Full Three-dimensional Finite Element Research Articles

Numerical Study on Mechanical Behavior and Electromechanical Properties of Solder-Jointed REBCO-Coated Conductors.

As the second-generation high-temperature superconducting conductors, rare earth-barium-copper-oxide (REBCO) coated conductor (CC) tapes have good potential as high-field and high-energy superconductors. In superconducting applications, several joints are required for conjugating comparatively short REBCO CC tapes. Soldering lap joints are the simplest and most commonly applied REBCO CC joints. In addition to joint resistance, the mechanical behavior and electromechanical properties are also crucial for superconducting applications. In this paper, the electromechanical properties and mechanical behaviors of soldering lap joints at 77 K under a self-field were studied. The mechanical behavior was addressed by using a full three-dimensional multilayer elastic-plastic finite element model (FEM) with REBCO CC tape main layers and solder connecting layers. Then, the electromechanical properties were analyzed by using Gao's strain-Ic degradation general model on the basis of the FEM results. Both the mechanical behavior and electromechanical properties were verified by experimental results. The effects of soldering lap conditions including lap length, soldering thickness and lap style on the electromechanical properties and mechanical behaviors were discussed. The results indicate that shorter overlap lengths and a thinner solder can reduce the premature degradation of Ic due to stress concentrations nearby the joint edges; moreover, the irreversible critical strain is significantly higher in the back-to-back joint approach compared to the widely used face-to-face joint approach.

Ballistic performance of UHMWPE fiber laminates with pre-formed holes

Understanding how previous ballistic impacts affect the subsequent penetration resistance of ultra-high molecular weight polyethylene (UHMWPE) fiber laminates is crucial for their application in multi-hit scenarios. In order to investigate the effect of fiber fracture, a systematic examination of the ballistic performance of UHMWPE laminates with pre-formed holes is conducted through a combined experimental and numerical approach. Penetration resistance, dynamic penetration process, and deformation/failure modes of laminates with different configurations of pre-formed holes are tested and compared. A full three-dimensional finite element model is established, and a continuum homogenized model is utilized to simulate the laminate. The effectiveness of numerical model is validated by achieving a reasonable agreement between predictions and measurements. The presence of a single pre-formed hole will change the severity of delamination and result in tear failures, while it has minimal effect on penetration resistance until the spacing distance reaches 10 mm. When spacing distance remains the same, the change in orientation of a single pre-formed hole has little influence on the velocity history. Further, an enhancement in ballistic performance is observed when the number of pre-formed holes is increased to four, due mainly to the significant pull-in at the edge of pre-formed hole and the released fiber tensile stresses. The results of this study are valuable for comprehending the ballistic performance of UHMWPE laminate when subjected to multiple projectile impacts and have practical implications for the design of advanced protective systems.

Improved-FSDT-based solid-shell element for buckling analysis of plate, spherical cap, and cylindrical shell of FG porous materials

This study's objective is to propose a full three-dimensional finite element modeling for examining the buckling behaviors of functionally graded (FG) porous materials with plates, spherical cap, and cylindrical shapes. An improved first-order shear deformation theory (IFSDT) is utilized in order to develop the three-dimensional solid-shell element. The governing equations are developed in a way that offers a parabolic distribution of the transverse shear strains through the FG porous shell thickness and a zero condition of the transverse shear stresses on the top and bottom surfaces. The given IFSDT solid-shell element has the ability to model any kind of shell structures and incorporates a three-dimensional material law. In this study, two types of porosity distribution functions are considered. The performance of the current IFSDT solid-shell element has been demonstrated by examining the buckling behavior of Functionally Graded Porous plates, spherical caps, and cylindrical shells. The effect of the porosity distribution, porosity coefficient, power-law index, geometrical design parameters and boundary conditions on the buckling behaviors of FG porous shells structures is evaluated.

