Finite Element Modelling of Bi-Material Interface for Crack Growth Evaluation: Technical Note

2018 ◽  
Vol 9 (5) ◽  
Author(s):  
M. Logesh ◽  
S. Palani ◽  
S. Shanmugan ◽  
M. Selvam ◽  
K.A. Harish
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Degrees Of Freedom ◽  
Technical Note ◽  
Fe Model ◽  
J Integral ◽  
Fe Method ◽  
Material Interface ◽  
Determine Stress Intensity Factor ◽  
Fiber Metal

Finite element (FE) method is commonly used to study cracks in structures. In this paper, J-integral method is applied over FE model of a cracked body to determine stress intensity factor (SIF) in the domain of linear elastic fracture mechanics (LEFM). This paper formulates the J-integral methodology for 2D FE model using a coarse mesh with less degrees of freedom. Two cases , a finite plate with edge cracks and a normal crack growth in fiber metal laminated plate, are demonstrated. Numerical implementation and mesh refinement issues to maintain path independent J-integral values are explored.

Output-Only Modal Analysis of an Internal Unreachable Module Embedded in a Space Electronic Equipment

2012 ◽  
Author(s):  
Lassaad Ben Fekih ◽  
Georges Kouroussis ◽  
David Wattiaux ◽  
Olivier Verlinden ◽  
Christophe De Fruytier
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Mode Shapes ◽  
Fe Model ◽  
Fe Method ◽  
Numeric Model ◽  
Stiffness Matrices ◽  
Output Only

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.

scholarly journals 3D Finite Element Model Simulating the Behaviour of Filling Soils Used to Set Up a New Placement Method for Separate Sewer Systems

2019 ◽  
Vol 8 (3) ◽  
pp. 87-98
Author(s):  
Alaa Abbas ◽  
Felicite Ruddock ◽  
Rafid Alkhaddar ◽  
Glynn Rothwell ◽  
Iacopo Carnacina ◽  
...  
Keyword(s):  
Finite Element ◽  
Soil Properties ◽  
Model Simulation ◽  
New Method ◽  
Traffic Load ◽  
Scale Model ◽  
Fe Model ◽  
Fe Method ◽  
Buried Pipes ◽  
The Impact

The use of a finite element (FE) method and selection of the appropriate model to simulate soil elastoplastic behaviour has confirmed the importance and sensitivity of the soil properties on the accuracy when compared with experimental data. The properties of the filling soil play a significant role in determining levels of deformation and displacement of both the soil and subterranean structures when using the FE model simulation. This paper investigates the impact of the traffic load on the filling soil deformation when using the traditional method, one pipe in a trench, and a new method, two pipes in a single trench one over the other, for setting up a separate sewer system. The interaction between the buried pipes and the filling soils has been simulated using an elastoplastic FE model. A modified Drucker–Prager cap constitutive model was used to simulate the stress-strain behaviours of the soil. A series of laboratory tests were conducted to identify the elastoplastic properties of the composite soil used to bury the pipes. The FE models were calibrated using a physical lab model for testing the buried pipes under applied load. This allows the FE model to be confidently upgraded to a full-scale model. The pipe-soil interactions were found to be significantly influenced by the soil properties, the method of placing the pipes in the trench and the diameters of the buried pipes. The deformation of the surface soil was decreased by approximately 10% when using the new method of setting up the separate sewer.

Effect of a Degenerated C5-C6 Disc on the Biomechanics of Adjacent Levels: A Poroelastic Finite Element Investigation

2007 ◽  
Author(s):  
Mozammil Hussain ◽  
Raghu N. Natarajan ◽  
Gunnar B. J. Andersson ◽  
Howard S. An
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Morphological Changes ◽  
Axial Strain ◽  
Fe Model ◽  
Fe Method ◽  
Regional Effect ◽  
In Vitro Techniques

Degenerative changes in the cervical spine due to aging are very common causes of neck pain in general population. Although many investigators have quantified the gross morphological changes in the disc with progressive degeneration, the biomechanical changes due to degenerative pathologies of the disc and its effect on the adjacent levels are not well understood. Despite many in vivo and in vitro techniques used to study such complex phenomena, the finite element (FE) method is still a powerful tool to investigate the internal mechanics and complex clinical situations under various physiological loadings particularly when large numbers of parameters are involved. The objective of the present study was to develop and validate a poroelastic FE model of a healthy C3-T1 segment of the cervical spine under physiologic moment loads. The model included the regional effect of change in the fixed charged density of proteoglycan concentration and change in the permeability and porosity due to change in the axial strain of disc tissues. The model was further modified to include various degrees of disc degeneration at the C5-C6 level. Outcomes of this study provided a better understanding on the progression of degeneration along the cervical spine by investigating the biomechanical response of the adjacent segments with an intermediate degenerated C5-C6 level.

