Metall.Trans. 21A, 935-948, 1990


FATIGUE AND FRACTURE OF HIGH-ALLOYED STEEL
SPECIMENS SUBJECTED TO PURELY THERMAL CYCLING

F.D. Fischer¹, F.G. Rammerstorfer² and F.J. Bauer³

¹Institute of Mechanics,
University of Mining and Metallurgy, Leoben, Austria
²Institute of Lightweight Structures and Aerospace Engineering,
TU Wien, Vienna, Austria
³Böhler AG, Kapfenberg, Austria


Abstract - High-alloyed steel specimens subjected to hundreds of thermal cycles (heating up in a furnace to about 900&°C, quenching in water, resting in air) are considered. Contrary to standeard "low-cycle fatigue" tests with a cyclically varying applied mechanical load, the driving "force" is a cyclic temperature field with self-equilibrating residual stress states. Despite the cyclic character of this temperature field and no applied load, a significant monotonic change of the shape and metallurgical structure of the specimens can be observed depending strongly on the material and the initial geometry. Preciptiations along the grain boundaries and remarkable residual stress states are responsible for internal cracks and damage. An experimental program is reported and metallurgical and mechanical interpretations are presented.


(hjb,960710)