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Ontology-Enabled Generation of Simulation Software for a Complex Dynamic System

JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2018年第7期15卷 462-470页

作者： Sankari, S. S. Uma Kumar, P. Sreenivasa Geethaikrishnan, C. Indian Inst Technol Madras Dept Comp Sci & Engn Artificial Intelligence & Database Res Lab Chennai 600036 Tamil Nadu India Indian Space Res Org Vikram Sarabhai Space Ctr Qual Assurance Mission Div Thiruvananthapuram 695022 Kerala India

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Computationally efficient predictions of crystal plasticity based forming limit diagrams using a spectral database

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INTERNATIONAL JOURNAL OF PLASTICITY 2018年 103卷 168-187页

作者： Gupta, Akash Ben Bettaieb, Mohamed Abed-Meraim, Farid Kalidindi, Surya R. Tata Res Dev & Design Ctr Tam Consultancy Serv TCS Res Pune 411013 Maharashtra India Georgia Inst Technol Woodruff Sch Mech Engn Atlanta GA 30332 USA Arts & Metiers Paris Tech CNRS Lab Etud Microstruct & Mecan Mat LEM3 UMR 7239 4 Rue Augustin Presnel F-57078 Metz 3 France Univ Lorraine Lab Excellence Design Alloy Met Low mAss Struct D Lorraine France CNRS Georgia Tech UMI 2958 2-3 Rue Marconi F-57070 Metz France

The present investigation focuses on the development of a fast and robust numerical tool for the prediction of the forming limit diagrams (FLDs) for thin polycrystalline metal sheets using a Taylor-type (full constraints) crystal plasticity model. The incipience of localized necking is numerically determined by the well-known Marciniak-Kuczynski model. The crystal plasticity constitutive equations, on which these computations are based, are known to be highly nonlinear, thus involving computationally very expensive solutions. This presents a major impediment to the wider adoption of crystal plasticity theories in the computation of FLDs. In this work, this limitation is addressed by using a recently developed spectral database approach based on discrete Fourier transforms (DFTs). Significant improvements were made to the prior approach and a new database was created to address this challenge successfully. These extensions are detailed in the present paper. It is shown that the use of the database allows a significant reduction in the computational cost involved in crystal plasticity based FLD predictions (a reduction of about 96% in terms of CPU time).

关键词： Crystal plasticity Viscoplastic material numerical algorithms Localized necking Spectral method

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Compact reconstruction of orientation distributions using generalized spherical harmonics to advance large-scale crystal plasticity modeling: Verification using cubic, hexagonal, and orthorhombic polycrystals

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ACTA MATERIALIA 2018年 155卷 418-432页

作者： Eghtesad, Adnan Barrett, Timothy J. Knezevic, Marko Univ New Hampshire Dept Mech Engn 33 Acad WayKingsbury HallW119 Durham NH 03824 USA

Compaction of crystallographic texture data is highly desirable in crystal plasticity simulations because the computational time involved in such calculations scales linearly with the number of crystal orientations. In a recent publication, we have reported a rigorous procedure for reducing large datasets of crystal orientations for cubic-orthotropic and hexagonal-orthotropic polycrystalline metals using symmetrized generalized spherical harmonics (GSH) functions. The procedure relies on a quantitative description of crystallographic texture using an orientation distribution function (ODF) and its series representation using GSH. The core procedure consists of matching the spectral representation of a fullsize ODF containing any number of crystal orientations with that of an ODF containing a compact set of orientations. In this paper, we generalize the procedure to any crystal structure with no restrictions to sample symmetry. These major extensions are accompanied by dealing with significantly more dimensions as well as imaginary terms. Two approaches for generating an initial set of orientations in the compact ODF are explored, one based on binning of a given fundamental zone in the Bunge-Euler orientation space and another that takes advantage of MTEX to maximize the compaction. The overall procedure has been successfully applied to compaction of large ODFs for cubic, hexagonal, and orthorhombic polycrystalline metals with orthotropic and no sample symmetry. It is quantitatively demonstrated that texture evolution, twin volume fraction evolution, stress-strain response, and geometrical changes of samples can be accurately simulated to large plastic strains with compact ODFs using crystal plasticity finite element models. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Orientation distribution function Microstructures Anisotropic material Crystal plasticity numerical algorithms

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EFFICIENT COMPUTATION OF HIGHER-ORDER CUMULANT TENSORS

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SIAM JOURNAL ON SCIENTIFIC COMPUTING 2018年第3期40卷 A1590-A1610页

作者： Domino, Krzysztof Gawron, Piotr Pawela, Lukasz Polish Acad Sci Inst Theoret & Appl Informat Baltycka 5 PL-44100 Gliwice Poland

In this paper, we introduce a novel algorithm for calculating arbitrary order cumulants of multidimensional data. Since the dth order cumulant can be presented in the form of a d-dimensional tensor, the algorithm is presented using tensor operations. The algorithm provided in the paper takes advantage of supersymmetry of cumulant and moment tensors. We show that the proposed algorithm considerably reduces the computational complexity and the computational memory requirement of cumulant calculation as compared with existing algorithms. For the sizes of interest, the reduction is of the order of d! compared to the naive algorithm.

