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A combined Computer Aided Engineering (CAE) simulation and physical fatigue testing of a passenger car exhaust system resonator with wire mesh seal between the inlet and outlet pipe is performed to evaluate the durability and improvise the design. The outlet pipe end cap of the exhaust system resonator deformed and cracked at the fillet region repeatedly upon the application of the maximum load from a pre developed accelerated specification test. However, the system meets the end usage on-road durability target of 5 years / 1,00,000 km. There is a gap between the accelerated bench test and the end usage durability target. The current study correlates CAE simulation and biaxial fatigue testing and improvise possible alternate resonator design. Conventionally, components passing the accelerated test always meets the end usage durability target whereas components meeting the end usage durability target need not necessarily pass the accelerated test.

The objective of the present paper, is to present the methodology and results of an ongoing work related to automated sizing of beam cross sections of major load carrying members and selection of optimum joint stiffness properties of an automobile to meet static bending and torsion, first bending and torsion frequency targets with minimum weight. In an automobile body design, initial selection of cross sectional properties of major load carrying members and selection of optimum joint stiffness properties will essentially define its characteristic behavior. Past experience shows that any further design modifications of the panels in terms of additional stiffeners, upgaging etc., will not appreciably improve the characteristic behavior in terms of tactile and acoustic response. The cost effectiveness in terms of performance and design changes, results mainly from the changes to the major load carrying members and optimum joint stiffness characteristics.

The paper presents the mathematical formulation and procedure of an ongoing developmental work on the optimum design of engine and body mounts at a total system level. The objective of this study is to develop engine and body mount characteristics to minimize the engine induced and the road load induced vibrations over a wide frequency range. The computer software LOHITSA/SYS_OPT, a total system level non-linear unconstrained optimizer with built-in component mode synthesis solution technique, is used to develop the optimum engine and body mount characteristics. A typical total system level model consists of the body and/or frame, powerplant, suspension, body mount, engine mount etc. Complex structural systems such as body, frame and powertrain are represented as typical modal models (assumed), along with typical physical models of engine mount, body mount and suspension.

The paper presents the results of the development work on engine mounts. The objective of the present study is to develop idealistic hydromount stiffness and damping characteristics, to minimize the engine induced vibrations over a wide frequency range. A total system level non-linear unconstrained optimizer is used to develop the optimum frequency dependent stiffness and damping characteristics, locations and orientations. Typical engine inertial values and packaging constraints representing a traditional three mount rear wheel drive power plant system, is used in the present study. The front two mounts are hydromounts and the rear mount is an elastomeric mount The study is performed using unit harmonic excitations with a broad frequency range, since the typical engine inertial values are modeled and not an actual engine.