Showing papers on "Disc brake published in 2018"

Selective laser melting of 24CrNiMo steel for brake disc: Fabrication efficiency, microstructure evolution, and properties

Abstract: 24CrNiMo alloy steel used for brake disc was prepared by selective laser melting technology with the processing parameters of high power input and thicker powder layer. The Microstructure and mechanical properties of as-fabricated part were characterized. Effects of processing parameters on the production efficiency, thermal history and microstructure evolution mechanism were studied. The results of this work indicate that the as-fabricated steel microstructure mainly consist of granular bainite and meta bainite, which results in a high microhardness and fine strength. High laser power input leads to a high thermal accumulation level in a SLM process and the microstructure mainly transforms into bainite. In addition, compared to the commonly used parameters, the overall preparation efficiency in this study is enhanced by 82.9%. These presented results provide an insight on how to improve SLM efficiency, and preparation of high-performance 24CrNiMo alloy steel by SLM technology shows high potential for manufacturing of the brake disc core part.

Finite element analysis on squeal-noise in railway applications

Abstract: In this paper, we present the results of an experimental investigation on squeal noise emitted by a disc brake for railway applications. The measurement, that show in an evident manner the onset of instability forms during the braking phase were made on a test-rig in real scale on which we measured by means of a sound intensity probe the noise emitted by the disc brake. By using a Fast Fourier Transform (FFT) we identified the strongest detected frequencies. The aim of this paper is to analyse such phenomena by conducting a Finite Element Analysis (FEA) of the 3D CAD model of the disk modelled in Ansys Workbench FEM software, in order to, better understand the path that leads a stable system to unstable behaviour. The system analysed is composed of a steel disk and four pads made of an array of cylinders made of frictional material. Such pad system has been designed in order to simplify the simulation, assuming that it acts on the disk surface just in some points. The numerical results agree with the experimental ones.

CFD analysis of the brake disc and the wheel house through air flow: Predictions of Surface heat transfer coefficients (STHC) during braking operation

Abstract: Braking system is one of the basic organs to control a car. For many years, the disc brakes have been used in automobiles for safe retardation of the vehicles. During braking, enormous amount of heat will be generated, and for effective braking, sufficient heat dissipation is essential. The specific air flow surrounding the brake rotor depends on the thermal performance of the disc brake and hence, the aerodynamics is an important in the region of brake components. A CFD analysis is carried out on the braking system as the study of this case, to make out the behavior of air flow distribution around the disc brake components using ANSYS CFX software. The main object of this work is to calculate the heat transfer coefficient (h) of the full and ventilated brake discs as a function of time using the CDF analysis, which will be used later in the transient thermal analysis of the disc in ANSYS Workbench 11.0.

Preparation and printability of 24CrNiMo alloy steel powder for selective laser melting fabricating brake disc

Abstract: Spherical 24CrNiMo alloy steel powder used for selective laser melting (SLM) fabricating high-speed train brake disc was prepared by the vacuum induction melting gas atomisation (VIGA) method. Powd...

A human factors systems approach to exploring vehicle rollaway

Abstract: Failure of a parked unattended vehicle to remain stationary, otherwise known as vehicle rollaway, can result in property damage, injury or even fatality. Although the incidence of vehicle rollaway may be under reported, around 8% of drivers and 13% of Approved Driving Instructors surveyed indicated they had experienced a vehicle rollaway event. Unlike previous studies which focused only on the mechanical factors that may contribute to this phenomenon, the research presented in this thesis employed a more comprehensive, systems approach to explore additional factors related to the driver s interaction with the parking brake system at various interface levels. A mixed methods strategy collated data through two online surveys and three observational studies to explore the organisational, mechanical and driver related factors identified in a fault tree framework. The results indicated that current driver practice and interaction with the parking brake system may be contrary to legislative requirements and manufacturer s instruction. The findings suggested that a past experience of vehicle rollaway or parking brake system failure, had a statistically significant influence on whether the driver complied with the recommended practice. Driver interaction and the holding capability of the parking brake system were observed in 53 vehicles parked on three test gradients. The observations indicated that drivers were able to apply sufficient force to the parking brake lever to hold the vehicle stationary and that an additional degree of confidence in the system was provided by parking in gear. But, after driving a short commuting route, when the vehicle was parked with the parking brake lever applied to the lowest position to hold the vehicle and a gear was not selected, 63% of vehicles fitted with disc brakes rolled as the temperature returned to ambient. Discussion relates to the organisational, driver related and mechanical components of the parking brake system and in reference to Reason s Swiss Cheese model, considers how latent failures within the defensive layers of the system can contribute to rollaway. The research findings contributed to a change in UK driving standards and since 2015, drivers are recommended to park in gear at all times to reduce the risk of rollaway. This recommendation is likely to require a change in practice for up to 80% of Approved Driving Instructors who would not normally instruct new drivers in this way. Although this research focused on the manually operated parking brake system, the studies have uncovered results that can contribute to knowledge and are applicable to interaction with electronic parking brake systems. As parking brake systems develop, the Human Factors systems approach can be applied retrospectively and proactively to explore that interaction and prevent passenger vehicle rollaway.

