<title>Evaluation of local contact stress/strain by moire interferometry and thin-coating photoelasticity</title>

ABSTRACT It is well known that there still exist several difficulties in the analysis of contact stress or strain around the region nearcontact because of unexpected irregular boundary data obtained by the current experimental techniques, such as Moireinterferometry, in spite of highly accurate and precise information of continuous distribution of fringes inside a body. In order to overcome the type of difficulties, a combined technique with Moire interferometry and thin-coating photoelasticity is discussed to analyze stress/strain near a contact region, utilizing their features in either macro- ormicro-scopic analysis of displacement and strain distribution on the surface of a body.Keywords: Contact Stress, Moire Interferometry, Thin-coating Photoelasticity, Photoelastic Modulator 1. INTRODUCTION Recent techniques in Moire interferometry' have, as well known, an advantage in measuring microscopic local displacements using very fine gratings of 1,000 4,000 lines/mm. So it is very useful for many measurements such aselastic-plastic displacements, transient displacements ofa crack tip and creep displacements under high temperature andso on. As for analysis of strain in this method, fringe pattern analysis using carrier fringes2 or phase shifting method usingFourier transform3 have been developed. But on the other hand, because the fringe image obtainable by Moire methodare merely a contour map ofdisplacement field, it can not be enough to analyze such a case as a contact problem betweentwo different objects, in which the images includes discontinuity offringe pattern arising from discontinuous displacementat the interface, namely the fringe pattern corresponding to each contact part are superimposed or separated each otherif the two surfaces does not placed in the same plane. Here the authors would propose a useful method for analyzing