The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform

Jasbir S. Arora - One of the best experts on this subject based on the ideXlab platform.

  • Design Sensitivity Analysis in dynamic thermoviscoelasticity with implicit integration
    International Journal of Solids and Structures, 1996
    Co-Authors: Michael J. Poldneff, Jasbir S. Arora
    Abstract:

    Design Sensitivity equations for coupled thermoviscoelastic systems are discretized via the finite element method. The approach is developed for structural systems by using the total Lagrangian approach and the reference domain concept. The discretization is based on implicit integration schemes. The implementation of finite element and Design Sensitivity Analysis utilizes the Christensen-Naghdi free energy function and the direct differentiation approach, which is most suitable for the systems under consideration. A relationship between the discretized Sensitivity equations and the equations for the original Analysis is shown. Use of the same discretization for Analysis and Sensitivity Analysis is emphasized. Partial derivatives of the right-hand side required for Sensitivity calculations are implemented via the central difference method, which provides greater flexibility without sacrificing accuracy. Examples of Analysis and Design Sensitivity Analysis for a thermoviscoelastic non-linear truss and a plate with a hole are given. The calculated Sensitivity results are verified by comparison with overall finite difference calculations.

  • Structural Design Sensitivity Analysis: Continuum and Discrete Approaches
    Advances in Structural Optimization, 1995
    Co-Authors: Jasbir S. Arora
    Abstract:

    A unified approach for structural Design Sensitivity Analysis involving both shape and sizing variables is presented. Starting with a continuum formulation and a general response functional needing Sensitivity Analysis, the direct variation and adjoint approaches are derived. Discretization of the continuum expressions for the two approaches is presented and the numerical implementation aspects are discussed. The discretized forms of the continuum Sensitivity expressions are compared with the ones obtained by starting with the discretized model ab initio. This comparison shows that the two approaches give similar discretized expressions for numerical calculations. Therefore, exactly same procedures can be used for computer implementation of both the approaches. The continuum approach, however, gives certain insights that would not be possible with only the discrete approach. The presented analyses and insights lead to a unified view point for numerical implementation of Design Sensitivity Analysis which is quite straightforward with existing or new finite element Analysis codes. The explicit Design variations (partial derivatives with respect to the Design variables) of the internal and external nodal forces are the major calculations needed to implement the Design Sensitivity Analysis. An implementation scheme is suggested that is quite general and simple needing minimal programming.

  • Design Sensitivity Analysis for dynamic thermoviscoelastic problems
    5th Symposium on Multidisciplinary Analysis and Optimization, 1994
    Co-Authors: Michael J. Poldneff, Jasbir S. Arora
    Abstract:

    Design Sensitivity equations for coupled thermoviscoelastic systems are discretized via finite element method. The approach is developed for structural systems using the total Lagrangian approach and the reference domain concept. The temporal discretization is based on the implicit integration schemes. The implementation of finite element and Design Sensitivity Analysis utilizes the ChristensenNaghdi free energy function and the direct differentiation approach which is most suitable for the systems under consideration. A relationship between the discretized Sensitivity equations and the equations for the original Analysis is shown. Partial derivatives of the right hand side required for Sensitivity calculations are implemented via the central difference method which provides greater flexibility without sacrificing accuracy. Example of Analysis and Design Sensitivity Analysis for a thermoviscoelastic nonlinear truss is given. The calculated Sensitivity results are verified by comparison with overall finite difference calculations.

  • Design Sensitivity Analysis of elastoplastic structures
    International Journal for Numerical Methods in Engineering, 1994
    Co-Authors: Makoto Ohsaki, Jasbir S. Arora
    Abstract:

    An iterative and incremental algorithm is presented for the Design Sensitivity Analysis (DSA) of elastoplastic structures. Geometrical non-linearity is included in the formulation, and the structure may be subjected to a cyclic loading. The key concept is discussed using an elastoplastic truss. It is shown that the Design Sensitivity Coefficients (DSCs) are path-dependent and discontinuous at the time at which yielding takes place in a member (yield time). In the proposed algorithm, the yield time is considered to be a function of the Design variables. In this way, the discontinuity in the DSCs at the material transition points can be overcome in a simple and routine way. Incremental response Analysis and DSA are carried out simultaneously using the Newton–Raphson type iterative procedure. Since the proposed algorithm is completely consistent with the Analysis procedure, it can be implemented into an existing code for structural Analysis. Application to distributed parameter structures with kinematic and/or isotropic hardening is discussed using the von Mises yield condition and the elastic-predictor radial-return method. DSA is carried out for a ten-bar truss with a piecewise linear constitutive relation. It is shown that the DSCs found using the proposed method agree quite well with those calculated by the central difference method. Finally, an alternate method without any iteration for DSA is proposed and the results from the two methods are compared.

