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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Thermal buckling of symmetrically laminated composite plates

This paper discusses an investigation into the thermal buckling of symmetrically laminated composite plates. In this study thermal buckling is investigated for laminates under two different simple support conditions, fixed and sliding. These laminates are subjected to the conditions of a uniform temperature change, and a temperature change varying linearly along the length of the plate. The effects of the principal material axes not being aligned with the edges of the plate are also investigated. The buckling response is studied using variational methods, specifically the Trefftz criterion. A Rayleigh-Ritz formulation is used to obtain numerical results from the formulations for the prebuckling response and the buckling response.

Meyers, C. A.↗
NASA NTRS1993

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

Chiang, C. K.↗
NASA NTRS1992

Propagation of flexural mode AE signals in GR/EP composite plates

A Fourier phase technique has been used to measure the dispersion of the flexural plate mode in graphite-epoxy composite laminates. Classical plate theory is shown to be of limited value in predicting the dispersion of this mode because it assumes that the effects of shear deformation and rotatory inertia are negligible. Higher-order plate theory, which includes these effects, gives much better agreement with measured values.

Prosser, W. H.↗
NASA NTRS1957

Handbook of structural stability part III : buckling of curved plates and shells

Available theories and test data on buckling of curved plates and shells are reviewed. For torsion and external-pressure loadings, the test data are correlated in terms of linear buckling theories for both the elastic and inelastic ranges. The cases which exhibit a marked disagreement between linear theory and test data include those of curved plates and cylinders under axial compression, cylinders under bending, and spherical plates under external pressure. These cases have been analyzed by a unified semiempirical approach for both the elastic and inelastic ranges which is satisfactory for analysis and design purposes. The effects of internal pressure on buckling of elements under uniaxial loads are discussed and data on various combined loadings are presented in interaction form. (author)

Gerard, George↗
NASA NTRS1958

Handbook of structural stability part VI : strength of stiffened curved plates and shells

A comprehensive review of failure of stiffened curved plates and shells is presented. Panel instability in stiffened curved plates and general instability of stiffened cylinders are discussed. The loadings considered for the plates are axial, shear, and the combination of the two. For the cylinders, bending, external pressure, torsion, transverse shear, and combinations of these loads are considered. When possible, test data and theory were correlated. General instability in stiffened cylinders was investigated. For bending and torsion loads, test data and theory were correlated. For external pressure several existing theories were compared. As a result of this investigation a unified theoretical approach to analysis of general instability in stiffened cylinders was developed. (author)

Becker, Herbert↗
NASA NTRS1953

Influence of End Plates on Lift and Flow Field of a Canard-type Control Surface at a Mach Number of 2.00

The influence of triangular-shaped end plates on the lift and the flow field of a canard-type control surface mounted on a symmetrical fuselage was investigated in the Lewis 8- by 6-foot supersonic wind tunnel at a Mach number of 2.00, body angle of attack of 2 degrees, and control-surface deflection angles of 3 degrees, 6 degrees, 8 degrees, and 10 degrees. The investigation demonstrated that the addition of end plates to a canard-type control surface increased its lift and rearranged the single vortex into a two-vortex system. Perforating the end plates reduced these effects and resulted in a decrease in lift and a change in the flow-field characteristics.

DIHEDRAL - COMPLETE WINGS↗
NASA NTRS1954

Formulas for the elastic constants of plates with integral waffle-like stiffening

Formulas are derived for the fifteen elastic constants associated with bending, stretching, twisting, and shearing of plates with closely spaced integral ribbing in a variety of configurations and proportions. In the derivation the plates are considered, conceptually, as more uniform orthotropic plates somewhat on the order of plywood. The constants, which include the effectiveness of the ribs for resisting deformations other than bending and stretching in their longitudinal directions, are defined in terms of four coefficients, and theoretical and experimental methods for the evaluation of these coefficients are discussed. Four of the more important elastic constants are predicted by these formulas and are compared with test results. Good correlation is obtained. (author)

Dow, Norris R↗
NASA NTRS1942

Normal-Pressure Tests of Circular Plates with Clamped Edges

A fixture is described for making normal-pressure tests of flat plates 5 inches in diameter in which particular care was taken to obtain rigid clamping at the edges. Results are given for 19 plates, ranging in thickness form 0.015 to 0.072 inch. The center deflections and the extreme-fiber stresses at low pressures were found to agree with theoretical values; the center deflections at high pressures were 4 to 12 percent greater than the theoretical values. Empirical curves are derived of the pressure for the beginning of the permanent set as a function of the dimensions of the plate and the tensile properties of the material.

