ON THE INFLUENCE OF MULTIPLE EQUILIBRIUM POSITIONS ON BRAKE NOISE

Abstract

Brake noise, especially brake squeal, has been a subject of intensive research both in industry and academia for several decades. Nevertheless, the state of the art simulations does not provide a predictive tool, and extensive experimental investigations are still necessary to find an appropriate design. Actual investigations focus on the consideration of nonlinearities which are in fact essential for this phenomenon. Unfortunately, by far not all relevant effects caused by nonlinearities are known. One of these nonlinear effects that the actual research focuses on is the limit cycle behavior representing squeal. In contrast to this, the actual paper considers the influence of the equilibrium position established while applying the brake pressure. The elements of the brake, namely, the carrier, caliper and pad, are highly nonlinear and elastically coupled and allow for multiple equilibrium positions depending e.g. on the initial conditions and transient application of the brake pressure while the frictional contact between the pads and the disk may excite small amplitude self-excited vibrations around this equilibrium, i.e. squeal. The current paper establishes a method and corresponding setup, to measure the position engaged by the brake components using an optical 3D-measuring system. Subsequently, it is demonstrated that in fact different equilibrium positions can be engaged for the same operation parameters and that the engaged position can be decisive for the occurrence of squeal. In fact, certain positions result in squeal while others do not for the same operation parameters. Taking this effect into consideration may have significant consequences for the design of brakes as well as simulation and experimental investigation of brake squeal.