no papers published by the engineers on this topic.
This is a nice topic for erudite discussion, so we can,
together, come to an educated conclusion; so I'll do my part by researching, what we can easily find on the net, by way of engineering studies.
Below are first pass engineering studies
which all purport to explain, measure, and model brake judder.
UPDATE: I have read all these papers - and I am in the process of summarizing them (which isn't easy).
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"Aspects of disc brake judder"
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering
abstract said:
Abstract: Brake judder is a braking induced, forced vibration occurring in different types of vehicles. The judder frequency is directly proportional to the revolution speed of the wheel and therefore also to the velocity of the vehicle. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. In the higher frequency range, the structural vibrations are accompanied by a sound. Brake judder primarily affects the comfort but could, when confronting an inexperienced driver for the first time, lead to faulty reactions and reduced driving safety. Furthermore, a specific type of judder, so-called hot judder, is related to disc cracking. There are numerous publications available dealing with high frequency vibrations, such as brake squeal, including mathematical models for analysis and simulation. However, low frequency phenomena, such as brake judder and groan, have received much less attention. There is a growing interest from the automotive industry concerning brake judder. Even though few companies would admit that they have the problem, it is not unusual to meet people who have experienced the problem in their own passenger cars. Much of the knowledge concerning brake judder remains within the companies. Hence, very few people have the full picture. The purpose of the present paper is to give an overview of the brake judder problem.
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Analysis of the vehicle brake judder problem by employing a simplified source***8211;path***8211;receiver model
Acoustics and Dynamics Laboratory, Department of Mechanical Engineering, The Ohio State University, Columbus, Ohio, USA
Abstract: An analytical formulation of the brake judder problem caused by disc thickness variation is described by using a simplified source***8211;path***8211;receiver model. Eigenvalue analysis is first conducted to determine the transfer mechanism from the brake source to the steering- wheel receiver. Calculations show that the peak vibration levels of the steering wheel are seen when the rotational frequency of the tyre coincides with the resonant frequency of the transfer path; in this case, only the first-order disc thickness variation is considered. The effects of two key parameters, associated with the source and the path respectively, are analytically and computationally studied. Analysis suggests that the lower pad stiffness and/or the higher bushing stiffness should effectively reduce the vibration levels. Finally, a new vibration control concept is proposed that modulates the actuation pressure; it is based on an approximate solution for the angular displacement of the disc in the model developed here. Preliminary work indicates that this concept could be very effective in reducing the receiver vibration level without sacrificing the brake performance.
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A Parametric Study of Brake Roughness
Robert Bosch Corporation
abstract said:
Abstract Brake roughness is a low frequency vehicle vibration during braking. It is perceived by the driver as steering wheel shake and nibble, pedal pulsation, seat track and floor pan shake, or their combinations. Although the vibrations occur only when brake is applied, both brake and suspension systems are involved in transmitting the vibration from brake to the driver. Since numerous parameters can affect this transferring process, understanding of their interactions and influences upon roughness is of great interest to brake engineers. In this paper, a parametric analysis process of brake roughness is described. Experimental techniques and simulation tools are utilized to evaluate the influences of brake and suspension parameters. This process can facilitate the resolution of existing roughness issues. It also provides useful information for the future design of brake-suspension systems.
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Judder, Diagnosis, & Prevention,
Mohamed Khalid Abdelhamid, AlliedSignal Automotive, Europe
abstract said:
This paper addresses both theoretical and practical aspects of judder. Judder, a problem investigated by many NVH centers of brake suppliers and vehicle manufacturers, has attracted large resources yet still is considered a major warranty cost to the automotive industry. In this work a reduced order model is presented that provides a first step to judder engineering. A model is presented for the friction force variation due to rotor topography. Simulation results are analyzed in both time and spectral domains. In a parallel effort ior practical analysis 01 judder, an experimental merhod is provided for testing judder sensitivity of a certain brake-vehicle application. Case studies are (pen. Included in this section is a host of techniques for signal analysis used to process the vast data that are collected in this type of test. This part provides the means for NVH engineers to diagnose the judder problem. The next section of this paper addresses the prevention phase of the judder problem. In this section of the paper, a series 01 steps are described to quantify the mobility of the vehicle, and ior testing rhe brake vibration output under controlled condition of support mobility. The scheme then suggests how this information may be used in engineering the brake for a certain vehicle such that judder sensitivity is minimized
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Improved mathematical models of vehicle brake judder and experimental observations
Osman Taha Sen (a) Rajendra Singh (b) Acoustics and Dynamics Laboratory, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210 USA
abstract said:
The brake judder phenomenon, typically associated with torque variations in ground vehicles during high speed braking events, is poorly understood. This vibration source is of vital importance as the braking, suspension, and steering wheel sub-systems undergo dynamic amplification due to one or more resonances. To understand this speed-dependent torque behavior, vibration measurements are acquired on a specially designed laboratory experiment as the system decelerates. The focus is on the cold judder as the rotor surface variations are assumed to be the main source of speed-dependent torque amplitudes. Key speed regimes during a typical braking event are identified using order domain processing. Three nonlinear models of this experiment are developed. Model I is solved with an event detection type numerical integration technique, and Model II estimates the envelope curve using the Hilbert Transform. Model III employs the multi-term harmonic balance method to construct both stable and unstable solutions at multiple orders of rotor distortions. The predictions of all models match well with experiments. The proposed methods provide much insight into the brake judder source including resonant amplifications.
