426 



THE SCIENTIFIC PAPERS OF 



In the discussion of the Papers 



"ON STEEL IN THE SHIPBUILDING YARD," by 

 Mr. TV. DENNY, and 



ON STEEL FOR SHIPBUILDING," by Mr. WEST, 



DB. C. TV. SIEMENS * said : My Lord and Gentlemen, we have 

 listened to two, in my opinion, very valuable papers, one written 

 by an eminently practical shipbuilder, and the other by a gentle- 

 man who has had great experience in the testing of a material now 

 largely used in construction. I agree with many of the opinions 

 advanced in both these papers. Both seem to advocate advance 

 in the same direction ; but there are certain points on which I 

 must, with all respect to the authors, differ from them in opinion. 

 The all-important question which has been put forward in these 

 papers, is the question of the absolute maximum strength to be 

 required or accepted in mild steel. If you take a bar of compara- 

 tively hard steel steel that will stand 50 tons to the inch it will 

 at the time of its breakage have elongated perhaps only 6 or 7 per 

 cent. But take a material of 30 tons to the inch and it will have 

 elongated 20 per cent. Now, to begin with, it is not strictly 

 correct to say that this latter material broke under a tensile strain 

 of 30 tons to the inch, because whatever might have been the 

 sectional area of the original bar at the time it broke, it had 

 bodily elongated 20 per cent. ; therefore, the strain was no longer 

 30 tons to the inch, but 36 tons to the inch, and I claim for the 

 mild material at any rate this advance of strength. What, how- 

 ever, is the condition of things before we have reached this 

 ultimate limit ? Take one bar with a breaking strain according 

 to the usual test of 30 tons to the inch, and another of 50 ; weight 

 both these bars with 5 tons to the inch and you will find that these 

 bars have elongated to exactly the same extent. Weight both 

 these bars to the limit of 10 tons to the inch, and again it will be 

 found that the elongation is the same. Therefore, up to that 



* Excerpt Transactions of the Institute of Naval Architects, Vol. XXI. 1880, 

 pp. 216, 217. 



