﻿420 Prof. E. L. Hancock on the Effect of Combined 



load, a compression test was made by lowering the moving 

 head. The amount of compression was measured by means 

 of an Olsen Compressometer. The details of these torsion- 

 compression tests will be given in a subsequent report. 



Results, 



The lowering of the elastic limit in tension due to the 

 presence of various torsional stresses is shown in Plate VIII. 

 figs. 1, 4, and 6 (3) (for steel tubing 0*85 inch inside 

 diameter). In this case the amount of torsional load applied 

 was sufficient to stress the piece to J, f-, and full elastic 

 limit in torsion respectively. Fig. 2 shows the lowering 

 of the elastic limit in tension of steel tubing 0'90 inch inside 

 diameter, the torsion being applied in the same way as in 

 the case of the pieces represented in fig. 1. Figs. 4 and 

 6 also show this same lowering of the elastic limit. In 

 each of the cases A and B the curves represent an average 

 of two or more tests. Fig. 3 shows the effect of torsion 

 on the elastic limit in tension of steel tubing 0*50 inch inside 

 diameter. In this case the torsional load was applied and the 

 piece tested in tension as indicated on the curves. Each 

 curve represents an average of three or more tests. The 

 lowering of the elastic limit in tension is also shown for this 

 case by figs. 4 and 6 (3). 



Fig. 6 (3) shows graphically the lowering of the elastic 

 limit in tension for various degrees of torsion, and includes, 

 in addition to the steel tubing, the results obtained from the 

 nickel- and carbon-steel solid rounds (see Preliminary Eeport). 

 The ordinates represent the percentage of lowering of the elastic 

 limit and the abscissae the amount of torsional stress applied. 

 A similar statement is true for the rest of the diagrams in 

 fig. 6 as well as for those in figs. 4 and 5. It is seen 

 from this representation on fig. 6 that the variation in the 

 elastic limit is a linear one, and might be represented by a 

 straight line. Fig. 4 shows this straight line with the in~ 

 dividual points'represented. The equation of the line, referred 

 to the horizontal and vertical lines as axes, might be written 



y=(pjZp s ){2p s -x), 



where p and ^> s represent unit simple tension and unit simple 

 torsion respectively. This same lowering of the elastic limit 

 is shown in Tables I. and II. Table I. also shows the 

 lowering of the elastic limit of low carbon-steel in com- 

 pression due to different torsional stresses. These latter 

 results are shown graphically in comparison with those of the 



