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GEOMETRICALLY NONLINEAR FINITE ELEMENT MODEL OF SPATIAL THIN-WALLED BEAMS WITH GENERAL OPEN CROSS SECTION 被引量:11
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作者 Xiaofeng Wang Qingshan Yang 《Acta Mechanica Solida Sinica》 SCIE EI 2009年第1期64-72,共9页
Based on the theory of Timoshenko and thin-walled beams, a new finite element model of spatial thin-walled beams with general open cross sections is presented in the paper, in which several factors are included such a... Based on the theory of Timoshenko and thin-walled beams, a new finite element model of spatial thin-walled beams with general open cross sections is presented in the paper, in which several factors are included such as lateral shear deformation, warp generated by nonuni- form torsion and second-order shear stress, coupling of flexure and torsion, and large displacement with small strain. With an additional internal node in the element, the element stiffness matrix is deduced by incremental virtual work in updated Lagrangian (UL) formulation. Numerical examples demonstrate that the presented model well describes the geometrically nonlinear property of spatial thin-walled beams. 展开更多
关键词 spatial beams thin-walled structures geometrically nonlinear finite element stiffness matrix
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Modeling and Free Vibration Behavior of Rotating Composite Thin-walled Closed-section Beams with SMA Fibers 被引量:4
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作者 REN Yongsheng YANG Shulian DU Xianghong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2012年第5期1029-1043,共15页
Smart structure with active materials embedded in a rotating composite thin-walled beam is a class of typical structure which is using in study of vibration control of helicopter blades and wind turbine blades. The dy... Smart structure with active materials embedded in a rotating composite thin-walled beam is a class of typical structure which is using in study of vibration control of helicopter blades and wind turbine blades. The dynamic behavior investigation of these structures has significance in theory and practice. However, so far dynamic study on the above-mentioned structures is limited only the rotating composite beams with piezoelectric actuation. The free vibration of the rotating composite thin-walled beams with shape memory alloy(SMA) fiber actuation is studied. SMA fiber actuators are embedded into the walls of the composite beam. The equations of motion are derived based on Hamilton's principle and the asymptotically correct constitutive relation of single-cell cross-section accounting for SMA fiber actuation. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin's method. The formulation for free vibration analysis includes anisotropy, pitch and precone angle, centrifugal force and SMA actuation effect. Numerical results of natural frequency are obtained for two configuration composite beams. It is shown that natural frequencies of the composite thin-walled beam decrease as SMA fiber volume and initial strain increase and the decrease in natural frequency becomes more significant as SMA fiber volume increases. The actuation performance of SMA fibers is found to be closely related to the rotational speeds and ply-angle. In addition, the effect of the pitch angle appears to be more significant for the lower-bending mode ones. Finally, in all cases, the precone angle appears to have marginal effect on free vibration frequencies. The developed model can be capable of describing natural vibration behaviors of rotating composite thin-walled beam with active SMA fiber actuation. The present work extends the previous analysis done for modeling passive rotating composite thin-walled beam. 展开更多
关键词 free vibration thin-walled composite beams shape memory alloy rotating beams pich angle precone angle
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Nonlinear Free Vibration Analysis of Thin-walled Curved Beam with Non-symmetric Open Cross Section
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作者 段海娟 宋振森 《Journal of Shanghai Jiaotong university(Science)》 EI 2008年第2期150-154,共5页
A finite element formulation was presented for the nonlinear free vibration of thin-walled curved beams with non-symmetric open across section. The kinetic and potential energies were derived by the virtual principle.... A finite element formulation was presented for the nonlinear free vibration of thin-walled curved beams with non-symmetric open across section. The kinetic and potential energies were derived by the virtual principle. The energy function includes the effect of fiexural-torsional coupling, the torsion warping and the shear centre location. For finite element analysis, cubic polynomials were utilized as the shape functions of the two nodal thin-walled curved elements. Each node possesses seven degrees freedom including the warping degree of freedom. The nonlinear eigenvalue problem was solved by the direct iteration technique. The results are compared with those for straight beams as available in the literature. The results for nonlinear free vibration analysis of curved beams for various radii and subtended angle are presented. 展开更多
关键词 nonlinear vibration thin-walled curved beam finite element method virtual principle
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A new finite element of spatial thin-walled beams
