A two-dimensional simulation of solidification processes in materials with thermo-dependent properties using XFEM

2016 ◽  
Vol 26 (6) ◽  
pp. 1661-1683 ◽  
Author(s):  
Pawel Stapór
Keyword(s):  
Finite Element ◽  
Phase Change ◽  
Dimensional Space ◽  
Benchmark Problems ◽  
Liquid Region ◽  
Two Dimensional ◽  
Linear Phase ◽  
Content Type ◽  
Non Linear ◽  
Non Linear System

Purpose – The purpose of this paper is to carry out a finite element simulation of a physically non-linear phase change problem in a two-dimensional space without adaptive remeshing or moving-mesh algorithms. The extended finite element method (XFEM) and the level set method (LSM) were used to capture the transient solution and motion of phase boundaries. It was crucial to consider the effects of unequal densities of the solid and liquid phases and the flow in the liquid region. Design/methodology/approach – The XFEM and the LSM are applied to solve non-linear transient problems with a phase change in a two-dimensional space. The model assumes thermo-dependent properties of the material and unequal densities of the phases; it also allows for convection in the liquid phase. A non-linear system of equations is derived and a numerical solution is proposed. The Newton-Raphson method is used to solve the problem and the LSM is applied to track the interface. Findings – The robustness and utility of the method are demonstrated on several two-dimensional benchmark problems. Originality/value – The novel procedure based on the XFEM and the LSM was developed to solve physically non-linear phase change problems with unequal densities of phases in a two-dimensional space.

Numerical Simulation of Inner Support for Excavation Based on FEM Software ABAQUS

2012 ◽  
Vol 236-237 ◽  
pp. 632-635
Author(s):  
Yue Sun ◽  
Yue Nan Chen ◽  
Zhi Yun Wang
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Computational Model ◽  
Dimensional Space ◽  
General Purpose ◽  
Two Dimensional ◽  
Clay Layer ◽  
Finite Element Software ◽  
Spring Element

In two-dimensional space, an elasto-plastic finite element computational model was established to simulate inner support for excavation on the basis of the general-purpose finite element software ABAQUS. The soil was assumed to be a uniform and normally consolidated clay layer and strut was discreted by spring element. Compared with published case study, it can be concluded that FEM software AQAQUS can present one reliable simulation progress of inner support for excavation.

Robustness evaluation of CSMM based finite element for simulation of shear critical hollow RC bridge piers

2019 ◽  
Vol 37 (1) ◽  
pp. 313-344
Author(s):  
Vijay Kumar Polimeru ◽  
Arghadeep Laskar
Keyword(s):  
Finite Element ◽  
Earthquake Engineering ◽  
Bridge Piers ◽  
Fe Model ◽  
Content Type ◽  
Aspect Ratios ◽  
Linear Behavior ◽  
Non Linear ◽  
Reversed Cyclic ◽  
Rc Bridge Piers

Purpose The purpose of this study is to evaluate the effectiveness of two-dimensional (2D) cyclic softened membrane model (CSMM)-based non-linear finite element (NLFE) model in predicting the complete non-linear response of shear critical bridge piers (with walls having aspect ratios greater than 2.5) under combined axial and reversed cyclic uniaxial bending loads. The effectiveness of the 2D CSMM-based NLFE model has been compared with the widely used one-dimensional (1D) fiber-based NLFE models. Design/methodology/approach Three reinforced concrete (RC) hollow rectangular bridge piers tested under reversed cyclic uniaxial bending and sustained axial loads at the National Centre for Research on Earthquake Engineering (NCREE) Taiwan have been simulated using both 1D and 2D models in the present study. The non-linear behavior of the bridge piers has been studied through various parameters such as hysteretic loops, energy dissipation, residual drift, yield load and corresponding drift, peak load and corresponding drift, ultimate loads, ductility, specimen stiffness and critical strains in concrete and steel. The results obtained from CSMM-based NLFE model have been critically compared with the test results and results obtained from the 1D fiber-based NLFE models. Findings It has been observed from the analysis results that both 1D and 2D simulation models performed well in predicting the response of flexure critical bridge pier. However, in the case of shear critical bridge piers, predictions from 2D CSMM-based NLFE simulation model are more accurate. It has, thus, been concluded that CSMM-based NLFE model is more accurate and robust to simulate the complete non-linear behavior of shear critical RC hollow rectangular bridge piers. Originality/value In this study, a novel attempt has been made to provide a rational and robust FE model for analyzing shear critical hollow RC bridge piers (with walls having aspect ratios greater than 2.5).

