CAE Virtual Durability Tests of Automotive Products in the Frequency Domain 2008-01-0240
Both NVH and durability performance of automotive products are mainly related to their structural frequency characteristics, such as their resonant frequencies, normal modes, stiffness and damping, and transfer function properties. During the automotive product development, product design validation test loads for NVH and durability are, therefore, often specified in the frequency domain, in terms of either swept sinusoidal vibration or random vibration in power spectral density function. This paper presents a procedure of CAE virtual design validation tests for durability evaluation due to the frequency domain vibration test loads. A set of frequency domain simulation techniques and durability evaluation methodologies, for material fatigue damage due to either random or sinusoidal vibration loads, are introduced as well. Finite element models of automotive products are developed along with their nonlinear frequency dynamic stiffness and damping elements and properties, such as those related to the mounts and rubber bushings. The dynamic stress simulation is realized by utilizing the frequency response analysis technique. Statistical properties are employed to account for the scatter nature of material fatigue S-N raw data, and a damage model for durability performance is then established by using the reliability and tolerance interval techniques. The durability life evaluation is based on the simulated dynamic stresses and the newly defined material fatigue damage model. Two examples of virtual durability evaluation tests of automotive products are also provided to illustrate applications of the proposed procedure and techniques, with respect to the random and swept sine vibration loads, respectively.