The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
John W. Hutchinson - One of the best experts on this subject based on the ideXlab platform.
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Knockdown factors for buckling of cylindrical and spherical shells subject to reduced biaxial membrane stress
International Journal of Solids and Structures, 2010Co-Authors: John W. HutchinsonAbstract:Abstract Cylindrical shells under uniaxial compression and spherical shells under equi-biaxial compression display the most extreme buckling sensitivity to Imperfections. In engineering practice, the reduction of load carrying capacity due to Imperfections is usually addressed by use of a knockdown factor to lower the critical buckling stress estimated or computed without accounting for Imperfections. For thin elastic cylindrical shells under uniaxial compression and spherical shells under equi-biaxial compression, the knockdown factor is typically as small as 0.2. This paper explores the alleviation of Imperfection-sensitivity for loadings with a reduced circumferential (transverse) membrane stress component. The analysis of Koiter (1963) on the effect of an Axisymmetric Imperfection on the elastic buckling of a cylindrical shell under uniaxial compression is extended to both cylinders and spheres for loadings that produce general combinations of biaxial membrane stresses. Increases in the knockdown factor due to a reduction of the transverse membrane component are remarkably similar for cylindrical and spherical shells.
Stelios Kyriakides - One of the best experts on this subject based on the ideXlab platform.
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plastic buckling of circular tubes under axial compression part ii analysis
International Journal of Mechanical Sciences, 2006Co-Authors: F C Bardi, Stelios KyriakidesAbstract:Abstract In the second part of this study, the evolution of uniform Axisymmetric wrinkling in axially compressed cylinders is modeled using the principle of virtual work. A version of this formulation also allows localization of wrinkling. The model domain is assigned an initial Axisymmetric Imperfection of a chosen amplitude and the wavelength yielded by the first bifurcation check. The solution correctly simulates the growth of wrinkles and results in a limit load instability. The limit strain is influenced by the amplitude of the Imperfection. Beyond the limit load, wrinkling tends to localize, eventually leading to local folding. The possibility of bifurcation of the Axisymmetric solution to non-Axisymmetric buckling modes is examined by using a dedicated bifurcation check. The bifurcation check was found to yield such buckling modes correctly. The evolution of such buckling modes is simulated by a separate non-Axisymmetric model assigned Imperfections with Axisymmetric and nonAxisymmetric components. The domain analyzed is one characteristic wavelength long (2λC). Initially, compression activates mainly Axisymmetric deformation. In the neighborhood of the bifurcation point, non-Axisymmetric deformation starts to develop, eventually leading to a limit load instability. Experimental responses were simulated with accuracy by assigning appropriate values to the two Imperfection amplitudes. Prediction of the limit strains for the whole range of diameter-to-thickness ratios (D/t) considered in the experiments was achieved by making the amplitude of the non-Axisymmetric Imperfection proportional to (D/t)2/m3 (m is the circumferential wavenumber). Matching all aspects of the experiments required inclusion of the anisotropy measured in the tubes tested through Hill's yield criterion in all models.
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Plastic buckling of circular tubes under axial compression—part II: Analysis
International Journal of Mechanical Sciences, 2006Co-Authors: F C Bardi, Stelios Kyriakides, Heedo YunAbstract:Abstract In the second part of this study, the evolution of uniform Axisymmetric wrinkling in axially compressed cylinders is modeled using the principle of virtual work. A version of this formulation also allows localization of wrinkling. The model domain is assigned an initial Axisymmetric Imperfection of a chosen amplitude and the wavelength yielded by the first bifurcation check. The solution correctly simulates the growth of wrinkles and results in a limit load instability. The limit strain is influenced by the amplitude of the Imperfection. Beyond the limit load, wrinkling tends to localize, eventually leading to local folding. The possibility of bifurcation of the Axisymmetric solution to non-Axisymmetric buckling modes is examined by using a dedicated bifurcation check. The bifurcation check was found to yield such buckling modes correctly. The evolution of such buckling modes is simulated by a separate non-Axisymmetric model assigned Imperfections with Axisymmetric and nonAxisymmetric components. The domain analyzed is one characteristic wavelength long (2λC). Initially, compression activates mainly Axisymmetric deformation. In the neighborhood of the bifurcation point, non-Axisymmetric deformation starts to develop, eventually leading to a limit load instability. Experimental responses were simulated with accuracy by assigning appropriate values to the two Imperfection amplitudes. Prediction of the limit strains for the whole range of diameter-to-thickness ratios (D/t) considered in the experiments was achieved by making the amplitude of the non-Axisymmetric Imperfection proportional to (D/t)2/m3 (m is the circumferential wavenumber). Matching all aspects of the experiments required inclusion of the anisotropy measured in the tubes tested through Hill's yield criterion in all models.
