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Coupling of WCSPH and RKPM for the simulation of incompressible fluid-structure interactions

JOURNAL OF FLUIDS AND STRUCTURES 2021年 102卷 103254-103254页

作者： Peng, Yu-Xiang Zhang, A. -Man Wang, Shi-Ping Harbin Engn Univ Coll Shipbldg Engn Harbin 150001 Peoples R China

A 2D fluid-structure interaction (FSI) solver based on Smoothed particle Hydrodynamics (SPH) and RKPM is established in this paper. Since we focus on the incompressible flow problem, the WCSPH is adopted to simulate the fluid. Meanwhile, the structure is modeled by the RKPM beam formulation, in which the plane strain hypothesis is adopted, and only a column of particles is needed to discretize the beam. Since the support domain of the fluid particle near the FS interface is truanted, the so-called normal-flux method is adopted to consider surface integration terms. Moreover, we propose a new excess pressure for the incompressible fluid flow based on Bernoulli's principle, which is more accurate for the simulation of incompressible FSI problems. Besides, the particle shifting scheme near the fluid-structure interface is modified. Finally, the accuracy and stability of the present FSI solver are verified by several numerical examples. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Fluid-structure interaction Weakly-compressible SPH reproducing kernel particle method Elastic structure Degenerated continuum approach

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A hyper-reduction computational method for accelerated modeling of thermal cycling-induced plastic deformations

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2021年 151卷 104385-104385页

作者： Kaneko, Shigeki Wei, Haoyan He, Qizhi Chen, Jiun-Shyan Yoshimura, Shinobu Univ Tokyo Sch Engn Bunkyo Ku Tokyo Japan Univ Calif San Diego Dept Struct Engn La Jolla CA 92093 USA ANSYS Livermore Software Technol Livermore CA USA Pacific Northwest Natl Lab Phys & Computat Sci Directorate Richland WA 99352 USA

For materials under cyclic thermal loadings, temperature and strain rate-dependent creep deformation can occur due to the thermal expansion mismatch near material interfaces, leading to deterioration of fatigue life. Simulation of the nonlinear mechanical deformation processes of materials subjected to thermal cycling with high-fidelity numerical models often consume high computational costs due to material nonlinearities and long thermal loading period. To accelerate such thermal cycling simulation, an efficient reduced-order modeling framework is proposed. We adopt the reproducing kernel particle method (RKPM) to generate offline high-fidelity model snapshots, which are utilized to create low-dimensional surrogate models based on the proper orthogonal decomposition under Galerkin projection. Based on the stabilized conforming nodal integration technique, gradient smoothing at single integration point per integration cell is employed in conjunction with a least-squares stabilization for high computational efficiency. To further speed up the simulation, a hyper-reduction method is introduced to avoid the full domain integration during the elastoplastic online simulation. Numerical examples on modeling of thermal cycling-induced plastic deformation and thermal fatigue life prediction of a flip chip assembly are analyzed to demonstrate the effectiveness of the present hyper-reduced-order model in significant reduction of computational time while preserving desired accuracy.

关键词： Thermo-visco-plastic deformation Thermal cycling simulation Thermal fatigue analysis Reduced-order model Hyper-reduction method Proper orthogonal decomposition reproducing kernel particle method

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A concurrent atomistic-crystal plasticity multiscale model for crack propagation in crystalline metallic materials

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COMPUTER methodS IN APPLIED MECHANICS AND ENGINEERING 2021年 379卷 113748-113748页

作者： Chakraborty, Subhendu Ghosh, Somnath Johns Hopkins Univ Dept Mech Engn Baltimore MD 21218 USA Johns Hopkins Univ Dept Civil & Syst 3400 N Charles St Baltimore MD 21218 USA Johns Hopkins Univ Dept Mech 3400 N Charles St Baltimore MD 21218 USA Johns Hopkins Univ Dept Mat Sci & Engn 3400 N Charles St Baltimore MD 21218 USA