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Judder vibration in disc brakes excited by thermoelastic instability
Oscar Altuzarra, Enrique Amezua, Rafael Avilés, Alfonso Hernández, (2002), Engineering Computations, Vol. 19 Iss: 4, pp.411 - 430
abstract said:
Friction vibrations and noises which are common in brakes, have attracted a great deal of attention lately. This paper analyses low frequency vibrations in disc brakes excited at high car speed. This vibration, called judder, has a frequency in the range 10 to 300 Hz and usually comes in association with hum noises. The dynamic phenomenon shows two principal components, one normal and the other one tangential to the disc brake surface. It is explained how variations of friction coefficient, and thermoelastic instability caused by the tangential component, contribute to the appearance of judder. A numerical analysis in 3D using the finite element method has been implemented combining both tangential and normal components, and solving the thermoelastic process. Special attention is dedicated to the simulation of the thermoelastic process showing the correlation with experiments.
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Experimental Analysis of Disc Thickness Variation Development in Motor Vehicle Brakes
School of Aerospace, Mechanical & Manufacturing Engineering (SAMME)
NOTE: The PDF was too large to attach as one file so it was broken into three files.
abstract said:
Over the past decade vehicle judder caused by Disc Thickness Variation (DTV) has become of major concern to automobile manufacturers worldwide. Judder is usually perceived by the driver as minor to severe vibrations transferred through the chassis during braking [1***8211;9]. In this research, DTV is investigated via the use of a Smart Brake Pad (SBP). The SBP is a tool that will enable engineers to better understand the pro- cesses which occur in the harsh and confined environment that exists between the brake pad and disc whilst braking. It is also a tool that will enable engi- neers to better understand the causes of DTV and stick-slip the initiators of low and high frequency vibration in motor vehicle brakes. Furthermore, the technology can equally be used to solve many other still remaining mysteries in automotive, aerospace, rail or anywhere where two surfaces may come in contact. The SBP consists of sensors embedded into an automotive brake pad enabling it to measure pressure between the brake pad and disc whilst braking. The two sensor technologies investigated were Thick Film (TF) and Fibre Optic (FO) technologies. Each type was tested individually using a Material Testing System (MTS) at room and elevated temperatures. The chosen SBP was then successfully tested in simulated driving conditions. A preliminary mathematical model was developed and tested for the TF sensor and a novel Finite Element Analysis (FEA) model for the FO sensor. A new method called the Total Expected Error (TEE) method was also de- veloped to simplify the sensor specification process to ensure consistent com- parisons are made between sensors. Most importantly, our achievement will lead to improved comfort levels for the motorist.
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Thermal Brake Judder Investigations Using a High Speed Dynamometer
David Bryant, John Fieldhouse, Andrew Crampton and Chris Talbot, University of Huddersfield
NOTE: The PDF was too large to attach as one file so it was broken into two files.
