Nonlinear inversion of geoelectric data acquired across 3D objects using a finite-element approach

Geophysics ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. F121-F133 ◽  
Author(s):  
Laurent Marescot ◽  
Sérgio Palma Lopes ◽  
Stéphane Rigobert ◽  
Alan G. Green
Keyword(s):  
Finite Element ◽  
Objective Function ◽  
Reference Model ◽  
Element Model ◽  
Gradient Algorithm ◽  
Complex Object ◽  
Nonlinear Inversion ◽  
Finite Element Approach ◽  
Element Approach ◽  
Geoelectric Data

We introduce a new finite-element-based scheme for the fast nonlinear inversion of large 3D geoelectric data sets acquired around isolated objects or across the earth’s surface. The principal novelty of this scheme is the combination of a versatile finite-element approach with (1) a method involving minimization of an objective function using a conjugate-gradient algorithm that includes an adjoint-field technique for efficiently establishing the objective-function gradient and (2) parabolic interpolation for estimating suitable inversion step lengths. This scheme is capable of handling large volumes of data acquired using diverse electrode configurations located around or across 3D structures. Only three solutions to the forward problem are required for each iteration. Computation of the Jacobian matrix, which might require computers with a large amount of memory, is not necessary. To minimize artificial irregularities in the inverted models, particularly near the electrodes, we smooth the model parametersafter each iteration. By including the influence of a reference model in the objective function, a priori information can be incorporated in the inversion process. Our new scheme is tested successfully on synthetic data generated for current and potential electrodes distributed around the surface of a complex object of finite extent. We also demonstrate the utility of the new scheme on geoelectric data acquired around a laboratory-scale object. Tomographic inversion of the 52,272 simulated voltage values in terms of an 8775-element model requires less than 45 minutes on a relatively slow Sun workstation. For the inversion of the 1016 observed voltage values in terms of an 81,480-element model, approximately 60 minutes of computer time is required. The rapid and flexible inversion scheme opens up new possibilities for resistivity imaging in geology, hydrology, engineering, nondestructive testing, and even biology and medicine, fields of study in which finite-element models are already used to represent complicated targets.

scholarly journals Statistical Analysis of Industrial Grinding Brush Force Characteristics Based on Finite Element Approach

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Chong Wang ◽  
Hongqiang Guo ◽  
Ying Zhao ◽  
Qun Sun ◽  
Ling Zhao
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Robot System ◽  
Finite Element Approach ◽  
Depth Study ◽  
Element Approach ◽  
Mathematical Equations ◽  
Control Application ◽  
The Mathematical Model ◽  
Force Characteristics

This paper presents an in-depth study of the helical grinding brush force characteristics aiming at developing a mobile robot system to perform rust removal and other surface processing tasks. Based on an off-line Finite Element model that can calculate brush filament deformation and force behaviors, a mathematical regression model has been developed to summarize brush force changes subjected to varying conditions into a series of mathematical equations. The predictions of the mathematical model are well converged with the Finite Element modeled results and the R-squared value is up to 0.95. The paper presents the model form and calibrated coefficients, which may provide an advantageous tool to predict the grinding brush force changes in real time and contribute well to an automatic grinding control application.

A FINITE ELEMENT APPROACH USING EQUIVALENT PLANE RECTANGULAR TRUSS ELEMENT IN NONLINEAR ANALYSIS OF REINFORCED CONCRETE STRUCTURES

2007 ◽  
Vol 04 (03) ◽  
pp. 383-396 ◽  
Author(s):  
FANGBO WU ◽  
XIANLI DING ◽  
SHAOYAO HE
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Nonlinear Analysis ◽  
Concrete Structures ◽  
Element Model ◽  
Reinforced Concrete Structures ◽  
New Approach ◽  
Finite Element Approach ◽  
Truss Element ◽  
Element Approach

A new finite element approach described in this paper uses an equivalent plane rectangular truss element to replace the traditional plane rectangular element in the nonlinear analysis of reinforced concrete structures. The major advantage of this approach is the simplified finite element model with reduced degrees of freedom and without the need of using displacement functions. The new approach can also trace the formation, development, and location of cracks in the reinforced concrete structures. The results of numerical analyses of structural examples showed that this new approach gave satisfactory results to the engineering problems in comparison with those obtained using the more complicated FE package ANSYS8.0.

scholarly journals Mechanical Properties of Group Iv Single-walled Nanotubes: A Finite Element Approach Based on the Density Functional Theory

2021 ◽  
Author(s):  
Mohammad Dastmard ◽  
Reza Ansari ◽  
Saeed Rouhi
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Finite Element ◽  
Density Functional ◽  
Element Model ◽  
Group Iv ◽  
Functional Theory ◽  
Finite Element Approach ◽  
The Density Functional Theory ◽  
Element Approach

Abstract In this article, the density functional theory is applied to investigate the mechanical properties of single-walled nanotubes of group IV of periodic table including carbon nanotube, silicon nanotube, germanium nanotube and stanene nanotube. (10,10) armchair nanotube is selected for the investigation. By establishing a link between potential energy expressions in the molecular and structural mechanics, a finite element approach is proposed for modeling the nanotubes. In the proposed model, the nanotubes are considered as an assemblage of beam elements. Young’s modulus of the nanotubes is computed by the proposed finite element model. Young's modulus of carbon, silicon, germanium, and tin nanotubes are obtained as 1029, 159.82, 83.23 and 18.15 GPa respectively, using the density functional theory. Also, the finite element approach gives the values as 1090, 154.67, 85.2 and 82.6 GPa respectively. It is shown that the finite element model can predict the results of the density functional theory with a good accuracy.