Mcpherson, Albert E↗
NASA NTRS1942

Normal-Pressure Tests of Rectangular Plates

Report presents the results of normal-pressure tests made of 56 rectangular plates with clamped edges and of 5 plates with freely supported edges. Pressure was applied and the center deflection and the permanent set at the center were measured. For some of the plates, in addition, strains and contours were measured.

Ramberg, Walter↗
NASA NTRS1945

Principles of moment distribution applied to stability of structures composed of bars or plates

The principles of the cross method of moment distribution, which have previously been applied to the stability of structures composed of bars under axial load, are applied to the stability of structures composed of long plates under longitudinal load. A brief theoretical treatment of the subject, as applied to structures composed of either bars or plates, is included, together with an illustrative example for each of these two types of structure. An appendix presents the derivation of the formulas for the various stiffnesses and carry-over factors used in solving problems in the stability of structures composed of long plates.

Lundquist, Eugene E↗
NASA NTRS1949

Plastic buckling of a rectangular plate under edge thrusts

The fundamental equations for the plastic buckling of a rectangular plate under edge thrusts are developed on the basis of a new set of stress-strain relations for the behavior of a metal in the plastic range. These relations are derived for buckling from a state of uniform compression. The fundamental equation for the buckling of a simply compressed plate together with typical boundary conditions is then developed and the results are applied to calculating the buckling loads of a thin strip, a simply supported plate, and a cruciform section. Comparisons with the theories of Timoshenko and Ilyushin are made. Finally, an energy method is given which can be used for finding approximate values of the critical load.

Handelman, G H↗
NASA NTRS1954

Charts relating the compressive buckling stress of longitudinally supported plates to the effective deflectional and rotational stiffness of the supports

A stability analysis is made of a long flat rectangular plate subjected to a uniform longitudinal compressive stress and supported along its longitudinal edges and along one or more longitudinal lines by elastic line supports. The elastic supports possess deflectional and rotational stiffness. Such configuration is an idealization of the compression cover skin and internal structure of a wing and tail surfaces. The results of the analysis are presented in the form of charts in which the buckling-stress coefficient is plotted against the buckle length of the plate for a wide range of support stiffnesses. The charts make possible the determination of the compressive buckling stress of plates supported by members whose stiffness may or may not be defined by elementary beam bending and twisting theory but yet whose effective restraint is amenable to evaluation. The deflectional and rotational stiffness provided by longitudinal stiffeners and full-depth webs is discussed and numerical examples are given to illustrate the application of the charts to the design of wing structures.

Anderson, Roger A↗
NASA NTRS1958

On flow of electrically conducting fluids over a flat plate in the presence of a transverse magnetic field

The use of a magnetic field to control the motion of electrically conducting fluids is studied. The incompressible boundary-layer solutions are found for flow over a flat plate when the magnetic field is fixed relative to the plate or to the fluid. The equations are integrated numerically for the effect of the transverse magnetic field on the velocity and temperature profiles, and hence, the skin friction and rate of heat transfer. It is concluded that the skin friction and the heat-transfer rate are reduced when the transverse magnetic field is fixed relative to the plate and increased when fixed relative to the fluid. The total drag is increased in all of the areas.

Rossow, Vernon J↗
NASA NTRS1938

The lift distribution of wings with end plates

The object of the present report is to ascertain the relationship of the circulation distribution over the wing and of the lift to the height and position of the end plate. The side forces and moments on the end plates were also determined. It is found that moving an end plate of certain length up from the symmetrical position, is followed by a slight increase of the total lift.

Mangler, W↗
NASA NTRS1933

The critical shear load of rectangular plates

This report gives formulas for analyzing the critical shear load of a simply supported square, isotropic (simple flat plate), or orthogonal anisotropic plate (a plate in which the rigidity in two directions perpendicular to each other is different, i.e. plywood or corrugated sheet), these formulas, although arrived at by approximation method, seem to agree fairly well with experimental results.

Seydel, Edgar↗
NASA NTRS1994

Forming Weld Lands On Metal Plates

Forming shoe pounds edge of newly inserted plate workpiece. After many passes of shoe and advances of plate, thick land builds up at edge. Workpiece heated to enable metal to flow without strain hardening. Proposed upset-forming process replaces relatively expensive, time-consuming, and wasteful process in which integral weld lands created by machining metal away from plates everywhere except at lands.

Weddendorf, Bruce↗