. Development of a spherical acrylic plastic pressure hull for hydrospace application. Hulls (Naval architecture); Submersibles. that were already present in the joints because the surface of the preceding pour was not removed were eliminated in some cases by drilling or milling out (trepanning) the separation space and refilling it with fresh PS-18. No reliable method was found to prevent formation of small dispersed cavities in the set adhesive, although it can be hypothesized that a too-rapid setting rate (triggered by high ambient atmospheric temperature) was probably their cause. This hyp
. Development of a spherical acrylic plastic pressure hull for hydrospace application. Hulls (Naval architecture); Submersibles. that were already present in the joints because the surface of the preceding pour was not removed were eliminated in some cases by drilling or milling out (trepanning) the separation space and refilling it with fresh PS-18. No reliable method was found to prevent formation of small dispersed cavities in the set adhesive, although it can be hypothesized that a too-rapid setting rate (triggered by high ambient atmospheric temperature) was probably their cause. This hypothesis is substantiated by the fact that some of the pours resulted in completely cavity-free joints, while others had many cavities even though the chemical composition of the mix was identical in all cases. Most of the cavities were too small to merit a trepanning operation, particularly since it was felt that in joints subjected to operational tensile stresses less than 200 psi, the debilitating effect of cavities on the 4,000-to-5,000-psi ability of the joint to withstand 200-psi stresses was negligible. Only in very few cases where the cavities appeared to be interconnected was a trepanning operation performed and the cut refilled with fresh PS-18 adhesive. The tre- panning and refilling of separation spaces in the joint, however, generally did not decrease the peak residual stress level at that location, and in most cases introduced many incipient fine cracks (Figures 53 and B-2b). For this reason, it was used only when the separation space penetrated the whole joint width creating a leak (three locations).. Figure 49. Bonded hemisphere after removal from assembly jig. 78. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Stachiw, Jerry D. , 1931-; Naval Civil Engineering Laboratory (Port Hueneme, Calif
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