qe eae 
ON IMPACT TESTS. 23 
Ratio of weight of hammers to anvil and foundations 1:277 and 
1 : 832 respectively, so that, as far as rigidity of the anvil is concerned, 
the effect of the blows of the hammer would be as severe as possible 
under the circumstances, and the results would be much less than with 
an anvil on springs or timber. 
The recording apparatus for determining the energy of rupture con- 
sists of a drum rotated at a constant speed by means of an electric motor. 
A style attached to the falling hammer describes a diagram on the drum 
showing the velocities of the tup just before and after impact. The 
apparatus can be attached to the frame of the machine and adjusted 
to suit the heights required for various tests. 
In order to determine the losses of energy due to the friction of the 
hammer on the guides of the machine, and also that due to the deforma- 
tion of the hammer and the frame, we may proceed in the following 
manner :— 
First, calibrate a strong spring, such as a triple carriage-spring, in a 
static compression-machine by obtaining a diagram of the loads and 
corresponding deformations. The area of the diagram up to any given 
deformation gives the work done or energy corresponding with this de- 
formation. Place the spring on the anvil of the impact machine and 
determine the deformations due to various heights of drop, and find 
the ratio of the height corresponding with the deformation of the spring 
to the actual height of the fall. Ifh = actual height, and h,= the height 
corresponding with the energy represented by the deformation of the 
spring, and » the ratio of h, to h, then— 
hy 
opie 
and the energy = n Wh. 
It should be noted, however, that we here assume that the work 
done in compressing a spring a definite amount is the same whether 
the load is applied steadily or by impact. This assumption is probably 
incorrect. 
Copper crusher gauges may be used instead of or as a check on the 
spring. 
P Mr. P. Wélikhow, of Moscow, in order to show the relationship between 
the ordinary static tension tests and impact tension tests, used an impact 
machine precisely the same as that used by the authors, and, by means 
of a calibrated spring, determined the value of the energy due to a given 
fall, then placing a standard tension test-piece in the shackles of the 
machine resting upon a weaker calibrated spring, and noting the com- 
pression of this spring representing the kinetic energy remaining in the 
hammer after rupture of the test-piece. The energy required to break 
the test-piece was clearly the energy of the hammer found by the first 
test on the triple spring, less the work absorbed by the second spring. 
All the conditions are practically identical in the two cases. The 
friction against the guides is exactly the same, the losses due to the de- 
formation of the hammer, and the frame carrying the test-piece are the 
same in both cases, so that the fracture of the test-piece alone diminishes 
the work absorbed by the spring. Three kinds of steel were tested in 
tension by impact and by ordinary static tension, soft cast-steel, hard 
