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Brake squeal is uncomfortable noise that occurs while braking. So, it is an important issue of automobile quality to reduce the brake squeal occurrence. Although many researchers had reported about brake squeal, there are many examples that have not been understood well. For those squeals, some of occurrence mechanisms are assumed. The dµ/dv<0 theory is one of them, and the dµ/dv represents a slope of friction coefficient for sliding velocity. If the frictional force has a negative damping characteristic, that is dµ/dv<0, disc vibration may increase. It has been said for a long time that a negative dµ/dv characteristic affects brake squeal occurrence. Many researchers had measured the dµ/dv to clarify brake squeal factors. In those results, the slope of friction coefficient at steady sliding speed was used for the dµ/dv. However, the pad undergoes minute vibrations while the brake is squealing.

It is necessary to consider both pad stiffness in static and dynamic situations to develop brake pads that create effective braking and squeal less. Brake pads that have a high degree of static stiffness generally respond well when braking. A past study clarified that stiffness when vibration is added to a pad differs from static stiffness. This pad stiffness in dynamic situations depends on braking pressure and it is one of the causes of squeal generation. This research clarified that pad stiffness depends on the amplitude of excitation and its frequency, which was measured by using an experimental apparatus. This apparatus gave sufficient displacement to a pad for measuring static stiffness and gave vibration with sufficient frequency and amplitude to assess the stiffness of the pad when squeal was generated. First, the static stiffness of the pad was measured by adding static pressure.

The prevention of brake squeal in disc brakes is an important concern in designing a brake system because, in terms of quietness, brake squeal reduces a car's commercial value. Over the past years, many studies have been conducted to elucidate the mechanism underlying the occurrence of brake squeal. However, since disc brake squeal is a complex issue caused by the compound influence of friction phenomena and vibrations in the brake system, the problem of brake squeal still has not been completely resolved, even today. In order to propose an effective measure for the prevention of brake squeal, it is necessary to understand the nature of the brake squeal phenomenon. We have investigated the influence of the dynamic stiffness of a brake pad (hereinafter referred to as pad stiffness). The pad stiffness was evaluated the results by a pad excitation at frequencies and vibration amplitudes that would cause brake squeal.

The prevention of brake squeal is a significant task in brake development, because brake squeal is bothersome to users and consequently reduces a vehicle's commercial value. Due to the progress made by researchers in their efforts to gain insight into the mechanisms and causes of brake squeal, the number of brake squeal complaints has declined. However, brake squeal can appear long after the vehicle is produced, without any early sign. In order to maintain long-term high satisfaction among the vehicle owners, it is important to find the factors that create a gradual increase in the occurrence of brake squeal. In this study, we focus on the stiffness factor of brake pads. Also, brake-pad wear due to braking is virtually impossible to completely eliminate. Here, we examine the correlation between pad stiffness and squeal occurrence. This study presents experimental and analytical results of the influence of pad surface texture on disc brake squeal.

This study aims to incorporate the dynamic stiffness of pads into the finite element method (FEM) used for brake design in order to improve the accuracy of FEM analyses. In the first step, the vibration caused by a disk brake squeal is simulated in order to measure the dynamic stiffness of the brake pads. We then compare this result with the static stiffness result obtained from a past static compressive strain and show that these different modes of stiffness have different characteristics. The dynamic stiffness of the pad is higher than the static stiffness and is greatly dependent on pressure load. The next step is to show, from the squeal experiments using a simple squeal tester and FEM analysis, that it is dynamic stiffness and not static stiffness of the pads that correlates to squeal.

This research examined the squeal generation mechanism of a disk brake focusing on the stiffness of the frictional contact surface between the disk and the pad (contact stiffness). To clarify the influence of the contact stiffness, an experimental apparatus with a simple structure was used for squeal tests instead of an actual disk brake, and the dynamic stiffness of the contact surface was measured. In addition, a surface-contact model that includes the frictional contact surface composed of the distributed spring and three degrees of freedom was made. The results show that the pressure dependency of the contact stiffness is the cause of squealing.