• A 3D Finite Element Simulation of Ventilated Brake Disc Hot Spotting

      Tang, Jinghan; Bryant, David; Qi, Hong Sheng (2016-06-15)
      Hot spots are high temperature thermal gradients and localisations that are circumferentially distributed on a disc surface which can occur during heavy duty braking. Vibrations and noise can be triggered by hot spotting as well as damage to the disc surface. The experimental investigations suggest that the trigger condition and distribution of hot spots are related to the disc geometry, especially for ventilated discs. To investigate the effects of geometry and structure of a ventilated disc on hot spotting, a 3D finite element model was established. A fast simulation method of hot spotting in 3D was implemented in the model to enable a parametric analysis to be performed more efficiently. The results were validated using experimental data from a laboratory dynamometer.
    • Active cutting edges in vitrified CBN grinding wheels.

      Cai, R.; Qi, Hong Sheng; Cai, G.Q. (2006)
      Wheel structure has a critical influence on grinding performance especially active cutting edge density. Experiments were carried out to find out the relationshipbetween active and staticcutting edge density. It was found that there are many more active cutting edges in grinding than expected based on chip thickness formulae mainly due to wheel deflection in grinding.
    • Analysis of heat partition ratio in vehicle braking processes.

      Loizou, Andreas; Qi, Hong Sheng; Day, Andrew J. (Institution of Mechanical Engineers, 09/06/2009)
      An examination of the heat partition ratio between the friction surfaces of a disc braking system is presented using finite element analysis (FEA). This includes a 2D static analysis of two semi-infinite bodies in contact with and without an interface layer which represents the interface tribo-layer (ITL). An analytical approach with a finite difference solution was used for cross-comparison with the static FE models. Results from the static model have provided the boundary conditions for a 2D dynamic model, where one rectangular block slides on another (fixed) rectangular block. The effects of normal loads and real contact area have also been studied.
    • Analysis of the interface heat partition in a friction brake system with 2D Fe models

      Qiu, L.; Qi, Hong Sheng; Wood, Alastair S. (2016-11-04)
      A 2D finite element model of frictional heating in a pad-disc brake system is proposed for analyzing the heat partition and heat flux at the pad/disc interface during braking. And further find out how long the model can reach a thermal stable situation. The temperature on the friction surfaces of automotive brake is an influential factor of the brake performance. A formulation of friction heat generation during braking with constant velocity is presented, and the effects of thermal contact resistance on a contact surface are simulated by ABAQUS with different thermal contact conductance/clearance settings. The heat partition at contact surface with different time instants are analyzed. Results show that the heat partition along the interface is affected by the interface contact pressure and the thermal contact conductance. Additionally, results based upon the proposed model show that at normal thermal contact conductance conditions, typically 104 W/m2K for friction brake applications, the heat partition and the interface temperature become sensitive to the interface pressure variation, in comparison with that under ideal high thermal contact conductance condition (or low thermal contact resistance condition), typically 106 W/m2K. The comparison between results from simulations with different interface thermal conductance values indicate the parameters are sensitive in normal thermal conductance applications and how thermal conductance affect brake performance. And it is worthy to try control interface thermal conductance by using different pad/disc materials to make interface thermal conductance at a proper value.
    • Analysis of the transient thermomechanical behaviour of a lightweight brake disc for a regenerative braking system

      Sarip, S. Bin; Day, Andrew J.; Olley, Peter; Qi, Hong Sheng (2013)
      Regenerative braking would extend the working range of an EV or HV provided that any extra energy consumption from increased vehicle mass and system losses did not outweigh the saving from energy recuperation, also reduce duty levels on the brakes themselves, giving advantages including extended brake rotor and friction material life, but more importantly reduced brake mass, minimise brake pad wear. The objective of this research is to define thermal performance on lightweight disc brake models. Thermal performance was a key factor which was studied using the 3D model in FEA simulations. Ultimately a design method for lightweight brakes suitable for use on any car-sized hybrid vehicle was used from previous analysis. The design requirement, including reducing the thickness, would affect the temperature distribution and increase stress at the critical area. Based on the relationship obtained between rotor weight, thickness, undercut effect and offset between hat and friction ring, criteria have been established for designing lightweight brake discs in a vehicle with regenerative braking.
    • Applications of Contact Length Models in Grinding Processes

