Local Maximum Entropy Shape Functions Based FE-EFGM Coupling

In this paper, a new method for coupling the finite element method (FEM)and the element-free Galerkin method (EFGM) is proposed for linear elastic and geometrically nonlinear problems using local maximum entropy shape functions in theEFG zone of the problem domain. These shape functions possess a weak Kroneckerdelta property at the boundaries which provides a natural way to couple the EFGand the FE regions as compared to the use of moving least square basis functions.In this new approach, there is no need for interface/transition elements between theEFG and the FE regions or any other special treatment for shape function continuity across the FE-EFG interface. One- and two-dimensional linear elastic and two-dimensional geometrically nonlinear benchmark numerical examples are solved by the new approach to demonstrate the implementation and performance of the current approach

Public Sector Crises: Realizations from Covid-19 for Crisis Communication

This article reflects upon the communicative demands COVID-19 created for public sector crisis managers. Those demands include anxiety, empathy, efficacy, fatigue, reach, and threat. The conclusion reviews the realizations COVID-19 has created for those tasked with managing public health crises

Magnetization of YBCO film with ac travelling magnetic waves of relatively short wavelengths

© 2017 Author(s). The magnetizations of the YBCO film with ac travelling magnetic waves of relatively short wavelengths were studied. The results have verified that the reported “intermediate value” of the superconducting current density [Wang et al., Appl. Phys. Lett. 104(3), 032602 (2014)] was caused by the existence of multiple transition regions in the sample: the magnetic poles induce ±JC in the pole regions, which produces two transition regions within each wavelength λ ( +JC→−JC→+JC, and vice versa, while the symbol → indicates the transition region). The current densities in the transition region are with intermediate values, which are smaller than the critical value. In case of relatively short wavelength, there are multiple transition regions, which occupy a large fraction of the YBCO sample with intermediate current values. Moreover, the wavelike current distributions might help explain the flux transportation and dc output voltage in HTS flux pump

Fabric anisotropy & DEM informed two-surface hyperplasticity : constitutive formulation, asymptotic states & experimental validation.

In geotechnical analysis continuum idealisations of the bulk material still provide the most appropriate approach for engineers designing large-scale structures. In this area, the most successful framework for describing the behaviour of soils is Critical State (CS) soil mechanics. However, the findings from discrete element method (DEM) analysis, such as the uniqueness of the CS, can provide invaluable information in the development such models. This paper details the key concepts behind a two-surface hyperplasticity model (?) whose development was informed by recent DEM findings on the uniqueness of the CS. Asymptotic states of the model will be confirmed and the DEM-continuum-experimental loop will be closed through comparison of the developed model with experimental data on coarse-grained particulate media. This will demonstrate, that providing the previous stress history is accounted for, the proposed model is suitable for a variety of particulate media

Three-dimensional FE-EFGM adaptive coupling with application to nonlinear adaptive analysis

Three-dimensional problems with both material and geometrical nonlinearities are of practical importance in many engineering applications, e.g. geomechanics, metal forming and biomechanics. Traditionally, these problems are simulated using an adaptive finite element method (FEM). However, the FEM faces many challenges in modeling these problems, such as mesh distortion and selection of a robust refinement algorithm. Adaptive meshless methods are a more recent technique for modeling these problems and can overcome the inherent mesh based drawbacks of the FEM but are computationally expensive. To take advantage of the good features of both methods, in the method proposed in this paper, initially the whole of the problem domain is modeled using the FEM. During an analysis those elements which violate a predefined error measure are automatically converted to a meshless zone. This zone can be further refined by adding nodes, overcoming computationally expensive FE remeshing. Therefore an appropriate coupling between the FE and the meshless zone is vital for the proposed formulation. One of the most widely used meshless methods, the element-free Galerkin method (EFGM), is used in this research. Maximum entropy shape functions are used instead of the conventional moving least squares based formulations'. These shape functions posses a weak Kronecker delta property at the boundaries of the problem domain, which allows the essential boundary conditions to be imposed directly and also helps to avoid the use of a transition region in the coupling between the FE and the EFG regions. Total Lagrangian formulation is preferred over the updated Lagrangian formulation for modeling finite deformation due to its computational efficiency. The well-established error estimation procedure of Zienkiewicz-Zhu is used in the FE region to determine the elements requiring conversion to the EFGM. The Chung and Belytschko error estimator is used in the EFG region for further adaptive refinement. Numerical examples are presented to demonstrate the performance of the current approach in thre

A survey of weather information possessed by thirty-two pupils randomly selected from sixth and eleventh grades and from special classes

Thesis (Ed.M.)--Boston Universit