F C Bardi - One of the best experts on this subject based on the ideXlab platform.
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plastic buckling of circular tubes under axial compression part ii analysis
International Journal of Mechanical Sciences, 2006Co-Authors: F C Bardi, Stelios KyriakidesAbstract:Abstract In the second part of this study, the evolution of uniform Axisymmetric wrinkling in axially compressed cylinders is modeled using the principle of virtual work. A version of this formulation also allows localization of wrinkling. The model domain is assigned an initial Axisymmetric Imperfection of a chosen amplitude and the wavelength yielded by the first bifurcation check. The solution correctly simulates the growth of wrinkles and results in a limit load instability. The limit strain is influenced by the amplitude of the Imperfection. Beyond the limit load, wrinkling tends to localize, eventually leading to local folding. The possibility of bifurcation of the Axisymmetric solution to non-Axisymmetric buckling modes is examined by using a dedicated bifurcation check. The bifurcation check was found to yield such buckling modes correctly. The evolution of such buckling modes is simulated by a separate non-Axisymmetric model assigned Imperfections with Axisymmetric and nonAxisymmetric components. The domain analyzed is one characteristic wavelength long (2λC). Initially, compression activates mainly Axisymmetric deformation. In the neighborhood of the bifurcation point, non-Axisymmetric deformation starts to develop, eventually leading to a limit load instability. Experimental responses were simulated with accuracy by assigning appropriate values to the two Imperfection amplitudes. Prediction of the limit strains for the whole range of diameter-to-thickness ratios (D/t) considered in the experiments was achieved by making the amplitude of the non-Axisymmetric Imperfection proportional to (D/t)2/m3 (m is the circumferential wavenumber). Matching all aspects of the experiments required inclusion of the anisotropy measured in the tubes tested through Hill's yield criterion in all models.
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Plastic buckling of circular tubes under axial compression—part II: Analysis
International Journal of Mechanical Sciences, 2006Co-Authors: F C Bardi, Stelios Kyriakides, Heedo YunAbstract:Abstract In the second part of this study, the evolution of uniform Axisymmetric wrinkling in axially compressed cylinders is modeled using the principle of virtual work. A version of this formulation also allows localization of wrinkling. The model domain is assigned an initial Axisymmetric Imperfection of a chosen amplitude and the wavelength yielded by the first bifurcation check. The solution correctly simulates the growth of wrinkles and results in a limit load instability. The limit strain is influenced by the amplitude of the Imperfection. Beyond the limit load, wrinkling tends to localize, eventually leading to local folding. The possibility of bifurcation of the Axisymmetric solution to non-Axisymmetric buckling modes is examined by using a dedicated bifurcation check. The bifurcation check was found to yield such buckling modes correctly. The evolution of such buckling modes is simulated by a separate non-Axisymmetric model assigned Imperfections with Axisymmetric and nonAxisymmetric components. The domain analyzed is one characteristic wavelength long (2λC). Initially, compression activates mainly Axisymmetric deformation. In the neighborhood of the bifurcation point, non-Axisymmetric deformation starts to develop, eventually leading to a limit load instability. Experimental responses were simulated with accuracy by assigning appropriate values to the two Imperfection amplitudes. Prediction of the limit strains for the whole range of diameter-to-thickness ratios (D/t) considered in the experiments was achieved by making the amplitude of the non-Axisymmetric Imperfection proportional to (D/t)2/m3 (m is the circumferential wavenumber). Matching all aspects of the experiments required inclusion of the anisotropy measured in the tubes tested through Hill's yield criterion in all models.
