24 REPORTS ON THE STATE OF SCIENCE.—1918. 
cast-steel, and extra hard cast-steel. The area of the stress-strain diagrams 
obtained in the static tension machine were determined. Thus, if P = 
the breaking load, T = the energy of rupture, Al = the total elongation, 
and a the diagram factor, then :— 
T=aPAl and P=. 
aAl 
The test-pieces had a length of 110 mm. and a diameter of 10 mm. 
The results are shown in the following Table I. :— 
TaBLe I. 
— | = Static tests | hbnpact tests 
Soft Steel. . . =| Breakingload. . =| 3050 3040 
Elongation ce, SP, 319% 32% 
| Contraction ... .| 63% 66% 
Hard Steel ; ; . | Breaking load . ‘ sik 5240 4750 
Elongation : : oH 20% 20% 
Contraction . . . 43% 48% | 
Extra Hard Steel .  .| Breakingload. . . 6630 | 6930 
Elongation : ; ; 8% 11% 
Contraction . . . 23% 24% 
The results show that impact tension tests not only supplement the 
static tension tests by giving the kinetic strength of the material, but 
in certain cases can replace it as it gives all the characteristic values of 
the properties of the material, excepting the elastic limit. It should 
be noted, however, that the relatively massive frame forming the tension 
shackles in the Martens machine absorbs a large portion of the energy 
of the hammer at the moment of striking. Impact tests on steels in 
tension, in which a triangular or circular notch has been cut, give results 
similar to those obtained in static tension after local extension has com- 
menced. Impact tension tests do not reveal the brittleness of the material 
like the notched bar tests. In regard to the determination of losses in 
the direct fall machine, we have adopted the following method :— 
MARTENS’ DROP HAMMER. 
Method of determining the Energy of Rupture. 
The energy of rupture is obtained by determining the energy of the 
tup just previous to and just after the impact, and taking the difference. 
Thus if h; =equivalent height for veloc. before impact, 
oo ye) 2? 2? 2 after 29 
=weight of tup, 
K=energy absorbed in rupturing test-piece, 
then K=W (h, — hz). 
h, and h, are determined by taking an autographic diagram on a 
revolving drum, and simultaneously recording the velocity of the drum 
by means of a chronograph. 