  • Shape Design Sensitivity Analysis of viscoplastic structures
    Computer Methods in Applied Mechanics and Engineering, 1993
    Co-Authors: Jasbir S. Arora, V Kumar
    Abstract:

    Abstract Design Sensitivity Analysis of nonlinear viscoplastic structures is developed in the continuum form starting from Hamilton's principle. Constitutive models based on internal variable theory are incorporated in response Analysis. Such models are described by a set of first order nonlinear differential equations with respect to time and some of them allow development of the yield surface. The direct variation method is employed to obtain the Sensitivity of the response. Discretization of the Analysis and Sensitivity equations, and computer implementation aspects are discussed. The discretized equations are implemented into a computer program and two numerical examples are solved to demonstrate the theory. In the numerical examples, only material nonlinearity under quasi-static loading history is considered and the explicit integration method is employed to integrate the constitutive equations and their Design variations. The accuracy and efficiency of the developed Sensitivity Analysis are compared with the central finite difference method. Cyclic loading and loading rate effects are studied and discussed to show the general applicability of the developed Sensitivity formulation.

Kyung K. Choi - One of the best experts on this subject based on the ideXlab platform.

  • Continuum-Based Design Sensitivity Analysis and Optimization of Springback in Stamping Process
    Volume 2: 31st Design Automation Conference Parts A and B, 2005
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    The springback is a significant manufacturing defect in the stamping process. A serious impediment to the use of lighter-weight, higher-strength materials in manufacturing is the relative lack of understanding about how these materials respond to the complex forming process. The springback problem can be reduced by using appropriate Designs of die, punch, and blank holder shape together with friction and blank holding force. That is, an optimum stamping process can be determined using a gradient-based optimization to minimize the springback. However, for an effective optimization of the stamping process, development of an efficient analytical Design Sensitivity Analysis method is crucial. In this paper, a continuum-based shape and configuration Design Sensitivity Analysis (DSA) method for the stamping process has been developed. The material derivative concept is used to develop the continuum-based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step in the finite deformation elastoplastic nonlinear Analysis with frictional contact, which makes the Design Sensitivity calculation very efficient. The accuracy and efficiency of the proposed method is illustrated by minimizing springback in an S-rail part, which is often used as an industrial benchmark to verify the numerical procedures employed for stamping processes.Copyright © 2005 by ASME

  • Design Sensitivity Analysis for sequential structural acoustic problems
    Journal of Sound and Vibration, 2003
    Co-Authors: Nam H. Kim, Kyung K. Choi, Jun Dong, Nickolas Vlahopoulos, Matthew P. Castanier, Christophe Pierre
    Abstract:

    Abstract A Design Sensitivity Analysis of a sequential structural–acoustic problem is presented in which structural and acoustic behaviors are de-coupled. A frequency-response Analysis is used to obtain the dynamic behavior of an automotive structure, while the boundary element method is used to solve the pressure response of an interior, acoustic domain. For the purposes of Design Sensitivity Analysis, a direct differentiation method and an adjoint variable method are presented. In the adjoint variable method, an adjoint load is obtained from the acoustic boundary element re-Analysis, while the adjoint solution is calculated from the structural dynamic re-Analysis. The evaluation of pressure Sensitivity only involves a numerical integration process for the structural part. The proposed Sensitivity results are compared to finite difference Sensitivity results with excellent agreement.

  • Design Sensitivity Analysis of Nonlinear Shell Structure With Frictionless Contact
    Volume 2: 29th Design Automation Conference Parts A and B, 2003
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    A continuum-based shape and configuration Design Sensitivity Analysis method for a finite deformation elastoplastic shell structure with frictionless contact has been developed. Shell elastoplasticity is treated based on the projection method that performs the return mapping on the subspace defined by the zero-normal stress condition. An incrementally objective integration scheme is used in the context of finite deformation shell Analysis, wherein stress objectivity is preserved for finite rotation increments. The penalty regularization method is used to approximate the contact variational inequality. The material derivative concept is used to develop continuum based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step. Numerical implementation of the proposed shape and configuration Design Sensitivity Analysis is carried out using the meshfree method. The accuracy and efficiency of the proposed method is illustrated using numerical examples.© 2003 ASME