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作者 王晓峰 张其林 杨庆山 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2010年第9期1141-1152,共12页
Based on the theories of Timoshenko's beams and Vlasov's thin-walled members, a new spatial thin-walled beam element with an interior node is developed. By independently interpolating bending angles and warp, factor... Based on the theories of Timoshenko's beams and Vlasov's thin-walled members, a new spatial thin-walled beam element with an interior node is developed. By independently interpolating bending angles and warp, factors such as transverse shear deformation, torsional shear deformation and their Coupling, coupling of flexure and torsion, and second shear stress are considered. According to the generalized variational theory of Hellinger-Reissner, the element stiffness matrix is derived. Examples show that the developed model is accurate and can be applied in the finite element analysis of thinwalled structures. 展开更多
关键词 spatial beams thin-walled section stiffness matrix shear deformation coupling of flexure and torsion second shear stress
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Elastic buckling analysis and optimization of thin-walled bamboo-like pipe beam subjected to pure bending
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作者 Yayun YU Dongli MA +2 位作者 Liang ZHANG Xiaopeng YANG Hao GUAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第3期133-152,共20页
In this paper,a stiffening design imitating the bamboo node is proposed for weight reduction of the long composite pipe beam subjected to bending load.The distribution of bamboo nodes can efficiently suppress the oval... In this paper,a stiffening design imitating the bamboo node is proposed for weight reduction of the long composite pipe beam subjected to bending load.The distribution of bamboo nodes can efficiently suppress the ovalization of the section,thus significantly improving the bending resistance of the bamboo.Based on this principle,ring stiffeners are proposed to be fixed to the pipe beam,making the long beam equivalent to the combination of a series of short pipes that suffered less section ovalization.A database of the optimal laminate orientations for different normalized lengths is obtained through optimizations,where the discreteness of the ply count is considered.Based on this database,weight optimizations are conducted,and the optimal designs of beams with and without stiffeners are obtained and compared.The comparison results show that the proposed bamboo-like stiffened beam not only regains a near-linear load–displacement relationship,but also reduces the weight by up to 16%under the same buckling load.In addition,it is found that for the pipe beams with radius-to-thickness ratios of more than 18,increasing the radius leads to a decrease in elastic buckling resistance when the weight remains a constant,which is opposite to the design for strength and stiffness.The model and database developed in this paper can provide a reference for weight reduction design and weight estimation for composite pipe beams. 展开更多
关键词 Composite beam BUCKLING thin-walled structure Unmanned aerial vehicles BAMBOO
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A nonlinear explicit dynamic GBT formulation for modeling impact response of thin-walled steel members
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作者 Duan Liping Zhao Jincheng 《Journal of Southeast University(English Edition)》 EI CAS 2018年第2期237-250,共14页
A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impu... A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impulsive loads.Considering the rate strengthening and thermal softening effects on member impact behavior,a modified Cowper-Symonds model for constructional steels is utilized.The element displacement field is built upon the superposition of GBT cross-section deformation modes,so arbitrary deformations such as cross-section distortions,local buckling and warping shear can all be involved by the proposed model.The amplitude function of each cross-section deformation mode is approximated by the cubic non-uniform B-spline basis functions.The Kirchhoff s thin-plate assumption is utilized in the construction of the bending related displacements.The Green-Lagrange strain tensor and the second Piola-Kirchhoff(PK2)stress tensor are employed to measure deformations and stresses at any material point,where stresses are assumed to be in plane-stress state.In order to verify the effectiveness of the proposed GBT model,three numerical cases involving impulsive loading of the thin-walled parts are given.The GBT results are compared with those of the Ls-Dyna shell finite element.It is shown that the proposed model and the shell finite element analysis has equivalent accuracy in displacement and stress.Moreover,the proposed model is much more computationally efficient and structurally clearer than the shell finite elements. 展开更多
关键词 generalized beam theory impact loading thin-walled steel member explicit dynamic integrations strain rate strengthening effect thermal softening effect
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Application of stiffness matrix of a beam element considering section distortion effect 被引量:2
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作者 李海锋 罗永峰 《Journal of Southeast University(English Edition)》 EI CAS 2010年第3期431-435,共5页
