Generally, the collapse strength of models that fail inelastically 

 is proportional to the yield strength of the material and to the weight- 

 to-displacement ratios. This permits comparison of collapse strengths 

 among similar models. The scaled collapse pressures for Models PJ-1S and 

 PJ-1L were obtained by scaling the model yield strengths to 62,000 psi. 

 The scaled collapse pressure for Model PJ-2 represents a semi-infinite 

 hull of the same typical bay geometry and with a yield strength of 150,000 

 psi. The collapse strength of Model DSRV-P was scaled to 62,000 psi yield 

 strength and a weight-to-displacement ratio of 67.9 percent. The collapse 

 strength of Model OV-4 was scaled to a yield strength of 150,000 psi and a 

 weight-to-displacement ratio of 53.8 percent. 



The comparisons shown in Table 3 illustrate that ring construction 

 need not result in any sacrifice in collapse strength compared to monolithic 

 hulls. Since the distortion and weakening effect of welding stresses are 

 not present, ring construction may permit some increase in collapse strength 

 relative to welded hulls. 



A submarine pressure hull is designed principally to resist external 

 hydrostatic pressure. However, in addition to the hydrostatic loads, a 

 submarine or other structure is subjected to overall bending moments. To 

 resist these bending moments, the structure must possess longitudinal 

 tensile strength in addition to its hydrostatic collapse strength. This 

 tensile strength is required only when operating on or near the surface. 

 At deeper depths, the longitudinal, hydrostatic compressive load exceeds 

 the tensile load of the bending moments and less longitudinal tensile 

 strength is required. For example, an oceanographic research station and 

 bottom-based vehicles could be assembled on site with a minimum of tensile 

 bending. 



For vehicles which must operate on the surface or at high speed, 

 some form of mechanical joining is required. The fundamental considerations 

 in designing a joining device are weight, volume, and stress concentration 

 in the pressure hull. For a given level of longitudinal strength, it is 

 desirable that the least excess weight be added to the structure by the 

 joints. In addition, it is desirable to consume as little as possible of 

 the valuable interior space. Any joining procedure which induces stress 

 concentration in the pressure hull may lower the collapse strength or 



