Maximally stable lobed balloons

Pagitz, Markus; Pellegrino, Sergio

doi:10.1016/j.ijsolstr.2010.02.013

Cited by 13 publications

(9 citation statements)

References 10 publications

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“…They are realized with a polyethylene sealed membrane stiffened by meridional tendons (Smith and Rainwater, 2004;Cathey, 2009). In the past years, research efforts were focused on the balloon inflation in order to avoid instabilities which were leading to an incomplete deployment of the structure (Wakefield, 2005;Pagitz and Pellegrino, 2010). Nowadays, a design of cleft-free balloons is possible through a numerical clefting test (Deng and Pellegrino, 2011).…”

Section: Introductionmentioning

confidence: 99%

Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes

Bosi

Pellegrino

2018

Mechanics of Materials

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Thin films of linear low-density polyethylene show a significant time-dependent behavior, strongly reliant on temperature and strain rate effects. A constitutive nonlinear thermo-viscoelastic relation is developed to characterize the response of thin membranes up to yielding, in a wide range of temperatures, strain rates, and mechanical loading conditions. The presented plane stress orthotropic formulation involves the free volume theory of viscoelasticity and the time-temperature superposition principle, necessary to describe non-linearities and non-isothermal conditions. Uniaxial tension tests at constant strain rate and long-duration biaxial inflation experiments have been employed in the calibration of the material parameters. The model has been implemented in the Abaqus finite element code by means of a user-defined subroutine based on a recursive integration algorithm. The accuracy of the constitutive relation has been validated against experimental data of full field diaphragm inflation tests and uniaxial tension, relaxation and cyclic experiments, covering sub-ambient temperatures and strain rate ranges observed during the operation of stratospheric balloons.

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Section: Introductionmentioning

confidence: 99%

Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes

Bosi

Pellegrino

2018

Mechanics of Materials

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“…However, the computations were relatively time consuming, so that large parameter studies or an optimization of the balloon were out of reach. Exploiting the symmetry of lobed balloons [7] reduced the simulation time by several orders of magnitude [8] so that it became possible to apply optimization algorithms that increased the stability by up to 300% without increasing the membrane stresses, [9]. This paper continues the previous work by investigating the stability of lobed superpressure balloons during ascent.…”

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confidence: 69%

“…Another key finding is that optimized balloons leave this unstable region much earlier so that they experience larger shape changes in a potentially stable region before arriving at the desired flight altitude. Hence, it might be possible to overcome the observed deployment problems by using optimized cutting patterns [9].…”

Section: Discussionmentioning

confidence: 99%

Stability of Lobed Superpressure Balloons During Ascent

Pagitz

2011

Journal of Aircraft

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It is known from large-scale experiments that the successful deployment of lobed superpressure balloons can depend on the used gas. Some balloons deployed properly during an inflation with air but failed to reach the desired equilibrium configuration for helium. Furthermore, depending on the desired flight altitude, a helium-filled balloon might or might not deploy properly. This paper investigates this phenomenon by studying the stability of lobed superpressure balloons during ascent. It is shown that wrinkles increasingly reduce the stiffness of balloons for a decreasing gas density and an increasing flight altitude such that clefts can develop at very low differential pressures in nearly fully inflated balloons. Nomenclature C nv = symmetry group without horizontal symmetry plane (balloons during ascent) D nh = symmetry group with horizontal symmetry plane (balloons at flight altitude) F = lifting force of balloon at flight altitude f = frequency of buckling mode g = standard gravity h = altitude above sea level h b;t = altitude of bottom, top of balloon above sea level h fli = flight altitude above sea level M hel = molar mass of helium divided by the ideal gas constant m hel = helium mass n = number of lobes of balloon p 0 = air pressure at sea level p air;hel = air, helium pressure p fli air;hel = air, helium pressure at flight altitude r = equatorial radius of fully inflated balloon T 0 = air temperature at sea level T air;hel = air, helium temperature T fli air;hel = air, helium temperature at flight altitude V = volume of balloon V fli = volume of fully inflated balloon at flight altitude p b;t = differential pressure at bottom, top of balloon p fli = differential pressure of balloon at flight altitude during maximum solar exposure = eigenvalue 0 = air density at sea level air = air density fli air;hel = air, helium density at flight altitude 1;2 = first, second principal stress vm = von Mises stress

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“…The present work considers the symmetry and regularity aspects in the context of instability analyses of thin pressurized membranes with a highly symmetric shape. This class of simulations is valid for a large variety of thin threedimensional inflatable structures used in several engineering and medical contexts [23,26,29]. These situations are often both geometrically non-linear due to finite deformations and materially non-linear through the constitutive relationship.…”

Section: Introductionmentioning

confidence: 99%

Symmetry aspects in stability investigations for thin membranes

Eriksson

Nordmark

2016

Comput Mech

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Modelling of structural instability problems is considered for thin square membranes subjected to hydrostatic pressure, with a focus on the effects from symmetry conditions considered or neglected in the model. An analysis is performed through group-theoretical concepts of the symmetry aspects present in a flat membrane with one-sided pressure loading. The response of the membrane is described by its inherent differential eigensolutions, which are shown to be of five different types with respect to symmetry. A discussion is given on how boundary conditions must be introduced in order to catch all types of eigensolutions when modelling only a subdomain of the whole. Lacking symmetry in a FEM model of the whole domain is seen as a perturbation to the problem, and is shown to affect the calculated instability response, hiding or modifying instability modes. Numerical simulations verify and illustrate the analytical results, and further show the convergence with mesh fineness of different aspects of instability results.

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Maximally stable lobed balloons

Cited by 13 publications

References 10 publications

Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes

Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes

Stability of Lobed Superpressure Balloons During Ascent

Symmetry aspects in stability investigations for thin membranes

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