The effects of well damage and completion designs on geo-electrical responses in mature wellbore environments

Geophysics ◽  
2021 ◽  
pp. 1-50
Author(s):  
Gungor D. Beskardes ◽  
Chester J. Weiss ◽  
Evan Um ◽  
Michael Wilt ◽  
Kris MacLennan
Keyword(s):  
Finite Element ◽  
Electrical Potential ◽  
Real Life ◽  
Element Model ◽  
Computational Effort ◽  
Real Surface ◽  
Well Completion ◽  
Geologic Storage ◽  
Well Damage ◽  
Electrical Responses

Well integrity is one of the major concerns in long-term geologic storage sites due to its potential risk for well leakage and groundwater contamination. Evaluating changes in electrical responses due to energized steel-cased wells has the potential to quantify and predict possible wellbore failures as any kind of breakage or corrosion along highly-conductive well casings will have an impact on the distribution of subsurface electrical potential. However, realistic wellbore-geoelectrical models that can fully capture fine scale details of well completion design and state of well damage at the field scale require extensive computational effort or can even be intractable to simulate. To overcome this computational burden while still keeping the model realistic, we utilize the Hierarchical Finite Element Method which represents electrical conductivity at each dimensional component (1-D edges, 2-D planes and 3-D cells) of a tetrahedra mesh. This allows us to consider well completion designs with real-life geometric scales and well systems with realistic, detailed, progressive corrosion and damage in our models. Here, we present a comparison of possible discretization approaches of a multi-casing completion design in the finite element model. The impacts of the surface casing length and the coupling between concentric well casings, as well as the effects of the degree and the location of well damage on the electrical responses are also examined. Finally, we analyze real surface electric field data to detect the wellbore integrity failure associated with damage.

Effect of cracks and pitting defects on gear meshing

2012 ◽  
Vol 226 (11) ◽  
pp. 2805-2815 ◽  
Author(s):  
Alfonso Fernandez del Rincon ◽  
Fernando Viadero ◽  
Miguel Iglesias ◽  
Ana de-Juan ◽  
Pablo Garcia ◽  
...  
Keyword(s):  
Finite Element ◽  
Computational Models ◽  
Inequality Constraints ◽  
Variable Stiffness ◽  
Element Model ◽  
Equation System ◽  
Transmission Error ◽  
Computational Effort ◽  
Gear Mesh ◽  
Non Linear

The development of vibration-based condition monitoring techniques, especially those focused on prognosis, requires the development of better computational models that enable the simulation of the vibratory behaviour of mechanical systems. Gear transmission vibrations are governed by the so-called gear mesh frequency and its harmonics, due to the variable stiffness of the meshing process. The fundamental frequency will be modulated by the appearance of defects which modify the meshing features. This study introduces an advanced model to assess the consequences of defects such as cracks and pitting on the meshing stiffness and other related parameters such as load transmission error or load sharing ratio. Meshing forces are computed by imposing the compatibility and complementarity conditions, leading to a non-linear equation system with inequality constraints. The calculation of deformations is subdivided into a global and a local type. The former is approached by a finite element model and the latter via a non-linear Herztian-based formulation. This procedure enables a reduced computational effort, in contrast to conventional finite element models with contact elements. The formulation used to include these defects is described in detail and their consequences are assessed by a quasi-static analysis of a transmission example.

A METHOD TO CALCULATE THE AIS TRAUMA SCORE FROM A FINITE ELEMENT MODEL

2020 ◽  
Vol 20 (06) ◽  
pp. 2050034 ◽  
Author(s):  
C. BASTIEN ◽  
C. NEAL-STURGESS ◽  
J. CHRISTENSEN ◽  
L. WEN
Keyword(s):  
Finite Element ◽  
Head Trauma ◽  
Head Injuries ◽  
Real Life ◽  
Element Model ◽  
Organ Injury ◽  
Trauma Severity ◽  
Lagrangian Finite Element ◽  
Trauma Model ◽  
Gray Matters

In the real world, traumatic injuries are measured using the Abbreviated Injury Scale (AIS), however, such a scale cannot be computed to date or the injury precisely located by using human computer models. These models use stresses and strains to evaluate whether serious or fatal injuries are reached, which unfortunately bear no direct relation to AIS. This paper proposes to overcome this deficiency and suggests a unique Organ Trauma Model (OTM) able to calculate the risk to life of any organ injury, focussing in this case on real-life pedestrian head injuries. The OTM uses a power method, named Peak Virtual Power (PVP), and defines a brain white and gray matters trauma response as a function of impact direction and impact speed. The OTM was tested against four real-life pedestrian accidents and proved to predict the head trauma severity and location. In some cases, the method did however under-estimate the trauma by 1 AIS level because of post-impact haemorrhage which cannot be captured with Lagrangian Finite Element solvers. The OTM has the potential to create an important advance in vehicle safety by adding more information on the risk of head trauma.