关键词： high-order cumulants nonnormally distributed data numerical algorithms

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An implicit formulation of the elasto-plastic self-consistent polycrystal plasticity model and its implementation in implicit finite elements

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MECHANICS OF MATERIALS 2019年 136卷 103065-000页

作者： Zecevic, Milovan Knezevic, Marko Univ New Hampshire Dept Mech Engn Durham NH 03824 USA

Elasto-plastic self-consistent (EPSC) polycrystal plasticity theory has been used extensively in understanding and predicting anisotropic thermo-mechanical response and underlying microstructure evolution of polycrystalline metals. This paper describes the first implicit formulation of the EPSC model and its implementation in implicit finite elements. To this end, a suitably defined system of non-linear equations at the single crystal level and that at the polycrystal level homogenizing the single crystal solutions in terms of the rotation-neutralized increments in Cauchy stress and strain are formulated and numerically solved. The implicit EPSC model is first validated using the original explicit EPSC model. Subsequently, the implicit EPSC model is coupled with implicit finite elements (FE) through the use of the user material subroutine in Abaqus. To facilitate the efficient coupling, a stress update algorithm is developed and the consistent tangent stiffness operator is analytically derived. Here, every FE integration point embeds the implicit EPSC constitutive law taking into account microstructure evolution and the directionality of deformation mechanisms acting at the single crystal level. The multi-level FE-EPSC model is benchmarked using the single crystal data for copper and then applied to simulate drawing of a cup from an AA6022-T4 sheet. The implementation and insights from these predictions are presented and discussed in this paper.

关键词： Polycrystalline material Crystal plasticity numerical algorithms Finite elements Deep drawing

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Construction of knotted vortex tubes with the writhe-dependent helicity

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PHYSICS OF FLUIDS 2019年第4期31卷 047101-047101页

作者： Xiong, Shiying Yang, Yue Peking Univ Coll Engn State Key Lab Turbulence & Complex Syst Beijing 100871 Peoples R China Peking Univ CAPT Beijing 100871 Peoples R China Peking Univ BIC ESAT Beijing 100871 Peoples R China

We propose a feasible method for constructing knotted vortex tubes with the finite thickness and arbitrary complexity and develop an accurate algorithm to implement this method in numerical simulations. The central axis of the knotted vortex tube is determined by the parametric equation of a given smooth and non-degenerate closed curve. The helicity of the vortex tube is only proportional to the writhe of the vortex axis, a geometric measure for coiling of vortex tubes. This vortex construction can facilitate the investigation of the conversion of writhe to twist in the helicity evolution of knotted vortex tubes. As examples, we construct velocity-vorticity fields of trefoil, cinquefoil, and septafoil vortex knots. These vortex knots are used as initial conditions in the direct numerical simulation of viscous incompressible flows in a periodic box. In the evolution of vortex knots from simple flows to turbulent-like flows, all the knots are first untied. Then the vortex topology is invariant and the helicity is almost conserved for the trefoil knot, whereas the helicity decays rapidly during the breakdown and coaxial interactions of pinch-off vortex rings for cinquefoil and septafoil knots. Published under license by AIP Publishing.

关键词： Incompressible flow Vortex tube Computational fluid dynamics numerical algorithms Vortex dynamics

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Two definitions of the inner product of modes and their use in calculating non-diffuse reverberant sound fields

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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019年第6期145卷 3330-3340页

作者： Nolan, Melanie Davy, John L. Tech Univ Denmark Dept Elect Engn Acoust Technol Bldg 352 DK-2800 Lyngby Denmark RMIT Univ Sch Sci Melbourne Vic Australia CSIRO Infrastruct Technol Private Bag 10 Clayton Vic 3169 Australia

There are two definitions of the inner product of modal spatial functions used in the literature. Both definitions integrate the product of the modal spatial functions over a line, area, or volume. The only difference is that one of the definitions takes the complex conjugate of one of the modal spatial functions before multiplying the modes together. The definitions are the same if the modal spatial functions are real. If the modal spatial functions are complex, only the definition which takes the complex conjugate is an inner product. If the specific acoustic impedance of the boundaries has a real part, then the modes are only orthogonal with the definition which does not take the complex conjugate, although this definition is not strictly an inner product because the modal spatial functions are complex in this situation. However, this definition of inner product can be used to calculate the coefficients in the modal expansion of the system response. On the other hand, when it comes to calculating the mean pressure squared and the mean sound intensity, the modal spatial functions cross-products cannot be ignored because the modes are not orthogonal for the definition which takes the complex conjugate.

