2 

 Poisson's ratio of 0.19, and a specific gravity of 2.23 . A sketch of the 



cylinders is given in Table 1, together with nominal dimensions and a 

 limited number of measured dimensions. The thickness and diameter measure- 

 ments listed in Table 1 were obtained at a single location along the length 

 of each cylinder away from the tapered ends. However, spot checks made 

 along the length of the cylinders indicated that the thickness was quite 

 consistent. Cylinders 1 through 6 were about 6 diameters long, and the 

 other cylinders were 10 diameters long or greater. 



Local imperfections were observed in the cylinder walls in addition 

 to the variations in thickness and diameter indicated in Table 1. Small 

 "bubbles" and surface scratches were observed in many of the models although 

 no record of these observations was made. Numerous irregularities were 

 also present in the buildup area where the tapered flange was welded to 

 the cylinderical portion. 



TEST PROCEDURE AND RESULTS 



Each cylinder was sealed by a lead disk placed between the glass and 

 heavy steel end plates and was subjected to external hydrostatic pressure. 

 Cylinders 1 through 6 were tested in the Model Basin's l3-in., 9000-psi 

 pressure tank, and Cylinders 7 through 20 were tested in the Model Basin's 

 new 17 l/2-in., 25,000-psi tank. Cylinders 1 and 6 were subjected to a 

 maximum pressure of 9000 psi without collapsing. All other cylinders were 

 tested to collapse. 



Pressure was applied in increments during each test. Each new pressure 

 level was held at least 1 min, and the final pressure increment was nor- 

 mally less than 2 percent of the maximum pressure applied. 



The collapse of the cylinders caused complete crystalization of the 

 glass walls and was accompanied by a loud, sharp noise. Most of the 

 cylinders collapsed while the pressure load was being increased. In no 

 case was a "fall off" in pressure observed prior to collapse. The 

 collapse pressure of all cylinders except 1 and 6 are presented in Table 2. 



Large cracks, apparently originating at the ends of the cylinder, were 

 observed in Cylinders 1 and 6 after they were subjected to 9000 psi. Al- 

 though the cracks extended throughout the thickness of the glass, no leak- 

 age of water into the cylinders occurred during the test. It may be worth 



