Thermal Degradation of Extension Springs

Abstract

Extension springs are used to apply a constant force at a set displacement in a wide variety of components. When subjected to an abnormal thermal event, such as in a fire, the load carrying capacity of these springs can degrade. In this study, relaxation tests were conducted on extension springs where the heating rate and dwell temperature were varied to investigate the reduction in force provided by the springs. Two commonly used spring material types were tested, 304 stainless steel and Elgiloy, a cobalt-chrome-nickel alloy. Challenges associated with obtaining accurate spring response to an abnormal thermal event are discussed. The resulting data can be used to help develop and test models for thermally activated creep in springs and to provide designers with recommendations to help ensure the reliability of the springs for the duration of the thermal event.