  • Design Sensitivity Analysis for sequential structural–acoustic problems
    Journal of Sound and Vibration, 2003
    Co-Authors: Nam H. Kim, Kyung K. Choi, Jun Dong, Nickolas Vlahopoulos, Matthew P. Castanier, Christophe Pierre
    Abstract:

    Abstract A Design Sensitivity Analysis of a sequential structural–acoustic problem is presented in which structural and acoustic behaviors are de-coupled. A frequency-response Analysis is used to obtain the dynamic behavior of an automotive structure, while the boundary element method is used to solve the pressure response of an interior, acoustic domain. For the purposes of Design Sensitivity Analysis, a direct differentiation method and an adjoint variable method are presented. In the adjoint variable method, an adjoint load is obtained from the acoustic boundary element re-Analysis, while the adjoint solution is calculated from the structural dynamic re-Analysis. The evaluation of pressure Sensitivity only involves a numerical integration process for the structural part. The proposed Sensitivity results are compared to finite difference Sensitivity results with excellent agreement.

  • Meshfree Analysis and Design Sensitivity Analysis for shell structures
    International Journal for Numerical Methods in Engineering, 2002
    Co-Authors: Nam H. Kim, Jiun-shyan Chen, Kyung K. Choi, Mark E. Botkin
    Abstract:

    A unified Design Sensitivity Analysis method for a meshfree shell structure with respect to size, shape, and configuration Design variables is presented in this paper. A shear deformable shell formulation is characterized by a CAD connection, thickness degeneration, meshfree discretization, and nodal integration. Because of a strong connection to the CAD tool, the Design variable is selected from the CAD parameters, and a consistent Design velocity field is then computed by perturbing the surface geometric matrix. The material derivative concept is utilized in order to obtain a Design Sensitivity equation in the parametric domain. Numerical examples show the accuracy and efficiency of the proposed Design Sensitivity Analysis method compared to the analytical solution and the finite difference solution. Copyright © 2002 John Wiley & Sons, Ltd.

Douglas E Smith - One of the best experts on this subject based on the ideXlab platform.

  • Design Sensitivity Analysis and optimization for polymer sheet extrusion and mold filling processes
    International Journal for Numerical Methods in Engineering, 2003
    Co-Authors: Douglas E Smith
    Abstract:

    A polymer processing Design methodology is presented which can be used to improve the production of plastic components manufactured via extrusion and injection molding processes. The Design method combines polymer process modelling, Design Sensitivity Analysis and numerical optimization. It is applicable to systems with creeping flow of purely viscous non-Newtonian fluids through thin cavities where the lubrication approximation may be applied. An Analysis and an adjoint Design Sensitivity Analysis are presented for the steady-state coupled system which describes the pressure and residence time distributions in sheeting dies. The resulting methodology is then used to define the optimal die cavity shape and relevant process parameters in a sheeting die Design example. A second example considers tooling and process Design for the polymer injection molding process. A coupled transient mold filling Analysis and Design Sensitivity Analysis based on the direct differentiation method are developed where attention is given to describing the location of the gates in the mold cavity. The latter is illustrated through the process Design of a plastic automotive component. Copyright © 2003 John Wiley & Sons, Ltd.

  • Design Sensitivity Analysis and optimization for polymer sheet extrusion and mold filling processes
    International Journal for Numerical Methods in Engineering, 2003
    Co-Authors: Douglas E Smith
    Abstract:

    A polymer processing Design methodology is presented which can be used to improve the production of plastic components manufactured via extrusion and injection molding processes. The Design method combines polymer processmodelling, Design Sensitivity Analysis and numerical optimization. It is applicable to systems with creeping flow of purely viscous non-Newtonian fluids through thin cavities where the lubrication approximation may be applied. An Analysis and an adjoint Design Sensitivity Analysis are presented for the steady-state coupled system which describes the pressure and residence time distributions in sheeting dies. The resulting methodology is then used to define the optimal die cavity shape and relevant process parameters in a sheeting die Design example. A second example considers tooling and process Design for the polymer injection molding process. A coupled transient mold filling Analysis and Design Sensitivity Analysis based on the direct differentiation method are developed where attention is given to describing the location of the gates in the mold cavity. The latter is illustrated through the process Design of a plastic automotive component.

Nam H. Kim - One of the best experts on this subject based on the ideXlab platform.