Damiano Pasini - One of the best experts on this subject based on the ideXlab platform.
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Elastic thin shells with large Axisymmetric Imperfection: from bifurcation to snap-through buckling
Journal of the Mechanics and Physics of Solids, 2020Co-Authors: Chuan Qiao, Lu Liu, Damiano PasiniAbstract:Abstract Elastic thin shells are well-known for their highly unstable post-buckling, a response that exhausts their pressure bearing capacity and leads to catastrophic collapse. This paper examines elastic thin shells with a large Axisymmetric Imperfection that can escape the classical bifurcation of perfect spherical shells. We employ a shell theory formulation with exact expressions of the middle surface strains, curvature changes, and live pressure along with validating experiments and numerical simulations. The results show that a large Axisymmetric Imperfection in the form of a circular arc can induce snap-through buckling followed by a stable post-buckling that offers increasing resistance to pressure over a large change in volume. In addition, a sensitivity analysis on the role of defect geometry and shell radius to thickness ratio reveals the emergence of four buckling modes. For small Imperfections, bifurcation buckling (mode 1) is dominant and resembles the typical dimple-like mode of perfect spherical shells. For larger Imperfections, the shell attains the maximum pressure at the snap-through buckling where strain localization appears either within the Imperfection (mode 2) or just below (mode 3). In the fourth mode, snap-through buckling precedes the attainment of the maximum pressure following a post-buckling path characterized by a large change of volume that makes the shell harder and stronger. These findings show that harnessing defect geometry and shell radius to thickness ratio can be effective in programming the post-buckling characteristics and transition between buckling modes, thus offering potential routes for the design of soft metamaterials with application to soft robotics and other sectors.
Heedo Yun - One of the best experts on this subject based on the ideXlab platform.
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Plastic buckling of circular tubes under axial compression—part II: Analysis
International Journal of Mechanical Sciences, 2006Co-Authors: F C Bardi, Stelios Kyriakides, Heedo YunAbstract:Abstract In the second part of this study, the evolution of uniform Axisymmetric wrinkling in axially compressed cylinders is modeled using the principle of virtual work. A version of this formulation also allows localization of wrinkling. The model domain is assigned an initial Axisymmetric Imperfection of a chosen amplitude and the wavelength yielded by the first bifurcation check. The solution correctly simulates the growth of wrinkles and results in a limit load instability. The limit strain is influenced by the amplitude of the Imperfection. Beyond the limit load, wrinkling tends to localize, eventually leading to local folding. The possibility of bifurcation of the Axisymmetric solution to non-Axisymmetric buckling modes is examined by using a dedicated bifurcation check. The bifurcation check was found to yield such buckling modes correctly. The evolution of such buckling modes is simulated by a separate non-Axisymmetric model assigned Imperfections with Axisymmetric and nonAxisymmetric components. The domain analyzed is one characteristic wavelength long (2λC). Initially, compression activates mainly Axisymmetric deformation. In the neighborhood of the bifurcation point, non-Axisymmetric deformation starts to develop, eventually leading to a limit load instability. Experimental responses were simulated with accuracy by assigning appropriate values to the two Imperfection amplitudes. Prediction of the limit strains for the whole range of diameter-to-thickness ratios (D/t) considered in the experiments was achieved by making the amplitude of the non-Axisymmetric Imperfection proportional to (D/t)2/m3 (m is the circumferential wavenumber). Matching all aspects of the experiments required inclusion of the anisotropy measured in the tubes tested through Hill's yield criterion in all models.