Study on estimation of contact pressure distribution at the rubber sphere - Glass plate interface based on luminance distribution analysis

In this study, a simplified system to measure contact area and contact pressure distribution of rubber-glass interface was developed by using a total reflection method. In order to visualize the contact state by the total reflection method, high luminance LEDs(light-emitting diode) were set at double side of glass plate and the contact image was recorded by using high speed camera at 1.0 kHz of a shatter speed. The Laplacian filter was applied to the contact image for a detection of an edge between contact and non-contact areas. Threshold luminance value can be determined based on the Laplacian filtered image. It was clarified that the luminance value increases toward the center of contact area and the contact area determined using the threshold luminance value has close agree with the contact area calculated based on Hertzian elastic contact theory under the elastic region. Furthermore, a contact pressure distribution was estimated based on the relationship between the distribution of luminance values in the contact area and the Hertzian contact pressure distribution.