  • Continuum-Based Design Sensitivity Analysis and Optimization of Springback in Stamping Process
    Volume 2: 31st Design Automation Conference Parts A and B, 2005
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    The springback is a significant manufacturing defect in the stamping process. A serious impediment to the use of lighter-weight, higher-strength materials in manufacturing is the relative lack of understanding about how these materials respond to the complex forming process. The springback problem can be reduced by using appropriate Designs of die, punch, and blank holder shape together with friction and blank holding force. That is, an optimum stamping process can be determined using a gradient-based optimization to minimize the springback. However, for an effective optimization of the stamping process, development of an efficient analytical Design Sensitivity Analysis method is crucial. In this paper, a continuum-based shape and configuration Design Sensitivity Analysis (DSA) method for the stamping process has been developed. The material derivative concept is used to develop the continuum-based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step in the finite deformation elastoplastic nonlinear Analysis with frictional contact, which makes the Design Sensitivity calculation very efficient. The accuracy and efficiency of the proposed method is illustrated by minimizing springback in an S-rail part, which is often used as an industrial benchmark to verify the numerical procedures employed for stamping processes.Copyright © 2005 by ASME

  • Design Sensitivity Analysis for sequential structural acoustic problems
    Journal of Sound and Vibration, 2003
    Co-Authors: Nam H. Kim, Kyung K. Choi, Jun Dong, Nickolas Vlahopoulos, Matthew P. Castanier, Christophe Pierre
    Abstract:

    Abstract A Design Sensitivity Analysis of a sequential structural–acoustic problem is presented in which structural and acoustic behaviors are de-coupled. A frequency-response Analysis is used to obtain the dynamic behavior of an automotive structure, while the boundary element method is used to solve the pressure response of an interior, acoustic domain. For the purposes of Design Sensitivity Analysis, a direct differentiation method and an adjoint variable method are presented. In the adjoint variable method, an adjoint load is obtained from the acoustic boundary element re-Analysis, while the adjoint solution is calculated from the structural dynamic re-Analysis. The evaluation of pressure Sensitivity only involves a numerical integration process for the structural part. The proposed Sensitivity results are compared to finite difference Sensitivity results with excellent agreement.

  • Design Sensitivity Analysis of Nonlinear Shell Structure With Frictionless Contact
    Volume 2: 29th Design Automation Conference Parts A and B, 2003
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    A continuum-based shape and configuration Design Sensitivity Analysis method for a finite deformation elastoplastic shell structure with frictionless contact has been developed. Shell elastoplasticity is treated based on the projection method that performs the return mapping on the subspace defined by the zero-normal stress condition. An incrementally objective integration scheme is used in the context of finite deformation shell Analysis, wherein stress objectivity is preserved for finite rotation increments. The penalty regularization method is used to approximate the contact variational inequality. The material derivative concept is used to develop continuum based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step. Numerical implementation of the proposed shape and configuration Design Sensitivity Analysis is carried out using the meshfree method. The accuracy and efficiency of the proposed method is illustrated using numerical examples.© 2003 ASME

  • Design Sensitivity Analysis for sequential structural–acoustic problems
    Journal of Sound and Vibration, 2003
    Co-Authors: Nam H. Kim, Kyung K. Choi, Jun Dong, Nickolas Vlahopoulos, Matthew P. Castanier, Christophe Pierre
    Abstract:

    Abstract A Design Sensitivity Analysis of a sequential structural–acoustic problem is presented in which structural and acoustic behaviors are de-coupled. A frequency-response Analysis is used to obtain the dynamic behavior of an automotive structure, while the boundary element method is used to solve the pressure response of an interior, acoustic domain. For the purposes of Design Sensitivity Analysis, a direct differentiation method and an adjoint variable method are presented. In the adjoint variable method, an adjoint load is obtained from the acoustic boundary element re-Analysis, while the adjoint solution is calculated from the structural dynamic re-Analysis. The evaluation of pressure Sensitivity only involves a numerical integration process for the structural part. The proposed Sensitivity results are compared to finite difference Sensitivity results with excellent agreement.

  • Meshfree Analysis and Design Sensitivity Analysis for shell structures
    International Journal for Numerical Methods in Engineering, 2002
    Co-Authors: Nam H. Kim, Jiun-shyan Chen, Kyung K. Choi, Mark E. Botkin
    Abstract:

    A unified Design Sensitivity Analysis method for a meshfree shell structure with respect to size, shape, and configuration Design variables is presented in this paper. A shear deformable shell formulation is characterized by a CAD connection, thickness degeneration, meshfree discretization, and nodal integration. Because of a strong connection to the CAD tool, the Design variable is selected from the CAD parameters, and a consistent Design velocity field is then computed by perturbing the surface geometric matrix. The material derivative concept is utilized in order to obtain a Design Sensitivity equation in the parametric domain. Numerical examples show the accuracy and efficiency of the proposed Design Sensitivity Analysis method compared to the analytical solution and the finite difference solution. Copyright © 2002 John Wiley & Sons, Ltd.

