﻿428 Prof. E. L. Hancock on Jests of 



The elastic limit, as used in this paper, is the proportional 

 limit of the bar, and the yield-point, the yield-point of the 

 bar. This latter for torsion is not so definitely marked as in 

 the case of tension or compression, and might, more properly, 

 be called a yield region ; it is to be looked for, in ductile 

 materials, a little beyond the elastic limit where very great 

 deformations take place for small increase of torque. The 

 bars were considered overstrained when stress ceased to be 

 proportional to strain. 



Results. 



The results of the tests outlined are shown by the following 

 plates and tables : — 



Plate X. fig. 1, shows the results of tests made on nickel-steel 

 specimen (1 0). 



Test No. 1 : to elastic limit. 



Test No. 2 : reversed after 24 hours to a point a little 



beyond the elastic limit. 

 Test No. 3 : direct to yield-point (not shown on curve) 



after 151 days. 

 Test No. 4 : reversed to yield-point after 6 days (yield- 

 point not shown on curve). 

 Test No. 5 : direct test to rupture after 6 days. 

 Test No. 6 : portion of No. 5 to rupture — reverse — after 



2 days. 

 (Note : curves are drawn only a little beyond the elastic 

 limit in most cases.) 



Fig. 2 shows the results of tests made on nickel-steel 

 specimen (1 D). (The curves as numbered run from left to 

 right.) 



Test No. 1 : direct to elastic limit (set curve shown). 

 Test No. 2 : load of No. 1 held for 15 hours, then taken 



off and reversed a little beyond the elastic limit. 

 Test No. 3 : direct to yield-point after 158 days. 

 Test No. 4 : reversed to yield-point after 5 days. 

 (Note : yield-point in 3 and 4 not shown.) 

 Fig. 3 shows the results of tests of a nickel-steel spe- 

 cimen (2 C) (3). (The curves as numbered run from left 

 to right.) 



Test No. 1 : direct to yield-point. 

 Test No. 2 : reversed to yield-point after 30 days. 

 Test No. 3 : direct to yield-point after 151 days. 

 Test No. 4 : reversed to yield-point after 113 days. 

 Test No. 5 : direct to yield-point after 4 days. 

 (Note : No attempt has been made to show the yield-point in 

 fig. 3). Figs. (4), (5), (6), (7), and (8) are self-explanatory. 



