Sec. 1-2] 



MECHANICAL INPUT TRANSDUCERS 



57 



superimposed to the torsion, an asymmetric curve b results, and 

 beyond a critical value of longitudinal tension the response to torsion 

 changes to that of curve c. 



The magnetoelastic effect is particularly strong in nickel-iron 

 alloys (63 per cent Ni, 37 per cent Fe). 1 



1,000 - 



B 



500 



200 



100 



10 20 



Lood, kg 



Fig. (1-2)37. Magnetoelastic effect in 

 iron. 



Mechanical lood *■ 



Fig. (1-2)38. Magnetoelastic effect 

 in nickel; material subjected to 

 compression or tension. 



-100 



Fig. (1-2)39. Magneto- 

 elastic effect in nickel; 

 (a) nickel subjected to 

 torsion only; (b) sub- 

 jected to torsion plus 

 tension; (c) subjected to 

 torsion plus strong 

 tension. 



A schematic diagram and a response characteristic of a magneto- 

 elastic transducer are shown in Fig. ( 1 -2) 40. The transducer consists 

 of a probe P of magnetoelastic material around which a coil C is 

 wound. If a force is applied causing a stress in the probe, the per- 

 meability of the probe and thus the inductance L of the coil will 

 change as shown. 



1 See "Magnetostriction," The International Nickel Company, Inc., New 

 York. For further information on magnetostriction and magnetoelasticity, 

 see R. M. Bozorth, "Ferromagnetism," chap. 13, D. Van Nostrand Company, 

 Inc., Princeton, N. J., 1951. 