Effect of Chirality and Geometry on the Young’s Modulus of Graphene Structure Using Spring Based Finite Element Approach

2014 ◽  
Author(s):  
Moosa S. M. Al-Kharusi ◽  
Tasneem Pervez ◽  
Khalid Alz-Zebdeh
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Element Model ◽  
Technological Problem ◽  
Finite Element Approach ◽  
Carbon Carbon Bond ◽  
Element Approach ◽  
The Finite Element Model

The development of nanocomposite materials has led to vast progress in the field of composite materials as well as in finding new solutions to technological problem that have not been solved yet. Among the newly developed materials, the most attracting is the graphene based nanocomposites that has superior mechanical, thermal, optical and electrical properties. The hexagonal structure and the high strength of carbon–carbon bond in graphene yield strong material. Estimation of mechanical properties of the graphene becomes one of the important issues, which should be reasonably and accurately predicted to further promote its application development. Simulation and modeling techniques play a significant role in characterizing mechanical behavior especially for nanomaterials where the experimental measurements are very difficult to conduct. The aim of the current study is to estimate the Young’s modulus of elasticity of single layered graphene sheet using new spring based finite element approach. The use of spring finite elements help to accurately define the interatomic bonded interactions between carbon atoms based on potential energies obtained from molecular dynamics theory. The inclusion of both linear and torsion terms simultaneously has resulted in improved values of the Young’s modulus. The nodes in the finite element model define the position of carbon atoms in the graphene which are connected with appropriate spring-type elements. These elements are used to build the finite element model based on the observation that beam or truss elements require geometrical variables such as area and inertia, which are not required in the case of springs. Each node of this element provides six degrees of freedom (3 translations and 3 rotations) at which the complex interactions presented in the atomistic level can be considered. Parametric study is performed to investigate the effect of chirality and geometric parameters on the Young’s modulus of single graphene layer. The results are in good agreement with the published numerical and experimental results. The obtained results show an isotropic behavior, in contrast to limited molecular dynamic simulations. Young’s modulus of graphene shows a high dependency of stiffness on layer thickness.

A Finite Element Approach to Interface Cracks

1986 ◽  
Vol 53 (3) ◽  
pp. 573-578 ◽  
Author(s):  
H. D. van der Zande ◽  
H. J. Grootenboer
Keyword(s):  
Integral Equation ◽  
Finite Element ◽  
Stress Intensity ◽  
Interface Crack ◽  
Element Model ◽  
Mode Ii ◽  
Intensity Factors ◽  
Finite Element Approach ◽  
Finite Element Calculations ◽  
Element Approach

To investigate the behavior of cracks at the interface of materials with different elastic properties, a finite element model to calculate the Mode II stress-intensity factors was developed. The interface crack was considered to have locally closed tips, the size of which was determined from the finite element results. Numerical results of the integral equation for an interface crack were derived by M. Comninou for different applied loads. Comparing her results with our finite element calculations, some interesting differences have been discussed.

A Finite Element Approach to the Transient Dynamics of Rolling Tires with Emphasis on Rolling Noise Simulation4

2007 ◽  
Vol 35 (3) ◽  
pp. 165-182 ◽  
Author(s):  
Maik Brinkmeier ◽  
Udo Nackenhorst ◽  
Heiner Volk
Keyword(s):  
Finite Element ◽  
Traffic Noise ◽  
Complex Eigenvalue ◽  
Arbitrary Lagrangian Eulerian ◽  
Finite Element Approach ◽  
Road Systems ◽  
Element Approach ◽  
Road Surface Roughness ◽  
Complex Eigenvalue Analysis ◽  
Rolling Noise

Abstract The sound radiating from rolling tires is the most important source of traffic noise in urban regions. In this contribution a detailed finite element approach for the dynamics of tire/road systems is presented with emphasis on rolling noise prediction. The analysis is split into sequential steps, namely, the nonlinear analysis of the stationary rolling problem within an arbitrary Lagrangian Eulerian framework, and a subsequent analysis of the transient dynamic response due to the excitation caused by road surface roughness. Here, a modal superposition approach is employed using complex eigenvalue analysis. Finally, the sound radiation analysis of the rolling tire/road system is performed.

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