COMPARISON OF MEASUREMENT OF PISTON DEFORMATION USING HOLOGRAPHIC-INTERFEROMETRY AND FINITE-ELEMENTS

Holographic interferometry was used to measure the thermal expansion of a diesel-engine piston and the results are compared with those predicted by a finite-element model. Various assumptions were made in the generation of the model and the holographic results provided a means of assessing the effects of these assumptions on the deformed profile of the piston. A holographic rig has been developed that enables one to measure simultaneously the deformation on the front and rear surfaces of the piston using a single holographic plate and hence detect any body displacement. A simple 'mirror' concept is introduced that can be used to measure in-plane and out-of-plane displacements simultaneously. The holographic results showed expansion values of ten-percent greater than the predictions of the model at midskirt level of the piston. A closer agreement of the results were observed at other levels of the skirt.