Material characterisation of lightweight disc brake rotors

Abstract: Alumina coated lightweight brake rotors were investigated to evaluate the effect of coating properties on their friction performance and thermal durability. An alumina ceramic coating on AA6082 alu...

Design, Development and FE Thermal Analysis of a Radially Grooved Brake Disc Developed through Direct Metal Laser Sintering

Abstract: The present research work analyzed the effect of design modification with radial grooves on disc brake performance and its thermal behavior by using additive manufacturing based 3D printed material maraging steel. Temperature distribution across the disc surface was estimated with different boundary conditions such as rotor speed, braking pressure, and braking time. Design modification and number of radial grooves were decided based on existing dimensions. Radial grooves were incorporated on disc surface through Direct Metal Laser Sintering (DMLS) process to increase surface area for maximum heat dissipation and reduce the stresses induced during braking process. The radial grooves act as a cooling channels which provides an effective means of cooling the disc surface which is under severe condition of sudden fall and rise of temperatures during running conditions. ANSYS software is used for transient structural and thermal analysis to investigate the variations in temperatures profile across the disc with induced heat flux. FE based thermo-structural analysis was done to determine thermal strains induced in disc due to sudden temperature fluctuations. The maximum temperature and Von Mises stress in disc brake without grooves on disc surface were observed which can severely affect thermal fatigue and rupture brake disc surface. It was been observed by incorporating the radial grooves that the disc brake surface is thermally stable. Experimental results are in good agreement with FE thermal analysis. DMLS provides easy fabrication of disc brake with radial grooves and enhancement of disc brake performance at higher speeds and temperatures. Therefore, DMLS provides an effective means of implementing product development technology.

Influence of Thermal Fatigue on the Wear Behavior of Brake Discs Sliding against Organic and Semimetallic Friction Materials

Abstract: In this article, brake discs are exposed to high thermal stress, causing thermal fatigue damage. The aim of this work is to study the evolution of the wear behavior of brake disc materials, such as...

Low and high cycle fatigue of automotive brake discs using coupled thermo-mechanical finite element analysis under thermal loading

Abstract: To predict the thermal fatigue life and thermal stress phenomena of a brake disc, it is necessary to study the thermo-mechanical coupling effect in terms of braking conditions. Thermal fatigue stress of automotive brake discs was analyzed by using the coupled thermomechanical finite element (FE) simulation. The FE model was developed by considering the effect of conduction and convection heat transfer by frictional heat generation and film condition. Experimental boundary conditions of the brake dynamometer were applied to the simulation model. The structural stress due to the stress concentration effect on the bolt holes was also confirmed. The thermal fatigue life of the friction surface and the bolt holes was differently estimated depending on the influence of the stress amplitude. The strain-life relationship was used to predict thermal fatigue life in view of elastic and plastic deformation. The fatigue cycle ratio was also presented to calculate the fatigue life for different braking pressures.