This paper develops a coupled concurrent atomistic-continuum multiscale model for analyzing crack propagation and associated mechanisms in crystalline metallic materials. This modeling framework can be used to develop effective continuum-scale constitutive models for crack evolution in deforming domains characterized by crystal plasticity. The atomistic region is modeled by the molecular dynamics (MD) code LAMMPS, while the continuum region is modeled by a dislocation density crystal plasticity FE model. A novel method is developed to transfer discrete dislocations in the atomistic domains to dislocation densities in the continuum domain. Propagation of dislocation densities in the continuum domain is modeled by the advection equation of a conserved quantity using the reproducing kernel particle method (RKPM) in conjunction with the collocation method. Validation studies are conducted by comparing results of the concurrent model with those by MD for nickel single crystal specimen with an embedded crack. An analytical model of the crack tip nucleated dislocation density evolution is developed for inclusion in crystal plasticity models. The effect of applied strain-rate and temperature on the parameters of this model are studied. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Concurrent atomistic-crystal plasticity model Crack propagation Dislocation densities Advection equation reproducing kernel particle method Single crystal Nickel

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Meshless method ? Review on recent developments 10

Meshless method ? Review on recent developments

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10th International Conference of Materials Processing and Characterization (ICMPC)

作者： Patel, Vivek G. Rachchh, Nikunj V. Marwadi Univ Rajkot 360003 Gujarat India

The present article outlines the historical development of Meshless method. The high computational cost associated with conventional numerical methods and their lack of accuracy, particularly in the area of astrophysics is the motivation and an initiation towards the invention of latest meshless methods. The review starts with Smoothed particle hydrodynamics meshless method which was invented by Gingold, Monghan in 1977 for astrophysics applications. Furthermore, shortcomings of the SPH method, it's solution, and recent development has been reviewed for different applications. After that advent features of Element free Galerkin method with mean least square method and Lagrangian multiplier have been critically reviewed for different cases. Later, the radial basis function method is explained along with its extended version to solve a partial differential equation. Many types of RBF methods have been compared. Also, several consistency and accuracy problems are reviewed for reproducing kernel particle method. Recent advancement like generalization of RKPM method, hybrid of RKPM with Lagrangian multiplier has been briefed for a different approach. Additionally, feasibility, flexibility and several applications of Meshless local Petrov Galerkin have been reviewed. Lastly recent development of MLPG with Laplace transform to solve PDE have been studied. Afterwards, a different attribute of point collocation method for inherent multiresolution capability and error estimation has been reviewed for different applications. Briefly, the article provides a condensed overview of several meshless methods, its recent advancement and their applications. © 2019 Elsevier Ltd.

关键词： Element free galerkin Mean least square Meshless methods Radial basis function reproducing kernel particle method

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Penetration modeling of ultra-high performance concrete using multiscale meshfree methods

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INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL methodS IN GEOMECHANICS 2019年第14期43卷 2328-2351页

作者： Sparks, Paul A. Sherburn, Jesse A. Heard, William F. Williams, Brett A. US Army Engineer Res & Dev Ctr Vicksburg MS USA

Terminal ballistics of concrete is of extreme importance to the military and civil communities. Over the past few decades, ultra-high performance concrete (UHPC) has been developed for various applications in the design of protective structures because UHPC has an enhanced ballistic resistance over conventional strength concrete. Developing predictive numerical models of UHPC subjected to penetration is critical in understanding the material's enhanced performance. This study employs the advanced fundamental concrete (AFC) model, and it will run inside the reproducing kernel particle method (RKPM)-based code known as the nonlinear meshfree analysis program (NMAP). NMAP is advantageous for modeling impact and penetration problems that exhibit extreme deformation and material fragmentation. A comprehensive experimental study was conducted to characterize the UHPC. The investigation consisted of fracture toughness testing, the utilization of nondestructive microcomputed tomography analysis, and lastly projectile penetration shots on the UHPC targets. To improve the accuracy of the model, a new scaled damage evolution law (SDEL) is employed within the microcrack informed damage model. During the homogenized macroscopic calculation, the corresponding microscopic cell needs to be dimensionally equivalent to the mesh dimension when the partial differential equation becomes ill posed and strain softening ensues. To ensure arbitrary mesh geometry for which the homogenized stress-strain curves are derived, a size scaling law is incorporated into the homogenized tensile damage evolution law. This ensures energy-bridging equivalence of the microscopic cell to the homogenized medium irrespective of arbitrary mesh geometry. Results of numerical investigations will be compared with results of penetration experiments.

