TO SHIP CONSTRUCTION. 

 Trkble Riveted Lap Joints. 



219 



MARINE 



LABORATORY 



LIBRARY 



WOODS HOLE, MASS. \ 

 W. H. 0. I. 



OBSERVATIONS ON EXPERIMENTAL RESULTS. 



1. Static Elasticity. — It will be observed that the statical tests made to deter- 

 mine the elasticity indicate that, in general, the combination of welded and unwelded 

 material behaves practically homogeneously up to at least the elastic limit. More- 

 over, the experiments show that the process of welding is such that the stress is 

 distributed practically uniformly over the weld and also transmitted uniformly to the 

 adjacent plates. 



The material of the weld is practically pure iron, and from the tests made on a 

 specimen composed entirely of the deposited material of a weld it will be seen that, 

 for a given stress, the weld stretches slightly more than mild steel. This property 

 will enable any undue occurrence of load being transferred in a proper manner to ad- 

 jacent portions of the structure. 



When, however, the stress exceeds the elastic limit and is so great that the ex- 

 tension grows continuously without increase of load, the welded material fails sooner 

 than mild steel. But this disadvantage is of little practical importance in shipbuild- 

 ing and may be regarded as negligible in the particular problem under consideration. 



2. Dynamic Elasticity. — In a structure such as a ship, which is exposed to vari- 

 ations and reversal of stresses, it is extremely important to know whether the ma- 

 terial to be used is likely to break down rapidly under such alternations and ranges 

 of stress as are likely to be experienced. The modified Wohler tests employed in the 

 experiments certainly indicate, if considered solely by themselves, that whereas for 

 a given number of alternations mild steel would withstand a range of stress of, say 

 ±ioJ^ tons, the welded material might be expected to fail at about ±6}^ tons, a 

 figure which is more nearly experienced in ordinary ship construction. 