Experimental research of effectiveness of brakes in passenger cars under selected conditions

Abstract: The subject of the considerations presented herein is experimental research of effectiveness of disc brakes on various road surfaces in both dry and wet road conditions on the example of a passenger car equipped with different kinds of tyres. The factors affecting the length of the braking distance of a passenger car were described on the basis of which braking delays were measured for three selected tyre types with a different tread depth for three vehicle speeds of 50 km/h, 70 km/h and 100 km/h in order to determine how selected factors affect the braking distance of the vehicle. The experiments were conducted on a dry asphalt surface, a wet asphalt surface contaminated with sand as well as for comparison purposes, on a wet and dry concrete surface. The tests were conducted with the use of mid-range vehicles equipped with disc brakes with a diameter of 288 mm, 312 mm and 320 mm. The author hereof complied an analysis of the results for various combinations of discs, tyres, surfaces and vehicle speeds. The experiments demonstrated that the difference in the length of the braking distance between a dry and wet surface amounts to 1.87 m for 50 km/h, 3.18 m for 70 km/h and 4.97 m for 100 km/h. On the basis of the conducted experiments it might be concluded that braking is more efficient on an asphalt surface. With each type of the analysed brake discs, the distance needed stop the tested vehicle on a concrete surface was longer.

Theoretical and experimental investigations of the bifurcation behavior of creep groan of automotive disk brakes

Abstract: There are several low frequency vibration phenomena which can be observed in automotive disk brakes. Creep groan is one of them provoking noise and structural vibrations of the car. In contrast to other vibration phenomena like brake squeal, creep groan is caused by the stick-slip-effect. A fundamental investigation of creep groan is proposed in this paper theoretically and experimentally with respect to parameter regions of the occurrence. Creep groan limit cycles are observed while performing experiments in a test rig with an idealized brake. A nonlinear model using the bristle friction law is set up in order to simulate the limit cycle of creep groan. As a result, the system shows three regions of qualitatively different behavior depending on the brake pressure and driving speed, i.e. a region with a stable equilibrium solution and a stable limit cycle, a region with only a stable equilibrium solution, and a region with only a stable limit cycle. The limit cycle can be interpreted as creep groan while the equilibrium solution is the desired vibration-free case. These three regions and the bifurcation behavior are demonstrated by the corresponding map. The experimental results are analyzed and compared with the simulation results showing good agreement. The bifurcation behavior and the corresponding map with three different regions are also confirmed by the experimental results. At the end, a similar map with the three regions is also measured at a test rig with a complete real brake.

Experimental Evaluation of Brake Pad Material Propensity to Stick-Slip and Groan Noise Emission

Abstract: Frictional and dynamic responses of brake pad materials, when sliding on brake disc counterfaces, are at the origin of noise, vibration and harshness (NVH) issues such as brake noise emissions. In more detail, groan is a low frequency noise emission often associated to the stick-slip frictional response of the brake system. The instability of such contact is the result of the coupling between the system dynamics and the frictional response of the materials in contact. In this work, an experimental approach is proposed for measuring the frictional response and the propensity to generate stick-slip of different lining materials, coming from commercial brake pads, when sliding on a worn surface of a brake disc, under the same controlled boundary conditions. The proposed methodology allowed for comparing the propensity of the tested pad materials to stick-slip vibrations, which is in agreement with feedback from automotive industry on groan emission.

Computational fluid dynamics (CFD) analysis and numerical aerodynamic investigations of automotive disc brake rotor

Abstract: Braking system is one of the important control systems of an automotive. For many years, the disc brakes have been used in automobiles for the safe retarding of the vehicles. During the braking enormous amount of heat will be generated and for effective braking sufficient heat dissipation is essential. The thermal performance of disc brake depends upon the characteristics of the airflow around the brake rotor and hence the aerodynamics is an important in the region of brake components. A CFD analysis is carried out on the braking system as a case study to make out the behaviour of airflow distribution around the disc brake components using ANSYS CFX software. We are interested in the determination of the heat transfer coefficient on each surface of a ventilated disc rotor varying with time in a transient state using CFD analysis, and then imported the surface film condition data into a corresponding FEM model for disc temperature analysis.

The coupled thermoelastic instability of FGM coatings with arbitrarily varying properties: in-plane sliding

Abstract: The hot spot caused by frictional heat and thermal contact resistance is one of the most important reasons for hot-cracks and brake failure in brake systems. This paper simulates the brake system as a functionally graded material (FGM) coated half-plane sliding against a homogeneous half-plane. The motivation of using the FGM coating is to improve the coupled thermoelastic instability (TEI) of the brake system due to the thermal contact resistance and frictional heat. The thermoelastic properties of the FGM coating are assumed to vary arbitrarily along the thickness direction. The homogeneous multi-layered model is employed to simulate arbitrary properties of the coating. The perturbation method and transfer matrix method are used to derive the characteristic equation of the coupled TEI problem. The effects of the thermal contact resistance, friction coefficient, heat generation factor and different gradient types of the FGM coating on the stability boundaries are discussed in detail. The results show that the stability boundary is sensitive to the varying thermal parameters of the FGM coating, and an appropriate gradient type can adjust the coupled TEI of the sliding system.

