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Journal Article

Fatigue Behavior of Stainless Steel Sheet Specimens at Extremely High Temperatures

Active regeneration systems for cleaning diesel exhaust can operate at extremely high temperatures up to 1000°C. The extremely high temperatures create a unique challenge for the design of regeneration structural components near their melting temperatures. In this paper, the preparation of the sheet specimens and the test set-up based on induction heating for sheet specimens are first presented. Tensile test data at room temperature, 500, 700, 900 and 1100°C are then presented. The yield strength and tensile strength were observed to decrease with decreasing strain rate in tests conducted at 900 and 1100°C but no strain rate dependence was observed in the elastic properties for tests conducted below 900°C. The stress-life relations for under cyclic loading at 700 and 1100°C with and without hold time are then investigated. The fatigue test data show that the hold time at the maximum stress strongly affects the stress-life relation at high temperatures.
Technical Paper

Effect of Test Data Accuracy on Component Durability Life Prediction in the Weibull Application

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.
Technical Paper

Application of Verity Method to Predict Bushing Fatigue Life and Load Limit

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.
Technical Paper

Flow Uniformity Optimization for Diesel Aftertreatment Systems

In 2007 emissions regulations for on-road light to heavy duty Diesel trucks will require the use of Diesel Particulate Filters (DPFs). The uniform distribution of soot on the DPF is critical for adequate long term performance of these DPFs. This is especially true when cordierite is used instead of silicon carbide for the DPF substrate, due to the reduced thermal conductivity and reduced peak temperature capability of cordierite. In addition to flow uniformity, an inverted flow pattern where more of the flow is forced radially outward on the substrate face could be beneficial to counteract thermal losses in the converter. This paper describes a dispersion device that can improve flow geometry with a low backpressure penalty. Computational fluid dynamics (CFD) results and experimental data are presented for this device. Additionally, cone design options are explored, and CFD analysis results of the cone design are presented.
Technical Paper

The Impact of Worn Shocks on Vehicle Handling and Stability

The intent of this research is to understand the effects worn dampers have on vehicle stability and safety through dynamic model simulation. Dampers, an integral component of a vehicle's suspension system, play an important role in isolating road disturbances from the driver by controlling the motions of the sprung and unsprung masses. This paper will show that a decrease in damping leads to excessive body motions and a potentially unstable vehicle. The concept of poor damping affecting vehicle stability is well established through linear models. The next step is to extend this concept for non-linear models. This is accomplished through creating a vehicle simulation model and executing several driving maneuvers with various damper characteristics. The damper models used in this study are based on splines representing peak force versus velocity relationships.
Technical Paper

Project Management for Advanced Engineering Activities at Tenneco Automotive

Being a tier-one supplier to the automotive industry, TA has developed a methodology and tools since the beginning of the 90's to address its Advanced Engineering activities. These tools consist of tracking the technical needs of the carmakers and then setting up expertise to meet the future demands in terms of new products, engineering tools and systems. The developed tools are unique.
Technical Paper

Exhaust Catalytic Converter Bench Fatigue Test Specification Based on Equivalent Damage

Component bench fatigue testing is a cost-effective way to evaluate the durability of exhaust catalytic converters. A successful bench fatigue test depends on the development of a test specification. The test specification should represent the actual customer duty cycle that the component is exposed to. Based on the concept of equivalent fatigue damage, a systematic approach is presented to obtain the test specification from the acquired road load data. A method based on damage analysis is proposed to determine the effective notch factor, and an empirical relationship is presented to account for the thermal effect on the test specification. The principles and procedures of multiple block testing and constant amplitude testing are also presented.
Technical Paper

Shoebox Converter Design for Thinwall Ceramic Substrates

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.