An elastic 3D Finite-Element-Model for Grímsvötn, Iceland

2021 ◽  
Author(s):  
Sonja Heidi Maria Greiner ◽  
Halldór Geirsson
Keyword(s):  
Finite Element ◽  
Sea Level ◽  
Magma Chamber ◽  
Seismic Velocity ◽  
Source Parameters ◽  
Elastic Structure ◽  
Elastic Model ◽  
Magma Body ◽  
Dependent Relation ◽  
Deformation Models

<p>Deformation models are an important tool to study and monitor active volcanoes. However, in many cases models are strongly simplified either due to a lack of data or for the sake of speed and computational demands. The assumption of a magma body embedded in a homogeneous elastic half-space for example neglects the topography and heterogeneous crustal structures found at some volcanoes. This oversimplification can lead to a poor representation of individual systems and result in erroneous estimates of deformation source parameters like the location and geometry of a magma chamber.  The Finite Element Method (FEM) is a powerful tool to include complex heterogeneous structures and existing data sets into deformation models in order to create more realistic representations of individual volcanic systems. <br>In this study, the FEM-software COMSOL was used to build a three-dimensional elastic model of the subglacial volcano Grímsvötn, Iceland, accounting for the steep topography at the caldera rim, using a digital elevation model, as well as crustal heterogeneity. The elastic structure developed for this model is based on a density-structure, a seismic-velocity-structure and a pressure-dependent relation between the dynamic and static elastic moduli. The main feature of the elastic structure is a weak material (static shear modulus of G<sub>stat</sub>=0.6-9.8 GPa from 1 km above to 2 km below sea level) filing the caldera, which is surrounded by a stiffer, ring-like structure underneath the caldera rim (G<sub>stat</sub>=1.6-18 GPa from 1 km above to 2 km below sea level). The source parameters and geometry of forward models including the topography and elastic structure (individually and combined) were varied to fit the deformation observed at the nunatak GPS station GFUM, located at the caldera rim, during the last eruption (2011). While the topography has limited influence at the deformation at GFUM, the elastic structure requires the magma chamber to be significantly deeper than previous models suggested.</p>

Study on Welding Deformation and Residual Stress of H-Section Beam Based on Finite Element Method

2017 ◽  
Vol 753 ◽  
pp. 305-309 ◽  
Author(s):  
Xu Lu
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Finite Element ◽  
Source Parameters ◽  
Welding Process ◽  
Steel Structure ◽  
Bottom Plate ◽  
Welding Deformation ◽  
Element Simulation ◽  
Main Components

The welding H-section beam has good mechanical properties with its superior structure. So they become the main components of steel structure and have been widely used. In this paper, the welded H-section beam is used as the research object. The finite element simulation model is established. The heat source parameters are determined. The deformation of the steel due to the welding process is studied. The results show that the bottom plate and the bottom plate inward bending is about 2.32mm cause by welding process. The residual stress can reach 400MPa.

scholarly journals Monitoring southwest Greenland’s ice sheet melt with ambient seismic noise

2016 ◽  
Vol 2 (5) ◽  
pp. e1501538 ◽  
Author(s):  
Aurélien Mordret ◽  
T. Dylan Mikesell ◽  
Christopher Harig ◽  
Bradley P. Lipovsky ◽  
Germán A. Prieto
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Sea Level ◽  
Seismic Noise ◽  
Seismic Velocity ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sea Level Changes ◽  
Ice Sheet Mass Balance ◽  
Velocity Changes

The Greenland ice sheet presently accounts for ~70% of global ice sheet mass loss. Because this mass loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in ice sheet mass balance is of paramount concern. Spaceborne mass balance techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth’s crust, as measured with the correlation of seismic noise, may be used to infer seasonal ice sheet mass balance. Seasonal loading and unloading of glacial mass induces strain in the crust, and these strains then result in seismic velocity changes due to poroelastic processes. Our method provides a new and independent way of monitoring (in near real time) ice sheet mass balance, yielding new constraints on ice sheet evolution and its contribution to global sea-level changes. An increased number of seismic stations in the vicinity of ice sheets will enhance our ability to create detailed space-time records of ice mass variations.

