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A new rate-dependent unidirectional composite model - Application to panels subjected to underwater blast

JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2013年第6期61卷 1305-1318页

作者： Wei, Xiaoding de Vaucorbeil, Alban Phuong Tran Espinosa, Horacio D. Northwestern Univ Dept Mech Engn Evanston IL 60208 USA

In this study, we developed a finite element fluid-structure interaction model to understand the deformation and failure mechanisms of both monolithic and sandwich composite panels. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional glass fiber/matrix composites. The laminate model uses Hashin's fiber failure criterion and a modified Tsai-Wu matrix failure criterion. The composite moduli are degraded using five damage variables, which are updated in the post-failure regime by means of a linear softening law governed by an energy release criterion. A key feature in the formulation is the distinction between fiber rupture and pull-out by introducing a modified fracture toughness, which varies from a fiber tensile toughness to a matrix tensile toughness as a function of the ratio of longitudinal normal stress to effective shear stress. The delamination between laminas is modeled by a strain-rate sensitive cohesive law. In the case of sandwich panels, core compaction is modeled by a crushable foam plasticity model with volumetric hardening and strain-rate sensitivity. These constitutive descriptions were used to predict deformation histories, fiber/matrix damage patterns, and inter-lamina delamination, for both monolithic and sandwich composite panels subjected to underwater blast. The numerical predictions were compared with experimental observations. We demonstrate that the new rate dependent composite damage model captures the spatial distribution and magnitude of damage significantly more accurately than previously developed models. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Damage mechanics Finite element analysis fluid-structure interaction Underwater blast Composite failure Delamination Material strain rate effects

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A meshless finite point method for three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN fluidS 2013年第4期73卷 323-343页

作者： Ortega, Enrique Onate, Eugenio Idelsohn, Sergio Flores, Roberto Univ Politecn Cataluna Int Ctr Numer Methods Engn CIMNE Barcelona 08034 Spain

A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian-Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid-structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： mesh-free adaptivity compressible flow aerodynamics arbitrary Lagrangian-Eulerian (ALE) fluid-structure interaction

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Submerged circular cylindrical shell subjected to two consecutive shock waves: Resonance-like phenomena

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JOURNAL OF fluidS AND structureS 2013年 42卷 70-87页

作者： Iakovlev, S. Seaton, C. T. Sigrist, J. -F. Dalhousie Univ Dept Engn Math & Internetworking Halifax NS B3J 2X4 Canada Indret Dept Dynam Struct CESMAN DCNS Res F-44620 La Montagne France

A submerged evacuated circular cylindrical shell subjected to a sequence of two external shock waves generated at the same source is considered. A semi-analytical model combining the classical methods of mathematical physics with the finite-difference methodology is developed and employed to simulate the interaction. Both the hydrodynamic and structural aspects of the problem are considered, and it is demonstrated that varying the delay between the first and second wavefronts has a very significant effect on the stress-strain state of the structure. In particular, it is shown that for certain values of the delay, the constructive superposition of the elastic waves travelling around the shell results in a 'resonance-like' increase of the structural stress in certain regions. The respective stress can be so high that it sometimes exceeds the overall maximum stress observed in the same structure but subjected to a single-front shock wave with the same parameters, in some cases by as much as 50%. A detailed parametric analysis of the observed phenomenon is carried out, and an easy-to-use diagram summarizing the finding is proposed to aim the pre-design analysis of engineering structures. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Shock waves Stress analysis

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Including fluid shear viscosity in a structural acoustic finite element model using a scalar fluid representation

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JOURNAL OF COMPUTATIONAL PHYSICS 2013年 247卷 248-261页

作者： Cheng, Lei Li, Yizeng Grosh, Karl Univ Michigan Dept Mech Engn Ann Arbor MI 48109 USA Univ Michigan Dept Biomed Engn Ann Arbor MI 48109 USA

An approximate boundary condition is developed in this paper to model fluid shear viscosity at boundaries of coupled fluid-structure system. The effect of shear viscosity is approximated by a correction term to the inviscid boundary condition, written in terms of second order in-plane derivatives of pressure. Both thin and thick viscous boundary layer approximations are formulated;the latter subsumes the former. These approximations are used to develop a variational formation, upon which a viscous finite element method (FEM) model is based, requiring only minor modifications to the boundary integral contributions of an existing inviscid FEM model. Since this FEM formulation has only one degree of freedom for pressure, it holds a great computational advantage over the conventional viscous FEM formulation which requires discretization of the full set of linearized Navier-Stokes equations. The results from thick viscous boundary layer approximation are found to be in good agreement with the prediction from a Navier-Stokes model. When applicable, thin viscous boundary layer approximation also gives accurate results with computational simplicity compared to the thick boundary layer formulation. Direct comparison of simulation results using the boundary layer approximations and a full, linearized Navier-Stokes model are made and used to evaluate the accuracy of the approximate technique. Guidelines are given for the parameter ranges over which the accurate application of the thick and thin boundary approximations can be used for a fluid-structure interaction problem. (C) 2013 Elsevier Inc. All rights reserved.