Multi-Objective Structural Optimization of Vehicle Wheels

2021 ◽  
Author(s):  
P. Stabile ◽  
F. Ballo ◽  
M. Gobbi ◽  
G. Previati
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cross Section ◽  
Element Model ◽  
Computational Effort ◽  
Optimized Design ◽  
Support Design ◽  
Design Constraints ◽  
Multi Objective ◽  
Simplified Finite Element Model

Abstract This work focuses on the development of an innovative design methodology for lightweight wheels of road vehicles. In particular, the activity is carried out for the specific case of a wheel designed for an ultra-efficient vehicle for Shell Eco-marathon competition, with the aim of finding preliminary design solutions. A simplified finite element model of the tire structure is employed for an accurate modelling of the forces acting at the tire/rim interface. The material properties of the tire structure are identified by means of experimental tests. The computed tire/rim force distribution is applied to the rim exploiting a simplified finite element model of the wheel rim. A multi-objective optimization problem is formulated, based on mass and compliance minimization. Several wheel design layouts are investigated, which differ in terms of number of spokes (i.e. 3, 5 and 7), spokes layout (i.e. straight and Y-shape) and spokes cross section (i.e. rectangular, C and I). Geometric quantities related to the cross section dimensions of the spokes and to the rim thickness are optimized. Design constraints related to structural stiffness and elastic stability (both global and local buckling) are taken into account. The developed finite-element based model of the wheel is used to train a set of neural networks to approximate the objective functions and the design constraints to reduce the computational effort. A multi-objective genetic algorithm is adopted to obtain the Pareto-optimal solutions. The implemented method has proved to be a valuable tool to support design engineers in taking critical decisions in the early stages of the design process.

scholarly journals General Homogenised Formulation for Thick Viscoelastic Layered Structures for Finite Element Applications

Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 714 ◽  
Author(s):  
Ondiz Zarraga ◽  
Imanol Sarría ◽  
Jon García-Barruetabeña ◽  
María Jesús Elejabarrieta ◽  
Fernando Cortés
Keyword(s):  
Finite Element ◽  
Passive Control ◽  
Element Model ◽  
Computational Effort ◽  
Viscoelastic Layer ◽  
Flexural Stiffness ◽  
Constrained Layer Damping ◽  
Thin Beam ◽  
Passenger Vehicles ◽  
Shear Effects

Viscoelastic layered surface treatments are widely used for passive control of vibration and noise, especially in passenger vehicles and buildings. When the viscoelastic layer is thick, the structural models must account for shear effects. In this work, a homogenised formulation for thick N-layered viscoelastic structures for finite element applications is presented, which allows for avoiding computationally expensive models based on solids. This is achieved by substituting the flexural stiffness in the governing thin beam or plate equation by a frequency dependent equivalent flexural stiffness that takes shear and the properties of the different layers into account. The formulation is applied to Free Layer Damping (FLD) and Constrained Layer Damping (CLD) beams and plates and its ability to accurately compute the eigenpairs and dynamic response is tested by implementing it in a finite element model and comparing the obtained results to those given by the standard for the application—Oberst for the FLD case and RKU for the CLD one—and to a solid model, which is used as reference. For the cases studied, the homogenised formulation is nearly as precise as the model based on solids, but requires less computational effort, and provides better results than the standard model.

scholarly journals A Comparative Study of Helical and Cross-Wedge Rolling Processes for Producing Ball Studs

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2887
Author(s):  
Tomasz Bulzak ◽  
Janusz Tomczak ◽  
Zbigniew Pater ◽  
Krzysztof Majerski
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
Energy Efficient ◽  
Real Life ◽  
Element Model ◽  
Cross Wedge Rolling ◽  
Flow Lines ◽  
Life Conditions ◽  
Grain Flow ◽  
The Finite Element Model

This paper presents two rolling technologies: cross-wedge rolling (CWR) and helical-wedge rolling (HWR). The two rolling processes were compared using the example of rolling a ball stud forging. The technologies were modeled in the finite element model (FEM) environment. Calculations were performed to obtain distributions of strain and the Cockcroft–Latham damage criterion. The investigated processes were also performed under real-life conditions. The results of the experiments were used to compare the force and energy parameters of the rolling technologies. Tests were also carried out to investigate the microstructure of the studs and a grain size after rolling. The state of the macrostructure, i.e., the grain flow lines, was also compared. The experiments showed that HWR was a more energy-efficient process.

