ARTICLES BY BELL SYSTEM AUTHORS 207 



Abstract — In order to obtain a better understanding of the mechanism 

 of coercive force in modern permanent magnets, magnetostriction measure- 

 ments have been made on various alloys having coercive forces from 50 to 

 600 oersteds. The results can be summarized by discussing two types of 

 alloys. First are the older carbon-hardening permanent magnets, and for 

 these alloys high coercive force and high magnetostriction occur together. 

 Second are the new carbon-free permanent magnets and for these alloys 

 high coercive force does not occur with high magnetostriction. In fact for 

 the Mishima alloys having compositions near 29 per cent nickel, 12.5 per 

 cent aluminum, and 58.5 per cent iron, cooled at the rate of 3°C per second 

 (coercive force 400 oersteds), the magnetostriction actually passes through 

 zero. This is contrary to the classical strain theory of coercive force which 

 states that the latter is proportional to the product of the magnetostriction 

 and internal stress. To explain the mechanism of coercive force for these 

 alloys it is necessary to resort to more recent theories. 



Stress Analysis for Compressible Viscoelastic Materials * W. T. Read, 

 Jr.' //. Applied Phys., v. 21, pp. 671-674, July 1950. 



Abstbact — ^Mathematical methods of stress analysis are presented for 

 linear, compressible, viscoelastic, or anelastic, materials such as metals at 

 high temperatures or high polymers with small strains. For such materials 

 stress, strain and their time derivatives of all orders are related by linear 

 equations with coefficients which are material constants. Fourier integral 

 methods are used to show that static elasticity solutions can be used to de- 

 termine the time dependent stresses in viscoelastic bodies with any form of 

 boundary conditions. 



If stress and double refraction and their time derivatives are also linearly 

 related, the standard photoelastic techniques can be used to determine the 

 directions and difference in magnitude of the time dependent principal 

 stresses, even though the principal stress axes do not coincide with the 

 polarizing axes and both vary with time. When viscoelastic models are used 

 in photoelastic studies, the time variation of the stress distribution in the 

 model represents a first approximation to the dependence of the stress in 

 the elastic prototype on Poisson's ratio. 



Metallurgy Behind the Decimal Point.* E. E. Schumacher.' //. Metals, 

 V. 188, pp. 1097-1110, Sept. 1950. 



Abstracts — No one property has a monopoly as to being disproportion- 

 ately affected by minor elements. Nearly all properties are affected, but 

 there is time here to mclude only a selected few. I have chosen, therefore, 

 three of general mterest: strength, magnetic, and electrical properties. I 

 shall inquire into both the mechanisms and consequences of these dispro- 



* A reprint of this article may be obtained on request to the editor of the B.S.T.J. 

 1 B.T.L. 



