Effect of Temperature Variation on the Long-Time Rupture Strength of Steels

Abstract This paper presents a method of computing the factor of safety of a structural member with reference to a stated life, when operating under stress at high temperature when the temperature varies or when the stress varies moderately according to some definite pattern. The formulas presented herein are based on the supposition that the expenditure of each particular fraction of the life span at elevated temperature is independent of and without influence upon the expenditure of all other fractions of the life to rupture. The author makes no claim that this assumption is wholly true. The suggested procedure is offered simply to provide a means for making engineering estimates with some greater validity than always to assume that the worst conditions are present all the time. The desirability of taking account of certain additional influences which may differ from one material to another is recognized.