Upon completion of preliminary tests to obtain elastic strain data, the original model 

 which was not taken to failure was cut in half, as shown in Figure 2. Frame 7 was removed 

 and the two halves were designated Model EC-IA and Model F.C-IB. 



Model EC-IA was modified to study the influence of missile tubes in an oval cylinder. 

 Three tubes were incorporated and aligned in a transverse plane at midlength of the model, 

 as shown in Figure 3. Based on the outside diameter at the minor axis of the oval cylinder, 

 the tubes were designed to be geometrically similar to the missile tubes of FBM submarines; 

 see Figure 4. The tubes were machined from HY-80 forged steel tubing heat-treated to a yield 

 strength of 100,000 psi. 



Model EC-IB was used as a control cylinder for EC-IA and also to provide information 

 concerning the influence of reducing the overall length between rigid bulkheads. No missile 

 tubes were inserted in Model EC-IB. 



INSTRUMENTATION AND TEST PROCEDURES 



The models were instrumented with foil-type electrical resistance strain gages to 

 study the elastic behavior of the structures and to facilitate interpretation of the collapse 

 pressures. One- and two-element strain gages were used in the instrumentation of the models 

 except in the region near the penetration of Model EC-IA; there, three-element gages were 

 used to determine the direction and magnitude of the principal stresses. Figures 5 to 11 

 show the location of the strain gages and the strain sensitivity measured by the respective 

 gages. 



All three models were tested using oil as the pressurizing medium. Each model was 

 tested in two pressure runs. The maximum pressure of each run was as follows: 



Run 



Maximum Pressure, psi 



Model EC-1 



Model EC-IA 



Model EC-IB 



1 



500 



500 



500 



2 



620 



(Tubes 

 ^650 failed) 



1670 (collapse) 



Strain measurements were taken during each of the pressure runs. 



TEST RESULTS 



Model EC-1 was tested only to obtain elastic strain data. Strain-sensitivity factors 

 determined for each strain gage on this model are given in Figures 5, 6, and 7. The factors 

 are the slope of the linear portion of the pressure-strain curve and are measured in microinches 

 per inch per pound per square inch of pressure. The slope was found for each of the two 

 pressure runs, and an average value was determined for each gage. 



