Vibration Test Specification Design and Reliability Analysis

The purpose of this paper is to apply the concept of the frequency spectrum as derived from a Single Degree of Freedom (SDOF) system, establish the accelerated vibration specification, and investigate the specification under customer usage with reliability analysis. The main technique is to convert a time domain signal, which is derived from a Proving Ground or customer usage, to the frequency domain. An automotive headlamp was used in our research. The input signal from the Proving Ground was converted into an eight-hour bench test that is equivalent to a five-year/100,000 km field usage through the theory of Fatigue Damage Equivalence. The fatigue parameters of the materials were then estimated from various vibration conditions with the MIL-STD-810F standard. The benefit of this approach is that we could quickly obtain the material parameters of a complex structure made of composite plastics. Our research correlates customer usage with the Proving Ground and compresses the 100,000 km time domain history into an eight-hour laboratory bench test specification to accelerate the effect. In the end, life tests of eight headlamp pieces were conducted, and the Weibull distribution was used to perform reliability analysis. The results showed that the reliability is about 99.25% after the eight-hour bench test (or equivalently, after 100,000 km of field usage). At a 90% confidence level, the reliability becomes about 90%.