Exhaust System Flange Joint Accelerated Durability - A Novel Way Converting Challenges to Opportunity 2021-26-0472

The main objective of the exhaust system is to offer a leakage proof, noise proof, safe route for exhaust gases from engine to tailpipe, where they are released into the environment, while also processing them to meet the emission norms. New stringent emission norms demand ‘near-zero’ leakage exhaust systems, throughout vehicle life bringing the joints into focus as they are highly susceptible to leakage. Needless to say, this necessitates them to endure not only structural but also the environmental loads, throughout their life. Thus, the fatigue life or durability tests become the most critical part of the exhaust system development. Test acceleration and result correlation (for life prediction), to meet the stringent project timelines and stricter environmental norms are the key considerations for developing a new testing methodology. Quality of accelerated tests is ensured by deploying all possible multiple loads, to simulate real-life conditions.

Till recently (pre-BSVI), the bench level accelerated testing methodologies for structural validation of exhaust systems, employed standard vibration recipes derived from road load data applied to the system as a whole. This was mainly because the joints were permitted to leak upto certain limit. Hence, the fatigue [4] life of welded or mechanical joints did not demand complete leak tightness. This posed a challenge to develop a new validation method, which could give highly durable exhaust system joints, in a shorter test time while accommodating multiple design / testing iterations.

The methodology described in this paper embraces these aspects to address the most critical part of BS VI exhaust system, which was quicker flange joint testing, with due consideration to overall impact.