Title: CAE Virtual Test of Air Intake Manifolds Using Coupled Vibration and Pressure Pulsation Loads
text: A coupled vibration and pressure loading procedure has been developed to perform a CAE virtual test for engine air intake manifolds. The CAE virtual test simulates the same physical test configuration and environments, such as the base acceleration vibration excitation and pressure pulsation loads, as well as temperature conditions, for design validation (DV) test of air intake manifolds. The original vibration and pressure load data, measured with respect to the engine speed rpm, are first converted to their respective vibration and pressure power spectrum density (PSD) profiles in frequency domain, based on the duty cycle specification. The final accelerated vibration excitation and pressure PSD load profiles for design validation are derived based on the key life test (KLT) duration and reliability requirements, using the equivalent fatigue damage technique. The coupled vibration and pressure simulation is then implemented by applying both the base acceleration and pressure pulsation loads to the manifold CAE model, in terms of PSD functions, using the frequency response analysis technique. The computer simulation generates dynamic response of the air intake manifold structure, in terms of stress PSD results at identified hotspot locations. The durability life of the air intake manifold design is then evaluated based on the simulated stress and material fatigue damage model. The fatigue damage model is established from fatigue data of the manifold material obtained at different test temperatures. The presented procedure has helped the engineering team to identify potential durability design problems without a prototype, and to guide the design changes and modifications. It has shown that CAE virtual tests provide a way to speed up air intake manifold product development, and to minimize prototypes and costs.