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By RAS Corresponding Member Nikita MOROZOV, Professor Vadim SPIRO, Central Scientific-Research Institute named after Academician A. Krylov
Academician Valentin Ivanovich Novozhilov (1910 - 1987) belonged to the intellectual elite of St. Petersburg which included celebrities like academicians A. Krylov and Yu. Shimansky, Corresponding Member of the USSR Academy of Sciences P. Papkovich, physiologist Academician L. Orbeli, orientalist Academician I. Orbeli, historian and geographer L. Gumilyov, archeologist and orientalist Academician B. Piotrovsky, literary critic and public figure Academician D. Likhachev. The common factor which distinguished these very different men of science was their exceptionally high cultural level and their quest for understanding life in all its diversity.
Concerning the central character of this article-Academician Wentin Novozhilov-who devoted all of his life to studies of continuous medium and naval engineering-many of our specialists honor him as their teacher. As for the authors of this article, they were lucky enough to be associated and work together with him over a number of years...
To begin with, it was not right from the start that Wentin Novozhilov embarked on a carrier in science. Agraduate of the Leningrad Polytechnical Institute, he began his carrier as a design engineer, estimator, learning from practice what they call a real engineering structure, how it functions and what are the main factors which determine its strength, reliability and effective operation. At the early stages his activities were linked with airship construction and later, and to the end of his life- with submarine engineering.
Among the areas of science which attracted Prof. Novozhilov in particular was the theory of sheathing, or shell structure. This applied component of the theory of elasticity is really complicated and obtaining and applying some concrete results in this area requires considerable efforts. And the structures which belong to this category, which are among the lightest and most effective ones, are widely used in aircraft and marine engineering, rocket technology, civil construction, etc.
The skill of designing the body or a structure with the use of shell, or sheathing components consists in putting them under considerable loads, evenly distributed along their thickness and surface and exposed to the least possible bending stresses. This really "tall" order can never be carried out in full. But one can approach the ideal to a lesser or greater extent, if one designs some required structures relying on a theory, satisfactory for practice, and what we call a "developed apparatus" for working with the main equations. In the late 1940s and early 50s the need for solving these problems was especially acute in connection with this country's broad program of submarine construction. This work involved many scientists, but Prof. Wentin Novozhilov succeeded better than others in mapping out the road to building the applied theory of sheathing, or casing, and showing how it can be conveniently simplified and translated into practical engineering solutions.
The works of Academician Novozhilov in this field are of a fundamental and classical nature. In line with his ideas experts built later the linear and non-linear theories of fine anisotropic (depending on direction) sheathing, taking into account the crosswise shift deformation, linear theory of anisotropic plates and sheathing of medium thickness, etc.
And the scientist was concerned not only with theoretical, but also major practical engineering problems, working in a purposeful way in order to achieve the most effective results. Here is just one example. The hull or body of a submarine, or most of it, is a cylinder with bulkheads between compartments, girdled with annular transverse frames (transverse rigidity ribbing). In an approximate way one can calculate the rigidity, or stability of this structure under external hydrostatic pressure, as the stability of a bulkhead ring fitted with a girdle (it is assumed that the hull, or sheathing between the bulkheads is strong and resistant enough). What is not taken into account here is the bulkheads support which comes into play if the length of a compartment is not too great. Academician Novozhilov proved by his calculations that due to the aforesaid factor, which takes into account the potential energy of changing the shape of the sheathing due to the loss of stability between bulkheads together with ribs of the frame, one can reduce the required strength of the latter. This will reduce weight and provide additional space inside the sub, reducing bending stresses in the sheathing, due to its sagging on the ribs, in stable operating conditions.
All of the rules, norms of permissible strains, limits of strength, limits of deviations from the norm of the form of sheathing and ribs for Russian submarines, including our first nuclear sub, were examined and approved by an inter-departmental commission chaired by Academician Novozhilov.
Then it was time to deal with the problems of hydraulic resilience, underwater explosions, or to be more exact-their impact on the hull of the sub and its gear. And these problems were no freaks of imagination. Without an appropriate theoretical basis one could not move on in design engineering. And Academician Novozhilov set and solved the classical problem of the impact, upon a cylindrical hull in unbounded liquid medium, of a shock wave with a flat front. In fundamental science this research stimulated further interesting studies which yielded additional concrete results. As for the industry-it helped make Russian subs more "explosion-resistant".