      Qi, Hong Sheng; Mills, B.; Xu, X.P. (2009)
      The nature of the contact behaviour between a grinding wheel and a workpiece in the grinding process has a great effect on the grinding temperature and the occurrence of thermal induced damage on the ground workpiece. It is found that the measured contact length le in grinding is considerably longer than the geometric contact length lg and the contact length due to wheel-workpiece deflection lf. The orthogonal relationship among the contact lengths, i.e. lc2 = (Rrlf)2 + lg2, reveals how the grinding force and grinding depth of cut affect the overall contact length between a grinding wheel and a workpiece in grinding processes. To make the orthogonal contact length model easy to use, attempts on modification of the model are carried out in the present study, in which the input variable of the model, Fn’, is replaced by a well-established empirical formula and specific grinding power. By applying the modified model in this paper, an analysis on the contributions of the individual factors, i.e. the wheel/workpiece deformation and the grinding depth of cut, on the overall grinding contact length is conducted under a wide range of grinding applications, i.e. from precise/shallow grinding to deep/creep-feed grinding. Finally, using a case study, the criterion of using geometric contact length lg to represent the real contact length lc, in terms of convenience versus accuracy, is discussed.
    • The bedding-in process on disc brakes contact pressure distribution and its effects.

      Loizou, Andreas; Qi, Hong Sheng; Day, Andrew J. (24/11/2010)
      Given that most of the working life of a brake pad life is spent in the bedded condition, it is important to examine the conditions of a fully bedded contact interface. An experimental and a numerical method are combined. Contact pressure and its effects (heat generation/partition and temperature rise) for the drag braking process with and without bedding are compared. The real contact area is also measured and found to be increased for the bedded interface. This results to the contact pressure being ¿more¿ evenly distributed than before. Spreading the contact pressure also results in increasing the total heat transfer between the disc and pad since now more heat can be transferred from the pad (where it is generated) to the disc. It is concluded that in order to have a reliable simulation it is recommended that the bedding-in effects are introduced in the simulations.
    • Coupled CFD and FE Thermal Mechanical Simulation of Disc Brake

      Tang, Jinghan; Bryant, David; Qi, Hong Sheng (2014)
      To achieve a better solution of disc brake heat transfer problem under heavy duty applications, the accurate prediction of transient field of heat transfer coefficient is significant. Therefore, an appropriate coupling mechanism between flow field and temperature field is important to be considered. In this paper, a transient conjugate heat transfer co-simulation disc brake model has been presented in order to improve the accuracy and feasibility of conventional coupled FE and CFD method. To illustrate the possible utilizations of this co-simulation method, a parameter study has been performed e.g. geometric, material, and braking application. The results show the advantage of the co-simulation method in terms of computing time efficiency and accuracy for solving complex braking heat transfer problem.
    • Enhancement of Natural Convection Heat Transfer within Closed Enclosure Using Parallel Fins

      Gdhaidh, Farouq A.S.; Hussain, Khalid; Qi, Hong Sheng (2015-03)
      A numerical study of natural convection heat transfer in water filled cavity has been examined in 3-D for single phase liquid cooling system by using an array of parallel plate fins mounted to one wall of a cavity. The heat generated by a heat source represents a computer CPU with dimensions of 37.5∗37.5mm mounted on substrate. A cold plate is used as a heat sink installed on the opposite vertical end of the enclosure. The air flow inside the computer case is created by an exhaust fan. A turbulent air flow is assumed and k-ε model is applied. The fins are installed on the substrate to enhance the heat transfer. The applied power energy range used is between 15 - 40W. In order to determine the thermal behaviour of the cooling system, the effect of the heat input and the number of the parallel plate fins are investigated. The results illustrate that as the fin number increases the maximum heat source temperature decreases. However, when the fin number increases to critical value the temperature start to increase due to the fins are too closely spaced and that cause the obstruction of water flow. The introduction of parallel plate fins reduces the maximum heat source temperature by 10% compared to the case without fins. The cooling system maintains the maximum chip temperature at 64.68°C when the heat input was at 40W that is much lower than the recommended computer chips limit temperature of no more than 85°C and hence the performance of the CPU is enhanced.
    • FEM and CFD Co-simulation Study of a Ventilated Disc Brake Heat Transfer

