| Summary: | 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.
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