Abstract
In recent experimental work it has been observed that the position of the centre of pressure (CoP) at the brake pad/disc interface has an influence on the onset of brake squeal. To determine the CoP during a braking event, a simple two-dimensional analytical model of the brake pad or more complex numerical finite element model of a disc brake are commonly used. This paper presents a new three-dimensional analytical model of a brake pad that determines the CoP position in both circumferential and radial directions. Due to higher complexity, this model provides more realistic clamp and friction force values, which can be used together with the more accurate radial position of the CoP for evaluation of the brake torque. The CoP position calculated using the new model was compared with the CoP evaluated by a finite-element model of an equivalent 8-piston opposed disc brake. The CoP results across the whole pad/disc interface showed a close correlation between these two approaches, giving the new analytical model a potential use in applications where an instantaneous value of the CoP with good accuracy is required. Finally, the new model was used to demonstrate possible improvement of the traditional method of the friction coefficient calculation. Due to greater accuracy the new model gives an approximately 8% larger value of the friction coefficient than the traditional approach.
Highlights
Even though brake squeal has been intensively studied and numerous techniques have been proposed to eliminate this undesirable phenomenon during the last century, it still represents a major concern for the automotive brakes industry
It has been observed that the position of the centre of pressure (CoP) at the brake pad/disc contact area has an influence on the onset of brake squeal [3]
The paper presents a new three-dimensional (3D) rigid body model of the brake pad which is used to calculate centre of pressure (CoP) position in both circumferential and radial directions during a constant speed braking event. This mathematical model can be used to determine the CoP position and other parameters in a trailing abutment brake pad loaded with different numbers of pistons
Summary
Even though brake squeal has been intensively studied and numerous techniques have been proposed to eliminate this undesirable phenomenon during the last century, it still represents a major concern for the automotive brakes industry. A new 3D analytical rigid body model of a brake pad is proposed that enables determination of the CoP position at the pad/disc interface in both longitudinal and radial direction, and yields values of reaction forces acting on the pad. This model is mathematically described in the form of algebraic equations that can be solved by means of modern numerical techniques, and it can be used in simulations where instant values of the CoP position in both longitudinal and radial direction are needed. Where μ is the friction coefficient at the pad/disc interface, μA denotes the friction coefficient at the backplate/abutment surface, yA represents distance of the pad center to the abutment surface, P1 and P2 are piston forces, Ft and R are friction force and reaction force (clamp force) at the rubbing surface, respectively, FtA and RA are friction force and reaction force at the abutment surface, respectively, n1 and n2 represent distances of the pistons from the center of the pad, and tfm and tbp are thicknesses of the friction material and the backplate, respectively
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