      Tang, Jinghan; Qi, Hong Sheng (2013)
      This paper presents a two-way thermally-coupled FEM-CFD co-simulation method for ventilated brake disc rotor heat transfer analysis. Using a third party coupling interface for data mapping and exchange, the FEM and CFD models run simultaneously under a standard heavy duty braking test condition. By comparison with conventional one-way coupling methods and experimental results, the performance of the co-simulation system has been investigated in terms of prediction of the heat transfer coefficient (HTC) and disc temperatures as well as computing time used. The results illustrate that this co-simulation method has good capacity in providing cooling effect and temperature predictions. It also shows that the data exchange between the FEM and CFD codes at every time increment is highly accurate and efficient throughout 10 brake applications. It can be seen that the cosimulation method is more time efficient, convenient and robust compared to previous oneway coupling methods. To utilize the potential of this method, future works are proposed.
    • A Finite Element Simulation of Disc Brake Hot Band Migration

      Tang, Jinghan; Bryant, David; Qi, Hong Sheng (2015)
      The migration of hot banding is the phenomenon whereby hot bands or hot spots on the brake disc surface periodically migrate radially inward and outward. These migrations can cause the undesired brake torque variation (BTV) and further induce vibration problems such as brake judder. To investigate the forming and migration of hot banding problem, transient thermal mechanical finite element models of repetitive braking considering the effects of wear have been performed. The displacement, temperature, stress, and contact pressure distribution against time were obtained in this model. The thermal buckling, thermo-elastic instability (TEI) and hot band migration phenomena have been captured and investigated. The results suggest a cause-effect chain of radial hot band migration. Its determinants include mechanical loading, disc thermal buckling, and most importantly the transient interactions between TEI and wear.
    • A fundamental study on the heat partition ratio of vehicle disc brakes

      Loizou, Andreas; Qi, Hong Sheng; Day, Andrew J. (2013)
      The interface tribo-layer (ITL) in an automotive brake friction pair is a layer of material created from transfer films, wear particles, and surface transformations between the rotor and stator. Its presence in a brake friction interface has been proven, e.g. by the existence of a temperature ‘jump’ across the friction interface. In this paper two static transient heat transfer models which force one dimensional heat flow, have been used to investigate the ITL behaviour and obtain an equivalent thermal conductance value. The ITL equivalent thermal conductance value is important as it reduces computational requirements and software restrictions encountered in the physical model of the ITL. This approach is developed into a more realistic two-dimensional coupled temperature-displacement model using commercial FEA software (ABAQUS). A newly developed relationship that utilises the contact pressure, real contact area, and the ITL equivalent thermal conductance, has been used to estimate the effective thermal conductance at the friction interface. Subsequently the effective thermal conductance relationship is combined with the 2-D coupled temperaturedisplacement model. The combination of this relationship with the 2D FE model provides a new method of heat partition prediction in brake friction pairs. Heat partition at a brake friction interface is confirmed to be neither uniform nor constant with time.
    • Fuzzy contact and its effect on thermal damage in grinding processes

      Qi, Hong Sheng; Mills, B.; Rowe, W.B. (2001)
      Not available
    • Fuzzy criticality assessment for process equipments maintenance

      Qi, Hong Sheng; Liu, Q.; Wood, Alastair S.; Alzaabi, R.N. (2012)
      Criticality-based maintenance (CBM) is a prioritized approach to the maintenance of (industrial) process equipment. CBM requires personnel with a thorough knowledge of the process/equipment under scrutiny. In this paper a criticality assessment system that is implemented by a local company (which represents the expertise and knowledge of the company experts) is reviewed and fuzzy logic theory is applied to improve the system's capability and reliability. The quality of the fuzzy system is evaluated based on several case studies. The results show that the fuzzy logic based system does not only what the conventional system does, but also outperforms in terms of reliability and has a unique ranking capability.
    • A Fuzzy Criticality Assessment System of Process Equipment for Optimized Maintenance Management.

      Qi, Hong Sheng; Alzaabi, R.N.; Wood, Alastair S.; Jani, M. (2015-01)
      In modern chemical plants, it is essential to establish an effective maintenance strategy which will deliver financially driven results at optimised conditions, that is, minimum cost and time, by means of a criticality review of equipment in maintenance. In this article, a fuzzy logic-based criticality assessment system (FCAS) for the management of a local company’s equipment maintenance is introduced. This fuzzy system is shown to improve the conventional crisp criticality assessment system (CCAS). Results from case studies show that not only can the fuzzy logic-based system do what the conventional crisp system does but also it can output more criticality classifications with an improved reliability and a greater number of different ratings that account for fuzziness and individual voice of the decision-makers.
    • An integrated approach to Lean Systems and CADCAM methodology deployment in a SMME

