0.50-in. thick 



/ 



0.5 in. 

 ±0.010 



->^ 



/ 



0.10-in. 

 radius 



For this reason, no further efforts 

 were made to determine the strain 

 concentrations in the closure wall 

 and flange caused by hoop stresses 

 in the flange and adjacent closure 

 wall. 



The reflected light technique 

 was also employed to measure the 

 strains and strain concentrations in 

 the segmented-vessel wall laminae, 

 but instead of preparing a cross- 

 sectional model for the determination 

 of strains, scale segmented-vessel 

 wall laminae were used (Figure C-8). 

 To simulate the hydrostatic loading 

 on a typical segmented-vessel wall 

 laminae, several of them were assem- 

 bled into a ring which was then 

 placed over a hydraulic loading jig, 

 similar to the one used in testing 

 the vessel head flange (Figures C-9 

 andC-10). The modules in the top 

 layer of the ring were made from 

 epoxy sheets with a silvered back 

 surface, and reflected circularly 

 polarized light was used to deter- 

 mine the number and distribution 

 of photoelastic fringes (Figure C-1 1). 

 To observe the stress concentration 

 better around the shear-pin holes, 

 the nuts were removed for the test at locations where the fringes were to be 

 photographed. The laminae in the other layers of the ring were fabricated from 

 acrylic resin, a more economical and workable material. Since the modulus of 

 elasticity of epoxy is comparable to that of acrylic resin, the distribution and 

 magnitude of strains in the epoxy and acrylic resin laminae were approximately 

 the same. The photoelastic fringes in the segment laminae were photographed 

 at 50-psi load-level intervals until failure of the photoelastic model took place 

 at slightly more than 220 psi (Figures C-1 2 and C-1 3). 



Although both the stacked-ring vessel and the segmented vessel are 

 known to possess other structural components in which strain concentrations 

 occur that could not be analytically explored, it was impossible to evaluate 

 them experimentally by means of reflected polarized light because of lack of 

 time and funding. 



Figure C-2. Tensile load applicator for 

 two-dimensional tie-rod 

 head models investigated 

 photoelastically for stress 

 concentrations. 



80 



