204 MR W. GORDON AND MR G. H. GULLIVER ON 
TABLE IV. 
Extension oF Bars or Dirrerent Wiptus, Mrasurep uron Various Fixep Lenerus. 
Extension per cent. on a Length of 
Nominal Width, | Width 
Inches, Thickness’ | 
0 1 3 5 7 9 ital 13 | 15 Inches, 
4 1°76 179 | 45°0 | 30:2°) 25:3" | 23:8 | 22:25) 20:9) 19:3 19°1 
1 3°81 147 | 500 | 342] 288] 261 | 24:7 | 23°83) 22:8 22°2 
1} 5°64 128 | 550 | 389) 33:0 | 294] 271 | 255) 24:3 23°3 
2 757 122") O98 || 41e% | 347 | -3is0.) -28°251= 26:54 ore 24:0 
24 9°57 128 | 65:0 | 43:2) 35°3 | 314] 286) 268] 25:3 24°2 
3 11°14 AVY | 6233) 42:8) So | S12 | 28°25) Aoi yea 23°4 
3} 13°32 127 | 67:0 | 44:8) 365 | 32°4 | 29°3 |) 27:0 | 25:3 24:0 
4 15°39 121 | G80 | 47:3 | 386 | 344) 31:2 | 29:1 | 27-1 25°7 
of irregularity is the presence of one or more incipient constrictions along the length 
of a bar, other than that at which rupture has ultimately developed. ‘Such a constric- — 
tion gives rise to a local increase in the extension, and to a corresponding peak in the 
curve, but this is smoothed out by taking the average for each set of three bars. No 
allowance has been made for these small constrictions since they cannot be prevented — 
190 
110 
EXTENSION PER CENT. 
10 
WIDTH 
THICKNESS 
Fic. 6.— Variation of maximum extension at fracture of flat steel test-pieces with change in the ratio of width to thickness 
from 2 to 16, and a constant thickness of 4 inch. 
in an ordinary test. ‘The differences between the extensions of the bars in each set are 
due chiefly to these two causes. 
In fig. 5 are plotted the figures of Table IV. for each width of bar. The extension — 
for all bars decreases at first very rapidly from the fracture, and then more slowly, 
tending towards a minimum which is probably about constant for all. Generally 
speaking, the curve of extension for one bar lies completely above that for another of 
less width, but this is reversed in the case of the 24- and 38-inch bars. 
The extension at zero length, ¢.e. at the position of fracture, has been deduced from 
the area of the minimum cross-section. Let JA be the increase in length of an original 
length o/, through which the fracture passes. Let © be the original area of cross- 
