Browse Topic: Brake discs
The objective of this paper is to evaluate the thermal performance of the brake discs in the design stage of its life cycle by developing a methodology to replicate dynamometer testing using multi-disciplinary Finite Element Analysis (FEA) methods. A simulation workflow was formulated in which Computational Fluid Dynamics (CFD) was used to create temperature and velocity dependent Heat Transfer Coefficients (HTC) which were in turn used in Computer Aided Engineering (CAE) to do a thermo-mechanical analysis. With this workflow various designs of the brake discs were analyzed. A sensitivity study was done to determine critical design features that affected its thermal performance. A final design was fixed that met both the weight and thermal performance targets. This design was evaluated in dynamometer testing, and 93% correlation was achieved. Thus, the developed simulation workflow ensured that a first-time right brake disc can be finalized in the design stage, which will meet the performance in dynamometer testing.
As the ICE vehicle changes into the EV, we can use regenerative brake. It can improve not only the energy consumption but also reduce the hydraulic brake usage. The less hydraulic brake usage mitigates the heat loading on the brake disc. From this reason, the lightweight brake can be used in the EV. However, when the lightweight brake is applied, the brake NVH can be increased. The optimization design of the lightweight brake should be done to prevent the brake NVH. In this paper, the optimal brake disc thickness and brake interfaces are determined by using of disc heat capacity analysis. The lightweight brake should be optimized by using of the brake squeal analysis. We can verify the results from both analysis and test. Finally, we can have the lightweight brake, which is competitive in terms of cost, weight and robust to the brake NVH.
As Lowmet pad porosity increases, pad hardness decreases; pad ISO compressibility increases; the nominal friction coefficient increases (SAE J2522); and the disc wear/pad wear decreases. Brake squeal occurrence is affected by the total wear of disc and pads; the wear differential between the inboard pad and outboard pad; pad tangential taper; and pad hardness/material damping. Also, pad chamfer shape has a strong influence on brake squeal occurrence.
Disc brakes play a vital role in automotive braking systems, offering a dependable and effective means of decelerating or halting a vehicle. The disc brake assembly functions by converting the vehicle's kinetic energy into thermal energy through friction. The performances of the brake assembly and user experience are significantly impacted by squeal noise and wear behaviour. This paper delves into the fundamental mechanisms behind squeal noise and assesses the wear performance of the disc brake assembly. Functionally graded materials (FGMs) are an innovative type of composite material, characterized by gradual variations in composition and structure throughout their volume, leading to changes in properties such as mechanical strength, thermal conductivity, and corrosion resistance. FGMs have emerged as a groundbreaking solution in the design and manufacturing of brake rotors, addressing significant challenges related to thermal stress, wear resistance, and overall performance. These studies evaluate the noise and wear behaviour of disc brake assemblies made with FGMs. The paper also investigates the application of FGMs in brake rotors, highlighting their distinctive properties and the advantages they offer to automotive braking systems. The study underscores the importance of further research and development to fully leverage the benefits of FGMs in enhancing brake system performance.
Brake disc temperature is a critical factor influencing the performance and wear characteristics of braking systems in automobiles. Hence it is very important to optimize the correlation of brake disc temperature prediction with test. In this study critical parameters of Brake Disc temperature evaluation are identified, and algorithm is used to optimize the critical parameters to achieve the correlation of prediction with experiment data. Through a series of controlled experiments and simulations, disc temperatures are monitored under different braking conditions and simultaneously input parameters for prediction are optimized to achieve the correlation. Statistical methods were applied to evaluate the observed correlations and to model the predictive behavior of brake disc temperatures. Finally, A front-loading tool is developed to optimize the brake disc keeping target thermal capacity via algorithm. The findings of this study are expected to contribute to the enhancement of brake system design by providing insights into thermal dynamics during braking. This can lead to the development of more efficient cooling strategies and materials that are better suited to dissipate heat, thereby improving safety and performance.
Many performance sport passenger vehicles use drilled or grooved cast iron brake rotors for a better braking performance or a cosmetic reason. Such brake rotors would unfortunately cause more brake dust emission, appearing with dirty wheel rims. To better understand the effects of such brake rotors on particle emission, a pin-on-disc tribometer with two particle emission measurement devices was used to monitor and collect the emitted airborne particles. The first device was an aerodynamic particle sizer, which is capable of measuring particles ranging from 0.5 to 20 μm. The second device was a condensation particle counter, which measures and collects particles from 4 nm to 3 μm. The testing samples were scaled-down brake discs (100 mm in diameter) against low-metallic brake pads. Two machined surface conditions (plain and grooved) with uncoated or ceramic-coated friction surfaces were selected for the investigation. The results showed that the grooved friction surface led to a higher particle emission than a plain friction surface finish. The ceramic coating can indeed reduce the negative effect of the grooving through reductions of both the brake wear and particle emission.
Abrasion of the Electromechanical brake (EMB) brake pad during the braking process leads to an increase in brake gap, which adversely affects braking performance. Therefore, it is imperative to promptly detect brake pad abrasion and adjust the brake gap accordingly. However, the addition of extra gap adjustment or sensor detection devices will bring extra size and cost to the brake system. In this study, we propose an innovative EMB gap active adjustment strategy by employing modeling and analysis of the braking process. This strategy involves identifying the contact and separation points of the braking process based on the differential current signal. Theoretical analysis and simulation results demonstrate that this gap adjustment strategy can effectively regulate the brake gap, mitigate the adverse effects of brake disk abrasion, and notably reduce the response time of the braking force output. Monitoring is critical to accurately control EMB clamping force. Pressure transducers are often expensive and have limited accuracy in high-temperature environments, so an estimate of the clamping force is required. In this research, the clamping force is estimated based on the identified contact points and the stiffness profile of the EMB. This method performs exceptionally well under low stiffness conditions and maintains a narrow error range even in high-stiffness scenarios.
