615 



tLAStlC FAILURE OP CYLINDRICAL SHELLS. 3 



Scope of the Experiments. 



The original object of the investigation was to obtain information 

 about the behaviour of cylinders stiffened in a particular way which will 

 be described later. The manufacture of the test specimens was not easy 

 and was delayed by the usual war-time difficulties in obtaining suitable 

 material, scarcity of labour, and so on. During the waiting period certain 

 makeshifts were adopted which extended the scope of the original tests 

 and provided useful data of a more general character than was originally 

 contemplated. Steel drums normally used for storing cement in the 

 laboratory were found suitable for investigating the efficacy of the test 

 rig and the results of those preliminary experiments led to the manufacture 

 and test of a copper drum of approximately the same size for the purpose 

 of investigating certain peculiarities which the steel drums had revealed. 



It then appeared probable that useful results might be obtained from 

 tests on small unstiffened cylinders, an ample supply of which were avail- 

 able in the tins used to pack coffee and household milk. The former were 

 3J inches in diameter, 4 inches long and made of 0-010-inch sheet metal ; 

 the latter were 2| inches in diameter, 4f inches long and of the same 

 thickness. Those tins were sufficiently near to the proportions of the 

 standard test specimens in respect of diameter- thickness ratio to justify 

 results. Further, while it would have been very difficult, or even impos- 

 sible, to make laboratory tests on the standard specimens under impact 

 loading or hydraulic pressure, it was a simple matter to make such tests 

 on the small specimens. The experimental programme was therefore 

 extended to include the following : — 



(1) Preliminary tests on steel and copper drums. 



(2) Tests on small cylinders. 



(3) Tests on large cylinders. 



Tests were made on internally stiffened and unstiffened shells and on 

 specimens with end-plates of different degrees of stiffness. Sul)sidiary 

 tests of the material used and tests on single internal stiffening rings are 

 also described. 



Taylor's Hypothe«is of Distortion. 



Sir Geoffrey Taylor propounded the hypothesis that a thin cylindrical 

 shell would distort without any stretching of the cylinder wall provided 

 that the end plates had no stiffness out of their own plane and served only 

 to maintain the circular form. He observed that when such a shell was 

 subjected to a point load a transverse groove was formed and flats de- 

 veloped. The cross-section of the deformed cylinder through the groove 

 is shown in Fig. 1. 



If it be assumed that the lines running from the ends of the groove are 

 straight and tangential to the undistorted part of the cross-section and 



