STRESSES IN GUN FORGINGS. 
93 
pression of 71,260 pounds at the intermediate radius, 1.905 
inches, an applied interior pressure of 91,870 pounds would 
produce throughout the whole wall of the cylinder an uni¬ 
form tension of 65,225 pounds per square inch. 
The remaining points of the deduced curve of stresses for 
the state of rest are now derived by equation (5). Having 
0 u = 65,225 and I\ = 91,870, we find : 
P = 55488 — 
459970 
in which, by substituting the several values of r, there re¬ 
sults : 
D 0 = 3.6, R 0 = 1.8 : P = 55488 — 141965 = — 86477 
d = 3.81, r = 1.905: p = 55488 — 126750 = — 71260 
d = 4.41, r = 2.205: p = 55488 — 94604 = —39116 
&c., &c., 
as given in table A and shown on the accompanying 
plate 6. 
The “ deduced ” stress curves for the state of rest in the 
remaining sections considered are derived in a similar 
manner. In each case the measured stress which is taken 
as a basis and so forms a common point on both the meas¬ 
ured and deduced curves of stress is designated (see table 
and plate 6) by figures in parentheses, as, for example 
(75,000) in the breech middle section, (59,910) in the muzzle 
middle section, and so on. 
Resistance to Interior Pressure .—The limit of elastic resist¬ 
ance of the metal under extension will be taken as before 
stated, 0 — 60,000. The value of P 0 will then depend upon 
the condition that this limit shall not be exceeded at any 
point. By a comparison of the measured and deduced 
stress curves for the state of rest, or, if need be, by a pre¬ 
liminary computation, the most dangerous measured stress— 
that is to say, the one which, under the action of an interior 
pressure, would be the first to reach the limit, 0 — 60,000, 
can readily be selected. Consequently the points which 
must be taken upon which to base the value of P 0 for the 
several sections are selected and designated (see table) by 
