Photoelasticity for strain analysis of hole in center of octagonal PMMA plate

Abstract

The strain value caused by a hole in the center of plate is an important variable because it provides insight into how material deformation will occur around the hole, which in turn impacts the strength, fatigue resistance, failure prediction, and overall performance of the part. This research investigated the strain distribution associated with a square hole in the center of an octagonal acrylic (poly(methyl methacrylate) or PMMA) plate using reflection photoelasticity. The novelty of this research is the improved understanding it provided of the strain distribution in a rectangular hole in the center of a plate. Samples were compressed using two-point loading with a hydraulic press system. The results of images taken using a high-resolution, computer-controlled camera showed fringe patterns and the strain distribution resulting from varying the magnitude of loading, the size of the octagon, the size of the square hole and the position of loading. Based on the results, a high-strain region was produced around the contact point and around the corners of the square hole. The maximum strain around the corner edge region of the hole in the octagon was produced with 1000 microstrain for the highest loading (1071 N) and 1150 microstrain for the largest square hole size, and 1080 microstrain for the smallest-sized octagon with the direction of loading along the center of the square hole. The highest strain value of 1400 microstrain was recorded in the contact point region for the loading position at the corner edge of the octagonal PMMA.