abstract said:
This paper is concerned with addressing the problems experienced with the thermo-elastic behaviour of the disc - that of optimum heat dissipation, and equally important, even heating of the disc blade. The primary objective is to develop a more temperature-stable brake disc. The work presented approaches the problems of thermal judder through benchmarking the current situation. This is approached by modelling the current brake and its validation by means of vehicle and laboratory testing. The empirical work is centred on a bespoke high speed brake dynamometer which incorporates the full vehicle suspension for an accurate yet controlled simulation of brake and vehicle operating conditions. The dynamometer is housed in a purpose built laboratory with both CCTV and direct visual access. It is capable of dynamic measurement of DTV, caliper pressure fluctuations, disc surface temperature and vibration measurements at discrete points about the rig. This information is presented and supported by thermal imaging of the brake during a heavy brake application and subsequent thermal judder. The results also include surface scanning of the disc which is carried out at appropriate stages during testing to identify disc deformation including disc warping, "ripple" and the effects of "hot spotting". Disc run-out measurements via non-contacting displacement transducers show the disc taking up varying orders of deformation ranging from first to third order during high speed testing. The state of cold deformation of the disc is also shown to vary with the disc returning to first or second order deformation upon cooling. Thermal images of the brake disc have shown vane patterns to show through to the disc surface identifying uneven heat distribution.
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Braking Process in Automobiles: Investigation of the Thermoelastic Instability Phenomenon
M. Eltoukhy and S. Asfour, Department of Industrial Engineering, College of Engineering, University of Miami
abstract said:
During the braking action, the kinetic energy produced at the wheel is transformed into heat energy, which doesn't dissipate fast enough into the air stream from the brake to the brake disk; as a result, the thermal conductivity plays a critical role in handling such heat generated. Thermal judder, which is a result of non-uniform contact cycles between the pad and the disk brake rotor, which is primarily an effect of the localized Thermo-Elastic Instabilities (TEI) at the disk brake rotor surface. Localized TEI act at the friction ring surface generating intermittent hot bands around the rubbing path which may in turn leads to the development of so-called hot spots. In this chapter a case study regarding a transient analysis of the thermoelastic contact problem for disk brakes with frictional heat generation, performed using the finite element analysis (FEA) method is described in details. The computational results are presented for the distribution of the temperature on the friction surface between the contacting bodies (the disk and the pad). Also, the influence of the material properties on the thermoelastic behavior, represented by the maximum temperature on the contact surface is compared among different types of brake disk materials found in the literature, such as grey cast iron (grey iron grade 250, high-carbon grade iron, titanium alloyed grey iron, and compact graphite iron (CGI)), Aluminum metal matrix composites (Al-MMC's), namely Al2O3 Al-MMC and SiC Al-MMC (Ceramic brakes). This comparison was performed in order to improve the conceptual design of the disk brakes. The results obtained from the suggested model are compared with actual measurements obtained from experiments performed by Cueva et al.(2003). The FEA results were in excellent agreement with the actual measurements reported by Cueva et al. for all of the suggested brake disk materials. A comparison between two different brake disk rotor designs was performed as well in order to study the effect of the perforated brake disks on the maximum temperature, the temperature distribution, and the heat flux produced under the same braking conditions.
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Brake Vibration and Noise - A Review and Discussion
Dihua Guan, State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing, China
abstract said:
Brake vibration & noise is the friction induced phenomenon which has been studied by many researchers in a variety of ways due to its importance and complexity since the early 20th century. Recently rapid progress has been made in both theoretical and experimental studies, especially on the modeling and analytical methodology of solution to the practical problems. Present paper besides a general review of the literature concerned tries to make emphasize on the common points of different investigation works. The literature is including our own works since 1984 in Tsinghua University, but many of them are none published in English. For its presentation it takes some pages. The analysis made is from point of view for suppression of brake vibration & noise.
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NVH Simulation Technology for Disc Brake Calipers
Hitachi, To****sugu Suzuki Yoichi Kumemura Hayuru Inoue Yuichi Takagi Shinji Suzuki
abstract said:
A comfortable automobile is one in which both noise and vibration are suppressed, and in which the conditions are satisfied for a smooth ride. This is why NVH, which represents these conditions, has come to be used as an evaluation standard for automobile comfort. Noises that occur in disc brakes for automobiles come in a number of different categories, each with different causes. Of these categories, the noises referred to as "brake squeals" and the vibrations referred to as "brake judders" are caused by a complicated phenomenon whose reduction improves the value of automobiles on the market. Hitachi applies NVH analysis technology to make improvements through both experimental trials and simulations.
