STRESSES IN GUN FORGINGS. 
101 
equilibrium of the strains in the forging, and by construc¬ 
tion they have one point in common. Their further coin¬ 
cidence, therefore, is evidence of the uniformity of results 
obtained by the treatment. The somewhat marked irregu¬ 
larity of the measured stresses near the bore in the breech 
section, both before and after annealing, has led to the con¬ 
struction of two deduced curves, of which it will be seen 
that the one marked No. 2 coincides most nearly with the 
measured curve. This No. 2 is based upon the measured 
compression on the second circle from the bore. There is 
apparent evidence in this section that the contractile force 
of the outer layers of metal in cooling was sufficient to over¬ 
compress the metal near the bore. 
The strains engendered in all the sections by the interior 
cooling were apparently unnecessarily severe, and tended to 
produce too great a strain of tension toward the exterior for 
economy of resistance to interior pressure. Thus, in all of 
the sections, before annealing, it is seen that the curve of 
stress in action departs considerably from a horizontal line, 
and the limit of stress in action is reached first at or near 
the exterior surface.* Of the four, however, the breech 
middle section is exceptionally well disposed. 
It is important to note the general resemblance of the 
measured curves of stress in the four sections as showing 
the regularity of the cooling treatment throughout the length 
of the forging, and that an inspection of the end sections 
would have disclosed the condition of initial tension in the 
whole forging. This forging, as shown on the drawing, had 
marked irregularity of sectional dimensions, yet the degree 
of initial tension in the several sections is in general propor¬ 
tional to the thickness of the section, and there is no gen¬ 
eral abnormal distortion of either thin or thick sections. 
* The position of the stress curve for the state of action is necessarily 
influenced by the selection of the value 0 = 60,000. If this value had 
been taken equal to 68,000, as given in the report of physical qualities of 
the metal before quoted, the stress curves in action would be considerably 
more elevated next the bore, and the estimated values of P 0 would be 
correspondingly increased. 