关键词： Acoustical properties Acoustic signal processing Acoustic phenomena Complex analysis Optical absorption Sound source perception Thermal effects Room acoustics Chemically reactive flows numerical algorithms

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On ray tracing for sharp changing media

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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019年第3期146卷 1595-1604页

作者： Ramos Oliveira, Jorge A. Baltazar, Arturo Castelan, Mario CINVESTAV Robot & Manufactura Avanzada Ramos Arizpe 25900 Coahuila Mexico

Ray tracing is an integral part of modern imaging and inversion techniques. Several methods have been proposed depending on the requirements of the application. Some algorithms are best applied to fast changing material properties, like an interface between two differing media, while others are well suited to media with gradually changing properties, like composite materials. In this paper, an enhanced numerical algorithm for ray tracing is presented. Focus is given to solutions involving ordinary differential equations with initial-value conditions. The proposed algorithm is the result of a combination of two classical implementations and the authors show that it is well suited for media with both sharp and gradual changes in the index of refraction. Additionally, the authors present an application of ray path computation by using the technique known as the shooting method.

关键词： Visual system Computer graphics Perturbation theory Optical imaging Composite materials Rotational dynamics numerical algorithms Acoustics Geometrical optics Optical properties

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Efficient calculation of X-ray absorption spectra using Chebyshev-Slepian filter diagonalisation

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JOURNAL OF CHEMICAL PHYSICS 2019年第18期150卷 184115-184115页

作者： Neville, Simon P. Schuurman, Michael S. Univ Ottawa Dept Chem & Biomol Sci 10 Marie Curie Ottawa ON K1N 6N5 Canada Natl Res Council Canada 100 Sussex Dr Ottawa ON K1A 0R6 Canada

The efficient, yet accurate, simulation of X-ray absorption spectra represents a significant challenge for ab initio electronic structure methods. Conventional approaches involve the explicit calculation of all core-excited states spanning the energy range of interest, even though only a small number of these states will contribute appreciably to the spectrum. We here report a different approach, based on a time-independent Chebyshev filter diagonalization scheme, which allows for the X-ray absorption spectrum to be computed without the explicit calculation of the core-excited eigenstates. Furthermore, in a subsequent postprocessing calculation, selected peaks may be analyzed via the calculation of natural transition orbitals, if desired. The scheme presented here is based on a refinement of the time-independent Chebyshev filter diagonalization approach. Previous formulations of this method have been characterized by a requirement for significant user input via the (sometimes unintuitive) tuning of various numerical parameters. To circumvent this, we introduce a new class of filters based on discrete prolate spheroidal sequences. We demonstrate that the resulting method, which we term Chebyshev-Slepian filter diagonalization, makes filter diagonalization essentially a black-box procedure. The Chebyshev-Slepian filter diagonalization method is implemented at the second-order algebraic diagrammatic construction level of theory and validated through the calculation of the X-ray absorption spectra of trifluoroacetonitrile and 1,4-benzoquinone.

关键词： Electronic structure methods Excitation energies X-ray absorption spectroscopy numerical algorithms Oscillator strengths Black-box

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Determining the Optimal Geometry for Producing Isotherms on a Boundary Surface

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2019年第4期33卷 1026-1036页

作者： Huang, Cheng-Hung Li, Yuan-Yin Natl Cheng Kung Univ Dept Syst & Naval Mechatron Engn Tainan 701 Taiwan

A shape-design problem is examined in this study that consists of determining the optimal boundary shape of a conductive body with a heating object or heating substrate that will yield a uniform boundary temperature. The Levenberg-Marquardt method and CFD-ACE+ commercial software are used in this shape-design algorithm. The validity of the design analysis is verified using numerical experiments. Without considering the constraint of the domain area, different test cases examined previously by Mayeli et al. ("Inverse Shape Design for Heat Conduction Problems via the Ball Spine Algorithm," numerical Heat Transfer, Part B: Fundamentals, Vol. 69, No. 3, 2016, pp. 249-269) are reconsidered in this work to justify the validity and superiority of the present algorithm. The estimated results in the present work are then compared with the results given by Mayeli et al. It is found that the difficulty in choosing the best value for the overall underrelaxation factor reported by Mayeli et al. can be avoided by using the present algorithm, and it needs fewer iterations than reported by Mayeli et al. Next, when the constraint of the domain area is considered, the numerical experiments reveal that the optimal boundary shape with uniform temperature requirement can always be obtained.

关键词： Isotherms Conduction numerical Heat Transfer Heat Transfer Coefficients Proton Exchange Membrane Fuel Cells numerical algorithms Steepest Descent Method Newton's Method Heat Sinks Conjugate Gradient Method

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