关键词： fluid viscous boundary layer fluid-structure interaction Structural acoustic Finite element method

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A high-order based boundary condition for dynamic analysis of infinite reservoirs

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COMPUTERS & structureS 2013年 120卷 65-76页

作者： Samii, Ali Lotfi, Vahid Amirkabir Univ Technol Dept Civil & Environm Engn Tehran Iran

An approach for modeling the radiation damping of an infinite acoustic waveguide is the high-order absorbing boundary condition. This approach is employed in this study as a basis for analysis of an infinite water channel. In order to achieve an accurate and efficient approach for this purpose, the imposed boundary condition should have two features: (a) the reservoir's bottom absorption which highly affects the pressure distribution inside the reservoir should be included in the formulation of the ABC;(b) the far-field base excitation, which is a significant factor during the vertical excitation should also be considered in the analysis. By separating the overall hydrodynamic pressure into scattered and incident pressure and involving the scattered term in the formulation of the ABC, an accurate and versatile boundary condition is obtained. This boundary condition is then applied in the analysis of several benchmark examples and the obtained results demonstrate the efficiency of the proposed technique. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Infinite reservoir Acoustic waveguide fluid-structure interaction High-order

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Difference in hemodynamic and wall stress of ascending thoracic aortic aneurysms with bicuspid and tricuspid aortic valve

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JOURNAL OF BIOMECHANICS 2013年第10期46卷 1729-1738页

作者： Pasta, Salvatore Rinaudo, Antonino Luca, Angelo Pilato, Michele Scardulla, Cesare Gleason, Thomas G. Vorp, David A. Fdn Ri MED I-90133 Palermo Italy Univ Palermo Dipartimento Ingn Chim Gest Informat & Meccan I-90128 Palermo Italy Mediterranean Inst Transplantat & Adv Specialized I-90127 Palermo Italy Univ Pittsburgh Dept Cardiothorac Surg Pittsburgh PA 15213 USA Univ Pittsburgh Dept Bioengn Pittsburgh PA 15213 USA

The aortic dissection (AoD) of an ascending thoracic aortic aneurysm (ATAA) initiates when the hemodynamic loads exerted on the aneurysmal wall overcome the adhesive forces holding the elastic layers together. Parallel coupled, two-way fluid structure interaction (FSI) analyses were performed on patient-specific ATAAs obtained from patients with either bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) to evaluate hemodynamic predictors and wall stresses imparting aneurysm enlargement and AoD. Results showed a left-handed circumferential flow with slower-moving helical pattern in the aneurysm's center for BAV ATAAs whereas a slight deviation of the blood flow toward the anterolateral region of the ascending aorta was observed for TAV ATAAs. Blood pressure and wall shear stress were found key hemodynamic predictors of aneurysm dilatation, and their dissimilarities are likely associated to the morphological anatomy of the aortic valve. We also observed discontinues, wall stresses on aneurysmal aorta, which was modeled as a composite with two elastic layers (i.e., inhomogeneity of vessel structural organization). This stress distribution was caused by differences on elastic material properties of aortic layers. Wall stress distribution suggests AoD just above sinotubular junction. Moreover, abnormal flow and lower elastic material properties that are likely intrinsic in BAV individuals render the aneurysm susceptible to the initiation of AoD. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Aortic dissection Ascending thoracic aortic aneurysm Bicuspid aortic valve

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Numerical simulation of flow-induced bi-directional oscillations

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JOURNAL OF fluidS AND structureS 2013年 37卷 220-231页

作者： Lee, Hyun-Boo Lee, Tae-Rin Chang, Yoon-Suk Sungkyunkwan Univ Sch Mech Engn Suwon South Korea Northwestern Univ Dept Mech Engn Evanston IL 60208 USA Kyung Hee Univ Dept Nucl Engn Yongin South Korea

