647 



PLASTIC FAILURE OF CYLINDRICAL SHELLS. 29 



further removed from the loaded point. That appears to be the explanation 

 for the succession of comparatively straight sections which make up the 

 curves. 



6. A discrepancy between the energy required to deform an unstiffencd 

 steel cement drum in static and dynamic tests was not repeated when a 

 copper cylinder was subjected to the same tests. In the latter case the 

 energies were nearly the same and the distorted shapes were practically 

 identical. That suggests that the time factor was of some importance in 

 the case of the steel but not of the copper drum. That view was strength- 

 ened by the results of tests on small steel cylinders in which the same 

 amount of energy produced smaller dents when applied dynamically than 

 when applied statically. 



7. In tests on single rings two points remained undisplaced whatever 

 the magnitude of the applied load. That may be of importance in a 

 simplified mathematical approach to the treatment of the problem here 

 examined experimentally. 



Acknowledgement. 



The Authors wish to thank the Director of Scientific Research, Ad- 

 miralty, for whom the work was done, for permission to publish the results 

 in this form. 



The Paper is accompanied by thirty sheets of drawings and thirteen 

 photographs, from some of which Plates 1 and 2, the half-tone page plates, 

 and the Figures in the text have been prepared. 



