Table B-9. Reduction in Implosion Strength Due to 

 Out-of-Roundness 



Interestingly, the strain criteria that controlled in all cases, 

 except Case 2, was a tensile strain limit of 800 |jin./in., and not a 

 compressive strain limit. The limiting tensile strain occurred in the 

 radial direction of the wall (increase in wall thickness) at midlength for 

 the free-support specimens and at a distance of | - 0.4 from the end 

 for the simple- support specimens. Tensile strain had an influence on 

 faOure because the wall thickness would laminate and facilitate a shear- 

 compression type of material failure of the wall. Evidence of wall 

 lamination has been observed in fragments of thick-walled spheres 

 under hydrostatic loading (Ref 26) but was not observed in the frag- 

 ments of cylinder specimens. 



The effect of out-of- 

 roundness in reducing the 

 implosion strength of a per- 

 fectly circular cylinder is 

 shown in Table B-9. Cylin- 

 der t/D influenced the out- 

 o 



of-roundness effect con- 

 siderably. Cases 1 and 2 are 

 thinner specimens than Cases 

 3 and 4, but all have a 

 simple-support end-condition; 

 the thinner specimens showed 

 a 44% reduction due to out- 

 of- roundness, whereas the thicker specimens showed a 16% reduction. 

 A similar observation is made between Cases 5 and 6 which are thinner 

 than Cases 7 and 8, all having a free-support end-condition. 



The influence of end-condition on out-of-round effect can be 



observed with Cases 3 and 4 and 5 and 6, all of which have t/D' of 



o 



0.037. Cases 3 and 4 are simply supported and showed a reduction of 

 16%; whereas. Cases 5 and 6 are freely supported and showed a reduc- 

 tion of 46%. 





Perc 



:nt Reduction in Implosion Strength 



Failure- 

 Criteria 





Between Case Numbers" — 















1 & 2 



3&4 



5 &6 



7 &8 



Average 



Strain 

 Control 



31 



4 



38 



9 



20 



Stress 

 Control 



44 



16 



46 



18 



31 



First case number designates perfect cylinder, second 

 case number designates out-of-round cylinder. 



77 



