Failure Process after Peak Strength of Artificial Joints by Fractal Dimension

Because lack of information when the joints exhibit strain softening behavior, the transition from peak to residual values is assumed to decrease either linearly or exponentially. Also, displacement of slide side after peak is much larger than the peak displacement and the stress approaches the residual state, thus studying failure process after peak strength is very important. In this research, three types of artificial joints with tooth-shaped asperity under repeated direct-shear were tested. Continuously movement of slide side after peak strength was monitored during shearing test. Reduction of shear parameters was examined according to two failure criteria (Barton and Patton). JRC value (Joint Roughness Coefficient) for a given profile was estimated by fractal dimension. One of the results of this study is that Barton’s criterion predicts a good estimation of residual strength and the second result is when the amount of fractal dimension of a joint surface increases, the JRC amount also increases, and with having value of h (height average) and l (base average) of a tooth-shaped asperity can determine the JRC of joint surface. M. Askari is a M.Sc Student of Engineering Faculty, Mining Engineering Department, Tarbiat Modares University, Tehran.