The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Y.k. Cheung - One of the best experts on this subject based on the ideXlab platform.
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Refined discrete quadrilateral degenerated shell element by using Timoshenko's beam function
International Journal for Numerical Methods in Engineering, 2005Co-Authors: Chen Wanji, Y.k. CheungAbstract:A refined discrete degenerated 20-DOF quadrilateral shell element RQS20 is proposed. The exact displacement function of the Timoshenko's beam is used as the displacement on the element boundary. The re-constitute method for shear Strain Matrix is adopted. The proposed element can be used for the analysis of both moderately thick and thin plates/shells, and the convergence for the very thin case can be ensured theoretically. Numerical examples presented show that the new model indeed possesses higher accuracy in the analysis of thin and thick plates/shells, and that it can pass the patch test required for the Kirchhoff thin plate elements. Most important of all, it is free from the membrane and shear locking phenomena for extremely thin plates/shells, on the one hand, and it can also avoid the phenomenon of oscillatory solutions for thick plates/shells case on the other. Copyright © 2005 John Wiley & Sons, Ltd.
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Refined non-conforming triangular elements for analysis of shell structures
International Journal for Numerical Methods in Engineering, 1999Co-Authors: Chen Wanji, Y.k. CheungAbstract:Based on the refined non-conforming element method, simple flat triangular elements with standard nodal displacement parameters are proposed for the analysis of shell structures. For ensuring the convergence of the elements a new coupled continuity condition at the inter-element has been established in a weaker form. A common displacement for the inter-element, an explicit expression of refined constant Strain Matrix, and an adjustable constant are introduced into the formulation, in which the coupled continuity requirement at the inter-element is satisfied in the average sense. The non-conforming displacement function of the well-known triangular plate element BCIZ [1] and the membrane displacement of the constant Strain triangular element CST [2] are employed to derive the refined flat shell elements RTS15, and the refined flat shell elements RTS18 is derived by using the element BCIZ and the Allman's triangular plane element [3] with the drilling degrees of freedom. A simple reduced higher-order membrane Strain Matrix is proposed to avoid membrane locking of the element RTS18. An alternative new reduced higher-order Strain Matrix method is developed to improve the accuracy of the elements RTS15 and RTS18. Numerical examples are given to show that the present methods have improved the accuracy of the shell analysis. Copyright © 1999 John Wiley & Sons, Ltd.
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REFINED QUADRILATERAL DISCRETE KIRCHHOFF THIN PLATE BENDING ELEMENT
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Chen Wanji, Y.k. CheungAbstract:In order to improve the accuracy of the original quadrilateral discrete Kirchhoff thin plate bending element DKQ a simple explicit expression of refined constant Strain Matrix can be introduced into its formulation so as to establish a refined element RDKQ. Numerical examples are presented to show that the present model indeed possesses higher accuracy. © 1997 John Wiley & Sons, Ltd.link_to_subscribed_fulltex
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Refined non‐conforming quadrilateral thin plate bending element
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Chen Wanji, Y.k. CheungAbstract:A refined non-conforming quadrilateral thin plate bending element RPQ4 which can satisfy the requirement of convergence is established such that the non-conforming displacement function can be derived directly. A simple explicit expression of a refined constant Strain Matrix can be introduced into the formulation of the standard displacement element which results in the conStraint condition of interelement continuity being satisfied in an average sense. Numerical examples are presented to show that the present model can pass the patch test and possesses high accuracy. © 1997 John Wiley & Sons, Ltd.link_to_subscribed_fulltex
Chen Wanji - One of the best experts on this subject based on the ideXlab platform.
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Refined discrete quadrilateral degenerated shell element by using Timoshenko's beam function
International Journal for Numerical Methods in Engineering, 2005Co-Authors: Chen Wanji, Y.k. CheungAbstract:A refined discrete degenerated 20-DOF quadrilateral shell element RQS20 is proposed. The exact displacement function of the Timoshenko's beam is used as the displacement on the element boundary. The re-constitute method for shear Strain Matrix is adopted. The proposed element can be used for the analysis of both moderately thick and thin plates/shells, and the convergence for the very thin case can be ensured theoretically. Numerical examples presented show that the new model indeed possesses higher accuracy in the analysis of thin and thick plates/shells, and that it can pass the patch test required for the Kirchhoff thin plate elements. Most important of all, it is free from the membrane and shear locking phenomena for extremely thin plates/shells, on the one hand, and it can also avoid the phenomenon of oscillatory solutions for thick plates/shells case on the other. Copyright © 2005 John Wiley & Sons, Ltd.
