Low-cycle thermal mechanical fatigue testing

A thermal mechanical fatigue test method having the capability of controlling any mechanical strain-temperature-time cycle is described, with emphasis on those items or procedures which differ from isothermal LCF testing. A tubular specimen design is presented which can be used for either crack initiation or crack propagation testing. The axial total strains are measured with a unique extensometry system and separated into two components - thermal strains and mechanical strains - through the use of a thermal expansion compensator. The necessity for precise temperature control is demonstrated in terms of overall testing accuracy, along with how digital computer control can improve this type of testing. Load-strain hysteresis loops and strain-temperature plots can be recorded during the test.