3-D Heterogeneous Elastic Crustal Structure for Deformation Models in the Hengill Area, SW Iceland

2021 ◽  
Author(s):  
Cécile Ducrocq ◽  
Halldór Geirsson ◽  
Alex Hobé ◽  
Gylfi Páll Hersir ◽  
Thóra Árnadóttir ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Power Plants ◽  
Electrical Power ◽  
Element Model ◽  
Volcanic Complex ◽  
Elastic Model ◽  
Spatial Effects ◽  
Volcanic System ◽  
Shear Moduli ◽  
Deformation Models

<p>Crustal deformation in volcanic areas relates ground motions, measured by geodetic techniques, to physical (e.g. pressure or volumetric) changes of magmatic sources below the surface. These measurements contribute to studies of<!-- this is not optimal, changing it might require rewriting the entire sentence. Perhaps you want to break this sentence into two. --> ongoing processes at the source of possible unrest, and are thus key for hazard assessment in active volcanic areas around the globe. However, such assessments often rely on geodetic-based models with quite simplistic assumptions of the physical structure of the volcanic complex. Particularly, constant values of elastic parameters (e.g. Poisson’s ratio and shear moduli) are commonly used for entire active volcanic areas, thus overlooking the spatial effects of lithological properties, depth-dependant compression and temperature variations on those parameters. These simplifications may lead to inaccurate interpretation of the location, shape, and volume change of deformation sources.</p><p> </p><p>In this study we ask how the 3-D heterogeneities of the elastic crustal structure beneath the Hengill volcanic system, SW Iceland, affects models of deformation sources in the area. The Hengill area hosts two active volcanic systems (Hengill and Hrómundartindur), and two high-enthalpy geothermal power plants (Nesjavellir and Hellisheiði), which provide thermal and electrical power to Reykjavík, the capital of Iceland, only 30 km away. To retrieve information on the spatial heterogeneities in the shear moduli and Poisson’s ratio beneath the Hengill area, we first estimate the 3-D shallow density structure of the area using results from regional and local gravimetric surveys. We implement this structure, along with seismic tomographic studies of the SW Iceland, in a Finite Element Model to solve, using forward models, for the 3-D heterogeneities in the shear moduli and Poisson’s ratio beneath the Hengill area.<!-- This might be more effective if the order of these statements is changed, for example: To achieve [stated goal] we produce [FEM] using [results from geophysics]. --> Furthermore, we discuss the difference between static and kinematic elastic moduli, which is important when building deformation models from seismic tomography.<!-- My first reaction to this statement is: "How do you address this?" This could be answered directly, except if you think it detracts from the story. --> The new 3-D inferred elastic model is then used to re-estimate parameters for different sources of deformation causing uplift and subsidence in the area in the past decades. This study shows the importance of accounting for heterogeneities in the crustal elastic structure to estimate with higher accuracy the sources of deformation in volcanic areas around the world.</p>

scholarly journals Finite element modelling of an energy-geomembrane underground pumped hydroelectric energy storage system

2020 ◽  
Vol 205 ◽  
pp. 07001
Author(s):  
Hans Henning Stutz ◽  
Peter Norlyk ◽  
Kenneth Sørensen ◽  
Lars Vabbersgaard Andersen ◽  
Kenny Kataoka Sørensen ◽  
...  
Keyword(s):  
Finite Element ◽  
Energy Storage ◽  
Storage System ◽  
Constitutive Models ◽  
Energy System ◽  
Energy Storage System ◽  
Elastic Model ◽  
Hydroelectric Energy ◽  
Linear Elastic ◽  
Soil Behaviour

The increasing need for energy storage technology has led to a massive interest in novel energy storage methods. The energy geomembrane system is such a novel energy storage method. The concept of the system is briefly introduced, and a holistic numerical model of the system is presented. The model uses advanced finite-element techniques to model the energy storage system using fluid cavity elements. The developed geomembrane energy system is modelled with different constitutive models to represent the soil behaviour: a linear elastic model, a nonlinear Mohr-Coulomb model, and a hypoplastic constitutive model. The consequences of these different models on the results are studied. Hereby, the focus is the first inflation and deflation cycle of the system.

