502 MR JAMES RUSSELL ON THE SUPERPOSITION OF MECHANICAL VIBRATIONS 



At low inductions and in low fields the decrease and the increase of coercive force 

 respectively are both enormously great in annealed nickel as compared with iron or 

 steel. 



Hysteresis Loss in Relation to Field. — Permanently acting vibrations increase 

 hysteresis loss in low fields, diminish hysteresis loss in high fields. The former is 

 relatively the larger effect. In iron and steel the increase becomes less if the field be 

 unduly decreased, the ratio then being about two to one. In nickel, on the other 

 hand, the increase of hysteresis loss in similarly low fields of the order of H = 0*2 units 

 is enormous. Fig. VIII. shows that the hysteresis loss with vibrations must be about 

 twenty times as great as when no vibrations are acting. 



As the fields are increased, however, the increase and final decrease of energy loss 

 with vibrations in the three metals become quite compatible with each other. 



Hysteresis Loss in Relation to Induction. — When the induction at cyclic extremes 

 is the same, permanently acting vibrations cause a diminution of energy loss per 

 cycle in the three magnetic metals at all values of induction. For moderately small 

 inductions the decrease is approximately the same as that in my previous paper for 

 iron with electric oscillations (say about three times). As the induction is increased, 

 the diminution of energy loss becomes relatively less. 



When, however, the induction is further decreased than above indicated, the decrease 

 of energy loss is much greater in annealed nickel (see fig. VIII. , where the induction 

 at cyclic extremes is B = 260). In iron or steel, on the other hand (see fig. VII., where 

 the induction at cyclic extremes is B = 127), the decrease of energy loss is less than at 

 somewhat higher inductions, thus making the relative difference between nickel and 

 either iron or steel more marked at these low induction values. 



Annealed Metals, A Conditions. 



Cyclic Diagrams. — Figs. IX., X., and I. show for iron, and fig. XI. for nickel, the 

 effects of superposing vibrations under the A conditions. The dash-line curves measure the 

 instantaneous induction change which occurs when vibrations are superposed at all 

 stages of the normal loops (continuous-line curves). Figs. IX. and X., for iron, are for 

 low and high cyclic induction values respectively, fig. I. for an intermediate value. The 

 curves for steel are not given, as they are essentially similar. 



EXPERIMENTAL RESULTS. 



The superposition of vibrations at cyclic extremes produces, for all values of field, an 

 increase of induction. In high fields B v /B approximates to unity. 



The increase is enormous in nickel when field is sufficiently reduced. When H = 0'2, 

 B v /B =13 (fig. XL). In iron and steel this large increase in low fields is entirely absent 

 (fig. IX.). 



