The structural components of the stacked-ring model vessels were 

 machined from commercially available acrylic stock (Figures 14 and 15). 

 The rings, and the end-closure retaining flanges, were turned from flat acrylic 

 plates of 1 and 4 inches thickness, respectively. 



The tie rods were turned from 2-1/4-inch-diameter acrylic rods, while 

 the hemispherical end closures were contour-machined from 14-inch-diameter 

 by 12-inch-long custom acrylic castings. For the fabrication of modules for 

 the segmented-wall vessel, 1/4-inch-diameter rods were used for shear pins and 

 1/16-inch and 1/2-inch sheets for wall and retaining flange segments (Figures 

 16 through 20). Test specimens were taken from the commercial acrylic 

 stock to check on its conformance to the required 9,000-psi tensile strength. 

 Without exception, they have met this requirement by failing in the 9,200-to- 

 9,500-psi tensile-stress range. 



Instrumentation 



Instrumentation of the models tested to destruction under internal 

 hydrostatic pressure consisted of pressure gages and electrical-resistance strain 

 gages. The pressure gages were used with all of the vessels, while the electrical- 

 resistance strain gages were only used on the stacked-ring pressure vessel. 



The reasons for limiting the strain-gage instrumentation to the 

 stacked-ring pressure vessel were as follows: 



( 1 ) Since both the stacked-ring and the segmented-wall vessel models 

 utilized the same tie-rod system and hemispherical end closures, there was no 

 need to instrument them twice, as the strains measured during pressurization 

 of the stacked-ring model would be the same as during pressurization of the 

 segmented-wall model. 



(2) Only in the stacked-ring model was it possible to measure the actual 

 strains on the end-closure retaining flange and on the rings. In the segmented- 

 wall vessel, the failure of the end-closure retaining flange was predicted to be 

 due to rupturing of pins in that flange, and the failure of the wall segments by 

 shearing of pins and rupturing of segments. In neither case would it be possible 

 to attach strain gages to those structural members at the points of high stress 

 concentration and measure the actual strains. 



The actual strain gage installation on the stacked-ring pressure vessel 

 consisted of 15 rosettes placed on major structural components of the pressure 

 vessel model (Figure 21 ). Six of the rosettes were placed on the end closure, five 

 on the end-closure retaining ring, two on the tie rods, and two on the rings. Only 

 two rosettes, those at a penetration in the end closure, were sufficiently close 

 enough to a stress raiser to measure maximum stresses at a stress concentration. 

 The other rosettes simply measured the general stress level in the structural part 

 of which they were located. 



20 



