CALIFORNIA UNIV BERKELEY INST OF ENGINEERING RESEARCH
Very little is known about the separate or combined effects of intermittent heating and stressing on the elevated temperature creep and creep- rupture characteristics of aircraft structural metals. Such information is important since aircraft and engines will be subject to these conditions. Between flights, loads and temperatures are low during flights, they are high. Exact service conditions cannot be reproduced in the laboratory, but arbitrary cycles have been chosen for initial work. In view of the need for more complete information on the effects of such intermittent heating and stressing on the creep and creep-rupture properties of structural sheet materials, an experimental program on this subject was initiated. Possible theoretical analyses of the results will be made later. One of the major problems of the program was the development of suitable equipment for the investigation. A description of four creep testing machines, specially designed for this program, with automatic electronic control units is given herein. This equipment is designed to produce any combination, separately or simultaneously, of intermittent heating and stressing of creep-rupture sepcimens, in or out of phase.