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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.

In this paper, an analytical procedure for prediction of shell radiated noise of air induction systems (AIS) due to engine acoustic excitation, without a prototype and physical measurement, is presented. A set of modeling and simulation techniques are introduced to address the challenges to the analytical radiated noise prediction of AIS products. A filter seal model is developed to simulate the unique nonlinear stiffness and damping properties of air cleaner boxes. A finite element model (FEM) of the AIS assembly is established by incorporating the AIS structure, the proposed filter seal model and its acoustic cavity model. The coupled acoustic-structural FEM of the AIS assembly is then employed to compute the velocity frequency response of the AIS structure with respect to the air-borne acoustic excitations.

This paper presents a CAE virtual test procedure for automotive engine mount systems, which evaluates NVH and durability performance of an engine suspension design. Engine mount systems are virtually tested in terms of noise and vibration response characteristics, mount structural strength and fatigue durability, under the defined engine load conditions. The proposed procedure incorporates several CAE modeling and simulation technologies, including the definition of engine test loading environment, the modeling of nonlinear rubber bushings for their stiffness and damping properties, the frequency domain dynamic simulation, and fatigue damage prediction technologies. First, the test engine load specifications are defined from the measured engine vibration raw data with respect to engine speeds, and the engine speed duty cycle statistics.

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.

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.

A test load specification is required to validate an automotive product to meet the durability and design life requirements. Traditionally in the automotive industry, load specifications for design validation tests are directly given by OEMs, which are generally developed from an envelop of generic customer usage profiles and are, in most cases, over-specified. In recent years, however, there are many occasions that a proposed load specification for a particular product is requested. The particular test load specification for a particular product is generated based on the measured load data at its mounting location on the given type of vehicles, which contains more realistic time domain load levels and associated frequency contents. The measured time domain load is then processed to frequency domain test load data by using the fast Fourier transform and damage equivalent techniques.