Scaling effects of measuring disc brake airborne particulate matter emissions – A comparison of a pin-on-disc tribometer and an inertia dynamometer bench under dragging conditions

Abstract: An important contributor to non-exhaust emissions in urban areas is airborne particulate matter originating from brake systems. A well-established way to test such systems in industry is to use ine ...

A friction, wear and emission tribometer study of non-asbestos organic pins sliding against alsic mmc discs

Abstract: The friction, wear and particle emission from an AlSiC MMC brake disc/non-asbestos organic brake pad system is studied using a pin-on-disc tribometer. The results show that this unconventional AlSi ...

Analysis of Low-Frequency Squeal in Automotive Disc Brake by Optimizing Groove and Caliper Shapes

Abstract: A low-frequency squeal that occurs due to the coupling phenomena of various vibrational modes in a disc brake system may cause annoyance to passengers. In an effort to remove the irritating low-frequency squeal of the disc brake, we carried out complex eigenvalue analysis and investigated the contribution ratio of each part to the occurrence of squealing. To this end, we developed a reliable and accurate finite element (FE) model of each brake part and compared it to the model test results. Throughout the complex eigenvalue analysis for the FE models, all unstable modes and corresponding frequencies in the brake system were calculated. The dominant parts that contributed largely to the squealing of the brake system were also elicited by the component contribution factor (CCF) analysis. Parts such as the disc, carrier, pad, and knuckle, were determined as large contributors to squealing. To reduce squealing, the tie-bar shape and the groove shape around the disc hub were optimized by FE-based shape optimization. A new disc with an optimal groove and a new tie-bar were manufactured, and dynamo squeal tests were conducted for a comparison to the numerical prediction. A fairly good correlation was observed between the experimental and numerical analysis results.

Heat dissipation from a stationary brake disc, Part 1: Analytical modelling and experimental investigations

Abstract: The main aim of the research is to support the development of the commercial vehicle electric parking brake Though nowadays widely used on passenger cars, electric parking brake applications on co

Thermal Stress Coupling Analysis of Ventilated Disc Brake Based on Moving Heat Source

Abstract: There is a thermomechanical coupling phenomenon in the braking process of vehicle disc brakes. Since the solution time of the direct coupling method is long and it is hard to converge, it is not suitable for analyzing heavy-load braking conditions with long braking time. Meanwhile, the sequential coupling method based on fixed heat source cannot achieve the rotation of friction heat source of the brake disc or accurately simulate the change of temperature. Therefore, Abaqus user subroutine is invoked to achieve the heat source rotation. The results of the simulated temperature field are compared with the results of the complete thermodynamic coupling method, the sequential coupling method based on fixed heat source and dyno test. The comparison shows that the new method combines the advantages of the first two methods and has a better engineering value.

Frictional Properties and Mechanisms of an Organic–Metal Brake Pair Braking Repeatedly in Magnetic Field

Abstract: With the aim to investigate repeated braking of organic–metal brake pairs, tribological and scanning electron microscopy (SEM) experiments were performed to reveal the influence of a magnetic field on the tribological performance of brakes. A nonasbestos copper-based brake pad and gray cast iron brake disc were selected as the brake pair. The X-DM pad-on-disc friction tester was improved to set up a tribological tester under a magnetic field. The worn surfaces were observed by SEM to reveal the friction mechanisms. It was found that a magnetic field can ameliorate the dynamic friction and wear. In addition, the global mean friction coefficient increases and the wear resistance of brake materials improves. A magnetic field promotes surface oxidation and aggravates the surface heat emission condition. As a result, the mean temperature on the friction surface increases obviously. An appropriate magnetic field can improve the dynamic temperature rise and decrease the global temperature rise on the fri...

Passenger car active braking system: Pressure control design and experimental results (part II):

Abstract: This paper deals with the design of a brake caliper pressure controller for a conventional anti-lock braking system/electronic stability control system and the experimental validation of its tracki...