Non-Linear Signal Analysis Applied to Surface Wear Condition Monitoring in Reciprocating Sliding Testing Machines

Experiments conducted on elastic bodies under friction forces shown that the dynamical system is self-excited by the non-linear behavior of frictional forces. The main objective of this paper is to study the vibrations signals measured on a reciprocating wear testing machine using non-linear signal analysis formulation. A two input and one output MISO model is proposed to represent the non-linear system dynamics. The global output is the sum of two outputs produced by one linear path associated in parallel with a non-linear path. This last path has a non-linear model that represents the friction force and another linear transfer function connected in series. Since the linear path is identified by traditional signal analysis, the nonlinear function can be evaluated by the global input/output relationships, and can be correlated to wear conditions of the contact surfaces. Validation tests are conducted in a tribological system composed by a sphere in contact with a prismatic body witch has an imposed harmonic motion.