Abstract
The paper presents two plastic materials from epoxidic resins and compounded polymers families which have properties to visualize stress field produced by mechanical loadings. Using these properties two experimental techniques, photoelasticity and cromoplasticity, were developed for mechanical behaviour investigation of engineering structures. To illustrate the potential of these experimental techniques, in the paper are presented results of a combined analysis undertaken on the state stress in the fastening elements of a hidroagregate, loaded both in elastic and elastoplastic field. Keywords: epoxidic resins, compounded polymers, photoelasticity, cromoplasticity