Mark E. Botkin - One of the best experts on this subject based on the ideXlab platform.

  • Continuum-Based Design Sensitivity Analysis and Optimization of Springback in Stamping Process
    Volume 2: 31st Design Automation Conference Parts A and B, 2005
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    The springback is a significant manufacturing defect in the stamping process. A serious impediment to the use of lighter-weight, higher-strength materials in manufacturing is the relative lack of understanding about how these materials respond to the complex forming process. The springback problem can be reduced by using appropriate Designs of die, punch, and blank holder shape together with friction and blank holding force. That is, an optimum stamping process can be determined using a gradient-based optimization to minimize the springback. However, for an effective optimization of the stamping process, development of an efficient analytical Design Sensitivity Analysis method is crucial. In this paper, a continuum-based shape and configuration Design Sensitivity Analysis (DSA) method for the stamping process has been developed. The material derivative concept is used to develop the continuum-based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step in the finite deformation elastoplastic nonlinear Analysis with frictional contact, which makes the Design Sensitivity calculation very efficient. The accuracy and efficiency of the proposed method is illustrated by minimizing springback in an S-rail part, which is often used as an industrial benchmark to verify the numerical procedures employed for stamping processes.Copyright © 2005 by ASME

  • Design Sensitivity Analysis of Nonlinear Shell Structure With Frictionless Contact
    Volume 2: 29th Design Automation Conference Parts A and B, 2003
    Co-Authors: Kyung K. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    A continuum-based shape and configuration Design Sensitivity Analysis method for a finite deformation elastoplastic shell structure with frictionless contact has been developed. Shell elastoplasticity is treated based on the projection method that performs the return mapping on the subspace defined by the zero-normal stress condition. An incrementally objective integration scheme is used in the context of finite deformation shell Analysis, wherein stress objectivity is preserved for finite rotation increments. The penalty regularization method is used to approximate the contact variational inequality. The material derivative concept is used to develop continuum based Design Sensitivity. The Design Sensitivity equation is solved without iteration at each converged load step. Numerical implementation of the proposed shape and configuration Design Sensitivity Analysis is carried out using the meshfree method. The accuracy and efficiency of the proposed method is illustrated using numerical examples.© 2003 ASME

  • Meshfree Analysis and Design Sensitivity Analysis for shell structures
    International Journal for Numerical Methods in Engineering, 2002
    Co-Authors: Nam H. Kim, Jiun-shyan Chen, Kyung K. Choi, Mark E. Botkin
    Abstract:

    A unified Design Sensitivity Analysis method for a meshfree shell structure with respect to size, shape, and configuration Design variables is presented in this paper. A shear deformable shell formulation is characterized by a CAD connection, thickness degeneration, meshfree discretization, and nodal integration. Because of a strong connection to the CAD tool, the Design variable is selected from the CAD parameters, and a consistent Design velocity field is then computed by perturbing the surface geometric matrix. The material derivative concept is utilized in order to obtain a Design Sensitivity equation in the parametric domain. Numerical examples show the accuracy and efficiency of the proposed Design Sensitivity Analysis method compared to the analytical solution and the finite difference solution. Copyright © 2002 John Wiley & Sons, Ltd.

  • Design Sensitivity Analysis for the Meshfree Shell Structure
    Volume 2A: 27th Design Automation Conference, 2001
    Co-Authors: K.k. Choi, Nam H. Kim, Mark E. Botkin
    Abstract:

    Abstract A unified Design Sensitivity Analysis method for a meshfree shell structure with respect to sizing, shape, and configuration Design variables is presented in this paper. A shear deformable shell formulation is characterized by a CAD connection, thickness degeneration, meshfree discretization, and nodal integration. The Design variable is selected from the CAD parameters, and a consistent Design velocity field is then computed by perturbing the surface geometric matrix. The material derivative concept is used to obtain a Design Sensitivity equation in the parametric domain. Numerical examples show the accuracy and efficiency of the proposed Design Sensitivity Analysis method compared to the analytical solution and the finite difference solution.