Search Results

When two identical brakes are simultaneously tested on a vehicle chassis dynamometer, very often the left hand brake is found to squeal more or less than the right hand brake, all at different frequencies. This study was performed to develop some understanding of this puzzling phenomenon. It is found that as the wear rate difference between the inner pad and the outer pad increases, low frequency (caliper and knuckle) squeals occur more and more, and as the differential wear becomes larger and larger, high frequency (disc) squeals occur less and less, finally disappearing all together. Discs and calipers are found to affect the differential pad wear, in turn affecting brake squeal generation.

In spite of many squeal noise studies, it is still hard to predict squeal noise these days. Squeal analysis is a useful technique in reducing or removing squeal noise. As a result, several papers that contain reasonable finite element model with correlation, squeal mode analysis, and design proposals that can reduce the squeal noise have been released. In this paper, Generalized Frictional Stiffness Matrix was extracted using Generalized Coordinate in ABAQUS. GFSM(Generalized Frictional Stiffness Matrix) is an unsymmetrical matrix which creates a real-eigen-value (unstable mode) in complex eigenvalue problem. Then, sensitivity of each term in GFSM is calculated. The least modification was proposed from the sensitivities to reduce the squeal noise. To verify this proposal, a reasonable finite element model was generated by correlating component and assembly modal tests.

As environmental concerns have taken the spotlight, electrified powertrains are rapidly being integrated into vehicles across various brands, boosting their market share. With the increasing adoption of electric vehicles, market demands are growing, and competition is intensifying. This trend has led to stricter standards for noise and vibration as well. To meet these requirements, it is necessary to not only address the inherent noise and vibration sources in electric powertrains, primarily from motors and gearboxes, but also to analyze the impact of the spline power transmission structure on system vibration and noise. Especially crucial is the consideration of manufacturing discrepancies, such as pitch errors in splines, which various studies have highlighted as contributors to noise and vibration in electric powertrains. This paper focuses on comparing and analyzing the influence of spline pitch errors on two layout configurations of motor and gearbox spline coupling structures.

It is widely believed or speculated that higher pad compressibility leads to reduced brake squeal and that caliper design can affect brake squeal. After encountering anecdotal contradictory cases, this investigation was undertaken to systematically generate basic data and clarify the beliefs or speculations. In order to adjust pad compressibility, it is common to modify pad molding temperatures, pressures and times, which in addition to changing the compressibility, changes friction coefficient and physical properties of the pad at the same time. In order to separate these two effects, NAO disc pads were prepared under the same molding conditions while using different thicknesses of the underlayer to achieve different compressibilities, thus changing the compressibility only without changing the friction coefficient and physical properties of the pad.

As well as performance and safety, sensibility factor such as brake squeal noise has become an important factor to consider in today’s automotive industry. However, regardless of its importance, reduction of brake squeal noise has remained as one of the biggest challenges that have not yet been solved. Recently, many studies are being conducted to reduce squeal noise with the development of numerical analysis using FEM(Finite Element Method). This paper deals with complex eigenvalue analysis with commercial software program ABAQUS to resolve the squeal noise related to disc in-plane mode which is reported to occur frequently in the squeal noise frequency band 1~20kHz. As the reliability of the FE model is the most critical factor in numerical analysis, the FE model is first correlated with FRF modal test of each brake part and measurement of material property of pad with the anisotropic character through ultrasonic methods.

Nowadays, brake squeal noise is one of the most difficult problems and is a big issue in the automobile industry. Finite element analysis is a useful tool in predicting the noise occurrence of a conventional brake system during the design stage. This paper explains the technical procedure and method to resolve the squeal noise with commercial software programs. Friction coefficient under the operating conditions of the brake system was considered as a variable with respect to disc velocity and there was a dynamic behavior within the pad assembly during brake action. First of all, our Finite Element (FE) model was verified using the results of the parts and assembly's FRF measurements and an inertia noise dynamometer, followed by complex eingen value analysis to detect unstable frequencies. Subsequently, mode analysis was conducted for each part of the brake system through the MAC values.

Electric vehicles are considered not only eco-friendly but also quieter than vehicles with conventional internal combustion engines. However, less noisy environments in cabins make passengers feel uncomfortable to moderate noise. This paper discusses noise reduction for electric vehicles radiated from traction motors. In the analysis of the noise generation mechanisms it is demonstrated that frequency ranges of the highest level in the noise spectrum of electromagnetic harmonic orders of the induction motor coincide with structural resonances of the motor housing. Interfacial friction between the inner and outer housings of the motor is employed in reducing structural vibration of the motor. Measured noise in the cabin and vibration at the motor housing indicates that slip damping presented from interfacial friction between the inner and outer housing is effective in reducing noise from the traction motor and in the cabin.