Title: Localized Nonlinear Model of Plastic Air Induction Systems for Virtual Design Validation Tests
text: Plastic air induction system (AIS) has been widely used in vehicle powertrain applications for reduced weight, cost, and improved engine performance. Physical design validation (DV) tests of an AIS, as to meet durability and reliability requirements, are usually conducted by employing the frequency domain vibration tests, either sine sweep or random vibration excitations, with a temperature cycling range typically from -40°C to 120°C. It is well known that under high vibration loading and large temperature range, the plastic components of the AIS demonstrate much higher nonlinear response behaviors as compared with metal products. In order to implement a virtual test for plastic AIS products, a practical procedure to model a nonlinear system and to simulate the frequency response of the system, is crucial. The challenge is to model the plastic AIS assembly as a function of loads and temperatures, and to evaluate the dynamic response and fatigue life in frequency domain as well. This paper presents a modeling procedure for nonlinear plastic products, such as AIS assemblies, by using an array of locally linearized systems, for virtual design validation tests. The measurement results of physical DV tests are first presented to quantify the basic nonlinear response behaviors of the plastic AIS products. The proposed finite element modeling method is then evaluated based on correlation with the measured test results. The localized nonlinear model is thus employed to simulate the frequency response of the plastic AIS products and to identify weak spots of the design. Durability evaluation of the AIS product is then conducted in terms of estimated life, based on the simulated dynamic stresses and material fatigue properties. 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.