关键词： constitutive modeling multiscale modeling penetration modeling reproducing kernel particle method ultra-high performance concrete

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Semi-Lagrangian reproducing kernel particle method for fragment-impact problems

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INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 2011年第12期38卷 1033-1047页

作者： Guan, P. C. Chi, S. W. Chen, J. S. Slawson, T. R. Roth, M. J. Univ Calif Los Angeles Dept Civil & Environm Engn Los Angeles CA 90095 USA Natl Taiwan Ocean Univ Computat & Simulat Ctr Keelung Taiwan Natl Taiwan Ocean Univ Dept Syst Engn & Naval Architecture Keelung Taiwan USA Engineer Res & Dev Ctr Vicksburg MS USA

Fragment-impact problems exhibit excessive material distortion and complex contact conditions that pose considerable challenges in mesh based numerical methods such as the finite element method (FEM). A semi-Lagrangian reproducing kernel particle method (RKPM) is proposed for fragment-impact modeling to alleviate mesh distortion difficulties associated with the Lagrangian FEM and to minimize the convective transport effect in the Eulerian or Arbitrary Lagrangian Eulerian FEM. A stabilized non-conforming nodal integration with boundary correction for the semi-Lagrangian RKPM is also proposed. Under the framework of semi-Lagrangian RKPM, a kernel contact algorithm is introduced to address multi-body contact. Stability analysis shows that temporal stability of the kernel contact algorithm is related to the velocity gradient between two contacting bodies. The performance of the proposed methods is examined by numerical simulation of penetration processes. Published by Elsevier Ltd.

关键词： Semi-Lagrangian reproducing kernel particle method Penetration Meshfree

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The meshless analysis of wave equations based on the RRKPM

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RESULTS IN PHYSICS 2020年 16卷

作者： Ma, Jichao Gao, Hongfen Wei, Gaofeng Qiao, Jinwei Qilu Univ Technol Sch Mech & Automot Engn Shandong Acad Sci Shandong 250353 Peoples R China Shandong Management Univ Coll Mech & Elect Engn Shandong 250357 Peoples R China

In this paper, the method of radial basis function (RBF) is employed to construct the approximating function of the reproducing kernel particle method (RKPM), which can reduce the adverse effect of different kernel functions on computational accuracy and improve stability in the problem domain, and the radial basis reproducing kernel particle method (RRKPM) is presented. Compared with the RKPM, the RRKPM has higher computational accuracy and better stability. Then RRKPM is applied to wave propagation, and the discretized system equation can be obtained using the integral weak form. The penalty method is applied to imposing the essential boundary condition, and the two-point difference method is selected to discretize the time. The accuracy and stability of the RRKPM for wave propagation problem are illustrated by the numerical examples.

关键词： Radial basis functions reproducing kernel particle method Wave equations Numerical simulation Meshless methods

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MESHFREE VISCOELASTIC MODELING: TOWARD NUMERICAL SIMULATION OF PRINTING CONCRETE STRUCTURES

MESHFREE VISCOELASTIC MODELING: TOWARD NUMERICAL SIMULATION ...