After the revolution – new chances for service research in a digital world

2020 ◽  
Vol 31 (3) ◽  
pp. 597-607
Author(s):  
Werner H. Kunz ◽  
Gianfranco Walsh
Keyword(s):  
Digital Media ◽  
New Technologies ◽  
Dimensional Space ◽  
Literature Alert ◽  
Service Research ◽  
Two Dimensional ◽  
Content Type ◽  
Digital World ◽  
Business Perspective ◽  
Media Research

PurposeDigital media has revolutionized societies and changed forever how we do business. This paper aims to determine the current scope of service research in the area of digital media, identifying research gaps and introducing new research contributions to complement our knowledge of digital media.Design/methodology/approachBased on all service articles of the SERVSIG literature alert system from 2016 to 2019, a subset of digital media articles was identified and latent Dirichlet allocation (LDA) text-mining methods were used on the abstracts and titles of the articles for topic modeling of the field. Dominant research topics were identified and depicted in a two-dimensional space.FindingsThe study identifies eight distinct topic areas of digital media in service research and shows their relationship to each other in a two-dimensional space. A clear tendency in service research towards taking primarily a customer (versus business perspective) of digital media can be observed. Further, for some journals, a trend towards specialization on particular topics could be detected.Research limitations/implicationsThis article advocates for more digital media research with a stronger business perspective. Further, although particular new technologies are exciting to discuss, it seems that the importance of customer relationship topics in digital media is not reflected in the current digital media research as needed.Originality/valueThe article uses a quantitative–explorative approach to determine the current state of research in regard to digital media in services. The authors introduce 11 new studies that aim to close the knowledge gap in critical areas of digital media.

Design of H_/H∞ fault detection observer for closed-loop nonlinear system with disturbance

2020 ◽  
Vol 40 (4) ◽  
pp. 589-599
Author(s):  
Zhengquan Chen ◽  
Lu Han ◽  
Yandong Hou
Keyword(s):  
Fault Detection ◽  
Closed Loop ◽  
External Disturbance ◽  
Adaptive Threshold ◽  
Linear Matrix ◽  
Content Type ◽  
Non Linear ◽  
Runge Kutta ◽  
Non Linear System ◽  
Residual Generator

Purpose This paper proposes a novel method of fault detection, which is based on H_/H∞ Runge–Kutta observer and an adaptive threshold for a class of closed-loop non-linear systems. The purpose of this paper is to improve the rapidity and accuracy of fault detection. Design/methodology/approach First, the authors design the H_/H∞ Runge–Kutta fault detection observer, which is used as a residual generator to decouple the residual from the input. The H_ performance index metric in the specified frequency domain is used to describe how sensitive the residual to the fault. The H∞ norm is used to describe the residual robustness to the external disturbance of the systems. The residual generator is designed to achieve the best tradeoff between robustness against unknown disturbances but sensitivity to faults, thus realizing the accurate detection of the fault by suppressing the influence of noise and disturbance on the residual. Next, the design of the H_/H∞ fault detection observer is transformed into a convex optimization problem and solved by linear matrix inequality. Then, a new adaptive threshold is designed to improve the accuracy of fault detection. Findings The effectiveness and correctness of the method are tested in simulation experiments. Originality/value This paper presents a novel approach to improve the accuracy and rapidity of fault detection for closed-loop non-linear system with disturbances and noise.

