Review of methods for developing accelerated testing criteria

Accelerated vibration testing seeks to compress long service exposures to vibration into a reduced length laboratory test by increasing the amplitude and/or frequency of the applied inputs during the laboratory test relative to the amplitude and/or frequency experienced during service. This testing procedure provides an important tool that can reduce testing time associated with a new design and reduce time to market. This paper will summarize current methods that are employed to develop accelerated testing criteria and will highlight the attributes and limitations of these methods. Typically there are two ways of accelerating vibration testing. The first method involves testing at fewer cycles but at higher amplitude levels; and the second method involves testing at higher frequencies (rates). A combination of the two is also an option. Development of an accelerated test based on either of these methods requires a priori knowledge of the controlling failure mechanisms. The review will begin with a discussion of Miner's Rule for developing accelerated testing criteria. This rule, which is based on a linear damage accumulation assumption, was first proposed in the 1940's for fatigue failures of ductile metals loaded repetitively in bending. Confounding factors associated with developing accelerated testing criteria for nonlinear vibration response (e.g., rattling of components) will be illustrated with an example.