According to the stationary principle of potential energy and the generalized coordinate method, a stiffness matrix of a beam element considering distortion effects is derived. Using the stiffness matrix of the beam e... According to the stationary principle of potential energy and the generalized coordinate method, a stiffness matrix of a beam element considering distortion effects is derived. Using the stiffness matrix of the beam element, a finite element program for computing thin-walled box steel beams is developed. And the program can take the section distortion and warping effects into account. The influences of diaphragm spacing on the mechanical behavior of thin-walled box beams are analyzed by the program. The numerical analysis shows that setting diaphragms have the greatest influence on the distortion normal stress, while there is very little influence on the bending normal stress. Only when the distance of adjacent diaphragms decreases to a certain value, will the distortion normal stress in the thin-walled box beam obviously reduce under the distortion load. Finally, a distortion-warping coefficient γ is introduced for simplifying the calculation of the longitudinal normal stress of thin-walled box beams. When the ratio of diaphragms adjacent space L to the maximum section dimension H is less than 2, the distortion-warping coefficient γ tends to one, which means that the distortion normal stress of the thin-walled box beam tends to zero, and the effect of the section distortion can be ignored. 展开更多
关键词 thin-walled box beam stationary principle of potential energy generalized coordinate method DISTORTION WARPING distortion-warping coefficient
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Finite difference modeling of sinking stage curved beam based on revised Vlasov equations 被引量:1
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作者 张磊 朱真才 +1 位作者 沈刚 曹国华 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第11期4219-4227,共9页
For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with close... For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with closed sections were deduced considering the shear strain on the mid-surface of the cross-section. Then, the finite difference formulation of revised Vlasov equations was implemented with the parabolic interpolation based on Taylor series. At last, the finite difference model was built by substituting geometry and boundary conditions of the sinking stage curved beam into the finite difference formulation. The validity of present work is confirmed by the published literature and ANSYS simulation results. It can be concluded that revised Vlasov equations are more accurate than the original one in the analysis of thin-walled beams with closed sections, and that present finite difference model is applicable in the evaluation of the sinking stage curved beam. 展开更多
关键词 thin-walled curved beam CLOSED CROSS-SECTION sinki
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A new beam element for analyzing geometrical and physical nonlinearity 被引量:3
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作者 Xiao-Feng Wang Qing-Shan Yang Qi-Lin Zhang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2010年第4期605-615,共11页
Based on Timoshenko's beam theory and Vlasov's thin-walled member theory, a new model of spatial thin-walled beam element is developed for analyzing geometrical and physical nonlinearity, which incorporates an inter... Based on Timoshenko's beam theory and Vlasov's thin-walled member theory, a new model of spatial thin-walled beam element is developed for analyzing geometrical and physical nonlinearity, which incorporates an interior node and independent interpolations of bending angles and warp and takes diversified factors into consideration, such as traverse shear deformation, torsional shear deformation and their coupling, coupling of flexure and torsion, and the second shear stress. The geometrical nonlinear strain is formulated in updated Lagarange (UL) and the corresponding stiffness matrix is derived. The perfectly plastic model is used to account for physical nonlinearity, and the yield rule of von Mises and incremental relationship of Prandtle-Reuss are adopted. Elastoplastic stiffness matrix is obtained by numerical integration based on the finite segment method, and a finite element program is compiled. Numerical examples manifest that the proposed model is accurate and feasible in the analysis of thin-walled structures. 展开更多
关键词 Spatial beams thin-walled section beam element Geometrical and physical nonlinearity FEM
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Shear deformable finite beam elements for composite box beams 被引量:2
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作者 Nam-Il Kim Dong-Ho Choi 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2014年第2期223-240,共18页
The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated compo... The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated. 展开更多
关键词 thin-walled Composite box beam Deflection Twisting angle Buckling load Shear deformation
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Feasibility of developing composite action between concrete and cold-formed steel beam
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作者 S.O.Bamaga M.Md.Tahir +6 位作者 T.C.Tan S.Mohammad N.Yahya A.L.Saleh M.Mustaffar M.H.Osman A.B.A.Rahman 《Journal of Central South University》 SCIE EI CAS 2013年第12期3689-3696,共8页
