Achieving reliability goals for an EFV LRU through laboratory testing

Abstract

Aggressive field and laboratory testing of the Expeditionary Fighting Vehicle's (EFV) Hull Electronics Unit (HEU) resulted in a highly reliable product, and provides a qualitative comparison of different test technologies and philosophies. Test methods include qualification, reliability growth testing (RGT), statistical reliability testing (SRT), and hybrid SRT/RGT. Test technologies include traditional single-exciter single-axis (SESA) electrodynamic (ED) shakers, multi-exciter multi-axis (MEMA) ED shakers, and pneumatic repetitive shock (RS). Highly Accelerated Life Testing (HALT) is popularly defined as a RGT that uses pneumatic RS. All tests were performed using the procedures defined in MIL-STD-810G, with the exception of HALT, which is not compliant to the standard. Demand for rapid deployment required that units be fielded in parallel with laboratory test efforts. Laboratory test methods have replicated all field defects. Design changes as a result of defects detected, in combination with environmental stress screening (ESS) of the assembly have prevented any failures on the most recent iteration of the unit in the field. Combined laboratory data shows that the HEU meets its reliability objective with 80% confidence. Qualitative comparison of the different test methods show that qualification, RGT, and SRT with random vibration are all highly useful methods in determining design ruggedness. The applicability of either method is determined by the individual cost-schedule-quality needs of a program. Of the test technologies used, MEMA shaker technology produces greatest ability to apply test results to reliability information.