Validation of Embedded Element Method in the Prediction of White Matter Disruption in Concussions

2016 ◽  
Author(s):  
Harsha T. Garimella ◽  
Reuben H. Kraft
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Diffusion Tensor ◽  
Real Life ◽  
Human Head ◽  
Element Model ◽  
Diagnostic Tools ◽  
Fiber Tractography ◽  
Imaging Data ◽  
Element Method

A better understanding of the axonal injury would help us develop improved diagnostic tools, protective measures, and rehabilitation treatments. Computational modeling coupled with advanced neuroimaging techniques might be a promising tool for this purpose. However, before the models can be used for real life applications, they need to be validated and cross-verified with real life scenarios to establish the credibility of the model. In this work, progress has been made in validating a human head finite element model with embedded axonal fiber tractography (using embedded element method) using pre- and post-diffusion tensor imaging data (DTI) of a concussed athlete. Fractional anisotropy (FA) was used to determine the microstructural changes during injury. These damaged locations correlated well with the damaged locations observed from the finite element model. This work could be characterized as a first step towards the development of a more comprehensively validated human head finite element model.

Improved Calculation of Eigenvector Sensitivities Using Matrix Perturbation Analysis

1997 ◽  
Vol 119 (1) ◽  
pp. 137-141 ◽  
Author(s):  
R. M. Lin ◽  
M. K. Lim ◽  
Z. Wang
Keyword(s):  
Finite Element ◽  
Dynamic Control ◽  
Element Model ◽  
Research Area ◽  
Computational Effort ◽  
Matrix Perturbation ◽  
Practical Applications ◽  
Structural Design Optimization ◽  
Matrix Perturbation Analysis ◽  
Eigenvector Derivatives

Derivatives of eigenvalues and eigenvectors have become increasingly important in the development of modern numerical methods for areas such as structural design optimization, dynamic system identification and dynamic control, and the development of effective and efficient methods for the calculation of such derivatives has remained to be an active research area for several decades. Based on the concept of matrix perturbation, this paper presents a new method for the improved calculation of eigenvector derivatives in the case where only few of the lower modes of a system under study have been computed. By using this new proposed method, considerable improvement on the accuracy of the estimation of eigenvector derivatives can be achieved at the expense of very tiny extra computational effort since only few matrix vector operations are required. Convergency criterion of the method has been established and the required accuracy can be controlled by including more higher order terms. Numerical results from practical finite element model have demonstrated the practicality of the proposed method. Further, the proposed method can be easily incorporated into commercial finite element packages to improve the accuracy of eigenderivatives needed for practical applications.

Effect of Openings in Ring-Reinforced Shells

1990 ◽  
Vol 27 (01) ◽  
pp. 56-64
Author(s):  
Douglas Deans
Keyword(s):  
Finite Element ◽  
Real Life ◽  
Local Stress ◽  
Element Model ◽  
Entire Structure ◽  
Random Manner ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Reinforced Shell ◽  
Made In

The ring-reinforced shell is a primary structure used in the marine and industrial world. Stress and buckling analysis of such structures is generally based on axisymmetric analysis wherein all openings in the shell are neglected. In real life, such structures have a large number of openings often made in a random manner. In order to design an appropriate reinforcement at such an opening, it is necessary to carry out a detailed local stress analysis. Such an analysis can be made either through the use of part models or by superelements which include the entire structure, as well as the local reinforcement. Zoom analysis using the whole model is expensive and requires knowledge of multilevel super element techniques. Analysis using part models is cheaper and can be equally reliable. This paper investigates the effects of openings on the stress distribution in ring-reinforced shells, such as submarines, using a finite element model. The stress concentration factors (SCF's) in areas adjacent to the opening are determined from this analysis. Using these SCF's, modeling rules for utilization of part models are developed and recommended for use.

scholarly journals Comparison of Meshing Strategies in THR Finite Element Modelling

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2332 ◽  
Author(s):  
Alessandro Ruggiero ◽  
Roberto D’Amato ◽  
Saverio Affatato
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Modelling ◽  
Internal Surface ◽  
Element Model ◽  
Computational Effort ◽  
Von Mises Stress ◽  
Acetabular Cup ◽  
Element Modelling ◽  
Multibody Model

In biomechanics and orthopedics, finite element modelling allows simulating complex problems, and in the last few years, it has been widely used in many applications, also in the field of biomechanics and biotribology. As is known, one crucial point of FEM (finite element model) is the discretization of the physical domain, and this procedure is called meshing. A well-designed mesh is necessary in order to achieve accurate results with an acceptable computational effort. The aim of this work is to test a finite element model to simulate the dry frictionless contact conditions of a hip joint prosthesis (a femoral head against an acetabular cup) in a soft bearing configuration by comparing the performances of 12 common meshing strategies. In the simulations, total deformation of the internal surface of the cup, contact pressure, and the equivalent von Mises stress are evaluated by using loads and kinematic conditions during a typical gait, obtained from a previous work using a musculoskeletal multibody model. Moreover, accounting for appropriate mesh quality metrics, the results are discussed, underlining the best choice we identified after the large amount of numerical simulations performed.

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