A study is made of the free vibrations of laminated anisotropic elliptic The analytical formulati... more A study is made of the free vibrations of laminated anisotropic elliptic The analytical formulation is based on a Mindlin-plates with clamped edges. Reissner type plate theory with the effects of transverse shear deformation, rotary inertia, and bending-extensional coupling included. The frequencies and mode shapes are obtained by using the Rayleigh-Ritz technique in conjunction with Hamilton's principle. A computerized symbolic integration approach is used to develop analytic expressions for the stiffness and mass coefficients and is shown to be particularly useful in evaluating the derivatives of the eigenvalues with respect to certain geometric.and material parameters. Numerical results are presented for the case of angle-ply composite plates with skew-symmetric lamination.
A brief review is made of the fundamental concepts and basic issues of parallel processing. Discu... more A brief review is made of the fundamental concepts and basic issues of parallel processing. Discussion focuses on parallel numerical algorithms, performance evaluation of machines and algorithms, and parallelism in finite element computations. A computational strategy is proposed for maximizing the degree of parallelism at different levels of the finite element analysis process including: 1) formulation level (through the use of mixed finite element models); 2) analysis level (through additive decomposition of the different arrays in the governing equations into the contributions to a symmetrized response plus correction terms); 3) numerical algorithm level (through the use of operator splitting techniques and application of iterative processes); and 4) implementation level (through the effective combination of vectorization, multitasking and microtasking, whenever available).
Computational strategies are presented for the modeling and analysis of tires in contact with pav... more Computational strategies are presented for the modeling and analysis of tires in contact with pavement. A procedure is introduced for simple and accurate determination of tire cross-sectional geometric characteristics from a digitally scanned image. Three new strategies for reducing the computational effort in the finite element solution of tire-pavement contact are also presented. These strategies take advantage of the observation that footprint loads do not usually stimulate a significant tire response away from the pavement contact region. The finite element strategies differ in their level of approximation and required amount of computer resources. The effectiveness of the strategies is demonstrated by numerical examples of frictionless and frictional contact of the space shuttle Orbiter nose-gear tire. Both an in-house research code and a commercial finite element code are used in the numerical studies.
Some recent developments in reduction techniques, as applied to predicting the tire contact respo... more Some recent developments in reduction techniques, as applied to predicting the tire contact response and evaluating the sensitivity coefficients of the different response quantities, are reviewed. The sensitivity coefficients measure the sensitivity of the contact response to variations in the geometric and material parameters of the tire. The tire is modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in geometric and material parameters, transverse shear deformation, and geometric nonlinearities included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The elemental arrays are obtained by using a modified two-field, mixed variational principle. For the application of reduction techniques, the tire finite element model is partitioned into two regions. The first region consists of the nodes that are likely to come in contact with the pavement, and the second region includes all the remaining nodes. The reduction technique is used to significantly reduce the degrees of freedom in the second region. The effectiveness of the computational procedure is demonstrated by a numerical example of the frictionless contact response of the space shuttle nose-gear tire, inflated and pressed against a rigid flat surface. Also, the research topics which have high potential for enhancing the effectiveness of reduction techniques are outlined.
The role of computational structures technology (CST) in aerospace design is discussed. The histo... more The role of computational structures technology (CST) in aerospace design is discussed. The history of CST in this area is recapitulated and the major goals of aerospace-related CST are discussed. Current CST activities are examined, including commercial programs. Current trends in aerospace-related CST are addressed.
Economic stresses are forcing many industries to reduce cost and time-to-market, and to insert em... more Economic stresses are forcing many industries to reduce cost and time-to-market, and to insert emerging technologies into their products. Engineers are asked to design faster, ever more complex systems. Hence, there is a need for novel design paradigms and effective design tools to reduce the design and development times. Several computational tools and facilities have been developed to support the design process. Some of these are described in subsequent presentations. The focus of the workshop is on the computational tools and facilities which have high potential for use in future design environment for aerospace systems. The outline for the introductory remarks is given. First, the characteristics and design drivers for future aerospace systems are outlined; second, simulation-based design environment, and some of its key modules are described; third, the vision for the next-generation design environment being planned by NASA, the UVA ACT Center and JPL is presented. The anticipated major benefits of the planned environment are listed; fourth, some of the government-supported programs related to simulation-based design are listed; and fifth, the objectives and format of the workshop are presented.
Computational Science, Engineering & Technology Series
A brief history is given of the status and some recent developments in computing technology. Disc... more A brief history is given of the status and some recent developments in computing technology. Discussion focuses on recent advances in microelectronics, high-performance computing, adaptive/configurable computing, and user-interface hardware and software. Moore's law and the fundamental physical limits of computation are outlined. The emerging paradigms of grid computing, ubiquitous/pervasive computing and autonomic computing are described. Future computing environment and novel non-silicon computing paradigms are outlined.
