Introduction to Acceleration Models
Abstract
Adam and Fred discuss the fundamentals of Accelerated Life Testing (ALT)
Key Points
Join Adam and Fred as they discuss the fundamentals of ALT and how we use them in everyday life unknowingly.
- The more the stakeholders of ALT results understand the underlying principles the more effective ALT will be in influencing product development.
- The Arrhenius, Coffin Manson, and Inverse Power Law models are commonly used models in reliability wear-out studies.
- Most everyone has used the Arrhenius model when cooking or storing food at home.
- In any ALT it is critical to identify the primary wear-out failure mode first.
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SOR 035 Introduction to Acceleration ModelsAdam Bahret
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Accelerated Life Testing can be divided into two areas: Qualitative Accelerated Life Testing and Quantitative Accelerated Life Testing. In qualitative accelerated testing, the engineer is mostly interested in identifying failures and failure modes without attempting to make any predictions as to the product’s life under normal use conditions. In quantitative accelerated life testing, the engineer is interested in predicting the life of the product (or, more specifically, life characteristics such as MTTF, B(10) life, etc.) at normal use conditions, from data obtained in an accelerated life test.
Qualitative Accelerated Life Testing: Qualitative tests are tests that yield failure information (or failure modes) only. They have been referred to by many names including: * elephant tests * torture tests * HALT tests * shake and bake tests. Qualitative tests are performed on small samples with the specimens subjected to a single severe level of stress, to a number of stresses, or to a time-varying stress (i.e., stress cycling, cold to hot, etc.). If the specimen survives, it passes the test. Otherwise, appropriate actions will be taken to improve the product’s design in order to eliminate the cause(s) of failure. Qualitative tests are used primarily to reveal probable failure modes. It provides valuable information as to the types and level of stresses one may wish to employ during a subsequent quantitative test.
Quantitative Accelerated Life Testing: Quantitative accelerated life testing unlike the qualitative testing methods, consists of tests designed to quantify the life characteristics of the product, component or system under normal use conditions, and thereby provide reliability information. Reliability information can include the determination of the probability of failure of the product under use conditions, mean life under use conditions, and projected returns and warranty costs. It can also be used to assist in the performance of risk assessments, design comparisons, etc. Quantitative accelerated life testing can take the form of usage rate acceleration or overstress acceleration.