﻿Stresses on the Elastic Properties of Iron and Steel. 419 



made of the help given by Messrs. Carl Wagner, H. X. 



Hubbard, N. L. Arbuckle, 0. L. Arbuokle, R. Elsea, 



W. Thornton, and J. T. Voshell, senior students in enod- 



.... -i -i ° 



neenng, m connexion with the tests. 



Materials. 



It is known that, when a solid bar is subjected to torsion, 

 the outer fibres are stressed to the elastic limit first, and that 

 the stress varies linearly to zero at the centre. It was evident 

 that, in the case when a solid round was tested in tension while 

 under torsion to, or beyond, its elastic limit in torsion, consi- 

 derable tensional elasticity would be shown, since in such a 

 case there would be a certain body of fibres in the interior 

 of the piece that had not been stressed to their elastic limit. 

 It was thought that by doing away with this interior core 

 and using hollow tubes, the true effect of combined tension 

 and torsion would be more nearly shown. It will be 

 seen in what follows that the results of tests on thin tubing 

 do not differ materially from those obtained from the tests of 

 thick tubing and solid rounds, except as regards unit elon- 

 gation at the elastic limit (see Plate VIII. fig. (j). It is the 

 opinion of the writer at this time that nothing new would be 

 learned by using a thinner tubing than was used in these tests. 

 The steel tubing used in the torsion-tension tests had an 

 outside diameter of 1 inch. Three different thicknesses were 

 used as follows : 005 inch, 0'075inch, and 0*25 inch, giving 

 an inside diameter of 0'90 inch, 085 inch, and 050 inch 

 respectively. The tubes were thoroughly annealed before 

 using and were, as nearly as possible, of uniform thickness. 

 About forty torsion- tension tests were made on this material. 

 The material used in the torsion-compression tests was low 

 carbon-steel solid rounds : — The test pieces were 8 inches long 

 over all, and turned down to £ inch with a gauge portion 

 turned down to J inch diameter. This material was from the 

 same shipment as the low carbon-steel used in the torsion- 

 tension tests. 



Method of Test. 



The apparatus used in making the tests on steel tubing was 

 the same as that used in testing the nickel and carbon steel 

 solid rounds (see Preliminary Report*). 



To make the torsion-compression tests, however, one ball- 

 bearing head of the apparatus was placed on the platform of 

 the machine and the other attached to the moving head. 

 With the specimen inserted and under the desired torsional 

 * Phil. Map-. Feb. 1906. 

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