Stresses on the Elastic Properties of Steel. 219 
the carbon-steel 100, 87, and 67, and for the nickel- steel 100, 
90, 83, 77, and 70. The percentage of normal deflexion at 
the centre for carbon-steel is seen to be 100, 92, and 79, while 
for nickel-steel it is 100, 98, 100, 99, and 89. The modulus 
of elasticity is changed but little in either case, that is, the 
combined stresses have little effect upon the stiffness of the 
shafting. 
Table III. gives the bending moments in both torsion and 
flexure for both carbon- and nickel-steel shafting. Table IV. 
gives the results of computing unit stresses by the various 
formulas for combined stresses. The first and second columns 
give the greatest tension and shear respectively, on any internal 
plane, when no account is taken of the change of form due to 
the acting stresses. The third and fourth columns give the 
greatest tension and shear respectively, on any internal plane, 
when it is assumed that Poisson's ratio is 1/4. The fifth and 
sixth columns give the greatest tension and shear respectively, 
on any internal plane, when it is assumed that Poisson's ratio 
is 1/3. The last two columns give the unit tension and unit 
shear on the outer fibre applied to the specimen during the 
test. In the case of the compression-torsion tests the first, 
third, fifth, and seventh columns give unit compression instead 
of unit tension. (For the formulse from which these results 
have been computed, reference is made to a former com- 
munication of the author, see Proceedings of Amer. Soc. for 
Test. Mat. vol. vi. p. 295; Phil. Mag. vol. xii. p. 418, 1906.) 
Conclusions. 
The results of tests reported in this paper show : — 
(1) That combined tension and torsion lowers the elastic 
limit in torsion, as shown in fig. 7. 
(2) That combined compression and torsion lowers the 
elastic limit in torsion in about the same way as in the case 
of tension-torsion. 
(3) That combined torsion and flexure lowers the elastic 
limit of the materials in flexure, as shown in figs. 6 and 
7, and that this lowering seems to be less than for any 
other case of combined stresses thus far investigated. This 
lowering is slightly less for the nickel-steel shafting than for 
the carbon- steel shafting. 
(4) That the unit deformation at the elastic limit of the 
tubing in tension-torsion and compression-torsion is lowered, 
as shown in fig. 8. 
(5) That the deflexion of the steel shafting is made less 
when the torsion is increased, the change being greater in the 
case of the carbon-steel than in the case of the nickel-steel. 
(Deflexion here means deflexion at the elastic limit.) A 
