DIRECT RANDOM TESTING UTILIZING IMPROVEMENTS IN VIBRATION TEST CONTROL TO REPLACE BASE SHAKE FOR ELECTRONIC ASSEMBLIES

摘要

Random testing has long been a cheap alternative to acoustic testing. Base excitation methods are traditional and requirements are usually specified in terms of inputs at the interface rather than overall response matching. Assemblies dominated by direct acoustic inputs rather than base random inputs will show significant differences in responses from the base shake methods to responses from acoustic test. Typically these are larger assemblies. These larger assemblies are also made up of various components that have under gone testing at each supplier level where fatigue becomes an issue. Clean room and electrical safety requirements are hard to insure getting to a vibration test facility and may be just as bad near the shaker slip plates. Test fixtures required for larger assemblies are problematic for base random tests. This paper proposes an alternate random test method that effectively mitigates these problems. The Direct Random Test method uses common modal test hardware to excite the acoustically driven modes of an assembly, combined with the use of a vibration control system to shape the energy to various response profiles for various components. The use of this Direct Random Test method produces a very good overall response match to acoustic test, while being performed in a clean room on no special test fixture, where all procedures for minimizing contamination and electrical safety can be maintained.