THE STRENGTH AND DUCTILITY OF FLAT STEEL BARS. 207 
The form of the curves of extension given in figs. 7 and 8 differs from that obtained 
by Barsa (fig. 1), im showing no well-marked maximum. If the process of deformation 
were the same in all the bars, so that the geometrical shape of the constricted region 
remained invariable, the extension of a fixed length would increase continuously with 
increase in the width of the bar. The fact that it does not indicates that the shape of 
the constricted region varies in such a way that there is less constriction, and therefore 
less corresponding extension, in a wide bar than in a narrow one. But, on the other 
70 
60P 
eS nn 
i=) (2) 
EXTENSION PER CENT. 
ie) 
o 
20 
8 
WIOTH 
THICKNESS 
thickness of $ inch, and gauge-lengths proportional to the ratio width/thickness expressed in inches, 
hand, the extension of a fixed length of a wide bar is greater than that of a narrow bar 
because the length is relatively less. These two factors which influence the extension 
act therefore in opposite directions, and from the shape of the curves of figs. 7 and 8 
- it is evident that these factors approximately equalise each other over a certain range 
“of the ratio width/thickness, namely from about 7 to 12. 
_ That there is less constriction of the wider bars may be shown in two ways. In 
fig, 9 are plotted curves, from the values given in Table VI., showing the extension of 
engths proportional to the widths of the bars; the Soe diminishes generally as 