scholarly journals DEVELOPMENT OF THE METAL RHEOLOGY MODEL OF HIGH-TEMPERATURE DEFORMATION FOR MODELING BY FINITE ELEMENT METHOD

2019 ◽  
Vol 2 ◽  
pp. 52-60 ◽  
Author(s):  
Oleg Markov ◽  
Oleksiy Gerasimenko ◽  
Leila Aliieva ◽  
Alexander Shapoval
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Relaxation ◽  
Hot Deformation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Software Systems ◽  
Elastic Model ◽  
Communication Model ◽  
Element Method

It is shown that when modeling the processes of forging and stamping, it is necessary to take into account not only the hardening of the material, but also softening, which occurs during hot processing. Otherwise, the power parameters of the deformation processes are precisely determined, which leads to the choice of more powerful equipment. Softening accounting (processes of stress relaxation) will allow to accurately determine the stress and strain state (SSS) of the workpiece, as well as the power parameters of the processes of deformation. This will expand the technological capabilities of these processes. Existing commercial software systems for modeling hot plastic deformations based on the finite element method (FEM) do not allow this. This is due to the absence in these software products of the communication model of the component deformation rates and stresses, which would take into account stress relaxation. As a result, on the basis of the Maxwell visco-elastic model, a relationship is established between deformation rates and stresses. The developed model allows to take into account the metal softening during a pause after hot deformation. The resulting mathematical model is tested by experiment on different steels at different temperatures of deformation. The process of steels softening is determined using plastometers. It is established experimentally that the model developed by 89 ... 93 % describes the rheology of the metal during hot deformation. The relationship between the components of the deformation rates and stresses is established, which allows to obtain a direct numerical solution of plastic deformation problems without FED iterative procedures, taking into account the real properties of the metal during deformation. As a result, the number of iterations and calculations has significantly decreased.

Digital simulation trial of hydroisostasy by finite element method

2021 ◽  
pp. 26-32
Author(s):  
Rustam Bulgakov
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Sea Level ◽  
Digital Simulation ◽  
Critical Issue ◽  
Sea Level Changes ◽  
Main Method ◽  
Global Character ◽  
Facilities Design ◽  
Element Method

Hydroisostasy as a geodynamic phenomenon was discovered along investigation sea level changes of the World Ocean as result of intakes water to glaciers during Glacial period and releasing back during Interglacials. The water loads under sea level changes influenced the change of solid Earth shape and make the contribution to the vertical Earth crust movement along shorelines areas. A vertical shorelines movements are critical issue of the longtime living infrastructure coast facilities design with the overflooding and overdrainage forecast. The main method of hydroisostasy phenomenon investigation is remain the digital simulation. The global character of phenomenon require simulation involving all planet volume and detail accounting of the lithosphere and mantle layers features for each region which is forced to use 3-D modeling with high resolution and require big computing resources. Finite element method with ability to assign boundary conditions allow to use local-regions models with enough resolutions and take into accounts local lithosphere and mantle features without involving big computing resources. One of the free software packs with open code and possibility applying FEM for geodynamics simulations is — ELMER, software designed and supported by Finland CSC — IT CENTER FOR SCIENCE LTD. The trial applying of ELMER software packs for modeling hydroisostasy phenomenon for Earth interior conditions close to Deryugin depression in Okhotsk sea in this study has done. A plausible and encouraging result obtained for continuation of research in more detail.

A Multi-Field Space-Time Finite Element Method for Structural Acoustics

1995 ◽  
Author(s):  
Lonny L. Thompson
Keyword(s):  
Finite Element ◽  
Time Domain ◽  
Acoustic Waves ◽  
Space Time ◽  
High Order ◽  
Elastic Structure ◽  
Structural Acoustics ◽  
Field Representation ◽  
Element Discretization ◽  
Acoustic Fluid

