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XXXIX. 



THE SUBSIDENCE OF TORSIONAL OSCILLATIONS AND THE 

 FATIGUE OF NICKEL WIRES WHEN SUBJECTED TO 

 THE INFLUENCE OF ALTERNATING- MAGNETIC FIELDS 

 OF FREQUENCIES UP TO 250 PER SECOND. 



By WILLIAM BROWN, B.Sc, 



Professor of Applied Pliysies, Royal College of Science for Ireland, Dublin. 



[Read May 18. Published June 28, 1915.] 



Ix January iind in November of last year the present writer brought before 

 this Society the results of some experiments on the subsidence of torsional 

 oseillations, and on the fatigue of nickel wires when they were subjected to 

 the influence of alternating magnetic fields of low frequency.' 



The present communication gives some results obtained with nickel 

 wires, when alternating magnetic fields of higher frequency were applied, 

 these magnetic fields being produced by means of alternating currents 

 whose graphs — as obtained with an oscillograph — are practically pure sine 

 curves. For a description of the apparatus employed, and of the general 

 methods of experiment, reference should be made to the paj)ers above 

 mentioned. It will be found that in the eases already studied, the nickel 

 wires wlien under test were subjected to three different loads, and tlie results 

 showed the effect due to load. In the present investigation the wire was in 

 every case subject to the same load, viz., 1'5 xlO^ grammes per sq. cm., which 

 corresponded to the middle value of the loads used in the previous work. 

 With this constant particular load there was used in eaiih case the corre- 

 sponding magnetic field of 20 c.g.s. units, for wliich it had been shown that 

 the effects would be a maximum both for the subsidence of torsional 

 oscillations and for the fatigue.^ 



The nickel wires employed were each 226 cms. long, and 0T67O cms. in 

 diameter ; and the millimetre scale for reading off the amplitude of oscillation 



' Seient. Proc. Roy. Dub. Soc, vol. xiv, Nos. H .ind 26. 



^ Ibid., vol. xiii, No. 3, pp. 31 and 37, and vol. xiv, No. 26, p. 337. 



SCJENT. PROC. R.D.S., VOL. XIV., NO. XXXIX. 4 



Mcuim 



