Life testing is often misapplied during the acquisition process with verification usually too late to impact the design. The ability of the product to withstand long-term exposure to the operating environment is essential. One solution to the problem of life and life testing is an early recognition of the requirement with required test activities described in an integrated test plan. The integration will allow the design and test process to be closely aligned such that feedback of test results and projection of long-term performance can be efficiently made.
The structuring of a life test program follows the same basic fundamentals used to structure other environmental test programs. The test environments must be based on expected mission environmental profiles, rather than blindly applied MIL-STD or MIL-SPEC environments. Life tests should be scheduled for completion during the full-scale development phase, in order to establish life characteristics and allow the implementation of design changes prior to final design release. In the past, life tests have often been planned too late to influence the design, resulting in poor life characteristics or expensive and time-consuming retrofit programs.
Life tests can be time consuming and costly. To achieve maximum benefit (impact on design of the life testing effort), detailed analyses must be made of life characteristics concurrent with the initial design. Aging failure data must be collected and analyzed on components and like equipment from all possible sources. These analyses will help identify design risk and form the basis for planning life tests.
Ignoring life characteristics until test results are available could require extensive redesign and project delays. Therefore, in order to ensure that life characteristics are considered early in the design phase, field or corporate experience on similar items should be used to project life characteristics and to determine the initial equipment design. This technique should aid in minimizing design changes resulting from life testing and provide for shortened test schedules.
A commonly used technique, to provide the designer
with early life test results, is accelerated life testing. However, in an
attempt to shorten life tests, some projects have used unverified acceleration
factors, resulting in unrealistic projections of equipment life. This could
result in overdesign if the test was too stringent, or undersign if the test
was too benign. If accelerated testing is being considered, only proven, well
understood techniques should be used.