Comprehensive FEA of Thermal Mitigation Buoyancy Module (TMBM)–Soil Interaction Using the Coupled Eulerian–Lagrangian (CEL) Method

2010 ◽  
Author(s):  
Kenton Pike ◽  
Gang Duan ◽  
Jason Sun ◽  
Paul Jukes
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Lateral Displacement ◽  
Gas Production ◽  
Fe Model ◽  
Fe Method ◽  
Lateral Buckling ◽  
Global Buckling ◽  
Thermal Mitigation ◽  
Large Soil

Thermal expansion and global buckling is a critical design aspect for subsea flowline systems subjected to high pressure and high temperature (HPHT). In the Gulf of Mexico, HPHT oil/gas production is becoming exceedingly common as drilling and production depths extend deeper. Advanced finite element analysis becomes essential for flowline expansion and buckling design which is highly dependent on pipe-soil interaction behavior. For decades, pipe-soil interaction has been the focus of many research studies and joint industry projects. For HPHT flowline systems, thermal mitigation is decisive for safe design. Thermal mitigation acts to control global buckling at designate locations and avoid buckling in unknown locations. Thermal mitigation results in significant cost savings by lowering the welding class besides the buckling locations and increases safety in terms of local buckling, fracture, and fatigue. One widely used thermal mitigation method involves attaching a buoyancy module around a segment of the flowline. In this paper the Coupled Eulerian Langrangian (CEL) finite element (FE) formulation is utilized to simulate the interaction between soil and the thermal mitigation buoyancy module (TMBM). The paper demonstrates the capability of the CEL FE method to simulate large soil deformation without the numerical difficulties that are commonly associated with other numerical formulations e.g. ALE (Arbitrary Lagrangian Eulerian) or more conventional Lagrangian. Initially, a three dimensional (3D), continuum, FE model is used to establish the variation of initial embedment along the length of the buoyancy and adjoining pipe. The study then establishes the lateral displacement/resistance relationships under different levels of contact pressure and soil embedment for a series of buoyancy-soil interaction segments, also using the CEL FE method. Current practice for global pipeline thermal expansion FEA is to utilize the same friction model for both buoyancy-soil interaction and pipe-soil interaction. The obtained buoyancy-soil interaction model from the current study is to be used as input to the global FE model to more precisely simulate flowline lateral buckling behavior. This paper presents a practical application of the current state of the art in modeling large soil deformations in providing an improved approach for modeling buoyancy-soil interactions in the global FEA of pipeline thermal expansion and lateral buckling.

Modeling IPMC Material With Dynamic Surface Characteristics

2009 ◽  
Author(s):  
Deivid Pugal ◽  
Alvo Aabloo ◽  
Kwang J. Kim ◽  
Youngsoo Jung
Keyword(s):  
Finite Element ◽  
Time Moment ◽  
Surface Characteristics ◽  
Dynamic Resistance ◽  
Charge Movement ◽  
Fe Model ◽  
Metal Composite ◽  
Fe Method ◽  
Element Analysis ◽  
Dynamic Surface

This paper presents the Finite Element Analysis (FEA) of an ionic polymer-metal composite (IPMC) material. The IPMC materials are known to bend when electric field is applied on the electrodes. The material also produces potential difference on the electrodes when is bent. Several authors have used the FEA to describe that fenomenon and rather precise basic Finite Element (FE) models already exist. Therefore the current study is mainly focused on the modeling of the electrodes of IPMC. The first goal of this research is to model the electric currents in the electrodes. The basis of the electric current calculations is the Ramo-Shockley theorem, which has been used in the other areas of physics to describe the currents in a circuit due to a charge movement in a media. We have used the theorem to calculate the current density in the continuous electrodes of IPMC due to the ion migration in the backbone polymer. Along the current densities we are able to calculate voltage on the electrode at a given time moment. The model is demonstrated to give some physically reasonable results. However, the model is rather complex and as the solution times are quite large, some possible optimizations have been considered as well. The second goal of this study is to include the dynamic resistance and capacitance of the electrodes in our model. Lot of research has been done to develop a physically reasonable capacitor-resistor model of an IPMC and the results have been promising. Furthermore, some authors have managed to develop partial differential equations (PDE) to describe the model. We try to include some simplified versions of those equations into our physical model. As the FE model for IPMC is nonlinear and gets complicated very fast when additional equations are added, the final sections of this paper briefly considers some novel optimization ideas in regard to modeling IPMC with FE method.

