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



the inner layers to the surface sufficiently large to give the 

 delays. It we now revert to the cases where the exposed 

 plate receives an electric charge, as was the method o£ pro- 

 cedure in the majority of the experiments, it is obvious that 

 a metal will hold a charge with a greater force the more 

 electrons it has lost, and this being the case we shall have 

 rates of discharge and curves of the same nature in both 

 series of experiments. We suggest that the experiments 

 described furnish a step in the determination of the rate at 

 which the various forms of matter are undergoing disinte- 

 gration under normal conditions. 



Chemical Laboratory, 



University College, Loudon, 



July 1906. 



XLVI. The Effect of Combined Stresses on the Elastic 

 Properties of Iron and Steel. J5yE. L. Hancock, Assistant 

 Professor of Applied Mechanics, Purdue University^ La 

 Fayette, Indiana *. 



[Plate VIII.] 



THE tests reported below were carried out as a part of the 

 " programme of work" outlined by the writer, and ] re- 

 sented to the American Society for Testing Materials in a 

 " Preliminary Report of the Effect of Combined Stresses on 

 the Elastic Properties of Iron and Steel" (see Proceedings 

 of the Society, 1905). This report gave the results of tests 

 on certain specimens of low carbon-steel and nickel-steel. 

 The specimens were tested in tension while under different 

 torsional stresses, L e. in tension while under torsion to one- 

 third, two-thirds, and the full elastic limit in torsion, re- 

 spectively. Tbe results showed that the torsional sti 

 lowered the elastic limit in tension. 



The additional tests reported in this paper were made, for 

 the most part, on steel tubing, the method of testing and 

 general procedure being about the same as tbat reported for 

 the nickel- and carbon-steel solid rounds. Some tests were also 

 made on low carbon-steel solid rounds in compression while 

 under torsion, the latter being the beginning of a series of 

 tests in compression-torsion. Only a part of the results of 

 these tests is included in this report. The tests were all made 

 under the direction of the writer in the Laboratory for Testing- 

 Materials of Purdue University. Acknowledgment is here 



* Communicated by tbe Author, having been read before the American 

 Society for Testing Materials, June 1906. 



