Anti-coning brake discs are known for their superior NVH characteristics when compared to other disc designs, but also for poorer heat dissipation. Cooling characteristics of such a disc design are studied numerically and experimentally on a specially developed Thermal Spin Rig. The disc is installed inboard on a high-performance off-road vehicle, with portal axles and wheel drives, resulting in nearly fourfold higher disc rotational speeds in comparison to the wheel speeds. Being exposed to the free-flowing air and rotating much faster makes this application well worth the attention and deeper study in terms of disc cooling. Computational Fluid Dynamics (CFD) analyses show a detailed distribution of air velocities and pathlines, temperatures, pressures, and convective heat transfer coefficients. The results are all very coherent, conveying very useful information, both qualitatively and quantitatively. Their cumulative effect has been successfully validated by comparing the CFD predicted average convective heat transfer coefficients ( h conv ) with the experimental results obtained on the Thermal Spin Rig, in a controlled environment. CFD results show to be very close to average h conv values calculated from measured cooling curves. The agreement is very good for the wide temperature and speed range. The overall relative differences are under 5%, and in most cases under 3%, except for the low disc rotation speeds, which show a maximum relative difference of 12.5% calculated at 200 rpm, for the disc heated to 300°C. Such outcomes give confidence in the CFD results for future work in both disc design and vehicle installations.

The paper compares heat dissipation characteristics of two interchangeable ventilated brake discs, a standard solid hub and a newly developed fingered hub version, both single piece cast designs. The tests were conducted on a specially developed Thermal Flow Rig, which enables disc induction heating to 450°C and cooling for a range of rotational and air speeds, in parallel and angular cross flow. The Rig facilitated very accurate and repeatable experiments to be conducted for numerous combinations of operating conditions. From the recorded cooling curves, average heat transfer coefficients for convection and radiation were extracted and the results also presented in a generic form, using Nusselt numbers. The fingered design demonstrated superior convective heat dissipation, with the improvements varying depending on the rotational speed, air cross flow velocity and angle, as well as disc temperature. The gains were ranging from 3.5% to over 20%. The fingered design is 8.5% lighter and being a single piece cast disc, it remains inexpensive to mass produce.

The paper presents experimental investigation of the heat dissipation from stationary brake discs concentrated on four disc designs, a ventilated disc with radial vanes, two types of ventilated discs with curved vanes - a non-drilled and cross-drilled disc, and a solid disc. The experiments were conducted on a purpose built Thermal Spin Rig and provided repeatable and accurate temperature measurement and reliable prediction of the total, convective and radiative heat dissipation coefficients. The values obtained compare favourably with Computational Fluid Dynamics results for the ventilated disc with radial vanes and solid disc, though the differences were somewhat pronounced for the ventilated disc. The speeds of the hot air rising above the disc are under 1 m/s, hence too low to experimentally validate. However, the use of a smoke generator and suitable probe was very useful in qualitatively validating the flow patterns for all four disc designs. Convective heat transfer coefficients increase with temperature but the values are very low, typically between 3 and 5 W/m2K for the disc designs and temperature range analysed. As expected, from the four designs studied, the disc with radial vanes has highest convective heat dissipation coefficient and the solid disc the lowest, being about 30% inferior. Convective heat dissipation coefficient for the discs with curved vanes was about 20% lower than for the disc with radial vanes, with the cross drilled design showing marginal improvement at higher temperatures.

Battery models often either fail to deliver a complete picture of the physical phenomena occurring in the cell or fail to minimize computational effort. So far, the demand for a detailed internal thermal model of battery cells with a reasonable computation time has remained unanswered. This paper addresses such question introducing a multi-domain model whose accuracy makes it suitable for thermal management system development, at a lower computational cost than competing models. The approach features an equivalent circuit parameter model with chemistry-based parameters coupled with an internal heat transfer model. The internal heat transfer model includes different sections of the cell, addressing the anisotropy and the temperature-dependence of physical properties. Material properties are partly based on manufacturer's data sheet, partly taken from literature. The development software platform enables a sensible reduction of computational effort with respect to traditional modeling techniques. Results were validated against an aggressive current at different temperatures and against current profiles obtained from two different drive cycles at different ambient temperature. The model proves to be very good in terms of accuracy.

