an aluminum-impregnated, epoxy, which sealed the joint and provided limited 

 longitudinal strength. 



The titanium model (Model PJ-2) had a double shell separated by 

 thin webs. The typical bay weighed 53.8 percent of its displacement weight 

 in sea water. In this model, area per unit length of the hull section was 

 obtained by allowing the average circumferential stress over the section to 

 reach 150,000 psi at a pressure of 10,000 psi. The depth of the web and 

 the average thickness of the shells were chosen to obtain an elastic 

 general -instability pressure for a semi-infinite cylinder of about 

 25,000 psi. The shell segments were designed to eliminate bending due 

 to the hydrostatic load. This was done by varying the thickness of the 

 shell in the longitudinal direction. Also, as in the first two models, 

 the end bays of Model PJ-2 were shorter than the typical bay. 



Model PJ-2 was 1.6 diameters long and was closed at the ends with 

 flat steel plates. Grooves on the inside and outside at each web were 

 filled with an artificial rubber compound. The artificial rubber was 

 chosen for ease of application in the laboratory, rather than as a suggested 

 prototype material. It was also used to seal the closure plates to the 

 model . 



TEST PROCEDURES AND RESULTS 



The models were instrumented with foil-type resistance strain 

 gages. The arrangement of the gages is shown in Figure 3. Model PJ-1S was 

 tested to collapse in the 17-inch diameter, high-pressure test tank at 

 the Model Basin. Model PJ-1L was tested almost to collapse in the 17- 

 inch pressure tank and collapsed in the 9-inch-diameter, high-pressure test 

 tank. Model PJ-2 was tested to 7000 psi in the 13-inch diameter, high- 

 pressure test tank and collapsed in the 9-inch pressure tank. Strain data 

 were obtained only during tests in the 17 and 13-inch tanks. At least 

 three runs were made for each model to obtain strain data. The loads were 

 applied to Model PJ-2 at the same rate as the compression specimens. 



Model PJ-1S collapsed at 12,500 psi, Model PJ-1L at 11,900 psi, and 

 Model PJ-2 at 10,100 psi. Strain sensitivities devised from the initial 

 slopes of the pressure-strain plots are given in Figure 3. Figure 4 shows 

 Models PJ-1L and PJ-2 after test. 



