32 
MR. J. REGINALD ASHWORTH: 
Drawn Steel Wire No. 7. 
Temperature. 
Depression on arbitrary scale (load increment 
= 100 grammes). 
« 
Cold. 
145-8 
Hot. 
— 
147-6 
Cold. 
144-0 
— 
Hot. 
— 
146-6 
i Cold. 
1 
144-0 
— 
Each of these numbers has been arrived at after a series of loadings and 
unloadings as described above. Since the modulus is inversely proportional to the 
depression, the diminution of the latter from 145'8 to 144 means a “permanent” 
increase of 1‘25 per cent, in elasticity.'^ 
The amount of this increase of the modulus varies from stage to stage and roughly 
follows the variation of the temperature coefficient, large and small values of each 
being associated. Tlius there is a large “permanent” increase when the cyclic 
change is large. The average amount of the “ permanent ” increase of the modulus 
in these wires is about 2‘5 per cent, for 80° change of temperature, f 
The mean results of the several determinations of the temperature coefficient ot 
Young’s modulus on each wire are given in the sixth column of Table IX. 
The coefficient is throughout negative, implying that, in the cyclic state. Young’s 
modulus decreases with rise of temperature; the magnitude varies considerably, 
namely, from — r64 X 10“^ when annealed, at the 2nd stage, to a maximum of 
— 10’25 X at the 3rd stage, when hard drawn. There is a small value again 
of the coefficient at the 4th stage on tempering, and, after that, the figures for the 
cold drawn specimens j^resent apparently much irregularity, but if this column of 
figures be plotted, as in Diagram VIII., we get a curve which repeats in an inverse 
sense all the features of the modulus curve, so that a relation clearly exists betv^een 
the modulus and its temperature coefficient. Although the figures in the table do 
not exhibit a simple inverse j^roportion between the magnitude of the coefficient and 
Young’s modulus, yet the general statement may be made that larger and smaller 
values of the modulus are progressively associated respectively with smaller and 
larger values of its temperature coefficient. This law recalls the similar law 
connecting the resistivity of the iron carburets and their temi^erature coefficients, 
with this difference, that the coefficient for the modulus is negative, whereas the 
coefficient for resistivity is positive. The average value of the coefficient for Young’s 
* This “permanent” effect does not persist indefinitely, Imt probably disappears in a fev days 
or hours. 
t These curious effects of temperature on Young’s modulus are in accordance with results published by 
Mr. Shakspear in a paper which appeared just after these experiments were carried out. ‘Phil. Ma^,’ 
vol. 47, p. 539; also ride ToMLiNSON, ‘Roy. Soc. Phil. Trans.,’ vol. 174, Part L, p. 132. 