With brake squeal being the most prevalent noise vibration and harshness issue in modern vehicles, this paper presents an improved methodology for brake squeal propensity prediction at the design stage. The research established four clearly defined Stages' in conducting finite element squeal analyses, describing crucial input data, modelling procedures, output and validation results. Stage 1 deals with free-free modal characteristics of individual brake components and their material characteristics. Stage 2 combines individual parts, conducting brake assembly mechanical finite element analyses. Stage 3 concentrates on fully coupled thermo-mechanical finite element analyses, and the concluding stage, Stage 4, focuses on brake assembly stability analyses. Validations proved that very accurate predictions are possible, but the geometries, material characteristics and established modelling procedures must be strictly followed. Material characteristics were most prone to introduce discrepancies with measured values. Generic' values are found to be unacceptable and conducting own measurements was necessary, in particular for the friction material, whose anisotropic properties have been measured in detail, leading to high accuracy in predicting pad natural modes and frequencies. In Stage 4, the stability analyses of the full brake assembly were based on the complex eigenvalue analysis (which included thermal aspects), with the sign of the real part giving an indication of stability and the imaginary part defining the frequency of the unstable mode. Instabilities and frequencies predicted match well with the values measured in dynamometer tests, clearly demonstrating the influence of thermal effects. The final output of the procedures described in this paper is a validated three-dimensional thermo-mechanical finite element noise vibration and harshness brake assembly model in which natural frequencies and modes, instabilities and contributing factors can be predicted at any time during a brake application.

This article focuses on generating a monobloc fingered hub (top-hat) disc design, aiming at reducing disc mass but maintaining rotor thermal capacity, while also improving heat dissipation characteristics. The analyses and tests demonstrated that such a design is possible to achieve, with mass reduction of just over 9%. The activities included research into cast iron modelling, which gave very important insights into the limits of mechanical performance under bending. Initial finite element analyses enabled considerable progress to be made towards establishing a baseline design, but only through shape optimization and topology optimization procedures was the full potential of the design accomplished. Shape optimization facilitated the reduction of maximum principal stress by 32%, considerably improving disc torsional strength with practically no increase in mass. The safety factor in torsion achieved a value of 3.57. Topology optimization provided further, although small, mass reduction (1.5%) while maintaining low stress levels.

Following from the analytical modelling presented in Part 1, this paper details a comprehensive computational fluid dynamics modelling of the three-dimensional flow field around, and heat dissipation from, a stationary brake disc. Four commonly used turbulence models were compared and the shear stress turbulence model was found to be most suitable for these studies. Inferior cooling of the anti-coning disc type is well known but the core cause in static conditions was only now established. The air flow exiting the lower vane channels at the inner rotor diameter changes direction and flows axially over the hat region. This axial flow acts as a blocker to the higher vane inlets, drastically reducing convective cooling from the upper half of the disc. The complexity of disc stationary cooling is further caused by the change of flow patterns during disc cooling. The above axial flow effects slowly vanish as the disc temperatures reduce. Consequently, convective heat transfer coefficients are affected by both, the change in the flow pattern and decrease in air velocities due to reduced air buoyancy as the disc cools down. As in Part 1, the special thermal rig was used to validate the computational fluid dynamics results quantitatively and qualitatively. The former used numerous thermocouples positioned strategically around the brake disc, with the latter introducing the concept of laser generated light plane combined with a smoke generator to enable flow visualisation. Predicted average heat transfer coefficients using computational fluid dynamics correlate well with the experimental values, and even two-dimensional analytical values (as presented in Part 1) reasonably closely follow the trends. The results present an important step in establishing cooling characteristics related to the electric parking brake application in commercial vehicles, with future publications detailing heat transfer from the entire brake assembly.

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 commercial vehicles present completely different challenges. With the brake mass, thermal capacity and required clamp forces an order of magnitude higher, safe parking demands much more attention. In the first instance, the priority is placed upon predicting heat dissipation from the brake disc only. The research is presented in two parts; part one (presented here) focuses on analytical modelling and experimental verification of predicted disc temperatures over long cooling periods, with part two investigating the air flow, velocities and convective heat transfer coefficients using computational fluid dynamics modelling, also followed by experimental validations. To begin the analytical analysis, a study was conducted into the variance in mean local convective heat transfer coefficients over a simplified brake disc friction surface, by investigating typical dimensionless air properties. A nonlinear equation was derived for the average surface convective heat transfer coefficient ([Formula: see text]) variability with temperature drop for the entire cooling phase. Starting from fundamental principles, first-order differential equations were developed to predict the bulk disc temperature. By including variation of the convective and radiative heat dissipation throughout the cooling period, a good correlation was achieved with measured values, to within 10%. Experiments were conducted on a specifically designed thermal rig which uses 15 kW induction heater to heat the disc. Numerous experiments proved the results are very repeatable, throughout the cooling period. It was established, for the grey cast iron brake disc with a fully oxidised surface, the emissivity value are practically constant at ɛ = 0.92. Although the research is being conducted on a brake disc, the results have generic application to any disc geometry, whatever the application.

