This paper establishes a reliable heavy-duty braking system model that can be used for response time prediction and for vehicle braking calculations regarding the legislative requirements. For the response time prediction, a pneumatic system model of a heavy-duty vehicle is constructed by Matlab Simulink in consideration of service brake layout. To ensure the accuracy of system parameters related with pneumatic system response time experiments are conducted on two different 4 × 4 heavy-duty vehicles. The numerically calculated response time results are validated with experimental data. To improve the response time of the vehicle, design modifications are conducted on the pneumatic brake system properties. To check the compliance of the pneumatic brake system design with legislative requirements of UN Regulation 13, heavy-duty vehicle brake system (HVBS) model is developed by using Matlab Simulink. HVBS model is composed of longitudinal vehicle and wheel dynamics, Magic Formula tyre model, wheel slip and the experimentally verified heavy-duty pneumatic system model. The braking performance analyses are conducted by using HVBS model to compare the design alternatives in accordance with the legal requirements in terms of service braking and secondary braking conditions.

Reducing vehicle weight without compromising performance becomes an area which is important to improve fuel economy and reduce vehicle emissions. The possibility of reducing unsprung mass in a vehicle has led to many investigations of weight optimization studies of axle and wheel-end components. Therefore, structural design of a torque plate, which is one of the main parts of a Z-cam drum brake used in heavy-duty vehicles, is carried out by using topology optimization and finite element analyses. Firstly, finite element analysis of the original torque plate is conducted to determine critical stress levels and locations. Secondly, topology optimization is carried out on the original torque plate for specified loading conditions. Taking redundant volume and manufacturability constraints into account a new torque plate design is composed. Finally, finite element analysis is repeated to verify the final design. A significant decrease in stress level is accompanied by considerable reduction in casting and machined part masses by 11.9% and 12.2% respectively.

In this study, transient thermal analyses for a new integrated rotor and wheel hub concept are performed by consideration of convection, conduction and radiation effects. Test methods used for the characterization and certification purposes are constructed in a simulation environment and the effect of different ventilation vanes and rotor-hub arrangements on heat transfer mechanism is examined and the details are summarized for a reliable simulation process. Validated procedures are used to report a series of characterization and certification analyses, namely; CFD analyses including wheel assembly, cooldown analyses, R13 repeated stop fade and alpine hot descent analyses for current design and new integrated rotor and hub pair for alternative ventilation vane designs. The analyses are especially focused on predicting the cooling period and predicting maximum bearing temperatures for normal and excessive loading scenarios. To provide benchmark a commercial integrated rotor and hub pair used in heavy duty vehicles is also analysed. The average convective heat transfer coefficient and cooldown period of proposed integrated brake rotor are improved by 117.3% and 30.5% compared to the base design. The maximum wheel bearing temperature is decreased by 27.0% and by 27.1% for the proposed integrated brake rotor and wheel hub compared to the benchmark model, in accordance with the repeated stop and alpine hot descent analyses. In addition, the total weight reduction of 10 kg (15%) according to the base design is achieved.

In this study, computational fluid dynamics (CFD) and transient thermal analyses of heavy-duty ventilated brake discs are performed for the determination of the cooling behavior of different ventilation vane geometries. Results showed that the ventilation vane geometry has crucial influence on the average convective heat transfer coefficient and the cooldown period of the heavy-duty brake discs. Figure A. Ventilation vane geometries used in the numerical investigation: (a) Straight vane (Design-A), (b) Proposed vane design (Design-B), (c) Vane design used in heavy commercial brake disc (Design-C)Purpose: In this study, a validated simulation procedure is aimed for the examination of the effect of different ventilation vane geometries on the cooling performance of ventilated brake discs.Theory and Methods: Firstly, the convective heat transfer coefficients are calculated for a standard (non-anticoning) ventilated brake disc by CFD analyses and they are verified by comparing with the experimental results. After ensuring the reliability of CFD analysis, the transient thermal analyses of an anticoning heavy-duty disc with straight ventilation vanes are carried out to achieve the cooldown period results. The thermal analysis parameters are verified by using the experimental cooldown period results. Furthermore, CFD and transient thermal analyses are conducted for the determination of the influence of ventilation vane geometry on the cooling performance of the brake discs. Results:The results have shown that the correlation between numerical and experimental average convective heat transfer coefficients and cooldown periods is achieved by over 95 %. Furthermore, the proposed ventilation vane geometry provides the improvement in the average convective heat transfer coefficient by 18.5 % and the cooldown period by 23.5 %. The CFD and transient thermal analysis results are presented and compared in Section 4. Conclusion:The simulation process used in the study showed that a considerable correlation has been achieved. Therefore, the proposed approach can be used as the main tool for the ventilation vane development projects of heavy-duty brake disc. On the other hand, those results cannot present the conditions on the vehicle due to wheel cavity and the vehicle bodywork. Therefore, further research should be conducted on vehicle level in consideration of cross-flow and vehicle package constraints. The proposed approach within scope of this study can guide for the further research to be carried out on the vehicle level.

Bu çalışmanın ana hedefi, 4x4 ağır hizmet araçları için, araç testleri ile doğrulanmış ve fren tepki süresi tahminlerinde kullanılacak detaylı bir havalı (pnömatik) fren sistemi dinamik modelinin elde edilmesidir. Bu neden ile bu çalışmada, havalı fren sistemi dinamik davranışını belirleyebilmek amacıyla genel bir matematiksel model önerilmektedir. Bu amaca uygun olarak, öncelikle havalı fren sisteminin pnömatik ve mekanik alt sistemlerine ait detaylar incelenmiştir. Daha sonrasında benzetimlerde kullanılmak üzere elde edilen matematiksel ifadeler Simulink modeline uyarlanmıştır. Simulink modelinin oluşturulması esnasında sistem parametrelerinin bir kısmı literatürde bulunan temel modellerden ve/veya fren sistemine ait bileşenlerin teknik veri sayfalarından elde edilmiştir. Burada daha karmaşık bir havalı fren sistemi modellemesi amaçlandığı için daha fazla sistem parametresine ihtiyaç duyulmaktadır. Bu bilinmeyen parametreleri belirleyebilmek amacıyla, fren tepki süresi testleri kampana frenli bir 4x4 ağır hizmet aracı üzerinde gerçekleştirilmiştir. Bu testlere ait deneysel sonuçlar kullanılarak sistem modelindeki bilinmeyen parametreler ayarlanmıştır. Daha sonra elde edilen model, prototip seviyesindeki başka bir 4x4 araca uyarlanmış ve burada fren tepki süresi hesaplamaları doğrulanmıştır. Main objective of this study is to obtain a detailed dynamic model of pneumatic brake system that will be verified with vehicle tests and be used for response time prediction of 4x4 heavy duty vehicles. Hence, in this study, a general mathematical model is proposed to determine the dynamic characteristics of pneumatic brake system. For this purpose, first of all the details of pneumatic and mechanical subsystems of the air brake system are investigated. After that; in order to be able to execute the simulations, mathematical equations derived are adapted to the Simulink model. When constructing the Simulink model, some system parameters are obtained from the basic models in the literature and/or are taken from the technical datasheets of the brake system components. Since a more complicated pneumatic brake system is aimed to be modeled, much more system parameters are required to be estimated. To identify those unknown parameters, response time tests were performed on a 4x4 heavy-duty vehicle equipped with wedge drum brakes. The experimental results of those tests are used to tune the system model for the unknown parameters. After that, the model obtained is adapted to a prototype level 4x4 heavy duty vehicle and the break response time calculations are verified.