Abstract A Computational Structural Acoustics (CSA) capability for solving scattering, radiation, and other problems related to the acoustics of submerged structures has been developed by employing some of the recent algorithmic trends in Computational Fluid Dynamics (CFD), namely time-discontinuous Galerkin Least-Squares finite element methods. Traditional computational methods toward simulation of acoustic radiation and scattering from submerged elastic bodies have been primarily based on frequency domain formulations. These classical time-harmonic approaches (including boundary element, finite element, and finite difference methods) have been successful for problems involving a limited range of frequencies (narrow band response) and scales (wavelengths) that are large compared to the characteristic dimensions of the elastic structure. Attempts at solving large-scale structural acoustic systems with dimensions that are much larger than the operating wavelengths and which are complex, consisting of many different components with different scales and broadband frequencies, has revealed limitations of many of the classical methods. As a result, there has been renewed interest in new innovative approaches, including time-domain approaches. This paper describes recent advances in the development of a new class of high-order accurate and unconditionally stable space-time methods for structural acoustics which employ finite element discretization of the time domain as well as the usual discretization of the spatial domain. The formulation is based on a space-time variational equation for both the acoustic fluid and elastic structure together with their interaction. Topics to be discussed include the development and implementation of higher-order accurate non-reflecting boundary conditions based on the exact impedance relation through the. Dirichlet-to-Neumann (DtN) map, and a multi-field representation for the acoustic fluid based on independent pressure and velocity potential variables. Numerical examples involving radiation and scattering of acoustic waves are presented to illustrate the high-order accuracy achieved by the new methodology for CSA.

scholarly journals A Prediction Method for Acoustic Intensity Vector Field of Elastic Structure in Shallow Water Waveguide

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Wenbo Wang ◽  
Desen Yang ◽  
Jie Shi
Keyword(s):  
Spatial Structure ◽  
Shallow Water ◽  
Transfer Functions ◽  
Source Parameters ◽  
Prediction Method ◽  
Sound Field ◽  
Elastic Structure ◽  
Superposition Method ◽  
Acoustic Intensity ◽  
Sound Energy

Compared with scalar sound field, vector sound field explained the spatial structure of sound field better since it not only presents the sound energy distribution but also describes the sound energy flow characteristics. Particularly, with more complicated interaction among different wavefronts, the vector sound field characteristics of an elastic structure in a shallow water waveguide are worthy of studying. However, there is no reliable prediction method for the vector sound field of an elastic structure with a high efficiency in a shallow water waveguide. To solve the problem, transfer functions in the waveguide have been modified with some approximations to apply for the vector sound field prediction of elastic structures in shallow water waveguides. The method is based on the combined wave superposition method (CWSM), which has been proved to be efficient for predicting scalar sound field. The rationality of the approximations is validated with simulations. Characteristics of the complex acoustic intensity, especially the vertical components are observed. The results show that, with constructive and destructive interferences in the depth direction, there could be quantities of crests and vortices in the spatial structure of time-dependent complex intensity, which manifest a unique dynamic characteristic of sound energy. With more complicated interactions among the wavefronts, a structure source could not be equivalent to a point source in most instances. The vector sound field characteristics of the two sources could be entirely different, even though the scalar sound field characteristics are similar. Meanwhile, source types, source parameters, ocean environment parameters, and geo parameters may have influence on the vector sound field characteristics, which could be explained with the normal mode theory.

scholarly journals Analysis of Stress Deformation Characteristics of Composite Geomembrane Rock-Fill Dam with Core Wall

2013 ◽  
Vol 470 ◽  
pp. 962-965
Author(s):  
Dong Yan Ding ◽  
Jian Min Ren
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Elastic Model ◽  
Deformation Characteristics ◽  
Distribution Rule ◽  
Dimensional Finite Element ◽  
Stress And Deformation ◽  
Three Dimensional Finite Element ◽  
Nonlinear Elastic

The Chengzigou hydropower station of composite geomembrane rockfill dam as an example of the dam body and the composite geotechnical membrane stress and deformation characteristics are used nonlinear elastic model - Duncan EB model establish three-dimensional finite element model of rockfill,by using the large finite element softwareFLAC3D,whice provided geogrid element to simulate lexible geomembrane shear interaction with soil.The stress and deformation of the dam and the composite geomembrane is calculated under two conditionscompletion period and impoundment period.And analyze the change of the stress and strain distribution rule,whice will provide the basis for the design of the geomembrane.

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