Mechanism of Slow Crack Growth in Polyethylene: A Finite Element Approach

2015 ◽  
Author(s):  
Xiangpeng Luo ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Failure Time ◽  
Bulk Material ◽  
Slow Crack Growth ◽  
Damage Model ◽  
Constitutive Models ◽  
Fe Model ◽  
Notch Angle ◽  
Craze Zone

Slow crack growth (SCG) is a common failure mode in underground polyethylene (PE) piping which was designed for 50-year services. It had been revealed by experiments that the SCG process is caused by continuous propagation of the craze zone at the crack tip through the bulk material. However, the mechanism of SCG failure has not been understood clearly. The eXtended Finite Element Method (XFEM) is found to be an effective tool for locally non-smooth features (voids, cracks, etc.) in solid or fluid mechanics solutions. In this paper the time-dependent property of PE was considered, a viscoelastic constitutive model was used for the bulk material. To represent the material deterioration during SCG, a damage model was developed for the craze zone. Combined with the XFEM, the process of the Pennsylvania Notched Test (PENT), which had been widely applied for characterizing resistance of SCG for PE pipes or resins, was analyzed based on the proposed finite element (FE) model containing the two constitutive models. The numerical results were then compared with the experimental data in literatures. It showed that the failure time and final notch angle were in agreement with the experimental observations. Based on the verified FE model, strain distributions along the boundary of the crack were studied and the shortcomings of this model were discussed.

scholarly journals Numerical analysis of circular and square section concrete filled aluminum tubes under axial compression

2020 ◽  
Vol 14 (54) ◽  
pp. 169-181
Author(s):  
Pan Jinlong ◽  
Li Guanhua ◽  
Jingming Cai
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Axial Compression ◽  
Parametric Analysis ◽  
Concrete Strength ◽  
Fe Model ◽  
Fe Method ◽  
The Core ◽  
Aluminum Tubes ◽  
Core Concrete

In this paper, the finite element (FE) method was used to investigate the axial compressive behaviors of circular and square concrete filled aluminum tubes (CFAT). Firstly, the simulational results were compared with the experimental results and the accuracy of the proposed FE model was verified. On this basis, the FE model was further applied to compare the mechanical properties of both circular and square CFATs under axial compression. It was found that the circular CFATs have a better effect on restraining the core concrete than square CFATs. The parametric analysis was also conducted based on the proposed FE model. It was noticed that the mechanical differences of the two kinds of CFATs gradually decreased with the increase of the aluminum ratio, aluminum strength and concrete strength.

scholarly journals Application of Artificial Neural Networks in Hybrid Simulation

2019 ◽  
Vol 9 (21) ◽  
pp. 4495 ◽  
Author(s):  
Mucha
Keyword(s):  
Finite Element ◽  
Real Time ◽  
Degrees Of Freedom ◽  
Computational Cost ◽  
Hybrid Simulation ◽  
Time Algorithm ◽  
High Accuracy ◽  
Small Time ◽  
Fe Model ◽  
Artificial Neural

Hybrid simulation is a technique for testing mechanical systems. It applies to structures with elements hard or impossible to model numerically. These elements are tested experimentally by straining them by means of actuators, while the rest of the system is simulated numerically using a finite element method (FEM). Data is interchanged between experiment and simulation. The simulation is performed in real-time in order to accurately recreate the dynamic behavior in the experiment. FEM is very computationally demanding, and for systems with a great number of degrees of freedom (DOFs), real-time simulation with small-time steps (ensuring high accuracy) may require powerful computing hardware or may even be impossible. The author proposed to swap the finite element (FE) model with an artificial neural network (ANN) to significantly lower the computational cost of the real-time algorithm. The presented examples proved that the computational cost could be reduced by at least one number of magnitude while maintaining high accuracy of the simulation; however, obtaining appropriate ANN was not trivial and might require many attempts.

Development and Preliminary Validation of a Parametric Pediatric Head Finite Element Model for Population-Based Impact Simulations

2011 ◽  
Author(s):  
Jingwen Hu ◽  
Zhigang Li ◽  
Jinhuan Zhang
Keyword(s):  
Finite Element ◽  
Head Injury ◽  
Element Model ◽  
The United States ◽  
Population Based ◽  
Head Model ◽  
Fe Model ◽  
Fe Method ◽  
Preliminary Validation ◽  
Head Responses

Head injury is the leading cause of pediatric fatality and disability in the United States (1). Although finite element (FE) method has been widely used for investigating head injury under impact, there are only a few 3D pediatric head FE models available in the literature, including a 6-month-old child head model developed by Klinich et al (2), a newborn, a 6-month-old and a 3-year-old child head model developed by Roth et al. (3, 4, 5), and a 1.5-month-old infant head model developed by Coats et al (6). Each of these models only represents a head at a single age with single head geometry. Nowadays, population-based simulations are getting more and more attention. In population-based injury simulations, impact responses for not only an individual but also a group of people can be predicted, which takes into account variations among people thus providing more realistic predictions. However, a parametric pediatric head model capable of simulating head responses for different children at different ages is currently not available. Therefore, the objective of this study is to develop a fast and efficient method to build pediatric head FE models with different head geometries and skull thickness distributions. The method was demonstrated by morphing a 6-month-old infant head FE model into three newborn infant head FE models and by validating three morphed head models against limited cadaveric test data.

Identification of Free-Free Modes From Constrained Vibration Data for Flexible Multibody Models

1999 ◽  
Author(s):  
Tong Y. Yi ◽  
Parviz E. Nikravesh
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Multibody System ◽  
Element Model ◽  
Flexible Body ◽  
Fe Model ◽  
Modal Data ◽  
Vibration Data

Abstract This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.

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