Vibration Test Specification for Automotive Products Based on Measured Vehicle Load Data 2006-01-0729
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. The benefits from a defined specification for a particular product, as compared with the generic ones, include avoidance of an unnecessary over-design and different failure modes from the field, and thus reduced product development cost for both OEMs and suppliers.
In this paper, an engineering procedure is presented, to determine a justified vibration test load specification for design validation tests of automotive products based on the measured vehicle load data. Basic theoretical backgrounds and a set of key technologies for vibration test specification, such as the load data process in the time and frequency domains, CAE simulation, durability evaluation, damage equivalence and reliability requirement are introduced. The measured loads are divided into two types according to their original sources, the proving ground load data for body mounted products, and the engine load data for engine mounted products. The final vibration test load specification for an automotive product can be presented in either sinusoidal sweep or random vibration profile formats, as per the customer preferred, and both will have an equivalent durability damage level for the given test duration and reliability parameters. Four project examples of test specifications, from two different load sources (proving ground and engine), in the format of either random or sinusoidal vibration, are illustrated.