MULTI-ENVIRONMENT ACCELERATED DURABILITY TEST FOR EXHAUST SYSTEM FLANGE JOINTS

Accelerated testing is vital to meet stringent project timelines and is a key consideration for developing new testing methodology. Specifically, durability testing is one of the key fields of interest to deal with all aspects. Fatigue with exposure to multiple environments is a major cause of exhaust system flange joint failure. Physical verification of increased design life expectancy, demands longer testing time, while shorter time to market is main differentiator for competitiveness. Government policy induced timeline pressures added to the need of accelerated tests. The methodology described in this paper embraces these aspects to ensure a quicker flange joint testing, with due consideration to environmental impact. Until the BSVI norms, marginal leakage through the system joints was usual and acceptable. Stringent emission norms demand ‘near-zero’ leakage from exhaust systems. The system joints essentially being the most probable leakage zones, became the focus area, necessitating them to endure not only structural but also the environmental loads, throughout the life. This posed a challenge to develop a validation method, which can give highly reliable components, in a shorter test time to accommodate multiple design / testing iterations. The earlier test method employs standard vibration recipes derived from road load data but doesn’t consider environmental deterioration of exhaust system. Now, sustenance to the fatigue loads in response to road inputs, together with the environmental loads, became the important criteria for assessing the flange joints to ensure better performance. Clinical analysis of reference vehicle data, mapping of the environmental condition variations, methodical test acceleration factor calculation being the main inputs, a universal test procedure was developed. The paper sites this accelerated testing methodology and its correlation upon deployment. The method ensures a holistic validation and was already used to validate a variety of flange joints on test bench.