Design and Stress Analysis of Extraterrestrial ... - The Black Vault

The locus of points equidistant from the main surfaces of the
shell is called the middle surface. The gecmetric shapes of a shell
are completely determined by the shape of the middle surface and the
law of variation for the shell thickness. As a rule, this thickness
is constant.
The most widely used are shells of revolution, i.e., shells
which have a middle surface formed by the rotation of any plane
curve around an axis lying in the plane of this curve and called
the generatrix.
If the middle surface is a plane, the shell is called a plate.
The curve formed on the surface of the shell by the intersection
of it by the plane passing through the axis is called the meridian.
Obviously the meridians agree with the generatrices of the shell.
The meridian's radius of curvature at any point is called the first
principal radius of curvature R1 of the surface at a given point;
the radius of curvature of the curve obtained from the intersection
of the surface by a plane perpendicular to the meridian is called
.the second principal radiusjR of the 4urface at a given point.
Sometimes the word "principal" is omitted.
The radii R1 and R2 are variable quantities characterizing th,•
geometry of a shell of rotation. Completely geometric forms of
a shell of revolution are characterized by these two radii and the
angle 0, formed by the normal to the middle surface and the axis
of symmetry. Figure 2.20 presents these parameters for various
types of single-layer shells.
In engines, in addition to simple single-layer shelis, complex
two- and multilayer shells are used, which have, as a rule, the
shape of a body of revolution. Between the walls of the shells
flows liquid or gas, frequently used for cooling the walls. Various
types of complex multilayer shells are shown in Fig. 2.21.
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