628 



14 PIPPARD AND CHITTy ON EXPERIMENTS ON THE 



Tests under hydrostatic pressure. — Tests were also made on house- 

 hold milk tins under hydrostatic pressure. The test specimens were 

 filled with molten lead up to a diametral plane to stabilize that portion 

 against failure, and the seam and cover were carefully soldered to make the 

 whole shell watertight. They were then immersed in water in a pressure 

 chamber. In the first test, pressure was raised continuously. Collapse 

 occurred suddenly at 50 lb. per square inch, and was, in that resjjcct, so 

 unlike the failure observed under steadily increasing static loads that a 

 second specimen was subjected to 5 lb. increments of pressure and was 

 removed for inspection after each increase. Up to 25 lb. per square inch 

 no effect was discernible, but at 27 lb. per square inch a slight flicker of 

 the pressure gauge gave warning of a collapse. On removal from the 

 chamber an elliptical dent with a double margin was found in the shell 

 as shown in Fig. 22. That dent extended the whole length of the specimen. 



T 



Dent Formed dotsino Hydrostatic Test 

 ON Tin with Unreinforoed Ends. 



The test was continued and flickers of the gauge were noted at 21 lb. per 

 square inch and 24 lb. per square inch but the specimen was not removed 

 until at 30 lb. per square inch it was found impossible to maintain the 

 pressure. Complete collapse similar to that in the first test had occurred ; 

 this is-shown at (c) in Fig. 19 (facing p. 5) which clearly indicates the double 

 margin. Agreement with Taylor's model shown at (a) in Fig. 19 is again 

 striking. 



Specimens with stiff ends as previously described [Fig. 11) were next 

 half-filled with lead and subjected to hydrostatic pressure. The pressure 

 was slowly increased to 38'5 lb. per square inch when a flicker of the 

 gauge indicated that collapse had occurred. A small elliptical dent about 

 2-8 inches long (the free length between reinforcing disks) and 0-95 inch 

 wide had formed. Its position is shown on the developed surface of the 

 specimen at (a) in Figs 23. The specimen was replaced and the pressure 

 again raised until the gauge indicated further failure ; inspection was then 

 made. That process was repeated and the history of the collapse deter- 

 mined. At 42 lb. per square inch a second slightly unsymmetrical ellip- 

 tical dent formed adjacent to the first as shown at (6) in Figs 23. That 

 was also 2-8 inches long and 1-05 inches wide ; the dimensions of the first 

 dent were unchanged. At 4G lb. per square inch a click was heard but 