Internal policies of the major car markets are urging for a cut in oil imports, leading to powertrain electrification. Due to their high weight-to-power ratio, Lithium-ion batteries, especially Lithium-Nickel-Manganese-Cobalt Oxide 21700 cylindrical cells, are rapidly becoming the most diffused electric powertrain energy storage devices. These devices need to be operated in a tight temperature range to prevent major power drops and also for safety reasons. It is therefore essential to provide an accurate but computationally inexpensive battery model. Current models are either too simplistic and not applicable for thermal management design purposes or too computationally expensive and impractical for heat exchange modelling purposes. This work was focused on a computationally convenient system-level-modelling-oriented battery cell model. Starting from a 1D model obtained from manufacturer’s data, experiments were carried out on real cells, a more sophisticated 3D model for cell characterization was implemented and then a lighter 1D model obtained from it was proposed. The outcome is a novel thermal model of batteries, with a reasonable computational cost, developed on the purpose of thermal management design. This represents an advancement in battery thermal management design, as no such model is currently available in literature.

The use of optical fibre Bragg gratings (FBGs) to monitor the Interface Pressure Distribution (IPD) on an automotive disc brake pad under a variety of loading conditions is studied. The results demonstrate successful strain transfer from the brake pads to the attached FBG sensors under static loading, with a linear response to increasing pressure, and with the measured IPD showing good agreement with that recorded using pressure sensitive paper. Results are also presented demonstrating that changes in the IPD as a result of torque acting on the brake pads can be monitored by the FBG sensors.

Successful brake caliper designs must be light and stiff, preventing excessive deformation and extended brake pedal travel. These conflicting requirements are difficult to optimize owing to complex caliper geometry, loading and interaction of individual brake components (pads, disc and caliper). The article studies a fixed, four-pot (piston) caliper, and describes in detail the computer-based topology optimization methodology applied to obtain two optimized designs. At first sight, relatively different designs (named Z' and W') were obtained by minor changes to the designable volume and boundary conditions. However, on closer inspection, the same main bridge design features could be recognized. Both designs offered considerable reduction of caliper mass, by 19% and 28%, respectively. Further finite element analyses conducted on one of the optimized designs (Z caliper) showed which individual bridge features and their combinations are the most important in maintaining caliper stiffness.

Influence of whole-body vibration on reaction times was studied on a specially developed rig, with the subjects being exposed to no vibration, and vibration frequencies of 1, 5, 20 and 50 Hz. The shortest reaction times for both, sound and visual stimuli were measured for no vibration of the seating platform. The most detrimental influence was observed at vibration frequency of 5 Hz, with reaction times typically increasing between 50 and 70 ms. The shortest reaction times were always measured at the beginning of tests and the longest at the end. The increases in reaction times with elapsed time were typically more pronounced when subjects were exposed to sound stimuli. Equally, under the same conditions, reaction times to sound stimuli were longer than to visual stimuli (by approx. 60 to 100 ms). In all cases, changes in standard deviation values follow the same pattern as average reaction times.

Computer-based design optimisation methods are fast and powerful; however, recent experience from the oil and automotive industries suggests that patent protection of such methods and the resulting products may be problematic, particularly as regards obviousness and level of detail (so called ‘sufficiency’). The authors have explored these issues in detail based on the research work on optimisation methods applied to the design of high performance car brake callipers. Whilst the general design features obtained by such methods would appear to be obvious (and thus not patentable), certain sub-optimal and detailed optimal product designs would not. It becomes clear that the risk of invalidity may also be reduced by making the design method and the product design resulting from that method the subject of separate patent applications.

Improvement of convective heat dissipation from wheel-mounted discs presents a unique challenge due to the existence of a secondary air flow (in the circumferential direction), between the vanes and wheel web. Although this flow reduces pumping efficiency (air mass flow), it promotes air mixing between different channels and increases turbulence. Beginning with the existing design, a procedure was developed to maximise convective heat dissipation based on specific post-processing procedures and monitored parameters. These included the secondary flow (behind the vanes), air speed in the channels at specific planes and points, global air flow pattern and the distribution of the convective heat transfer coefficient. By analysing these plots and graphs it was possible to identify areas where flow and heat transfer characteristics could be improved. Ultimately, the specific power dissipation (the product of the average convective heat transfer coefficient and the disc wetted area), provided a single quantitative measure of disc design effectiveness in convective cooling. The newly developed design showed an increase in convective heat dissipation of over 10% when compared with the existing disc.

A wheel carrier is a commercial vehicle-specific component which connects the wheel to the wheel bearing and transfers the loads between the two parts. This paper presents a novel design, manufactured from an aluminium alloy. Finite Element (FE) modelling was extensively used to ensure structural strength, and brake cooling tests were used to assess improvements in heat dissipation. The newly developed prototype carrier has only half the mass of the original Spheroidal Graphite (SG) design, saving 11 kg per 'wheel end'. Brake cooling is also considerably improved, with the average convective heat transfer coefficient being increased by 50%.