Discretization Methods in Structural Mechanics, 1990
Novel computational strategies are presented for the analysis of large and complex structures. Th... more Novel computational strategies are presented for the analysis of large and complex structures. The strategies are based on generating the response of the complex structure using large perturbations from that of a simpler model, associated with a simpler structure (or a simpler mathematical/discrete model of the original structure). Numerical examples are presented to demonstrate the effectiveness of the strategies developed.
The potential of using mixed formulations in conjunction with splitting methodologies to substant... more The potential of using mixed formulations in conjunction with splitting methodologies to substantially improve the efficiency of the computational process is discussed. Numerical examples are presented to demonstrate the effectiveness of using mixed formulations in advanced structural applications.
Three recent developments in the sensitivity analysis for the thermomechanical postbuckling respo... more Three recent developments in the sensitivity analysis for the thermomechanical postbuckling response of composite panels are reviewed. The three developments are an effective computational procedure for evaluating hierarchical sensitivity coefficients of the various response quantities with respect to the different laminate, layer, and micromechanical characteristics; an application of reduction methods to the sensitivity analysis of the postbuckling response; and an accurate evaluation of the sensitivity coefficients of transverse shear stresses. Sample numerical results are presented to demonstrate the effectiveness of the computational procedures presented. Some of the future directions for research on sensitivity analysis for the thermomechanical postbuckling response of composite and smart structures are outlined.
International Journal for Numerical Methods in Engineering, 1989
thermomechanical treatment is described, in which the quenching process is mainly concerned. Owin... more thermomechanical treatment is described, in which the quenching process is mainly concerned. Owing to its contents, the book is very useful to those engineers who are involved in bulk metal forming. The theory and the methods are clearly described and explained so that they can be under-stood easily. As a book of metal forming, however. it would be better if sheet metal forming and slipline theory had been included.
International Journal for Numerical Methods in Engineering, 1977
Two aspects of the finite element analysis of mid‐plane symmetrically laminated anisotropic plate... more Two aspects of the finite element analysis of mid‐plane symmetrically laminated anisotropic plates are considered in this paper. The first pertains to exploiting the symmetries exhibited by anisotropic plates in their analysis. The second aspect pertains to the effects of anisotropy and shear deformation on the accuracy and convergence of shear‐flexible displacement finite element models. Numerical results are presented which show the effects of increasing the order of approximating polynomials and of using derivatives of generalized displacements as nodal parameters.
... The analytical formulation is based on the first-oder shear deformation theory and the plate ... more ... The analytical formulation is based on the first-oder shear deformation theory and the plate is ... Then, the membrane strains and curvatures need first derivatives of the shape functions for u0 ... Then, linear shape functions suffice for the in-plane displacements, whereas cubic ones ...
... In: Proc. 35th SDM Conf., Hilton Head, SC, Vol. AIAA-94-1599, pp. 2247-2257 (1994). 26. L. Be... more ... In: Proc. 35th SDM Conf., Hilton Head, SC, Vol. AIAA-94-1599, pp. 2247-2257 (1994). 26. L. Berke, W. Hez and Yon-Han Pao, Automated development of neural net analysis and optimization expert. Comput. Syst. Engng 5, 55-63 (1994). 27. ...
Computer Methods in Applied Mechanics and Engineering, 1996
... of the 34th AIAA ASME ASCE AHS ASC Structures, Structural Dynamics, and Materials Conference,... more ... of the 34th AIAA ASME ASCE AHS ASC Structures, Structural Dynamics, and Materials Conference, La Jolla, CA (April 1522, 1993) 19011905. [16] AK Noor and CM Andersen, Mixed models and reduced selective integration displacement models for nonlinear shell analysis. ...
Computer Methods in Applied Mechanics and Engineering, 1998
A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in ... more A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in laminated plates. The analytical formulation is based on the first-order shear deformation theory and the plate is discretized by using a single-field displacement finite element model. The ...
Computer Methods in Applied Mechanics and Engineering, 1995
A study is made of the effects of variation in the material and geometric parameters of curved sa... more A study is made of the effects of variation in the material and geometric parameters of curved sandwich panels on the accuracy of the static response predicted by nine different modeling appraoches based on two-dimensional shell theories. The standard of comparison is ...
A two-phase computational procedure is presented for the accurate prediction of the vibration fre... more A two-phase computational procedure is presented for the accurate prediction of the vibration frequencies, stresses and deformations in multilayered composite plates. In the first phase a two-dimensional first-order shear deformation theory is used to predict the global ...