Cold-formed steel structures are steel structure products constructed from sheets or coils using cold rolling, press brake or bending brake method. These structures are extensively employed in building construction in... Cold-formed steel structures are steel structure products constructed from sheets or coils using cold rolling, press brake or bending brake method. These structures are extensively employed in building construction industry due to their light mass, ductility by economic cold forming operations, favorable strength-to-mass ratio and other factors. The utilization of cold formed steel sections with concrete as composite can hugely reduce the construction cost. However, the use of cold formed steel members in composite concrete beams has been very limited. A comprehensive review of developments in composite beam with cold formed steel sections was introduced. It was revealed that employing cold-formed steel channel section to replace reinforcement bars in conventional reinforced concrete beam results in a significant cost reduction without reducing strength capacity. The use of composite beam consisting of cold-formed steel open or close box and filled concrete could also reduce construction cost. Lighter composite girder for bridges with cold-formed steel of U section was introduced. Moreover, types of shear connectors to provide composite action between cold-formed steel beam and concrete slab were presented. However, further studies to investigate the effects of metal decking on the behavior of composite beam with cold-formed steel section and introduction of ductile shear connectors were recommended. 展开更多
关键词 cold formed steel beam composite shear connection thin-wall composite girder
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Restrained torsion of open thin-walled beams including shear deformation effects 被引量:7
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作者 Zhao-qiang WANG Jin-cheng ZHAO +1 位作者 Da-xu ZHANG Jing-hai GONG 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2012年第4期260-273,共14页
A first-order torsion theory based on Vlasov theory has been developed to investigate the restrained torsion of open thin-walled beams. The total rotation of the cross section is divided into a free warping rotation a... A first-order torsion theory based on Vlasov theory has been developed to investigate the restrained torsion of open thin-walled beams. The total rotation of the cross section is divided into a free warping rotation and a restrained shear rotation. In first-order torsion theory, St. Venant torque is only related to the free warping rotation and the expression of St. Venant torque is derived by using a semi-inverse method. The relationship between the warping torque and the restrained shear rotation is established by using an energy method. The torsion shear coefficient is then obtained. On the basis of the torsion equilibrium, the governing differential equation of the restrained torsion is derived and the corresponding initial method is given to solve the equation. The relationship between total rotation and flee warping rotation is obtained. A parameter λ, which is associated with the stiffness property of a cross section and the beam length, is introduced to determine the condition, under which the St. Venant constant is negligible. Consequently a simplified theory is derived. Numerical examples are illustrated to validate the current approach and the results of the current theory are compared with those of some other available methods. The results of comparison show that the current theory provides more accurate results, In the example of a channel-shaped cantilever beam, the applicability of the simplified theory is determined by the parameter study of λ. 展开更多
关键词 thin-walled beam Restrained torsion Shear deformation WARPING Shear coefficient
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A geometrical and physical nonlinear finite element model for spatial thin-walled beams with arbitrary section 被引量:4
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作者 YANG QingShan 1 &WANG XiaoFeng 2 1 School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China 2 College of Civil Engineering,Tongji University,Shanghai 200092,China 《Science China(Technological Sciences)》 SCIE EI CAS 2010年第3期829-838,共10页
Based on the theories of Bernoulli-Euler beams and Vlasov's thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent ... Based on the theories of Bernoulli-Euler beams and Vlasov's thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent interpolations on bending angles and warp,in which factors such as traverse shear deformation,torsional shear deformation and their coupling,coupling of flexure and torsion,and second shear stress are all considered.Thereafter,geometrical nonlinear strain in total Lagarange(TL) and the corresponding stiffness matrix are formulated.Ideal plastic model is applied to physical nonlinearity to comply with the yield rule of Von Mises and incremental relationship of Prandtle-Reuss.Elastoplastic stiffness matrix is derived by numerical integration on the basis of the finite segment method.Examples show that the developed model is feasible in analysis of thin-walled structures with high accuracy. 展开更多
关键词 SPATIAL beams thin-walled structures GEOMETRICAL and PHYSICAL NONLINEARITY finite element ARBITRARY section
