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Fatigue life assessment is an integral part of the durability and reliability evaluation process of vehicle exhaust components and systems. The probabilistic life assessment approaches, including analytical, experimental, and simulation, CAE implementation in particular, are attracting significant attentions in recent years. In this paper, the state-of-the-art probabilistic life assessment methods for vehicle exhausts under combined thermal and mechanical loadings are reviewed and investigated. The loading cases as experienced by the vehicle exhausts are first categorized into isothermal fatigue, anisothermal fatigue, and high-temperature thermomechanical fatigue (TMF) based on the failure mechanisms. Subsequently, the probabilistic life assessment procedures for each category are delineated, with emphasis on product validation.

Thermo-mechanical fatigue (TMF) resistance characterization and life assessment are extremely important in the durability/reliability design and validation of vehicle exhaust components/systems, which are subjected to combined thermal and mechanical loadings during operation. The current thermal-fatigue related design and validation for exhaust products are essentially based on testing and the interpretation of test results. However, thermal-fatigue testing are costly and time consuming, therefore, computer aided engineering (CAE) based virtual thermal-fatigue life assessment tools with predictive powers are strongly desired. Many thermal-fatigue methods have been developed and eventually implemented into the CAE tools; however, most of them are based on deterministic life assessment approach, which cannot provide satisfactory explanation for the observed uncertainties introduced in thermal-fatigue failure data.