Linking Fatigue and Reliability Analysis with Time-Varying Stress Using the Cumulative Damage Model
October 3rd, 2017
Reliability HotWire is a monthly eMagazine by ReliaSoft providing information and tips on how to best improve your reliability practices and get the most out of ReliaSoft’s tools for reliability and life data analysis.
This Month’s Hot Topic
Fatigue and Reliability Analysis with Time-Varying Stress Using the Cumulative Damage Model
Fatigue is defined as weakness in metal or other materials caused by repeated variations of mechanical stress. Fatigue cracks are caused by cycling loading. Hence, if the loading does not change (stress stays constant), then there is no fatigue problem. On the other hand, varying stresses may lead to fatigue failure even though the magnitude of the stress is not high. In metallurgic terms, the microscopic damage caused by fatigue cyclic means there is no recovery from the fatigue failure mode.
Fatigue is a statistical problem, not a deterministic one, which means that we will not be able to calculate exactly how many cycles it takes for a product to fail. But we can estimate the reliability of that particular product at a given number of cycles via life-stress relationship models used in accelerated life testing (ALT) analysis. In this article, we will talk about two methods for analyzing fatigue failure data collected under time-varying stress, and then analyze an example data set in an ALTA folio to show how we can quickly analyze fatigue data. Read more
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