Repeated Loads Above the Proportional Limit on 24ST Aluminum Alloy

Citation

Bull, Edward George and Mastin, Robert L. (1947) Repeated Loads Above the Proportional Limit on 24ST Aluminum Alloy. Engineer's thesis, California Institute of Technology. doi:10.7907/BN3E-8T35. https://resolver.caltech.edu/CaltechETD:etd-12032008-093401

Abstract

The purpose of this investigation is to study the effect of repeated tensile stresses above the proportional limit on 24ST Aluminum Alloy.

The investigation consisted of two parts: the design and building of testing apparatus which would provide a pure tension stress capable of being repeated many times a minute without shock but with a high rate of loading, and to obtain data by means of runs on prepared samples of the metal under study.

It was found that permanent deformation caused by overstress is not a useful factor in forecasting life expectancy.

It was also found that the effects of "aging" (elapsed time between overstresses), initial cold work, and magnitude of over- stresses applied all have definite influence on the ability of 24ST Aluminum Alloy to withstand further overstressing and require more thorough investigation.

It is considered that this field offers attractive possibilities for further study of the behavior of aircraft materials above the proportional limit with an eye toward increasing accuracy of airplane design.

The investigation was carried out at the Daniel Guggenheim Aeronautical Laboratory, California Institute of Technology, Pasadena, California.

Thesis Files