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Refined 15‐DOF triangular discrete degenerated shell element with high performances
International Journal for Numerical Methods in Engineering, 2004Co-Authors: Chen WanjiAbstract:A refined discrete degenerated 15-DOF triangular shell element RDTS15 with high performances is proposed. For constructing the element displacement function, the exact displacement function of the Timoshenko's beam is used as the displacement on the element boundary, and the re-constitute method for shear Strain Matrix is adopted. The proposed element can be used in the analysis of both moderate thick and thin plates/shells. Numerical examples presented show that the new model indeed possesses higher accuracy in the analysis of thin and thick plates/shells, and that it can pass the patch test required for the Kirchhoff thin plate elements, and also passed the inf–sup test for free cylindrical shell problems and satisfied both the bending- and membrane-dominated test. Copyright © 2004 John Wiley Sons, Ltd.
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Refined non-conforming triangular elements for analysis of shell structures
International Journal for Numerical Methods in Engineering, 1999Co-Authors: Chen Wanji, Y.k. CheungAbstract:Based on the refined non-conforming element method, simple flat triangular elements with standard nodal displacement parameters are proposed for the analysis of shell structures. For ensuring the convergence of the elements a new coupled continuity condition at the inter-element has been established in a weaker form. A common displacement for the inter-element, an explicit expression of refined constant Strain Matrix, and an adjustable constant are introduced into the formulation, in which the coupled continuity requirement at the inter-element is satisfied in the average sense. The non-conforming displacement function of the well-known triangular plate element BCIZ [1] and the membrane displacement of the constant Strain triangular element CST [2] are employed to derive the refined flat shell elements RTS15, and the refined flat shell elements RTS18 is derived by using the element BCIZ and the Allman's triangular plane element [3] with the drilling degrees of freedom. A simple reduced higher-order membrane Strain Matrix is proposed to avoid membrane locking of the element RTS18. An alternative new reduced higher-order Strain Matrix method is developed to improve the accuracy of the elements RTS15 and RTS18. Numerical examples are given to show that the present methods have improved the accuracy of the shell analysis. Copyright © 1999 John Wiley & Sons, Ltd.
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REFINED QUADRILATERAL DISCRETE KIRCHHOFF THIN PLATE BENDING ELEMENT
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Chen Wanji, Y.k. CheungAbstract:In order to improve the accuracy of the original quadrilateral discrete Kirchhoff thin plate bending element DKQ a simple explicit expression of refined constant Strain Matrix can be introduced into its formulation so as to establish a refined element RDKQ. Numerical examples are presented to show that the present model indeed possesses higher accuracy. © 1997 John Wiley & Sons, Ltd.link_to_subscribed_fulltex
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Refined non‐conforming quadrilateral thin plate bending element
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Chen Wanji, Y.k. CheungAbstract:A refined non-conforming quadrilateral thin plate bending element RPQ4 which can satisfy the requirement of convergence is established such that the non-conforming displacement function can be derived directly. A simple explicit expression of a refined constant Strain Matrix can be introduced into the formulation of the standard displacement element which results in the conStraint condition of interelement continuity being satisfied in an average sense. Numerical examples are presented to show that the present model can pass the patch test and possesses high accuracy. © 1997 John Wiley & Sons, Ltd.link_to_subscribed_fulltex
Gary D Seidel - One of the best experts on this subject based on the ideXlab platform.
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self sensing of elastic Strain Matrix yielding and plasticity in multiwall carbon nanotube vinyl ester composites
Smart Materials and Structures, 2013Co-Authors: J J Kuherrera, F Aviles, Gary D SeidelAbstract:The piezoresistive response of multiwalled carbon nanotube/vinyl ester composites containing 0.3, 0.5 and 1% w/w carbon nanotubes (CNTs) loaded in tension and compression is investigated. The change in electrical resistance (ΔR) under tension loading was positive and showed a linear relationship with the applied Strain up to failure, with slightly increased sensitivity for decreased CNT content. In compression, a nonlinear and non-monotonic piezoresistive behavior was observed, with ΔR initially decreasing in the elastic regime, leveling off at the onset of yielding and increasing after Matrix yielding. The piezoresistive response of the composite is more sensitive to the CNT content for compression than for tension, and the calculated gage factors are higher in the compressive plastic regime. The results show that the piezoresistive signal is dependent on the CNT concentration, loading type and material elastoplastic behavior, and that recording ΔR during mechanical loading can allow self-identification of the elastic and plastic regimes of the composite.
