Nonlinear characteristics of floating involute spline coupling in a hydraulic disc brake with inner hub rim crack propagation

Spline coupling is the key component in a hydraulic disc brake (HDB) system, which has been widely used in many high power density industrial machinery. Crack failure, as one of the most widespread and dangerous spline defects, directly threatens the operating safety of HDB system. To this end, a dynamic modelling method for floating involute spline coupling system is presented to study the nonlinear characteristics caused by inner hub rim crack propagation, which can consider the varying stiffness caused by rim crack, impact forces of spline teeth pairs, and non-uniform clearances between spline teeth of floating friction plate and inner hub. Results show that both rotational speed fluctuation, impact force, acceleration and trajectory achieve nonlinear trends with crack propagation, among which the gradient of impact force outperforms other characteristics and may be suitable for crack detection. Besides, the stiffness model with rim crack fault is validated by FEM. And an impact force test bench is established to verify the correctness of the proposed dynamic model. Experimental results reveal that the proposed model is suitable for the estimation of nonlinear behaviors of floating involute spline coupling with rim crack propagation.