Flow-induced vibration (FIV) by vortex shedding behind a submerged cylinder can lead to damage of nuclear components. With respect to such a serious scenario, various experiments and numerical simulations have been conducted to predict the vibration phenomena. Especially in simulation, the immersed finite element method (IFEM) is a promising approach to solve fluid-structure interaction problems because it needs less computational resources. In this paper, two-dimensional motions of cylinders are simulated by using IFEM to obtain their vibration characteristics. Three benchmark tests such as flow past a fixed circular cylinder, in-line oscillation of a circular cylinder and flow-induced vibration with uni-directional motion are performed to verify the proposed numerical method. Furthermore, bi-directional motions of two horizontally and vertically arranged cylinders as well as that of a single cylinder in fluid flow are analyzed, and then key findings are fully discussed. (c) 2012 Elsevier Ltd. All rights reserved.

关键词： Bi-directional motions Directly coupled Euler-Lagrange method Flow-induced vibration fluid-structure interaction Immersed finite element method

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A direct coupling method for 3D hydroelastic analysis of floating structures

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2013年第13期96卷 842-866页

作者： Kim, Ki-Tae Lee, Phill-Seung Park, K. C. Korea Adv Inst Sci & Technol Div Ocean Syst Engn Taejon 305701 South Korea Univ Colorado Dept Aerosp Engn Sci Boulder CO 80309 USA Univ Colorado Ctr Aerosp Struct Boulder CO 80309 USA

This paper presents a complete formulation for three-dimensional hydrodynamic analysis of floating flexible structures subjected to surface regular waves, as well as other excitation forces, by employing a direct tight coupling method. The continuum mechanics-based finite element method is employed to model floating structures with arbitrary geometries, which can account for the geometric nonlinearities and initial stress effects that result from the hydrostatic analysis, whereas the boundary element method is used for the fluid via total potential formulation. The simplicity and generality of the present formulation are revealed as compared with the conventional formulation. Numerical examples demonstrate the general capability of the formulation proposed. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： fluid-structure interaction hydroelasticity free surface gravity waves direct coupling method total velocity potential Green's function FEM BEM

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Vibrations and stability of a periodically supported rectangular plate immersed in axial flow

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JOURNAL OF fluidS AND structureS 2013年 39卷 391-407页

作者： Tubaldi, E. Amabili, M. McGill Univ Montreal PQ H3A 0C3 Canada Ecole Polythecn Montreal Montreal PQ Canada

Vibrations and stability of a thin rectangular plate, infinitely long and wide, periodically supported in both directions (so that it is composed by an infinite number of supported rectangular plates with slope continuity at the edges) and immersed in axial liquid flow on its upper side is studied theoretically. The flow is bounded by a rigid wall and the model is based on potential flow theory. The Galerkin method is applied to determine the expression of the flow perturbation potential. Then the Rayleigh-Ritz method is used to discretize the system. The stability of the coupled system is analyzed by solving the eigenvalue problem as a function of the flow velocity;divergence instability is detected. The convergence analysis is presented to determine the accuracy of the computed eigenfrequencies and stability limits. Finally, the effects of the plate aspect ratio and of the channel height ratio on the critical velocity giving divergence instability and vibration frequencies are investigated. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Plate Static instability

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A coupled FDM-FEM method for free surface flow interaction with thin elastic plate

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JOURNAL OF MARINE SCIENCE AND TECHNOLOGY 2013年第1期18卷 1-11页

作者： Liao, Kangping Hu, Changhong Kyushu Univ Interdisciplinary Grad Sch Engn Sci Kasuga Fukuoka 8168580 Japan Kyushu Univ Appl Mech Res Inst Kasuga Fukuoka 8168580 Japan

A partitioned approach by the coupling finite difference method (FDM) and the finite element method (FEM) is developed for simulating the interaction between free surface flow and a thin elastic plate. The FDM, in which the constraint interpolation profile method is applied, is used for solving the flow field in a regular fixed Cartesian grid, and the tangent of the hyperbola for interface capturing with the slope weighting scheme is used for capturing free surface. The FEM is used for solving structural deformation of the thin plate. A conservative momentum-exchange method, based on the immersed boundary method, is adopted to couple the FDM and the FEM. Background grid resolution of the thin plate in a regular fixed Cartesian grid is important to the computational accuracy by using this method. A virtual structure method is proposed to improve the background grid resolution of the thin plate. Both of the flow solver and the structural solver are carefully tested and extensive validations of the coupled FDM-FEM method are carried out on a benchmark experiment, a rolling tank sloshing with a thin elastic plate.

关键词： fluid-structure interaction Free surface flow Thin elastic plate Coupled FDM-FEM CIP method Virtual structure method

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