plate used for the fabrication of each of the models are illustrated in 
Figure 1. 
Figure 2 shows the representative ratios of the square root of the 
multiplicand of the secant and tangent modulii to the elastic modulus as a 
function of uniaxial compressive stress for the curves of the inelastic 
models of Figure 1. These curves describe the plastic behavior of the 
material and were used in the calculations to obtain the Taylor Model 
Basin (TMB) inelastic buckling pressures PE presented indirectly later in 
this report. 
All the models, with the exception of Model 7A, were machined 
identically. First, the inside contour was machined using a form tool, 
then the outside contour was machined using a lathe and ball-turning 
attachment, and finally, the exterior ring-stiffened cylinder was machined. 
Model 7A, the last model fabricated, was machined more accurately using a 
method similar to that just mentioned but with the addition of a more 
recently developed system consisting of a support pot and mating mandrel.” 
All the models were designed for membrane deflection and no rotation 
at the intersections of the hemispheres and the cylinders. By maintaining 
lower stresses in the cylindrical than in the spherical portion of the 
model and thereby assuring failure in the area of interest, this design 
prevents the boundary with the cylinder from altering the stress pattern in 
the hemisphere from the pattern that would be created in a sphere of the same 
material, radius, and shell thickness. The inside diameters of the cyl- 
inders of Models 4A and 1CR were deSigned to be slightly smaller than those 
of the hemispheres for Model 1CR (Figure 3a). 
Because of machining error, the cylindrical portion of Model 4A 
was fabricated with a slight overcut; see Figure 3b. Although this resulted 
in a thinning of the cylindrical shell, thereby varying the ideal boundary 
condition somewhat, the spherical shell was machined correctly. Figure 3c 
illustrates the structural boundary configuration for Models 6 and 7A and 
also for the revised design of Models 4A and 1CR, all of which were 
fabricated with equal cylindrical and spherical radii. 
Model 6 was accidentally machined with a small gouge around the 
outer circumference of the third frame from the boundary juncture. AS a 
result, approximately 16 percent of the area of the frame was removed, 
