431 



Buckling of the shell takes place in the mode which gives the least 

 critical value of Ck , at pressures exceeding a critical pressure Pc, 

 corresponding to this value of 0^, We have 



vinless Ewc/il-}^) exceeds the yield stress o"" of the material of con- 

 struction, in which case 



Pc = ao-o/R. (13) 



It is foiind that the buckling mode corresponds to ^= 1 and to a value 

 of n, equal to the niomber of circumferential lobes excited, which in- 

 creases with decreasing ratio of shell length to diameter, 



2. Tables and Graphs of the Critical Buckling Pressure and the 

 Number of Lobes as a Function of the Shell Parameters 



The buckiing pressure Pc of cylindric.:xl shells has been calcu- 

 lated as a function of the parameters a/2ii and L/2R, the ratios of wall 

 thickness and shell length or frame spacing to the diaiaeter, with the use 

 of Equations (10), (11), (12), and (13). The following values of Young's 



modulus, Poisson's ratio, and yield stress were employed. 



E = 3 X 



y = 0.3 



E = 3 X 10' p.s.i. 



<r^ = 3 X 10^ p.s.i. 



The results are presented in nuraerical form in the accompanying tables 

 and graph (figure 1). In the tables, the lobe zones are marked out with 

 solid lines and the boundary between the plastic and elastic zones is 

 indicated by a dotted line. In Figure 1, the buckling pressure Pc is 



