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  • 1
    Electronic Resource
    Electronic Resource
    State-space representation and optimal control of non-linear material deformation using the finite element method (1993)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 36 (1993), S. 1967-1986 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A state-space model for representing the non-linear material deformation and an optimal control scheme for obtaining desired process conditions in the deforming material are presented in this paper. The formulation is general for various metal-forming processes including forging and extrusion operations. The state variables selected in the formulation are the die/billet contact nodal velocities and the nodal velocities of the critical finite elements of the billet. The control input is the ram velocity, which is determined by using the linear quadratic regulator (LQR) theory to maintain desired strain rates within the selected finite elements. The influence of an optimally designed ram velocity on the deforming material is studied using performance measures. This paper includes the development of the state-space model from non-linear finite element formulation, optimal control strategy and numerical example cases with discussions.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620361202
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Design of optimal process parameters for non-isothermal forging (1994)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 155-177 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a state space model and an optimal design scheme for non-isothermal metal forming processes. By selecting nodal velocity and temperature as the state variables, a non-isothermal state equation with coupled deformation and thermal terms is established. Based on this state space model, a control design scheme is developed to obtain the optimal die velocity and initial die temperature which will ensure that the effective strain-rate and temperature satisfy the design requirements. A titanium alloy engine disk forging is used to demonstrate two design examples. The results show that the proposed model and design scheme behave well for different design requirements.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620370111
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    p-ADAPTIVITY IN THE TIME DOMAIN USING MVpq MULTIVALUE TIME-MARCHING INTEGRATORS (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 2343-2367 
    Details
    ISSN: 0029-5981
    Keywords: transient ; time-marching ; single-step ; hierarchical ; p-adaptivity ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A unified set of MVpq multivalue algorithms for a single-step time-marching scheme is presented for the transient diffusion equation. These MVpq algorithms include the well-known SSij single-step algorithms as a special case. Non-uniform integrators are introduced in which discrete equations in the o.d.e. set each separately use a different order of integrator. Hierarchical variables are used in the time domain, firstly to facilitate non-uniform integrators and secondly to permit variable length timesteps. This paper is the first in a series. In the sequel (Part 2)17 error estimates are introduced and the non-uniform integrator concept is utilized to implement p-adaptivity in time. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    A fast solution method for three-dimensional many-particle problems of linear elasticity (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 42 (1998), S. 1215-1229 
    Details
    ISSN: 0029-5981
    Keywords: boundary element method ; fast multipole method ; many-particle problem ; linear elasticity ; iterative solution strategy ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A boundary element method for solving three-dimensional linear elasticity problems that involve a large number of particles embedded in a binder is introduced. The proposed method relies on an iterative solution strategy in which matrix-vector multiplication is performed with the fast multipole method. As a result the method is capable of solving problems with N unknowns using only O(N) memory and O(N) operations. Results are given for problems with hundreds of particles in which N=O(105). © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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