In conversations with his younger colleagues Academician Novozhilov used to say again and again that the part of their theoretical work, containing equations and their solutions, does not have to be clear to all, but flawless in the eyes of the professionals. He said-Your final results, expressed in figures, in principles or recommendations, should be worded in a way clear to all-be it a beginner scientist or engineer, and, finally, to the user.
In the following years the use in submarine construction of high-strength high-alloy welded steels and titanium alloys made it possible for Russia to match foreign powers in the depth of submersion of its subs and even surpass their results by 1.5 times. But at the same time there arose the problem of ensuring low-cycle fatigue and fracture- resistance of complex thick-wall welded sheathing or planking structures: their increased strength reduces their plasticity, makes them more brittle and reduces their fatigue and cyclic durability and fracture resistance. All of these problems called for new theoretical studies, including those of the properties of high-strength materials in welded structures. And one had to take into account the factors of welding and welding-and-assembly stresses, metallurgical defects and macrocracks hidden from technological control, etc.
Academician Novozhilov and his pupils provide a tangible contribution to all these studies. Thanks to his theories of loosening and plasticity, researchers developed a mechanism of assessment of resistance of materials to fatigue erosion, especially at stresses of more than half of the yield point. Scientists also worked out practical methods of assessment of damage probability of welded structures under the effect of repeated-static loads typical for operational conditions.
Academician Novozhilov devoted much attention to the problem of cracks. His views on the discrete nature of the processes of cracks formation and profound understanding of the physics of the process helped his colleagues to develop comprehensive, and easy to understand for engineers, methods of assessment of the limits of low-cycle fatigue of welded structures of submarines. These methods, confirmed by experiments, take into account resistance to the accumulation of microflaws and to the development of macrofractures, technological parameters (such as welding stresses, admissible defects), the factor of seawater exposure, etc.
The ability to recognize in time the importance of a problem and identify its main elements, Academician Novozhilov's talent of a theorist, which were all vividly manifested at the stage of fundamental studies, combined with the ability to rally around himself the necessary specialists in applied research, as well as his well- deserved prestige, made it possible for him to achieve some truly phenomenal results. His personal qualities, combined with outstanding engineering intuition which helped him to overcome all sorts of deadlocks, were an object of constant admiration of his co-workers and associates.
In his assessments of the achievements of his staff Academician Novozhilov was always strict and conservative. The formal defense of a thesis at the Krylov Institute was usually preceded by "informal debates" at the office of "Father Valya". On most such occasions he would first hear out the candidate for a degree and then say: "All this is clear and useful. But there is one snag at this or that point and you should bear this in mind." And it was really a pleasure to hear the "boss" say: "Yes, you do have something there."
Standing somewhat apart in the scientific legacy of Academician Novozhilov are his studies of turbulent fluxes (when portions of liquids or gases perform disorderly and chaotic movements along complex trajectories during intense mixing, heat exchanges and with big friction factors). This problem is one of the basic ones in the hydromechanics of boundary fluxes and is connected with the flowing around, or circumvention, of bodies by viscous fluids and the corresponding noises. The nature of the phenomenon has been the object of many long debates, but no common conclusion had been reached as yet. And it was not accidental that Academician Novozhilov turned to these problems in the early 1970s when circumvention (flowing around) noises and non-linear processes in the border layers attracted the attention of theorists of hydromechanics and of practitioners-designers of streamlined submarine hulls, propeller blades and other components.
The intrusion into an "alien" sphere proved to be a difficult task. Many specialists did not share the approach suggested by Academician Novozhilov. Nevertheless some of his results did achieve recognition and were accepted and confirmed by foreign researchers. Putting aside traditional approaches, the scientists tried to find new solutions on the basis of his own philosophical views and experience which rested on the firm foundation of studies of mechanics of continuum with respect to plasticity, creep and fatigue loosening, or disintegration.
Towards the end of his life (in the 1980s) Valentin Novozhilov outstepped the boundaries of his traditional domain once again. With his perfect command of English, he started translating English poetry of the 16th century, including, for example, Shakespeare's sonnets 71 and 100.
His translations were published with the help of his relatives and with the personal support of Academician V. Parshin, director of the Scientific-Research Institute named after Academician Krylov.
Valentin Novozhilov was also an enthusiast of painting and sports and informal meetings and discussions. People who often sought his advice and expert opinion included scientists, artists, and also translators.
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