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SURFACE TEMPERATURE DISTRIBUTION IN A COMPOSITE BRAKE ROTOR
A.A. Adebisi1, M.A. Maleque1 and Q.H. Shah2 1 Department of Manufacturing and Materials Engineering, 2Department of Mechanical Engineering
abstract said:
The prediction of surface temperature for brake rotor is regarded as an important step in studying the brake system performance. The frictional heat generated on the rotor surface can influence excessive temperature rise which in turn leads to undesirable effects such as thermal elastic instability (TEI), premature wear, brake fluid vaporization (BFV) and thermally excited vibrations (TEV). The purpose of this study is to investigate the temperature distribution profile for brake caliper pressure application of 0.5, 0.10, 1.5 and 2.0 MPa with a speed of 60km/h braking condition on the disc rotor surface. The brake rotor assembly is built by using a 3 dimensional finite element model of a real car brake rotor. To verify the simulation results, an experimental investigation is carried out. It is believed from the study that composite brake rotor influences the temperature distribution and heat dissipation rate which could prevent excessive temperature rise and subsequently prolong the service life of the rotor. The finite element method is cost effective and also assists the automotive industry in producing optimised and effective brake rotor for thermal distribution analysis.
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DISCUSSION OF THE CHARACTERISTICS OF BRAKE JUDDER AND THE NECESSARY DATA ACQUISITION SYSTEM FOR COMPLETE ANALYSIS
D. Bryant, A. Crampton, J. Fieldhouse and C. Talbot University of Huddersfield, Queensgate, Huddersfield HD1 3DH, UK
abstract said:
Brake judder is becoming an increasing concern within the automotive industry. Much research into brake judder relies on simulated dynamometer work without correlation to actual vehicle data. A data acquisition system has been used to collect data from on vehicle brake testing. The data has been compiled and analysed using different methods to provide an effective means of validating future work carried out on an in house brake dynamometer.
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Order domain analysis of speed-dependent friction-induced torque in a brake experiment
Osman Taha Sen, Jason T. Dreyer, Rajendra Singh n Acoustics and Dynamics Laboratory, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA
abstract said:
A friction-induced forced vibration problem, as excited by the geometric distortions of the brake rotor, is studied in this article. The focus is on the order domain analysis, as the speed-dependent behavior of friction torque is not well understood. First, a new laboratory experiment is constructed to simulate vehicle brake judder in a scientific and yet controlled manner. The variations in pressure and torque are measured as the rotor slows down, and the order domain tracking is used to construct shaft torque vs. speed diagrams. A quasi-linear model of the laboratory experiment is then developed to obtain an analytical solution and to estimate the torque envelope function. A nonlinear model of the laboratory experiment (with a clearance) is also investigated to examine the resonant amplitude growth. Finally, predictions are successfully compared with measurements. Several contributions emerge over the prior literature. In particular, the experimental data clearly show that multiple-orders of the rotor surface distortion profile excite the friction-induced torque, and a clearance in the torsional system controls the resonant amplitude regime. New analytical and numerical solutions provide much insight into the speed-dependent resonant amplitude growth process.
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Note: I was unable to get the papers for these, which seemed informative:
Vibration and noise in brake systems of mobile vehicles. Part 3: Forced low-frequency vibration (A Review) , Journal of Friction and Wear July 2012, Volume 33, Issue 4, pp 293-307, V. P. Sergienko, S. N. Bukharov, S. F. Mel'nikov
A Study of the Mechanism Causing High-Speed Brake Judder,Masahiro Kubota, Tomihiro Suenaga and Kazuhiro Doi Nissan Motor Co., Ltd.,
SAE TECHNICALPAPER SERIES, 980594
"
A Study of Judder Vibration in Automotive Disk Brakes",
Key Engineering Materials (Volumes 326 - 328, Ho Joon Cho et al., 2006, Key Engineering Materials, 326-328, 1301
An Experimental and Theoretical Study on the Vehicle Brake Judder, (Hajnayeb, A., Baghi Abadi, M., and Hosseingholizadeh, A., "An Experimental and Theoretical Study on the Vehicle Brake Judder," SAE Technical Paper 2012-01-1820, 2012, doi:10.4271/2012-01-1820.)
Hot Judder - An Investigation of the Thermo-Elastic and Thermo-Plastic Effects during Braking (Fieldhouse, J., Bryant, D., and Talbot, C., "Hot Judder - An Investigation of the Thermo-Elastic and Thermo-Plastic Effects during Braking,"
SAE Int. J. Passeng. Cars ***8211; Mech. Syst. 4(2):1086-1101, 2011, doi:10.4271/2011-01-1575.)