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

摘要

Random testing has long been a cheap alternative to acoustic testing. Base excitation methods aretraditional and requirements are usually specified in terms of inputs at the interface rather than overallresponse matching. Assemblies dominated by direct acoustic inputs rather than base random inputs willshow 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 componentsthat have under gone testing at each supplier level where fatigue becomes an issue. Clean room andelectrical safety requirements are hard to insure getting to a vibration test facility and may be just as badnear the shaker slip plates. Test fixtures required for larger assemblies are problematic for base randomtests. 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 drivenmodes of an assembly, combined with the use of a vibration control system to shape the energy tovarious response profiles for various components. The use of this Direct Random Test method producesa very good overall response match to acoustic test, while being performed in a clean room on no specialtest fixture, where all procedures for minimizing contamination and electrical safety can be maintained.