Uncertainty effect analysis on time to failure estimates through accelerated life tests

Abstract

Industrial firms face today the challenge to launch new products in shorter times keeping however their reliability in increasing higher levels. The most used method for gathering reliability information for new products is the accelerated life test (ALT), from which the manufacturer can derive information about the product's life and then its warranty period. ALT requires submitting the product to stress conditions and acquiring its time to failure, for which it is necessary to set up experiments where the stress loads are physically and nominally defined. However, experimental stress loads are always subjected to uncertainties that influence the tests results and so the product's reliability. This paper investigates the influences of experimental uncertainties in life estimates of electromagnetic relays, obtained through ALTs. Results show that, without the proper data analysis the uncertainty effects on life estimates may be significant also when the tests are performed in adequate shop floor conditions that consequently influence the product's lifetime estimates.