Methodology of Developing a Combined Environmental Stress Schedule for Reliability Growth Testing

摘要

Many U.S. Army systems require reliability growth testing to meet technical requirements for hardware durability during engineering development. Such tests are often performed in chambers that simulate multiple stressful environments. The usual environmental stresses include temperature, vibration, humidity, and power or voltage cycling. If it is apparent that other environments can cause or induce reliability-related failures, then they are also required. Because a combination of stresses will in most cases be experienced in actual use, these combined stresses are used in the environmental chambers. Hardware-related reliability weaknesses precipitated out during environmental testing will initiate the Failure Reporting and Corrective Action System (FRACAS) necessary to improve item design. This technical report demonstrates the development of a test schedule that uses the user's mission profile when combining operational and storage environmental stresses. Blind application of test parameters or schedules from MIL-STD-810D, Environmental Test Methods and Engineering Guidelines, from International Test Operational Procedures (ITOPs) especially for vibration stresses, is not acceptable, because they are designed to cause short-term failures unrelated to either a mission profile or to determine a mean time between failure (MTBF) over thousands of hours of testing. (aw)