      Esan, Adedeji O.; Khan, M. Khurshid; Naylor, C.; Qi, Hong Sheng (2008)
      Cost reduction through the use of technology has become the competitive strength of companies. The benefits of computer integration are quite credible and have been effective in beating the competition. This paper describes a manufacturing strategy for the implementation of lean systems and the development of an integrated CADCAM system in a Small Medium Manufacturing Enterprise (SMME). Using an end-to-end CADCAM system, organisational change paradigm, and lean philosophy of “minimum effort maximum output”—a system with extensive and completely integrated suite of tools for concurrent engineering, product life cycle engineering, PDM collaboration, and manufacturing planning was developed with the objective of creating a more responsive and interactive manufacturing environment.
    • Integrated manufacturing strategy for deployment of CADCAM methodology in a SMME

      Esan, Adedeji O.; Khan, M. Khurshid; Qi, Hong Sheng; Craig, N. (2013)
      Purpose – Cost reduction through the use of technology has become the competitive strength of companies. The benefits of technology integration are quite credible and have been effective in business competition. The purpose of this paper is to describe an integrated manufacturing strategy for the deployment of a CAD/CAM system in a small, medium manufacturing enterprise (SMME). Design/methodology/approach – A case study of a SMME is utilised in deploying an integrated CAD/CAM system for practical application of manufacturing technology for achieving sustainable growth through lean systems design (LSD). The paper presents a techno-economic and technology change management framework, with an application of a holistic set of lean deployment tools that include establishing a strategic and operational plan for implementing CAD/CAM systems as a means to achieving world-class performance. Findings – The paper shows that the CAD/CAM integration within the case company increased knowledge of CAD/CAM technology, productivity, and flexibility whilst reducing throughput times. Based on the literature review and the current case study, a framework for ideal CAD/CAM implementation has been proposed. The paper also shows that management and organisational structures are key inhibitors for successful implementation of technology integration. Research limitations/implications – The paper uses a single case study to validate deployment of the integrated manufacturing strategy in SMMEs. Hence there is a limitation to its generality. Practical implications – ThepaperprovidesanopportunitytofurtherunderstandCAD/CAMsystem implementation protocols within a well structured framework and its configuration within SMMEs. Social implications – The CAD/CAM implementation framework will allow the SMMEs to achieve Lean manufacturing (thereby minimising wastes) leading to improved growth and employment rates. Originality/value – The presentation of conceptualisation, development and implementation of an integrated CAD/CAM system in support of organisational wide Lean manufacturing initiative in SMMEs is an originality of this paper.
    • Interface temperatures in friction braking

      Qi, Hong Sheng; Noor, K.; Day, Andrew J. (2002)
      Results and analysis from investigations into the behaviour of the interfacial layer (Tribolayer) at the friction interface of a brake friction pair (resin bonded composite friction material and cast iron rotor) are presented in which the disc/pad interface temperature has been measured using thermocouple methods. Using a designed experiment approach, the interface temperature is shown to be affected by factors including the number of braking applications, the friction coefficient, sliding speed, braking load and friction material. The time-dependent nature of the Tribo-Iayer formation and the real contact area distribution are shown to be causes of variation in interface temperatures in friction braking. The work extends the scientific understanding of interface contact and temperature during friction braking.
    • Investigation of Disc/Pad Interface Temperatures in Friction Braking

      Qi, Hong Sheng; Day, Andrew J. (2007-02)
      Maintaining appropriate levels of disc-pad interface temperature is critical for the overall operating effectiveness of disc brakes and implicitly the safety of the vehicle. Measurement and prediction of the distribution and magnitude of brake friction interface temperatures are difficult. A thermocouple method with an exposed hot junction configuration is used for interface temperature measurement in this study. Factors influencing the magnitude and distribution of interface temperature are discussed. It is found that there is a strong correlation between the contact area ratio and the interface maximum temperature. Using a designed experiment approach, the factors affecting the interface temperature, including the number of braking applications, sliding speed, braking load and type of friction material were studied. It was found that the number of braking applications affects the interface temperature the most. The real contact area between the disc and pad, i.e. pad regions where the bulk of the kinetic energy is dissipated via friction, has significant effect on the braking interface temperature. For understanding the effect of real contact area on local interface temperatures and friction coefficient, Finite Element Analysis (FEA) is conducted. It is found that the maximum temperature at the friction interface does not increase linearly with decreasing contact area ratio. This finding is potentially significant in optimising the design and formulation of friction materials for stable friction and wear performance.