A Method for Predicting Creep Data for Commercial Alloys on a Correlation Between Creep Strength and Rupture Strength

Abstract

In this paper a method is presented for correlating the creep and rupture strengths of a wide variety of commercial alloys. The ultimate aim of this correlation is to predict design creep properties from rupture data alone. This is of considerable interest because rupture parameter or isothermal rupture curves are frequently the only data available since relatively little creep data is taken today. It is demonstrated in this work that reasonable predictions, useful in design, can be made. The alloys studied range from aluminum base through low alloy and stainless steels and include iron-nickel, nickel, and cobalt-base superalloys. Very long time data for single heats of each of the alloy types has been taken from either the literature or sources willing to make such data available. The construction is simple, and common techniques for determining scatter in the correlation are developed. The predictions include scatter bands of strain-time data developed from the 15 data sets encompassing all the alloys. It is suggested that some refinement might be gained by studying numerous heats of a single specification material where such data is available. A complicating problem of structural instability arises and is discussed in the paper.