HARDENED BY OVERSTRAIN. 
11 
Steel examined 
in the present 
paper 
(|-inch rod). 
Steel used 
previously 
(l-inch rod). 
Carbon ... 
0 • 35 
0-430 
Silicon ... 
0-102 
0-112 
Sulphur ... 
0-063 
0-010 
Phosphorus 
0-034 
0-016 
Maganese 
1-16 
0 - 450 
Iron (by difterence) 
98-291 
98-982 
100-000 
100-000 
The elastic properties of the two materials are compared in the table given below. 
In each case the results of an ordinary tensile test are given hrst, and then the data 
obtained by testing the material in the manner illustrated by Diagram 1 or 
Diagram 2 of this paper. In the second last column of the table there are tabulated 
the number of times the yield-point was raised in consequence of overstrain and 
recovery from overstrain when the material was tested in tlie manner just referred 
to, and in the last column the amount {in tons per sq. inch) by which the yield-point 
was raised each time. By way of illustration, in Diagram 1 the yield-point is sliown 
to have been raised twice by a step of about 11 tons per sq. inch, while in Diagram 2 
it is shown to have been raised four times by a step of 7|- tons per sq. incli. In an 
ordinary tensile test of course the specimen is not strained by steps. 
Material. 
Diameter of 
a turned 
specimen. 
Yield-point. 
Breaking stress. 
Ultimate extension. 
No. 
of 
steps. 
“Step.” 
l-in. steel rod, 1 
0 '40 of an in. 
37i tons/sq. in. 
47 tons/sq. in.* 
23 per cent, on 4 ins.* 
_ 
_ 
as supplied J 
0-10 ,. „ 
Q7.L 
^ * ‘1 >> ij 5) 
904 „ „ 
8 or 9 ,, ,, ,, 
2 
11 tons/sq. in. 
i-in. steel rod, 1 
0-44 „ ., 
29 ,j ,, 
44 „ ,. „ 
20 „ „ „ 
_ 
_ 
1 annealed J 
0-40 ., „ 
29 „ „ „ 
594 1. ., 
12 „ „ 
4 
74 tons/sq. in. 
1-in. steel rod,! 
0-80 ., „ 
23 „ ., .. 
,, ,, 
23 per cent, on 8 ins. 
_ 
_ 
as supplied j 
0-79 „ ., 
23 „ „ „ 
454 „ „ „ 
19 ,, ,, ,j 
4 
54 tons/sq. in. 
From this table it will be seen that the 1-inch steel rod as supplied resembled in 
elastic properties tlie ^-inch rod in the annealed state, and not in the condition as 
supplied by the makers. 
* These two figures were not obtained by experiment, but were estimated from results obtained with 
material very similar to the above, but containing more silicon (O'6 per cent.) and f inch in diameter. 
This thinner material gave when in the condition as supplied a yield-point at 36-^- tons.'sq. inch and 
broke under an ordinary tensile test at 43-^ tons with an elongation of 16 per cent, on 4 inches. After 
annealing, the yield-point occurred at 25 tons/sq.' inch and fracture at 39-1- tons/sq. inch, the elongation 
being 19^- per cent, on a 4-inch length. 
