130 
PROF. W. E. DALEY: RESEARCHES ON THE ELASTIC 
The effect of the arsenic is remarkable. It gives to the copper an elastic line with a 
distinguishable limit of proportionality of 1‘4 tons; 2*8 tons per sq. inch. 
There is no definite yield point. The loops are small and the rate of increase of 
loop area is small. 
The elastic line from the origin to l'l tons is thicker than the continuation of the 
line. This thickening is brought about by a removal and a re-application of the load. 
The spot of light travelled three times up and down this piece of the diagram, 
indicating that the elastic line, within" the limits of this load, is permanent. 
Brass. —Fig. 16. Composition 60 per cent, copper, 40 per cent, zinc, with traces 
Fig. 16 (brass). 
of tin and other impurities. The ultimate strength of the material is 32’6 tons per 
sq. inch. There is a marked limit of proportionality at 2^ tons; 7'33 tons per 
sq. inch. Y ield follows gradually. There is no contraction after the load has been 
removed, although the material contains so much zinc. 
Phosphor Bronze.- Fig. 17. The curve in this diagram shows a limit of 
proportionality at about 2 tons; 6‘5.tons per sq. inch; but it is difficult to locate 
the exact spot at which the line begins to curve away from the primitive straight 
element. 
Aluminium Alloy. Fig. 18. Diameter of test piece 0'625 inch. Gauge length 
5 inches, t his diagram is remarkable in that the removal and the re-application of 
the load in the plastic state shows no looping and therefore no hysteresis loss which 
can be calculated from the loop area. It appears as though the metal continually 
anneals itself at ordinary temperatures as plastic stretching proceeds. The material 