Just as NASA needs to reduce mass on a spacecraft so it can escape Earth’s gravity, automotive manufacturers work to reduce weight to improve vehicle performance. In the case of brake rotors, lighter is better for a vehicle’s acceleration, reliable stopping, and even gas mileage. Orbis Brakes Inc. licensed a NASA-patented technology to accomplish that and more. This revolutionary brake disc design is at least 42 percent lighter than conventional cast iron rotors, with performance comparable to much more expensive carbon-ceramic brakes.
During validation of a new brake lining on a light duty truck application, the brake rotor exhibited high lateral runout on the friction surfaces. As the engineering team investigated the issue more carefully, they noticed the rotor lateral runout was also changing from revolution to revolution. The team ran testing on multiple light pickup vehicles and found differences in the amount of rotor runout variation. The rotor lateral runout and runout variation can cause vibration and pulsation of the passenger seat and the steering wheel. To identify the root cause of the high level of rotor lateral runout and runout variation, measurement data was collected and analyzed from the vehicle level test. During further analysis, some of the runout variation corresponded to a wheel bearing internal frequency. The bearing internal geometry was studied to confirm what factors affected the runout variation. The team also conducted testing to see how the mating components may have affected the wheel bearing. In addition to the vehicle testing, fixtures were built to perform brake corner bench testing. This testing showed that both the total runout and runout variation increased as more mating components were added. Brake corners from two different vehicles were bench tested. The major difference between the vehicles was the mounting location of the splash shield. On one vehicle the splash shield is mounted (sandwiched) between the knuckle and the bearing’s outer ring flange and on the other vehicle, the splash shield is directly mounted with screws to the knuckle (not sandwiched). Splash shield distortion due to compression near the knuckle bolts and the bearing outer ring contact surface, caused the larger total runout value and the higher variation. The study also proved that continuous assembly/disassembly will increase the distortion on the mating parts, which leads to the greater total runout and variation values.
Despite efforts to reduce disc brake noise occurrence, it remains a significant concern in the automotive industry, particularly in the current era of electric vehicles, where it can be an intermittent issue. There is no standard solution available for every noise frequency, as it depends on various conditions and parameters that need to be experimentally identified and addressed. This paper specifically focuses on addressing low-frequency noise. During dynamic conditions, the contact pressure becomes uneven, leading to uneven pad wear and making the disc brake system susceptible to noise. In noise rigs, the paper selects the most suitable shim and pad geometry based on trials that analyze the interaction between the shim and pad. In conventional practice, shim modification was performed using computer-aided engineering, but obtaining accurate pressure patterns in dynamic conditions with CAE is challenging due to certain assumptions. Through dynamometer trials, the paper identifies that the critical frequency is caused by the coupling of the disc and pad mode shapes. Wear analysis reveals greater wear on the leading side of the piston, which can contribute to noise at critical frequencies. Pressure patterns were examined using Tekscan™ across different pressure ranges from 10 bar to 50 bar to understand the cause of uneven wear, confirming the bias in the caliper loading pattern. Consequently, the details of piston contact pressure were investigated, indicating higher pressure distribution on the leading end of the piston compared to the trialing side. Further analysis using finite element analysis (FEA) confirms a similar bias towards the caliper on the leading side. To modify the pressure pattern and reduce noise, a half-moon cut profile was introduced in the shim, resulting in the elimination of occurrences at 3.9 kHz.
Brake squeal is a common phenomenon across all types of vehicles. It becomes prominent in the absence of other noise sources, as in the case of electric vehicles. Earlier simulation attempts date back to late nineties and early 2000s. Identification of unstable modes of the coupled system of brake rotor and pads, and occasionally some caliper components, was the primary goal. Simulating the rotation of the rotor along with squeezing of the pads was attempted in a multi-body dynamics tools with flexible representation of rotor and pads. Though this gave some insights into the dynamics of stopping mechanism, squeal required capturing the nonlinearities of the contact in a more rigorous sense. Also, efforts were made to capture noise from vibrations using boundary- and finite- element methods [1]. In this attempt at digitalizing a brake dynamometer, the author used a nonlinear implicit solver to mimic the dynamics and transient vibro-acoustic solver to convert transient vibrations to transient squeal spectra. An icing on the cake is the auralization of the squeal event that generates the audio file which can be later re-played. To capture the stochastic nature of brake event in a more computationally efficient way, the author proposes a linear approximation and synthesizes multiple squeal events from a single nonlinear solution.
The braking system in a vehicle is one of the most crucial parts for proper and safe operation. It is required to slow down or stop the vehicle and work by converting the kinetic energy of the wheel to heat. It is essential to dissipate the generated heat for optimal working and the long life of the disc brakes. Heat generated is due to friction between the brake pad and disc. Due to overheating of brakes due to prolonged braking and heavy braking, brake fade occurs. This leads to boiling of the brake fluid, gassing, and glazing of brake pads, hence reducing braking performance. Therefore, in this study, we used computer simulations to determine the best design that allows for the most heat dissipation by analyzing four different conventional disc brake designs. It was found that the slotted disc brake design had the maximum value of heat transfer coefficient (87.2% more than that of the vented disc brake) and also correspondingly the most decrease in the maximum temperature (39.56% decrease than that of the vented disc brake). We used CFD to study the effects of airflow on convection and FEA for thermal analysis. This study aims to understand the heat transport behaviour, in general, and heat dissipation disc brakes in a comprehensive manner, in particular.
This SAE Recommended Practice is intended for measuring the static brake torque performance of a pnuematically actuated brake assembly, friction material, and drum/disc combination on an inertia brake dynamometer.
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