Model making and slicing for three-dimensional photoelasticity

Abstract

Problems which can occur during casting of epoxy resin are high exotherm, mottle and residual stress. Some methods for reducing these effects are discussed. Techniques for sawing, holding and machining epoxy models are presented. Particular attention is given to avoidance of chipping or cracking by use of proper tool profiles, cutting speeds and feed rates. Several ways of assembling models are discussed, including inspection of machined models and cemented joints. The effect of cemented joints on stress patterns is demonstrated. Suggestions for laying out, cutting and flattening slices are presented. The effect of scribed lines on a stress pattern is shown. A procedure for surface subslice preparation is given. Two types of edge effect can occur in epoxy frozen-stress models-temporary edge effect due to humidity and permanent edge effect due to oxidation. Methods for avoidance and treatment of edge effect are presented.