Abstract: Air brakes are power brake systems in which compressed air is used as the energy medium. It is generally used in heavy commercial vehicles. A brake chamber is an actuating device used in air brake systems, typically located at the vehicle’s front wheels. Compressed air is converted into mechanical force to apply the brakes and stop the vehicle. A brake chamber contains a flexible rubber diaphragm, a pushrod, and a return spring. When the brake pedal is pressed, compressed air fills the brake chamber, causing the diaphragm to move and push out the pushrod. The pushrod is connected to a slack adjuster lever, linking the brake chamber to the assembly. The slack adjuster transfers the load from the pushrod to the brake assembly, causing the brake shoes or pads to contact the brake drum and apply the brakes. When air pressure is released, the pushrod is returned to its original position by the spring inside the chamber, causing the brake to release. This operation continues at every braking event over the lifetime, so the product needs a high cycle fatigue performance. It is a critical safety device. Hence, it is essential to thoroughly validate its performances by lab test rigs and field tests. Still, it’s a time-consuming process that takes about 4 to 6 months for proto development and validation activities for a design. To overcome this, FE simulations are used in the design phase to develop a product on a first-time-right basis to reduce overall lead time and cost.
This paper validates a brake chamber under a pressure load of 10 bar. A simplified structural model is initially developed to perform static nonlinear analysis in Abaqus software. The FEA results are compared with physical strain gauge measurements on a proto-model; reasonable correlation is achieved in a few locations, but a considerable gap is observed in correlation levels at other locations. Clamping load due assembly process is considered to improve accuracy with a diaphragm made of fabric reinforced rubber, modeled using hyperelastic material models available in Abaqus. The correlation then improves to 85%. Further, considering thinning/thickening effect of sheet metal parts during forming operation, FE results correlated well with more than 95%. Accuracy is improved now, but with all these complexities added in the 3D model setup, the overall calculation time is increased drastically due to more node counts. To meet the fatigue performance of the structure, further design iterations and optimizations are needed. But with the detailed simulation model, performing multiple iterations is challenging to meet the project timelines. To overcome this difficulty, the model is simulated using the axisymmetric analysis capability in Abaqus by taking advantage of the axis-symmetric design of most of the parts. Now the model is simplified without compromising accuracy by retaining all the complexities and details included earlier in the study. With this new approach, multiple design iterations could be completed with a quick turnaround time, and the design is well optimized. At the end of the study, a simplified and more accurate simulation methodology is developed to validate and optimize the design for all future variants in this product range with the least computation time and good accuracy.
Biography: Dinesh Kumar J received his ME in Computer-Aided Design from College of Engineering, Guindy, Chennai, in 2018, and his BE in Mechanical Engineering from Karpaga Vinayaga College of Engg. & Tech. in 2012. He currently works as an assistant manager at Engineering, Research, and Development in Brakes India Pvt. Ltd, Chennai for developing CAE simulation methodology of new products in braking systems. With 9+ years of industrial experience, his expertise is in CAE validation for the automotive and heavy machinery domain.