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Electroluminescence explored internal behavior of carriers in InGaAsP single-junction solar cell
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作者 李雪飞 杨文献 +5 位作者 龙军华 谭明 金山 吴栋颖 吴渊渊 陆书龙 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第1期539-544,共6页
The internal behaviors of carriers in InGaAsP single-junction solar cell are investigated by using electroluminescence(EL) measurements. Two emission peaks can be observed in current-dependent electroluminescence spec... The internal behaviors of carriers in InGaAsP single-junction solar cell are investigated by using electroluminescence(EL) measurements. Two emission peaks can be observed in current-dependent electroluminescence spectra at low temperatures, and carrier localization exists for both peaks under low excitation. The trends of power index α extracted from excitation-dependent EL spectra at different temperatures imply that there exists a competition between Shockley–Read–Hall recombination and Auger recombination. Auger recombination becomes dominant at high temperatures, which is probably responsible for the lower current density of InGaAsP solar cell. Besides, the anomalous “S-shape” tendency with the temperature of band-edge peak position can be attributed to potential fluctuation and carrier redistribution, demonstrating delocalization, transfer, and redistribution of carriers in the continuum band-edge. Furthermore, the strong reduction of activation energy at high excitations indicates that electrons and holes escaped independently, and the faster-escaping carriers are holes. 展开更多
关键词 ELECTROLUMINESCENCE s-shaped InGaAsP solar cell molecular beam epitaxy
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Unveiling the Mechanism Behind the Asymmetric Bending Compliance of Thin-Walled U-Shaped Strips:A Study Inspired by Plant Leaves
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作者 Anran Wei Zhenbin Guo Fenglin Guo 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2023年第1期156-165,共10页
Inspired by the shape of some plant leaves,we find that the thin-walled U-shaped strips exhibit different compliances under bending with opposite orientations.The asymmetric bending compliance is attributed to the buc... Inspired by the shape of some plant leaves,we find that the thin-walled U-shaped strips exhibit different compliances under bending with opposite orientations.The asymmetric bending compliance is attributed to the buckling of sidewalls of strips caused by the bending-induced compression.Integrating the Euler-Bernoulli beam theory with the Kirchhoff-Love thin plate theory,a theoretical model is derived for the in-depth understanding of the sidewall buckling.For pure bending,the critical moment applied to the strip for the sidewall buckling is found to be insensitive to the height,width and length of strip,which is the result of the compromise between the opposite geometric effects on the buckling behavior of sidewalls and the characteristics of cross sections.Then the critical moment can be approximated as a linear function of flexural rigidity DEt^(3)/12(1-ν^(2)),where t is the wall thickness of strip,E is Young’s modulus,and v is Poisson’s ratio.These predictions by our model agree well with the results obtained by finite element analysis.We also investigate the buckling behavior of sidewalls for bending under transverse loads,considering the loading conditions of concentrated force and distributed force.Our study unveils the mechanism behind the asymmetric bending compliance of thin-walled U-shaped strips.These results would offer convenient guidance for the promising engineering applications related to this structure,such as the design of soft robots with enhanced locomotion performance. 展开更多
关键词 Bending BUCKLING thin-walled beam Thin plate Bioinspired study
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Vibration and flutter of wind turbine blade modeled as anisotropic thin-walled closed-section beam 被引量:4
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作者 LIU TingRui REN YongSheng 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第3期715-722,共8页
Based on a variational asymptotic analytical model, vibration and aeroelastic stability of rotor blades modeled as anisotropic thin-walled closed-section beams are systematically addressed. The analysis is applied to ... Based on a variational asymptotic analytical model, vibration and aeroelastic stability of rotor blades modeled as anisotropic thin-walled closed-section beams are systematically addressed. The analysis is applied to a laminated composite construction of the circumferentially asymmetric stiffness (CAS) that produces bending-twist coupling. The vibration characteristics of composite beam are determined by the Extended Galerkin Method. The unsteady aerodynamic loads and centrifugal force are integrated with the classical aerodynamic model to deal with aeroelastic stability analysis. The influence of some related factors, ply angle, rotating velocity, and wind speed, is investigated. The paper gives methods of eigenvalue analysis and aeroelastic response, and gives the approaches to restrain classical flutter. 展开更多
关键词 Extended Galerkin Method bending-twist coupling circumferentially asymmetric stiffness thin-walled closed-section beam FLUTTER
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