A machine was developed to study the low-cycle fatigue characteristics of refractory metals in vacuum at high temperatures. Operating capability included temperatures up to 1400 C, loads to 4.45 × 10⁴ N (10 ksi), and frequencies from static to 10 Hz. The machine operated in a push-pull mode and was stroke controlled.

To minimize material required for testing, grips were designed to operate at nearly the same temperature as the specimen. A typical specimen geometry was a rod, 76 mm long with a test section 12.7 mm long and 5.18 mm in diameter.

A series of tests was performed on a columbium alloy, D-43, at temperatures ranging from 20 to 1204 C and cyclic plastic strains from 0.3 to 4 percent. Data at 20, 871, and 1093 C revealed that D-43 conformed to the Coffin-Manson equation, wherein cycles to failure was related to plastic strain range by a power function.

The plastic strain resistance was found to increase with increasing temperature and to exhibit a maximum around 871 C. Up to 1024 C cyclic strain resistance remained better than or equivalent to that at room temperature.

Posttest examination of specimen revealed ductile, transgranular failures at all temperatures.