3-D strain analysis near contact by stereo image correlation technique

In ordinary stress and strain analyses under complicated loads, it is popular to assume boundary conditions by surface forces on contact both in theoretical and numerical approaches. The results, thus, depend more or less on the assumed boundary conditions. It should be pointed out that the kind of assumptions does not prove the validity of results in actual situation. Therefore, it is very important to know conditions of stress or strain on and around contact surface by experiment. The contact problem has been tackled theoretically, numerically or experimentally for long period. In order to evaluate more realistic stresses in the vicinity of contact, it is inevitable to determine actual boundary conditions after overcoming difficulties in experiments. Since it is not valid to assume 2-D state on and around contact surface, 3-D deformation analysis is required inevitably. Standing on the back ground mentioned above, the authors discuss displacement and strain distributions on and around contact by a stereo image hybrid technique in elastic plate under compression by a cylinder on one of its edges. The results are compared with the results obtained by Hertz theory and FEM, then the necessity of experimental and hybrid approaches is demonstrated for the determination of boundary surface force conditions.