Method of Producing Compression_Strains in Guns, Gun Barrels, Tubes, Cylinders and other Hollow Bodies subject to High Internal Pressure.
Year: 1890

page_text: Date of Application, 15th Nov., 1890-Accepted, 14th Nov., 1891
COMELLE DIFOLIATION
Method of Producing Compression_Strains in Guns, Gun Barrels,
Tubes, Cylinders and other Hollow Bodies subject to High
Internal Pressure.
I, REINHARD MANNESMANN, of Landore, R.S.O. South Wales, Engineer, do
hereby declare the nature of this invention and in what manner the same is
to be performed to be particularly described and ascertained in and by the
following statement :-
My invention relates to a method of putting under compression the inner layers
of guns, gun barrels, tubes cylinders and other hollow bodies that are subject to
high internal pressure by causing the interior of the gun, tube, &c. while this is in
a heated condition and is being worked externally by rolling forging pressing or
drawing to be cooled by means of gases, liquids, or solid bodies. The inner layers
are thereby made to offer greater resistance to change of form than the outer
heated layers, so that the former are subject during the working to a compression
strain, which is considerably increased by the cooling and consequent contraction
of the outer layers.
By regulating the degree to which the gun is heated before the said treatment,
and also the degree to which the inner layers are cooled during the working, the
strains in the several layers and in particular the proportion in which the com-
pression strains decrease from the interior to the exterior and become tensional
strains, can be regulated in such manner, that on the one hand the neutral zone is
made to occur at a greater or less distance from the inner surface, according to the
nature and extent of inner pressure to which the gun is subsequently to be subject,
or that, on the other hand, the compression strains in the innermost layers shall be
of a determined amount.
It will be evident that the above described method is not only applicable to
guns and gun barrels, whether built up of concentric tubes, or with solid walls, but
also to other tubes, cylinders or hollow bodies, such as the cylinders of hydraulic
presses, whether these have solid walls or built up of concentric tubes. Thus in
the application of the method to the manufacture of guns built up of concentric
tubes while the gun shewn in longitudinal section at Fig. 1, after being suitably
heated, is being subject to considerable external pressure in an inward radial
direction uniformly over its whole surface either by rolling forging or pressing, a
cooling fluid is introduced through the pipe A into the interior of the bore.
The effect of such simultaneous external compression and internal cooling may
be explained as follows:
If a heated cylindrical body is cooled internally while the outer layers are still
hot, the inner layers tend to contract while the outer ones retain their original
form.
In consequence hereof the mass forming the wall must occupy increased space,
whereby radial forces will be produced within the mass which tend to separate th
inner layers from the outer ones, as indicated by the double headed arrows in
Fig. 2. As the cooling extends from the interior outwards, the zone at which the
layers tend to separate from each other will travel outwards, as indicated at
Fig. 3, and on the complete cooling such zone will entirely disappear out of the
section, so that the strains will more or less completely cease.
If however during the internal cooling the outer layers be subject to pressure so
as to cause them to approach the inner layers, and thus follow the tensional forces
exercised by these, as indicated at Fig. 4, the tensional strains will disappear. If
now the external pressure be discontinued, the compression strains in the outer
layers will also disappear, and on the completion of the cooling the outer layers

page_text: will contract while the inner layers, which had already been cooled previously
cannot contract farther, or only slightly so, and in consequence thereof there will
now occur inward directed tensional strains in the outer layers, producing
compression strains in the inner layers, as indicated at Fig. 5.
If during such cooling the outer layers are still subject to external pressure by
rolling &c. the compression strains in the interior layers, and the tensional strains
in the outer layers, will be still further increased.
If, as before described, the gun or other tube or cylinder is built up of con-
centric tubes, the inner tubes will be subject to compression and the outer ones to
tension.
When such a gun, tube or cylinder is subsequently subject to considerable
internal strain, the internal diameter will be slightly increased thereby, and if the
internal pressure is sufficient the compression strains that existed in the inner
layers will be converted into tensional strains, so that all the layers of the gun will
then be subject to tension.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is :-
The process for producing compression strains in the inner layers of guns, gun
barrels, tubes, cylinders and other hollow bodies consisting in subjecting such guns
tubes or hollow bodies while in a heated condition to an external compressing
operation, while at the same time they are subjected internally to a cooling
operation.
Dated thin 15th 1...
1000