Commercial Vehicle’s Exhaust Front Pipe Reliability Improvement through Virtual Simulation and Experimental Validation

The exhaust front pipe is a critical structural component in commercial vehicles, ensuring the leak-proof flow of exhaust gases into the exhaust after-treatment system while withstanding engine and frame vibrations. To isolate these vibrations, the front pipe is equipped with a flex connector capable of enduring various displacements at frequencies between 8-25 Hz. The position of the flex connector relative to the engine crank axis significantly impacts its structural reliability over its service life. This paper compares the existing design, which features a horizontally positioned flex connector, with a modified design that positions the flex connector vertically and changes the material from SS-304 to SS-321. Finite element analysis was conducted using Nastran software. The fatigue life of the existing flex connector design is approximately 1015 cycles. In contrast, the improved design demonstrates a fatigue life of 1727 cycles, representing a 70% increase in durability compared to the existing design. The newly designed front pipe was then evaluated under the worst-case excitation conditions of 25 mm lateral displacement at 8 Hz frequency using experimental setup. A correlation was established between virtual simulations and experimental validations. Virtual and experimental results conclude that there is a 70% increase in front pipe life when the flex connector is placed vertically with respect to the engine crank axis and SS-321 is used for the flex connector material. This finding is recommended for consideration during vehicle design development.