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Driven by diesel engine emission regulation, more emission aftertretment products have been under development by Tenneco to address the Particular Matter (PM) and NOx reduction needs. The T.R.U.E. (Thermal Regeneration Unit for Exhaust) Clean active thermal management system is one of the examples to reduce PM. The system is designed to increase exhaust temperatures for DPF (Diesel Particulate Filter) regeneration. This product is exposed to high temperature and high oxidation. Therefore, thermal fatigue, creep, oxidation and the interaction become critical mechanism to be considered for its durability. One of the key challenges to validate this product is to find a way of accelerated testing for thermal, creep, and oxidation as well as for vibration. In this paper, accelerated durability test strategy for high temperature device like T.R.U.E Clean is addressed.

Durability life is one of the major concerns in the automotive industry. Road Load Data Acquisition (RLDA) is one of the most important steps to verify exhaust system durability performance. RLDA will not only provide data for system level rig testing drive file development but also for exhaust components validation (computing safety factors). Modal transient FEA can be utilized to simulate either vehicle durability testing or sub-system level rig testing. How to simulate correctly is critical in the simulation. One of the most challenging portions in the full exhaust system simulation is isolator modeling due to its non-linear characteristics. However, we have to use linear modeling to simulate isolator in modal transient analysis, which induces errors.

A statistic fatigue life assessment procedure is presented in this paper for estimating fatigue damage under stationary Gaussian multi-axial loadings with narrow-band frequency. The fatigue damage is determined by using the Miner-Palmgren rule in connection with a recently developed path-length based multi-axial cycle counting and fatigue life assessment method. In this procedure, the path length is determined by averaging sinusoidal waves with uniformly distributed phase angles while the cycles are estimated from the observation of peak counting results of stress components. Numerically simulated random loading paths with different degrees of non-proportionality are used here to compare the proposed statistical method with its time domain counterpart. Possible further improvement in this research direction is also indicated.

The equilibrium mechanism, which can be considered as the basis of least squares method for linear curve fitting, is investigated in this paper. Both conventional methods, such as vertical offsets method, and total least squares methods, such as perpendicular offsets method, are examined. It is found that both methods have the equilibrium bases. However, the conventional methods may give inaccurate prediction if using vertical offsets method to fit data with variation in horizontal direction or using horizontal offsets method to fit data with variation in vertical direction while the perpendicular method can give best fit solution to data with variation in both vertical and horizontal directions. The application of these methods is also presented in fatigue S-N curve data analysis and two-parameter Weibull distribution in exhaust component fatigue life prediction.

Weibull analysis is widely used in many industries to predict the fatigue life of different components. Three typical Weibull distributions are introduced in this paper. The application of two parameter Weibull distribution in exhaust component fatigue life prediction is presented. Potential issues in component testing are addressed. Criteria are provided to define normal test data, and when replacement of a tested sample is required. The studies demonstrate that Weibull method is effective to predict component R90C90 life. However, data investigation and processing are critical to predict component life properly. The predicted fatigue life may differ by more than an order of magnitude if the sample life data is unrepresentative of the testing and manufacturing conditions.

Durability performance is one of the most important aspects of exhaust system design. Great effort has been expended to develop the ability to accurately and quickly predict the durability of the system in the early development stages. Welded joints in an exhaust system are the most prone to failure; however, the fatigue life of a welded joint is usually much more difficult to predict than that of a base material. The difficulty of predicting the fatigue life of a welded structure lies primarily in the variability associated with the elements of a weldment, including differing material and gap requirements, notch generation, residual stresses, and imprecise application, among others. The experts at the Battelle Center for Welded Structures Research have developed an approach to predict the fatigue life of a welded structure known as the Verity method.

A newly developed approach, Virtual Rig Simulation for exhaust, is introduced in this paper. An OEM exhaust system durability performance is simulated and simulation results are correlated to test results. The correlation results prove that the Virtual Rig Simulation predicates critical locations very well. The modal transient analysis is applied and input loading is from full event RLDA data. The advantage of the approach is that it can be applied in upfront design stage to predict exhaust system durability performance so that test cost and time are reduced significantly. Also, the presented approach is not only useful for exhaust system development but also useful for other product development.

Shoebox catalytic converter design to securely mount thinwall substrates with uniform mounting mat Gap Bulk Density (GBD) around the substrate is developed and validated. Computational Fluid Dynamic (CFD) analysis, using heat transfer predictions with and without chemical reaction, allows to carefully select the mounting mat material for the targeted shell skin temperature. CFD analysis enables to design the converter inlet and outlet cones to obtain uniform exhaust gas flow to achieve maximum converter performance and reduce mat erosion. Finite Element Analysis (FEA) is used to design and optimize manufacturing tool geometry and control process. FEA gives insight to simulate the canning process using displacement control to identify and optimize the closing speed and load to achieve uniform mat Gap Bulk Density between the shell and the substrate.