Application of Alloy Steels to Aircraft Industry

INCREASED industrial production cannot by itself make a nation prosperous unless proper economic measures are resorted to in the use of such products. This is part-icularly true in the case of a vital product like steel. It is indeed most appropriate that this symposium on Production, Properties and Applications of Alloy and Special Steels ' should be held at a time when the country is on the threshold of rapid industrialization under the Second Five Year Plan with heavy targets in steel output. The subject of the symposium has a vast scope. I shall, however, confine my discussion to the application of alloy steels to aircraft industry. An insight into the steel requirements of the aircraft industry will assist in the formulation of definite standards for such of those varieties which can be made within the ambit of raw materials available in this country

Titanium: a prospective metal for aircraft

Using bathythermographs, the sea temperature was studied at 37 stations and to a depth of 900 feet during a cruise from Visakhapatnam around Ceylon to Cochin. Vertical temperature cross sections have been constructed for 2DegreeF. intervals. The results were compared with those of Raghu Prasad who recently made a study up to 200 feet in Bay of Bengal. Detailed discussion of structure is presented

Note on the Minimum-Weight Design of Thin-Walled Cells in Combined Bending and Torsion

In a recent paper the authors suggested that the minimum weight design of thin-walled cells in combined bending and torsion could be tackled by using the well-known concept of equivalent bending moment and torque. It is now felt that a more rational approach would be to base the analysis on the buckling behaviour of the walls of the cell under combined compression and shear and choose the dimensions such that the cell will just resist buckling. The second criterion for design is taken as a limit on the twist as adapted in the case of pure torsion. Two types of sections, rectangular and circular, are discussed in this note.</jats:p

Deflection of Clamped Plates by Two-Step Membrane Analogue

The Classical Kirchhofif–Love Theory for the deflection of thin plates leads to fourth order Lagrange's differential equation,D△4w — q = 0 for which a general solution is not always possible. Exact solutions are known so far only for a few special cases and, therefore, numerical solutions have often been tried. The advantage of numerical solution is that it can be applied easily to any plate plan form which is in marked contrast to the analytical method where, for mathematical reasons, definite restrictions have to be imposed on the geometrical shape of the plate. Among the various numerical methods, relaxation is the easiest, but when applied to solving a biharmonic equation, the process becomes extremely difficult and laborious as convergence is very slow and the unit relaxation operator cumbersome to deal with.</jats:p

The Natural Frequencies of Thin Skew Plates

SummaryUsing Rayleigh's principle, the natural frequencies of thin isotropic rhombic plates, with three possible combinations of boundary conditions obtained by combining clamped-clamped and clamped-supported edge conditions, are determined in Part I of this paper. To introduce constant limits of integration, non-orthogonal co-ordinate systems are used and the wave shape for the vibrating plate is approximated by using normal functions representing mode shapes of corresponding bars. To estimate the accuracy of these eigenvalues, Kato's theorem is used and the lower bounds for the natural frequencies are determined in Part II of the paper. It is also shown that normal beam functions are not generally suitable for the determination of eigenfrequencies of skew plates with large skew angles.</jats:p

Minimum Weight Design of Thin–walled Cells in Torsion

The minimum weight approach to structural design was introduced by F. R. Shanley with reference to narrow and wide columns and shells subjected to bending, and was later dealt with more comprehensively in a book by the same author. This was further extended to structures like tapered round thin-walled columns and frames. In this paper expressions giving optimum sectional dimensions for long thin walled cells of circular, semi–circular, rectangular and triangular shapes and uniform wall thickness have been derived. The design criteria used to obtain the minimum necessary conditions are (1) failure by local buckling and (2) a limit on the twisting deformation of the cells. Working curves from which the optimum sectional dimensions can be read for given torque and limiting twist have been plotted. And finally, a method of approach to the problem of combined bending and torsion has also been indicated.</jats:p