316 REPORTS ON THE STATE OF SCIENCE, ETC. 
(5) A. MusnaAGER.—Détermination compléte sur un modéle réduit des tensions 
qui se produiront dans un ouvrage. Utilisation de la double réfraction acci- 
dentelle du verre 4 l'étude des efforts intérieurs dans les solides. (Annales des 
Ponts et Chaussées, partie technique, Series 9, vol. 16, Part 4, pp. 135-186.) 
(6) G. WEINGARTEN.—Sur les surfaces de discontinuité dans la théorie de 
Vélasticité des corps solides. (Rome, Rend. Acc. dei Lincei, Series 5, vol. 
10, 1901.) 
(7) E.G. CoKER.—The Determination, by Photo-elastic Methods of the Distribution 
of Stress in Plates of Variable Section, with some applications to ships’ 
plating. (rans. of the Institution of Naval Architects, 1911.) 
—— The Optical Determination of Stress. (Phil. Mag., 1910.) 
(8) E. G. Coxnr and L. N. G. Fiton.—Experimental Determination of Stress and 
Strain in Solids. (B. A. Report, 1914, pp. 201 et seq.) 
(9) E. G. Coxur, K. CO. CHAKKO, and M. 8. AHMED.—Contact Pressures and Stresses. 
(Trans. of the Inst. of Mech. Eng., 1921.) 
(10) E. AtMAnsI.—Rend. Acc. dei Lincet, May 1901. 
—— Sopra una classe particolare di deformazioni a sposiamenti polidromi 
dei solidi cilindrici. (Rend. Acc. dei Lincei, June 1907.) 
—— Sulle deformazioni a spostamenti polidromi dei solidicilindrici. (Rend. 
di R. Instituto Lombardo, 1907.) 
(11) Mager. Sull’ interpretazione del nuovo teorema di Volterro sulla teoria 
dell’ Elasticiti. (Rend, Acc. dei Lincei, vol. 14.) : 
(12) O. M. Corpino and Trapaccui. (Rend. Acc. dei Lincei, vol. 18, 1909.) 
See also letter by O. M. Corbino in “ Nature,” Jan. 16, 1913. 
(13) Rowua. (Rend. Acc. dei Lincei, Vol. 16, 1907.) 
DV;. 
Stress Concentrations in Theory and Practice. 
By A. A. GrirrirH, D.Eng., of the Royal Aircraft Establishment. 
1. Introduction. 
It has long been realised,-as a result both of experience and theoretical con- 
siderations, that sharp re-entrant corners, rapid changes of section and the like, 
are, in general, undesirable in members subjected to considerable stresses, by 
reason of the local weakening which they cause. At the same time, very few 
attempts have been made to take account of these stress concentrations in 
design, partly because of the inherent difficulty of the subject, but also very 
largely because calculations based on the mathematical theory of elasticity have 
in some cases appeared to overrate greatly the weakening effect which is 
produced. 
During recent years, however, the greater stringency of the working con- 
ditions imposed on machines and structures has so largely increased the number 
of failures arising from stress concentration as to render imperative a better 
understanding of the mechanism of such failures, and particularly of the causes 
which limit the validity of the mathematical methods of attack. 
In the present paper it is proposed to review briefly the existing state of 
knowledge of this subject, and to discuss some of the problems which still 
await solution. 
2. Methods of Estimating Stresses. 
The following methods are at present available for estimating the magnitude 
of stress concentrations :— 
I. Direct Mathematical Calculation. 
II. The Photo-elastic Method. 
III. The Soap-film Method. 
IV. The Thermal Method. 
A 