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Self-sensing of elastic Strain, Matrix yielding and plasticity in multiwall carbon nanotube/vinyl ester composites
Smart Materials and Structures, 2013Co-Authors: J. J. Ku-herrera, F Aviles, Gary D SeidelAbstract:The piezoresistive response of multiwalled carbon nanotube/vinyl ester composites containing 0.3, 0.5 and 1% w/w carbon nanotubes (CNTs) loaded in tension and compression is investigated. The change in electrical resistance (ΔR) under tension loading was positive and showed a linear relationship with the applied Strain up to failure, with slightly increased sensitivity for decreased CNT content. In compression, a nonlinear and non-monotonic piezoresistive behavior was observed, with ΔR initially decreasing in the elastic regime, leveling off at the onset of yielding and increasing after Matrix yielding. The piezoresistive response of the composite is more sensitive to the CNT content for compression than for tension, and the calculated gage factors are higher in the compressive plastic regime. The results show that the piezoresistive signal is dependent on the CNT concentration, loading type and material elastoplastic behavior, and that recording ΔR during mechanical loading can allow self-identification of the elastic and plastic regimes of the composite.
Robert L. Taylor - One of the best experts on this subject based on the ideXlab platform.
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A systematic construction of B‐bar functions for linear and non‐linear mixed‐enhanced finite elements for plane elasticity problems
International Journal for Numerical Methods in Engineering, 1999Co-Authors: Reinhard E. Piltner, Robert L. TaylorAbstract:In a previous paper a modified Hu–Washizu variational formulation has been used to derive an accurate four node plane Strain/stress finite element denoted QE2. For the mixed element QE2 two enhanced Strain terms are used and the assumed stresses satisfy the equilibrium equations a priori for the linear elastic case. In this paper an alternative approach is discussed. The new formulation leads to the same accuracy for linear elastic problems as the QE2 element; however it turns out to be more efficient in numerical simulations, especially for large deformation problems. Using orthogonal stress and Strain functions we derive B functions which avoid numerical inversion of matrices. The B-Strain Matrix is sparse and has the same structure as the Strain Matrix B obtained from a compatible displacement field. The implementation of the derived mixed element is basically the same as the one for a compatible displacement element. The only difference is that we have to compute a B-Strain Matrix instead of the standard B-Matrix. Accordingly, existing subroutines for a compatible displacement element can be easily changed to obtain the mixed-enhanced finite element which yields a higher accuracy than the Q4 and QM6 elements. Copyright © 1999 John Wiley & Sons, Ltd.
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a systematic construction of b bar functions for linear and non linear mixed enhanced finite elements for plane elasticity problems
International Journal for Numerical Methods in Engineering, 1999Co-Authors: Reinhard E. Piltner, Robert L. TaylorAbstract:In a previous paper a modified Hu–Washizu variational formulation has been used to derive an accurate four node plane Strain/stress finite element denoted QE2. For the mixed element QE2 two enhanced Strain terms are used and the assumed stresses satisfy the equilibrium equations a priori for the linear elastic case. In this paper an alternative approach is discussed. The new formulation leads to the same accuracy for linear elastic problems as the QE2 element; however it turns out to be more efficient in numerical simulations, especially for large deformation problems. Using orthogonal stress and Strain functions we derive B functions which avoid numerical inversion of matrices. The B-Strain Matrix is sparse and has the same structure as the Strain Matrix B obtained from a compatible displacement field. The implementation of the derived mixed element is basically the same as the one for a compatible displacement element. The only difference is that we have to compute a B-Strain Matrix instead of the standard B-Matrix. Accordingly, existing subroutines for a compatible displacement element can be easily changed to obtain the mixed-enhanced finite element which yields a higher accuracy than the Q4 and QM6 elements. Copyright © 1999 John Wiley & Sons, Ltd.
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A general methodology for deriving shear conStrained Reissner‐Mindlin plate elements
International Journal for Numerical Methods in Engineering, 1992Co-Authors: Eugenio Oñate, O. C. Zienkiewicz, Benjamín Suárez, Robert L. TaylorAbstract:In this paper the necessary requirements for the good behaviour of shear conStrained Reissner–Mindlin plate elements for thick and thin plate situations are re-interpreted and a simple explicit form of the substitute shear Strain Matrix is obtained. This extends the previous work of the authors presented in References 18 and 31. The general methodology is applied to the re-formulation of some well known quadrilateral plate elements and some new triangular and quadrilateral plate elements which show promising features. Some examples of the good behaviour of these elements are given.
Kyung Hyun Choi - One of the best experts on this subject based on the ideXlab platform.
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Finite element simulation of welding processes using a solid-shell element
Journal of Physics D: Applied Physics, 2009Co-Authors: Kyung Hyun ChoiAbstract:A solid-shell finite element (FE), suitable for simulation of arc-welding processes, is developed. The element formulation is based upon the Taylor series expansion of the Strain Matrix, and the so-called hyperelastic formulation is adopted for FE formulation. The B-bar approach is employed and the shear-Strain operator is modified to eliminate various locking modes. The welding constitutive equation, including phase transformation and transformational plasticity, is implemented into the solid-shell element. This shows an excellent performance for large aspect ratios, so that this element surmounts the limitation of the regular solid element with regard to welding, particularly when specimens are subject to welding under mechanical loadings. (Some figures in this article are in colour only in the electronic version)