502 TRANSACTIONS OF SECTION G. 
WEDNESDAY, AUGUST 19. 
Joint Discussion with Section M (Agriculture) on Irrigation. 
See p. 655. 
The following Papers were then read :— 
1. The Dynamic Increment of a Single Rolling Load on a Supported 
Beam. By Professor H. Cuatuey, B.Sc. 
The author suggested the use of the following formula for the dynamic 
increment of a single concentrated rolling load on a beam supported at both ends, 
the load being at the centre, 
AS | 
3 . 
He showed that this is a close approximation to the solution of a complex 
differential equation which states the conditions of dynamic equilibrium in the 
given case. 
~The dynamic increment is due to the vertical accelerations experienced by the 
load as the result of the deflection of the beam, and is of course liable to a 
“compound interest’ effect. The latter will not ordinarily more than double the 
effect due to the static deflection alone. 
5f=the dynamic increment of the load W. 
V =the horizontal velocity of the load. 
L=the span of the beam. 
EK=the modulus of elasticity of the material of the beam. 
I=the moment of inertia of the beam section, assumed constant. 
g=the gravitational acceleration. 
c=WV°L/gEI. 
9 
2. The Change in the Modulus of Elasticity and of other Properties of 
Metals with Temperature.* By Professor F. C. Lea, D.Sc., and 
O. H. Crowtusr, M.Sc. 
The paper described experiments that had been carried out to determine the 
influence of temperature, varying from 15° C. to 650° C., on some of the 
properties of metals. The specimens were heated in an electrically heated fur- 
nace, the temperature of which could be maintained nearly constant for some 
hours, and were loaded by means of a horizontal hydraulic-lever testing machine. 
The form of the specimens and the arrangements used for connecting them to the 
shackles of the machine and also a special extensometer were described. Tem- 
peratures were determined by iron-constantin thermo-couples. The effect of 
temperature on the breaking stress, yield point, construction of area, elongation 
per cent., and the modulus of elasticity of mild steel and other metals was shown 
by curves plotted from the results of the experiments. The modulus of elasticity 
of mild steel was shown to vary from 13,000 tons to 6,000 tons per square inch 
as the temperature varied from 15° C. to 630° C. The breaking stress of mild 
steel as measured on the original area was shown to be a maximum at about 
250° C., but the stress obtained by dividing the breaking load by the fractured 
area was a minimum at this temperature. The modulus of elasticity of micro 
copper was shown to change from 5,100 tons per square inch to 3,270 tons per 
square inch as the temperature varied from 15° C. to 650° C. 
3. A Theory of Work Speeds in Grinding. By J. J. Guesy. 
* Published in LZngineering, September 11, 1914. 
* Published in Hngineering, October 16, 1914. 
