysis mean that it is becoming possible to do more complex analysis and to perform it more quickly. In this paper, the automatic methods of whole-field determination of isoclinic and isochromatic fringes are presented. The methods are based on phase-shifting and the application of digital image processing techniques. The new method makes use of three images of isoclinic angles ( 0, 22.5, 45 degrees ) to determine the principal stress direction in a full field. The three images, by image processing, are used for the computations. Additionally, the procedures developed determine the fringe orders of a full field from two isochromatic images with different wavelengths. After much calculation, the two fringe patterns can obtain three possible fringe orders in a point. Optimization of the least square method is used to form a set of prototype fringe order. The other points will be determined with prototype conditions. The results are presented from the analysis with a photoelastic circular disk model and three- dimensional photoelastic stress- freezing slice model.