Accelerated life testing

Accelerated life testing is the process of testing a product by subjecting it to conditions (stress, strain, temperatures, voltage, vibration rate, pressure etc.) in excess of its normal service parameters in an effort to uncover faults and potential modes of failure in a short amount of time. By analyzing the product's response to such tests, engineers can make predictions about the service life and maintenance intervals of a product.

In polymers, testing may be done at elevated temperatures to produce a result in a shorter amount of time than it could be produced at ambient temperatures. Many mechanical properties of polymers have an Arrhenius type relationship with respect to time and temperature (for example, creep, stress relaxation, and tensile properties). If one conducts short tests at elevated temperatures, that data can be used to extrapolate the behavior of the polymer at room temperature, avoiding the need to do lengthy, and hence expensive tests.

ALT is primarily used to speed up tests. This is particularly useful in several cases:

For instance, a reliability test on circuits that must last years at use conditions (high longevity) would need to yield results in a much shorter time. If the test wanted to estimate how frequently the circuits needed to be replaced, then the category of low failure would also be applicable. Furthermore, if the circuits wore out from gradual use rather than extreme use (such as a large sudden shock), the wear out category would be involved. If a sudden shock was the primary cause of failure, a Highly Accelerated Life Test may be more appropriate.

Designing a test involves considering what factors effect the test object, what you already know about the test object's behavior, and what you want to learn from the test.

All factors thought to influence the test object should be involved and tests should be conducted at various levels of each factor. Higher stress levels will speed up the test more however the cause of failure or other response measured must not be changed. For instance, melting components in a circuit would alter why the circuit failed. Increasing the number of tests or the number of test objects in each test generally increases how precisely one can infer the test objects behavior at operating conditions.

A model is an equation that accurately relates a test object's performance to the levels of stress on it. This can be referred to as an acceleration model, with any constants called acceleration factors. The acceleration model is usually related to the types of materials or components tested. A few equations used for acceleration models are the Arrhenius and Eyring equations and the Coffin-Manson model.

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