Disc brake calipers are subjected to significant mechanical loading, with design requirements being particularly stringent with respect to the stresses, the deflections, the installation envelope, the noise, vibration, and harshness, and the thermal aspects. Modern finite element (FE) techniques can successfully model caliper assemblies; however, the limitations in predicting the caliper behaviour are primarily related to accurate definition of the boundary conditions, because of complex interactions between the individual components. Traditionally, strain gauges and displacement transducers have been used for measuring the caliper strains and deflections. This approach is expensive and time consuming, requiring installation of numerous transducers and complex data processing, and has limited accuracy. The application of digital image correlation (DIC) to a commercial vehicle disc brake caliper provided valuable strain results. In comparison with strain gauges, DIC proved to be exceptionally easy to use and enables straightforward comparison of measured strains with FE predicted values. Initial work dealt with the static actuating forces, and excellent correlation between the predicted and the measured strain values was achieved throughout the operating range of clamp forces. The present authors are confident that the addition of the dynamic frictional forces will give even more interesting results, providing insight into the interaction of different components within the brake assembly.

A disc with radial vanes and circumferential pillars proves to be successful in operation and achieves energy efficiency improvements compared with those of traditional design. Cooling characteristics of this novel design are practically identical to the disc with tangential vanes but the equivalent aerodynamic (air pumping) losses are approximately 50% less. It is shown that these reductions in pumping losses can lead to substantial energy savings in train operations.When developing new designs and/or comparing different railway disc designs, the proposed disc cooling to aerodynamic efficiency ratio (eta(v),) was found to be a very useful parameter to assess. This 'efficiency ratio' - a ratio of convective power dissipation to aerodynamic power losses can help in achieving adequate balance of cooling efficiency and aerodynamic losses to suit particular application. The use of CFD is of enormous benefit in generating discs that fulfil these demanding requirements, with the spin rig being exceptionally useful for experimental work. (C) 2008 Elsevier Ltd. All rights reserved.

The measurement of moisture in building fabrics has been of interest for many years due to the potentially devastating consequences of moisture problems within buildings. A range of potential techniques are available with which to measure the moisture content of building fabrics in situ and this paper focuses on two techniques which offer the potential for some significant advantages over existing approaches: (1) thermal dual-probe and (2) time domain reflectometry. The two approaches have been tested against measurements of moisture content using a laboratory-based X-ray measurement facility. As a result of the work that has been undertaken, the authors are very confident that the two measurement techniques are indeed applicable to typical building fabrics.

Air flow and convective heat dissipation from a wheel-hub-mounted railway brake disc were studied using computational fluid dynamics (CFD). The analyses enabled detailed insight into air flow, temperature, speed, pressure, and convective heat transfer coefficient distributions, never before available to a brake designer. Such results are practically impossible to experimentally obtain at reasonable cost. Particularly interesting finding is the existence of relatively considerable secondary flow - circumferential flow behind the vanes. Although this effect may reduce air pumping, and therefore radial air speed, it increases turbulence by promoting airflow between channels.Average values of the convective heat transfer coefficients obtained using CFD are practically identical to the experimental values derived from cooling tests performed on dynamometer and spin rig. Compared with other railway disc designs, this disc demonstrates exceptionally good convective cooling characteristics, in particular considering its size and investigated operating condition (rotation in still air).The computational studies of air flow and heat dissipation characteristics are an excellent base for development work in improving existing and generating new disc designs with high heat dissipation characteristics. Future work is concentrated on conducting additional analyses of the current disc design, in order to investigate the most effective ways of maximizing convective cooling.

Detailed computational fluid dynamics (CFD) analyses of airflow and convective heat dissipation from a standard disc with radial vanes gave vital information regarding its weak points. Heat transfer from vanes is found to be particularly non-uniform, offering the largest scope for increasing local and average values of the coefficient of convective heat dissipation. A relatively simple modification — installation of an additional small vane (per channel, between the existing vanes) — demonstrated the ability to increase convective cooling from the ventilation channels. The radial position of these additional vanes was altered from disc ID towards OD, and best results were obtained with the vanes placed at the channel outlets (OD). An improvement in the total convective cooling (product of the average convective heat transfer coefficient and the entire disc wetted area) of nearly 14 per cent was achieved. In spite of better cooling, the new design has lower mass (air) flow when compared with the baseline design. The results are also presented in the form of Nusselt numbers, enabling their wider use. Conducted validation provided strong confidence in the accuracy of the results when searching for new solutions.