DISCUSSION 

 General 



The flat acrylic windows failed either in flexure or in shear, depending on 

 their t/D] ratio. The failure modes and mechanisms are discussed in detail in 

 Appendix B, and deflection data are presented in Appendix C. In most cases, the 

 center of the window was ejected in the form of small fragments, while in few cases 

 in the low t/Dj ratio range the center was not ejected, as the formation of large 

 cracks in the window at low pressure vented the pressurized water, and thus removed 

 the energy required for ejection of the window. The critical pressures of windows 

 were found to vary exponentially with their t/Dj ratio. When the critical pressures 

 of windows with the same Dq/D; and t/D; ratios, and effective diameters of 1.50, 

 3.33, and 4.00 inches were plotted on the same graph (Figure 10) they were found 

 to fall in the same failure region. This indicates that the critical pressure of a flat 

 acrylic window is dependent only on the t/Dj ratio (and the mounting of the window 

 in the flange). 



The displacement of the windows also varied with their t/Dj ratio. Comparison 

 of displacements of windows having effective diameters (D|) of 1.50 inches (Figure 11), 

 3.33 inches (Figure 12), and 4.00 inches (Figure 13) shows that the displacements, 

 besides being a function of t/Dj ratio are also a function of D;. Although there are 

 insufficient experimental data to establish a reliable relationship between the magni- 

 tude of displacement and the D; of the window in DOL type III flange, it appears 

 that the displacement is directly proportional to the D| of the window. 



The critical pressures of flat acrylic windows when compared to the critical 

 pressures of conical acrylic windows investigated in previous studies^ were found to 

 be approximately of the same magnitude as the critical pressures of conical windows 

 of same t/D| ratio and having an included angle equal to, or larger than 90 degrees. 

 Thus, it would appear that the flat acrylic windows mounted in the DOL type III 

 flange are as resistant to short-term hydrostatic loading as the conical windows with 

 included angle equal to, or larger than 90 degrees. 



A technical discussion of the relationship between the critical pressure, Dq/D; 

 ratio, radial clearance between the window and the flange, and the method of sealing 

 is presented in detail in Appendix A. 



A technical discussion of the mode of failure of flat acrylic windows is presented 

 in detail in Appendix B. 



11 