A study is made of the free vibrations of laminated anisotropic elliptic The analytical formulati... more A study is made of the free vibrations of laminated anisotropic elliptic The analytical formulation is based on a Mindlin-plates with clamped edges. Reissner type plate theory with the effects of transverse shear deformation, rotary inertia, and bending-extensional coupling included. The frequencies and mode shapes are obtained by using the Rayleigh-Ritz technique in conjunction with Hamilton's principle. A computerized symbolic integration approach is used to develop analytic expressions for the stiffness and mass coefficients and is shown to be particularly useful in evaluating the derivatives of the eigenvalues with respect to certain geometric.and material parameters. Numerical results are presented for the case of angle-ply composite plates with skew-symmetric lamination.
A brief review is made of the fundamental concepts and basic issues of parallel processing. Discu... more A brief review is made of the fundamental concepts and basic issues of parallel processing. Discussion focuses on parallel numerical algorithms, performance evaluation of machines and algorithms, and parallelism in finite element computations. A computational strategy is proposed for maximizing the degree of parallelism at different levels of the finite element analysis process including: 1) formulation level (through the use of mixed finite element models); 2) analysis level (through additive decomposition of the different arrays in the governing equations into the contributions to a symmetrized response plus correction terms); 3) numerical algorithm level (through the use of operator splitting techniques and application of iterative processes); and 4) implementation level (through the effective combination of vectorization, multitasking and microtasking, whenever available).
Computational strategies are presented for the modeling and analysis of tires in contact with pav... more Computational strategies are presented for the modeling and analysis of tires in contact with pavement. A procedure is introduced for simple and accurate determination of tire cross-sectional geometric characteristics from a digitally scanned image. Three new strategies for reducing the computational effort in the finite element solution of tire-pavement contact are also presented. These strategies take advantage of the observation that footprint loads do not usually stimulate a significant tire response away from the pavement contact region. The finite element strategies differ in their level of approximation and required amount of computer resources. The effectiveness of the strategies is demonstrated by numerical examples of frictionless and frictional contact of the space shuttle Orbiter nose-gear tire. Both an in-house research code and a commercial finite element code are used in the numerical studies.
Some recent developments in reduction techniques, as applied to predicting the tire contact respo... more Some recent developments in reduction techniques, as applied to predicting the tire contact response and evaluating the sensitivity coefficients of the different response quantities, are reviewed. The sensitivity coefficients measure the sensitivity of the contact response to variations in the geometric and material parameters of the tire. The tire is modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in geometric and material parameters, transverse shear deformation, and geometric nonlinearities included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The elemental arrays are obtained by using a modified two-field, mixed variational principle. For the application of reduction techniques, the tire finite element model is partitioned into two regions. The first region consists of the nodes that are likely to come in contact with the pavement, and the second region includes all the remaining nodes. The reduction technique is used to significantly reduce the degrees of freedom in the second region. The effectiveness of the computational procedure is demonstrated by a numerical example of the frictionless contact response of the space shuttle nose-gear tire, inflated and pressed against a rigid flat surface. Also, the research topics which have high potential for enhancing the effectiveness of reduction techniques are outlined.
The role of computational structures technology (CST) in aerospace design is discussed. The histo... more The role of computational structures technology (CST) in aerospace design is discussed. The history of CST in this area is recapitulated and the major goals of aerospace-related CST are discussed. Current CST activities are examined, including commercial programs. Current trends in aerospace-related CST are addressed.
Economic stresses are forcing many industries to reduce cost and time-to-market, and to insert em... more Economic stresses are forcing many industries to reduce cost and time-to-market, and to insert emerging technologies into their products. Engineers are asked to design faster, ever more complex systems. Hence, there is a need for novel design paradigms and effective design tools to reduce the design and development times. Several computational tools and facilities have been developed to support the design process. Some of these are described in subsequent presentations. The focus of the workshop is on the computational tools and facilities which have high potential for use in future design environment for aerospace systems. The outline for the introductory remarks is given. First, the characteristics and design drivers for future aerospace systems are outlined; second, simulation-based design environment, and some of its key modules are described; third, the vision for the next-generation design environment being planned by NASA, the UVA ACT Center and JPL is presented. The anticipated major benefits of the planned environment are listed; fourth, some of the government-supported programs related to simulation-based design are listed; and fifth, the objectives and format of the workshop are presented.
Computational Science, Engineering & Technology Series
A brief history is given of the status and some recent developments in computing technology. Disc... more A brief history is given of the status and some recent developments in computing technology. Discussion focuses on recent advances in microelectronics, high-performance computing, adaptive/configurable computing, and user-interface hardware and software. Moore's law and the fundamental physical limits of computation are outlined. The emerging paradigms of grid computing, ubiquitous/pervasive computing and autonomic computing are described. Future computing environment and novel non-silicon computing paradigms are outlined.
