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Marquardt Method (marquardt + method)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Backcalculating pavement structural properties using a Nelder,Mead simplex search

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 11 2009
Jin-Hak Yi
Abstract A structural integrity assessment technique of pavements that considers the backcalculation of material properties is herein proposed. In order to carry out the backcalculation, a Nelder,Mead simplex (NMS) search is applied to estimate the elastic moduli of layered structures using the deflection data simulated by falling weight deflectometer (FWD) tests. In order to utilize a forward calculation engine of the numerical simulation in the FWD testing, a wave analysis program of layered pavement systems is used based on a spectral element method. The performance of the NMS inversion technique is evaluated based on a comparison with the Levenberg,Marquardt method. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Inverse estimation of material properties for sheet metals

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2004
K. M. Zhao
The main objective of this paper is to estimate the material properties for sheet metals subjected to loading and reverse loading by using an inverse method. Cyclic three-point bending tests are conducted. Bending moments are computed from the measured data, namely, punch stroke, punch load, bending strain and bending angle. Bending moments are also calculated based on the selected constitutive model. Normal anisotropy and non-linear isotropic/kinematic hardening are considered. Material parameters are estimated by minimizing the difference between these two bending moments. Modified Levenberg,Marquardt method is used in the optimization procedure. Stress,strain curves are generated with the material parameters found in this way. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Path-generation of articulated mechanisms by shape and topology variations in non-linear truss representation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2005
A. Kawamoto
Abstract This paper presents studies on an optimization-based method for path-generation of articulated mechanisms. An extended truss ground-structure approach is taken in which both the shape and topology of the truss are designed using cross-sectional areas and nodal positions as design variables. This leads to a technique for simultaneous type and dimensional synthesis of articulated mechanisms. For the analysis part it is essential to control the mechanism configuration so that the mechanism remains within a given configuration space, thus stabilizing the optimization process and resulting in realistic solutions. This can be achieved by using the Levenberg,Marquardt method. The design method is illustrated by a number of design cases for both closed and open input and output paths. Copyright © 2005 John Wiley & Sons, Ltd. [source]

An inverse estimation of initial temperature profile in a polymer process

POLYMER ENGINEERING & SCIENCE, Issue 1 2008
Ali A. Ranjbar
Since one of the most important parameter in polymer processing such as injection stretch blow molding is temperature distribution in the thickness direction, an inverse method has been applied to estimate this profile. This process comprises of four steps. In the first step the preform is injection molded, and in the second and third step it is stretched by a rod to its final length and then inflated and in the last step it is discharged from the mold. In such kind of polymer flows viscous dissipation plays a remarkable role in the evolution of temperature profile. Some theoretical temperature profile has been applied to confirm the validation of the inverse algorithm. Different solution techniques are applied in this article to the inverse problem under consideration, namely: the conjugate gradient and Levenberg,Marquardt method. After the preform is injection molded, which is the first step, it is removed from the mold, which corresponds to time t = 0. At this moment an infrared camera is used to record the surface temperature of the preform with a certain time step. With regard to variation of thermal properties with temperature, the inverse problem becomes nonlinear. These experimental data provided by the infrared camera are then used to estimate the temperature profile at the end of injection process before stretching and inflation took place. POLYM. ENG. SCI., 48:133,140, 2008. © 2007 Society of Plastics Engineers [source]