Accelerated Reliability Testing for Environmental Control Systems

Reliability and lifetime performance data for environemntal control systems (ECS) is limited. Real-time tests require 5-15 years, and results often apply only to obsolete technology. Accelerated life testing (ALT) is a means by which reliability data may be obtained quickly and at a reasonable cost. A primary difficulty with ALT of ECS units is that typical service conditions impose multiple stresses on the hardware. Each stress must be accurately modeled in order to correlate normal aging with accelerated again at balanced so that the aging rates are equal for all induced stresses. ECS operating profiles will be characterized for different geographic areas, and these data will be used to design a complete, multiple stress, multiple accleration factor ALT. Included in the ALT design will be test apparatus diagrams, methods for accelerating normal aging rates using elevated stress levels, monitoring methods for the collection of relevant data, and statistical analysis technicques for producing reliability estimates from the ALT data. Initial aging investigations will be made using ON/OFF duty cycle acceleration for small air-conditioning units.