Discretization Methods in Structural Mechanics, 1990
Novel computational strategies are presented for the analysis of large and complex structures. Th... more Novel computational strategies are presented for the analysis of large and complex structures. The strategies are based on generating the response of the complex structure using large perturbations from that of a simpler model, associated with a simpler structure (or a simpler mathematical/discrete model of the original structure). Numerical examples are presented to demonstrate the effectiveness of the strategies developed.
The potential of using mixed formulations in conjunction with splitting methodologies to substant... more The potential of using mixed formulations in conjunction with splitting methodologies to substantially improve the efficiency of the computational process is discussed. Numerical examples are presented to demonstrate the effectiveness of using mixed formulations in advanced structural applications.
Three recent developments in the sensitivity analysis for the thermomechanical postbuckling respo... more Three recent developments in the sensitivity analysis for the thermomechanical postbuckling response of composite panels are reviewed. The three developments are an effective computational procedure for evaluating hierarchical sensitivity coefficients of the various response quantities with respect to the different laminate, layer, and micromechanical characteristics; an application of reduction methods to the sensitivity analysis of the postbuckling response; and an accurate evaluation of the sensitivity coefficients of transverse shear stresses. Sample numerical results are presented to demonstrate the effectiveness of the computational procedures presented. Some of the future directions for research on sensitivity analysis for the thermomechanical postbuckling response of composite and smart structures are outlined.
International Journal for Numerical Methods in Engineering, 1989
thermomechanical treatment is described, in which the quenching process is mainly concerned. Owin... more thermomechanical treatment is described, in which the quenching process is mainly concerned. Owing to its contents, the book is very useful to those engineers who are involved in bulk metal forming. The theory and the methods are clearly described and explained so that they can be under-stood easily. As a book of metal forming, however. it would be better if sheet metal forming and slipline theory had been included.
International Journal for Numerical Methods in Engineering, 1977
Two aspects of the finite element analysis of mid‐plane symmetrically laminated anisotropic plate... more Two aspects of the finite element analysis of mid‐plane symmetrically laminated anisotropic plates are considered in this paper. The first pertains to exploiting the symmetries exhibited by anisotropic plates in their analysis. The second aspect pertains to the effects of anisotropy and shear deformation on the accuracy and convergence of shear‐flexible displacement finite element models. Numerical results are presented which show the effects of increasing the order of approximating polynomials and of using derivatives of generalized displacements as nodal parameters.
... The analytical formulation is based on the first-oder shear deformation theory and the plate ... more ... The analytical formulation is based on the first-oder shear deformation theory and the plate is ... Then, the membrane strains and curvatures need first derivatives of the shape functions for u0 ... Then, linear shape functions suffice for the in-plane displacements, whereas cubic ones ...
... In: Proc. 35th SDM Conf., Hilton Head, SC, Vol. AIAA-94-1599, pp. 2247-2257 (1994). 26. L. Be... more ... In: Proc. 35th SDM Conf., Hilton Head, SC, Vol. AIAA-94-1599, pp. 2247-2257 (1994). 26. L. Berke, W. Hez and Yon-Han Pao, Automated development of neural net analysis and optimization expert. Comput. Syst. Engng 5, 55-63 (1994). 27. ...
Computer Methods in Applied Mechanics and Engineering, 1996
... of the 34th AIAA ASME ASCE AHS ASC Structures, Structural Dynamics, and Materials Conference,... more ... of the 34th AIAA ASME ASCE AHS ASC Structures, Structural Dynamics, and Materials Conference, La Jolla, CA (April 1522, 1993) 19011905. [16] AK Noor and CM Andersen, Mixed models and reduced selective integration displacement models for nonlinear shell analysis. ...
Computer Methods in Applied Mechanics and Engineering, 1998
A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in ... more A postprocessing procedure is presented for the evaluation of the transverse thermal stresses in laminated plates. The analytical formulation is based on the first-order shear deformation theory and the plate is discretized by using a single-field displacement finite element model. The ...
Computer Methods in Applied Mechanics and Engineering, 1995
A study is made of the effects of variation in the material and geometric parameters of curved sa... more A study is made of the effects of variation in the material and geometric parameters of curved sandwich panels on the accuracy of the static response predicted by nine different modeling appraoches based on two-dimensional shell theories. The standard of comparison is ...
A two-phase computational procedure is presented for the accurate prediction of the vibration fre... more A two-phase computational procedure is presented for the accurate prediction of the vibration frequencies, stresses and deformations in multilayered composite plates. In the first phase a two-dimensional first-order shear deformation theory is used to predict the global ...
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