Vibration Response Properties in Frame Hanging Catalyst Muffler 02-11-03-0016

Dynamic stresses exist in parts of a catalyst muffler caused by the vibration of a moving vehicle, and it is important to clarify and predict the vibration response properties for preventing fatigue failures. Assuming a vibration isolating installation in the vehicle frame, the vibration transmissibility and local dynamic stress of the catalyst muffler were examined through a vibration machine. Based on the measured data and by systematically taking vibration theories into consideration, a new prediction method of the vibration modes and parameters was proposed that takes account of vibration isolating and damping. A lumped vibration model with the six-element and one mass point was set up, and the vibration response parameters were analyzed accurately from equations of motion. In the vibration test, resonance peaks from the hanging bracket, rubber bush, and muffler parts were confirmed in three excitation drives, and local stress peaks were coordinate with them as well. The first resonance peak caused by the rubber bush had relatively low frequency, but the transmissibility was low by damping. The vibration magnitude from other parts was damped several times more by the rubber bush. The dynamic stress amplitudes from the vibration corresponded to the resonance of the catalyst muffler, and were proportional to the vibration accelerations. With an example where the spring coefficient and damping coefficient of a component in the sample were changed, the resonance frequency and transmissibility were obtained by calculation using the model while the dynamic stress was calculated using the stress scale factor, demonstrating the model’s general versatility and making it possible to predict the fatigue durability.