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作者： Chen, Guang PennState University Libraries

学位级别：Master of Science

The conventional way of construction in building industry has many disadvantages, for example, the environmental pollution, massive energy consumption, less customization, and the intense human labor involved. A new, more efficient way of manufacturing construction materials could reduce time, cost and labor intensity, while providing design freedom for complex architectural forms. Towards this end, three dimensional (3D) printing, or additive manufacturing of concrete structures offers great *** technology however is still in its relative infancy, and further research is needed in order to bring this technology to the market. Specifically, the materials aspect of 3D printing pose many open research questions, such as rheological properties of the concrete that enabling effective pumping and printing, while also hardening quickly enough to support the weight of subsequent layers. In order to address these questions, two approaches can be employed: experiment and mathematical modeling. While an experiment approach alone is time consuming and costly, numerical simulation properly validated with experiments offers a far less costly and more effective *** numerically model the behavior of concrete at fresh or solidified state, a viscoelastic constitutive law for both small-strain and finite-strain are introduced based on the generalized Maxwell model. In the solidified state, a small strain version of the viscoelastic constitutive relation can be used to model phenomena likestress relaxation and creep. While for fresh state mixture, the large strain version can model the finite deformation present in the deposition process, and interface evolution in 3D printing. However, careful selection of a numerical framework is necessary, since in the traditional finite element approach, large deformations can cause mesh distortion and entanglement, and topological changes in the domain (free surface formation, closure) require computationally intensive remes

关键词： reproducing kernel particle method viscoelastic modeling Meshfree methods 3D printing

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A DAMAGE particle method FOR SMEARED MODELING OF BRITTLE FRACTURE

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INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING 2018年第4期16卷 303-324页

作者： Wei, Haoyan Chen, Jiun-Shyan Univ Calif San Diego Dept Struct Engn La Jolla CA 92093 USA

Numerical procedures for brittle fracture modeling become tedious when many moving strong discontinuities have to be captured. A smeared fracture modeling approach formulated under the reproducing kernel particle discretization is presented. In this approach, the smeared strain is computed by the divergence operation with a boundary integral of displacements in each nodal representative domain, thus avoiding direct derivatives of displacements for strain computation in the smeared cracking region. To avoid discretization size sensitivity issues, a scaling law is introduced based on the equivalence between the bulk damage energy dissipation and the surface fracture energy of the associated crack segment over the nodal representative domain. This scaling law is introduced under the stabilized conforming nodal integration framework, where the nodal representative domain serves as the smearing domain, and the smeared strain over the nodal representative domain is used with the scaled damage law to determine the damage state. The employment of stabilized conforming nodal integration also allows the displacement and damage state variables to be calculated and stored for the same set of particles, avoiding interpolation of variables between nodal and Gaussian points in conventional finite elements. Several numerical examples are presented to examine the effectiveness of the proposed damage particle method for smeared modeling of fracture.

关键词： smeared strain stabilized conforming nodal integration reproducing kernel particle method smeared crack model continuum damage model

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Efficient searching in meshfree methods

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COMPUTATIONAL MECHANICS 2018年第6期62卷 1461-1483页

作者： Olliff, James Alford, Brad Simkins, Daniel C., Jr. Univ S Florida Dept Civil & Environm Engn 4202 E Fowler Ave ENB118 Tampa FL 33620 USA

Meshfree methods such as the reproducing kernel particle method and the Element Free Galerkin method have proven to be excellent choices for problems involving complex geometry, evolving topology, and large deformation, owing to their ability to model the problem domain without the constraints imposed on the Finite Element method (FEM) meshes. However, meshfree methods have an added computational cost over FEM that come from at least two sources: increased cost of shape function evaluation and the determination of adjacency or connectivity. The focus of this paper is to formally address the types of adjacency information that arises in various uses of meshfree methods;a discussion of available techniques for computing the various adjacency graphs;propose a new search algorithm and data structure;and finally compare the memory and run time performance of the methods.

关键词： Meshfree reproducing kernel particle method Acceleration data structure Nearest neighbour Adjacency Connectivity

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