DEVELOPMENT OF THE PHOTOELASTICITY METHOD IN THE USSR

L. E. Prokof’eva-Mikhailovskaya, Leningrad

The first works on experimental photoelasticity date to 1913. V. Kirpichev1 set up experiments in the laboratory of the Leningrad Polytechnic Institute. He was not satisfied with the design of the instruments then in existence, whose polarizing part limited the working field; at his instruction A. K. Zaitsev made a polariscope with a large working field, using incandescent lamps placed directly behind ground glass as the light source. The qualitative analysis of stresses in models by the method of color photography was reflected in a subsequent work by A. K. Zaitsev.[^2] However, the use of powerful light sources directly behind ground glass gives a spotty or striped picture of intensities covering the field of the photographic plate. In 1914 S. I. Druzhinin, in the Laboratory of the Leningrad Polytechnic Institute, made for measuring optical path differences in models paired prisms that were moved in the horizontal direction.

L. E. Prokof’eva-Mikhailovskaya[^3] (1927–1929), at Leningrad State University, attaching great importance to the role of the scale of the models, made a polariscope with a working field of \(600 \times 600\ \mathrm{mm}^2\) and later reached a field of \(1000 \times 1000\ \mathrm{mm}^2\). The principle taken as the basis was the replacement of light sources of great luminous intensity by sources of fields of great brightness. A white, specially treated screen with a series of lamps arranged around the frame was placed at the polarizer. Indeed, with a comparatively small increase in the dimensions of the instrument in comparison with the enlargement of the working field, a fully satisfactory picture is obtained. Elimination of the window for the camera makes it possible to increase the focal lengths of the lenses, which must be selected according to the thickness and size of the models. Thus a clear and faithful picture is obtained for isochromes and isoclinics.[^4],[^5] She provides a system of a polarization comparator (coordinator) for the quantitative investigation of models of a large working field (\(300 \times 150\ \mathrm{mm}^2\)).

Thereafter the development of photoelasticity methods continued at the Institute of Mathematics and Mechanics of Leningrad State University and, from 1930, assumed a planned character. The results of the Laboratory’s work were reflected in two collections[^6],[^7] and in the Tr—

conferences on the optical method of studying stresses1. The laboratory is engaged in developing systems of instruments, methodology, and the theory of photoelasticity. The instruments differ in their design from foreign ones, possessing various advantages noted in the corresponding articles by members of the laboratory.

As practice has shown, instruments of the bipolariscope type with a small electric lamp, moving over the points of the model with a working travel of \(300 \times 150\) mm, are especially convenient for pointwise methods of investigation. Placed on a lifting bench, the instrument can be oriented in any desired way. It is used not only for the analysis of plane models, but also for the analysis of stresses in spatial models, which can be investigated zonally as plane ones. For this purpose, during the manufacture of models or, if possible, during the experiment, foil is applied inside the model as a reflecting surface. Other laboratories of the USSR use systems of instruments and methodology developed at LGU[^9]–[^19].

In general, the instruments are based on schemes of polariscopes and bipolariscopes, a survey of which is given in Mindlin’s article1. A new principle was used by L. E. Prokof’eva-Mikhailovskaya[^20]; taking into account that, upon reflection, depolarization of light is insignificant, she gave a scheme of a multipolariscope that allows polarized light to be passed through the model any number of times. Thus a multiplier for the number of passes of the light ray through the model is introduced into the Neumann–Wertheim law. A detailed description can be found in the Soviet literature indicated in the list below.

D. K. Knol’ systematized the theory of singular points[^21]–[^23]. A new bakelite-type material is described by Prigorovskii and Kurochkina[^24], with an indication of the methodology for its investigation.

LITERATURE

1. V. Kirpichev, Fundamentals of the Optical Method of Studying Stresses, Bulletin of the Society of Technologists, Petersburg, 1913.
2. A. K. Zaitsev, The Optical Method of Studying Stresses, Izd. Prombyuro VSNKh, L., 1927.
3. L. E. Prokof’eva-Mikhailovskaya, Collection Autogenous Welding, Izd. KUBUCh, L., issue 4, 25, 1932.
4. Same, Izvestiya of the Artillery Academy of the RKKA, 4, 57, 1933.
5. Same, ibid., 5, 1, 1933.
6. Collection The Optical Method of Studying Stresses in Machine Parts, ONTI, L., 1935.
7. Collection Experimental Methods for Determining Stresses and Deformations in the Elastic and Plastic Zones, ONTI, 1935.
8. Proceedings of the Conference on the Optical Method of Studying Stresses, ONTI, 1937.
9. A. A. Popov, Proceedings of MIIT, issue 31, 1934.
10. K. V. Samsonov, Collection Research Works on Welding, M., 186, 1934.

Development of the Photoelasticity Method in the USSR

1. K. V. Samsonov, An Optical Method for Studying Stresses as Applied to the Investigation of the Work of Building Structures, Moscow Institute of Transport Engineers, Moscow, 1934.

2. G. A. Ozerov and M. M. Selivanova, Technical Notes of TsAGI, No. 70, 1, 1935.

3. G. A. Ozerov and M. M. Selivanova, Air Fleet Engineering, 14, 91, 1935.

4. N. I. Chentsov and G. A. Ozerov, Proceedings of TsAGI, issue 270, 1936.

5. L. E. Prokof’eva-Mikhailovskaya, Factory Laboratory, 3, 317, 1937.

6. The same, Factory Laboratory, 4, 458, 1937.

7. A. N. Dinnik, A. E. Morgaevskii, and G. N. Savin, Proceedings of the Conference on Rock-Pressure Control of the Academy of Sciences of the USSR, 7, 1938.

8. A. S. Malyshev, M. V. Nikolaeva, and L. M. Aleksandrov, Proceedings of the Leningrad Institute of Structures, issue 2, 1936.

9. L. I. Mal’ginov and G. I. Pokrovskii, Journal of Technical Physics, 6, 1093–1098, 1936.

10. L. E. Prokof’eva-Mikhailovskaya, Proceedings of the Conference on Rock-Pressure Control of the Academy of Sciences of the USSR, 6, 1938.

11. D. K. Knol’, Bulletin of Engineers and Technicians, No. 3, 175, 1938.

12. The same, Bulletin of Engineers and Technicians, No. 7, 430, 1935.

13. The same, Bulletin of Engineers and Technicians, No. 1, 45, 1937.

14. N. I. Grigorovskii and N. A. Kurochkina, Bulletin of Engineers and Technicians, No. 11, 699, 1938.

1. See p. 16 in this issue. ↩↩↩