Shear deflections and buckling characteristics of inflated members

Topping, A.

doi:10.2514/6.1964-74

Cited by 6 publications

(5 citation statements)

References 2 publications

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“…The relation between the shearing stiffness and inflation pressure, accounting for the beam edge effect, has been determined by Topping. 4 These investigators observed that the flexural stiffness is essentially independent of the internal pressure. But Douglas, 5 using the finite theory of elasticity, has shown how the structural stiffness of an inflated cylindrical cantilever is influenced by the large deformations which occur during inflation.…”

Section: Introductionmentioning

confidence: 97%

Flexural Study of a Neutrally Buoyant Inflated Viscoelastic-Structural Member

Misra

Modi

1976

Journal of Hydronautics

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Flexural deflection of a neutrally buoyant inflated viscoelastic cantilever is studied using the three parameter solid model. This is followed by a free vibration analysis in the presence of hydrodynamic drag and axial tension. The approximate solutions of the governing nonlinear, partial differential equation are substantiated through numerical and experimental data. The paper ends with the dynamical response analysis to surface wave excitation. The information so generated has direct relevance to the design of an underwater submarine detection system. Nomenclatureof a point from the fixed end = transverse distance of a point from the neutral axis -area of cross section = constants, Eq. (36) = coefficients of ^r(£) in the eigenfunction expansion of the initial displacement, Eq. (29) = drag coefficient based on projected area Ld = added inertia coefficient = coefficient of <$>, in the eigenfunction expansion ofd 2 $ k /d% 2 , Eq. (37) = Young's modulus = three parameters of viscoelastic solid = tip load = moment of inertia of the cross section = creep compliance in tension = creep compliance in shear = normalizing multiplier, Eq. (18b) = length of cantilever = pressure parameter = axial force = function of*, Eq. (1 1) = damping parameter, 2C d /TT ( C m + 1 ) = a constant, Eq. (30b) = nondimensional viscoelastic damping coefficient, measure of energy loss in the structure djj = deflection at station / due to the load at station.$ irs 7 17 (£,r) ri c ,T] s \*.' r ,it." p,p -dimensionless displacement, w Id = cosine and sine components of 17, Eq. (34) = dimensionless wave amplitude = principal stretches = modulus of rigidity -eigenvalues of a cantilever = functions of eigenvalues and pressure parameter, Eq. (19) = dimensionless distance from the fixed end, x IL = densities of structural material and water. respectively = functions of /x r , \L' T and /A", Eq. (19c) = stress tensor -dimensionless time, [El /Ap w (\ + C m )xL 4 ]*t = scalar functions of principal stretches, Eq.(3) = frequency = eigenvalues of a cantilever without axial force = eigenfunctions of a cantilever with axial force, Eq. (18) = eigenfunctions for the adjoint problem;

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Section: Introductionmentioning

confidence: 97%

Flexural Study of a Neutrally Buoyant Inflated Viscoelastic-Structural Member

Misra

Modi

1976

Journal of Hydronautics

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“…The idea of using thin films for space applications within inflatable structures was first developed in 1962 by Frei Otto[27], who published ideas for inflated tubular frames for use in structures such as orbiting platforms. Even though several papers on static structural analysis of inflated cylinders have been written[28,29,30,31,32,33,34,35,36], very little work has been done until recently to study the dynamics of these kinds of structures.Main et al contributed …”

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confidence: 99%

Pattern Evaluation for In-plane Displacement Measurement of Thin Films

Thota

2005

Experimental Mechanics

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ABSTRACT--Ultra-lightweight spacecraft incorporating "gossamer" structures are extremely compliant, which complicates control, design, and ground testing in full scale. One approach to model the behavior of a full-scale gossamer structure is to construct a small-scale model test article that can be used to verify a corresponding small-scale computer model. Once the predictions of the computer model have been verified by measurement of the physical test article, it can be scaled up to allow computation of the full-scale structure behavior. As model verification requires accurate deflection measurements at multiple points along the surface of the structure, a sensing system that provides full-field data without changing the dynamic response of the structure must be developed. Hence, an optical approach is taken. Since the thin films used in gossamer space structures are typically smooth and featureless, targets must be incorporated into the film surface to enable tracking of both in-plane and out-of-plane displacements. A krypton fluoride excimer laser system was used to etch 35 Ixm wide linear features approximately 0.1 Ixm into the surface metallization of both 50.8 I~m polyester and 127 Ixm polyimide films. These optically diffuse surface features, designed mainly to investigate the precision of the laser etching method, were used as targets for ultra-close-range photogrammetry, the method chosen for displacement tracking. A force applied to the surface of the etched mirror (test article) produced in-plane and out-of-plane deformations that were resolved via ultra-close-range photogrammetry. To measure the in-plane tracking resolution, 1.5 and 3.0 mm circular dots were added (using ink) to the surface of the thin film, and some of these targets were tracked as the test article was translated on a precision linear stage. In-plane tracking resolution using ultra-close-range photogrammetry was related to the ground sample distance of the camera, which in this case was 51.25 Ixm pixel -] (equal to the ratio of sample dimension to number of pixels in the field of view). Using a manual technique to identify features of the etched pattern for tracking, the mean tracking error was about 13 Ixm (or = 43 Itm). Using an automated, subpixel marking technique to identify the 1.5 mm circular targets, the mean tracking error was 22 Ixm (or = 13 Ixm). Neither of these methods achieved the desired 10 I~m tracking resolution.KEY WORDS--Gossamer spacecraft, in-plane displacement, laser ablation, photogrammetry, feature tracking P.

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“…There are two criteria that an inflated member subjected to external compressive loads must satisfy. 1 In the case of axially loaded straight columns, they are…”

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confidence: 99%

Ring Buckling of Inflated Drag Bodies

Topping

1971

Journal of Aircraft

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Buckling instability may occur in at least three types of aerodynamic decelerators, toroidal drag bodies, drag cones, and the tucked-back balloon-parachute (Ballute).f Buckling criteria for inflated compression members are reviewed, and tests of inflated columns of Mylar, Dacron-neoprene, and stainless steel-silicone fabrics are reported in support of the theoretical development. The theory is then extended to the buckling of a ring in and out of the plane of its centerline. A drag body consisting of a simple torus connected by a skirt to a forebody is used as an illustrative example.

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Shear deflections and buckling characteristics of inflated members

Cited by 6 publications

References 2 publications

Flexural Study of a Neutrally Buoyant Inflated Viscoelastic-Structural Member

Flexural Study of a Neutrally Buoyant Inflated Viscoelastic-Structural Member

Pattern Evaluation for In-plane Displacement Measurement of Thin Films

Ring Buckling of Inflated Drag Bodies

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