having a possible adverse effect on the ideal design of membrane deflection 
and no rotation of the juncture. 
Table 2 lists the measured spherical wall thicknesses for the 
hemispheres of all the models. Table 2 also indicates the initial 
departures from sphericity for the hemispheres of Models 4A Revised, 1CR 
Revised, and 7A. Because the importance of sphericity measurements had not 
been established at the beginning of the tests, they were not taken on the 
three models tested earlier. All the thickness measurements were taken 
uSing a vidigage, and the initial sphericity departures were measured from 
a fixed point using a dial gage in a ieenose ae 
TEST PROCEDURE AND RESULTS 
Each model was instrumented with strain gages in both the meridio- 
nal and circumferential directions of the spherical portions with 1/8- and 
1/16-in.-long foil-backed strain gages. The gages were placed in the 
configuration indicated in Table 2 to obtain strain distributions along the 
hemisphere toward the intersection with the cylinder. Strain gages could 
not be located at the boundary of the sphere and the cylinder because of 
the lack of clearance at the frame at this location. However, gages were 
located as close to this intersection as was physically possible. 
All models were tested using oil as an external pressure medium. 
The models were externally loaded in comparatively small pressure tanks to 
limit destruction after collapse. Model ICR Revised, however, which failed 
at a relatively high pressure, waS quite severely damaged. 
Pressure waS applied incrementally to each model as indicated in 
Table 3. Before the strains were read at each increment of load, pressure 
was maintained for 3 min to allow the stresses in the model to stabilize. 
The experimental strain-sensitivity coefficients, i.e., the slopes of the 
pressure-strain plots in inch per inch per pounds per square inch for each 
strain gage are presented in Table 4. Table 5 lists the collapse pressures 
of the six models. Photographs of collapsed Models 4A Revised, 1CR Revised, 
and 7A are shown in Figure 4. 
The pressure-Strain plots for Model 7A, the only model designed to 
fail within the elastic range, properly displayed no significant nonlinear 
Strain behavior for any of the loading cycles. Figure 5 is a plot of 