A non-smooth Newton method for the solution of magnetostatic field problems with hysteresis

2019 ◽  
Vol 38 (5) ◽  
pp. 1584-1594 ◽  
Author(s):  
Stephan Willerich ◽  
Hans-Georg Herzog
Keyword(s):  
Finite Element ◽  
Newton Method ◽  
Linear Equations ◽  
Element Formulation ◽  
Magnetostatic Field ◽  
Generalized Jacobian ◽  
Content Type ◽  
Non Linear ◽  
Generalized Framework ◽  
Gradient Based

Purpose The use of gradient-based methods in finite element schemes can be prevented by undefined derivatives, which are encountered when modeling hysteresis in constitutive material laws. This paper aims to present a method to deal with this problem. Design/methodology/approach Non-smooth Newton methods provide a generalized framework for the treatment of minimization problems with undefined derivatives. Within this paper, a magnetostatic finite element formulation that includes hysteresis is presented. The non-linear equations are solved using a non-smooth Newton method. Findings The non-smooth Newton method shows promising convergence behavior when applied to a model problem. The numbers of iterations for magnetization curves with and without hysteresis are within the same range. Originality/value Mathematical tools like Clarke's generalized Jacobian are applied to magnetostatic field problems with hysteresis. The relation between the non-smooth Newton method and other methods for solving non-linear systems with hysteresis like the M(B)-iteration is established.

scholarly journals Parallel computations in nonlinear solid mechanics using adaptive finite element and meshless methods

2016 ◽  
Vol 33 (4) ◽  
pp. 1161-1191 ◽  
Author(s):  
Zahur Ullah ◽  
Will Coombs ◽  
C Augarde
Keyword(s):  
Finite Element ◽  
Parallel Algorithms ◽  
Meshless Method ◽  
Three Dimensional ◽  
Meshless Methods ◽  
Basis Functions ◽  
Two Dimensional ◽  
Content Type ◽  
Linear Elastic ◽  
Geometrical Nonlinearities

Purpose – A variety of meshless methods have been developed in the last 20 years with an intention to solve practical engineering problems, but are limited to small academic problems due to associated high computational cost as compared to the standard finite element methods (FEM). The purpose of this paper is to develop an efficient and accurate algorithms based on meshless methods for the solution of problems involving both material and geometrical nonlinearities. Design/methodology/approach – A parallel two-dimensional linear elastic computer code is presented for a maximum entropy basis functions based meshless method. The two-dimensional algorithm is subsequently extended to three-dimensional adaptive nonlinear and three-dimensional parallel nonlinear adaptively coupled finite element, meshless method cases. The Prandtl-Reuss constitutive model is used to model elasto-plasticity and total Lagrangian formulations are used to model finite deformation. Furthermore, Zienkiewicz and Zhu and Chung and Belytschko error estimation procedure are used in the FE and meshless regions of the problem domain, respectively. The message passing interface library and open-source software packages, METIS and MUltifrontal Massively Parallel Solver are used for the high performance computation. Findings – Numerical examples are given to demonstrate the correct implementation and performance of the parallel algorithms. The agreement between the numerical and analytical results in the case of linear elastic example is excellent. For the nonlinear problems load-displacement curve are compared with the reference FEM and found in a very good agreement. As compared to the FEM, no volumetric locking was observed in the case of meshless method. Furthermore, it is shown that increasing the number of processors up to a given number improve the performance of parallel algorithms in term of simulation time, speedup and efficiency. Originality/value – Problems involving both material and geometrical nonlinearities are of practical importance in many engineering applications, e.g. geomechanics, metal forming and biomechanics. A family of parallel algorithms has been developed in this paper for these problems using adaptively coupled finite element, meshless method (based on maximum entropy basis functions) for distributed memory computer architectures.

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