Heterogeneous Beam Element for Multiscale Modeling of Non-prismatic Composite Beam-like Structures

Anisotropy, heterogeneity, and geometry make full system-level three-dimensional (3D) finite element analysis (FEA) simulation of real composite beam-like structures, such as wind blades, impossible due to limitations on computing resources. A popular approach is to cut the structure into multiple cross-sections, from which the beam properties based on the Euler-Bernoulli or Timoshenko beam models are extracted using two-dimensional (2D) cross-sectional analyses. These properties are then utilized in beam elements for system-level analyses. However, the mechanics behind 2D cross-sectional analyses are based on prismatic beams, limiting the accuracy of this approach on non-prismatic structures, especially in predicting stresses. In this work, we present a new multiscale method based on Mechanics of Structure Genome to analyze beam-like non-prismatic composite structures. A beam-like structure is homogenized into a series of 3-node Heterogeneous Beam Elements (HBE) with effective beam element stiffness matrices, which are then used as input for one-dimensional (1D) beam analysis using Abaqus User Element subroutine (UEL). Using the macroscopic beam analysis results as input, we can also perform dehomogenization to predict the stresses and strains in the original structure. We use three examples, a prismatic composite beam, an isotropic homogeneous tapered beam, and a composite tapered beam, to demonstrate the capability of HBE and show its advantages over the traditional cross-sectional analysis approach. HBE can capture macroscopic behavior and detailed stresses due to non-prismatic geometry. HBE provides a new concept to model non-prismatic composite beams by modeling heterogeneous beam-like structures as equivalent beam elements rather than beam properties of material points of the reference line.

Application of Equivalent Single Layer Approach for Ultimate Strength Analyses of Ship Hull Girder

The objective of this paper is to present the application of equivalent single layer (ESL) approach for the ultimate strength assessment of ship hull girder in the context of numerical finite element (FE) simulations. In the ESL approach, the stiffened panel is replaced with a single plate, which has the equivalent stiffness of the original panel. Removal of tertiary stiffening elements from the numerical model facilitates time-savings in pre-processing and FE analysis stage. The applicability of ESL approach is demonstrated with two case studies, one compartment model and full-sized double hull tanker model in intact and damaged conditions. The damage extents are determined based on the international association of classification societies from common structural rules (IACS-CSR) for oil tanker. Ship hull girder is exposed to distributed pressure with the sinusoidal shape that bends the hull girder. This pressure load is applied separately to bottom and side structures to obtain the vertical and horizontal bending moments of the hull girder, respectively. Ultimate strength predictions obtained from ESL approach are compared to full three-dimensional finite element method (3D FEM) and IACS incremental-iterative method. The comparison between different methods is provided in terms of longitudinal bending moment and cross sectional stress distribution. Overall, ESL approach yields good agreement compared to the 3D FEM results in predicting the ultimate strength of ship hull girder while providing up to 3 times computational efficiency and ease of modeling.

Impact of Manufacturing Flaw on Fatigue Damage Development and on Stiffness Variation in Woven Composite Plates

Abstract Under dynamic loading conditions, damage in a plain weave carbon fiber reinforced polymer (CFRP) composite is a complex and multiscale process, especially in the presence of a manufacturing flaw. In this context, this paper investigates the impact of an inserted flaw on the damage scenario and stiffness degradation over fatigue life. To achieve this objective, a full three-dimensional finite element model (FEM) is developed to evaluate the stress distribution induced by the local defect. Fatigue tests are then performed on two configurations with and without inserted flaws with continuous monitoring by using non-destructive testing (NDT) techniques. The acoustic emission (AE) method is used for damage quantification and source localization while digital image correlation (DIC) and air-coupled ultrasonics (ACU) are applied to evaluate the stiffness degradation. The cross results obtained using these three monitoring techniques provide an insight into the damage process and stiffness degradation in woven composite with a simulated manufacturing flaw.

Condensed finite element scheme for symmetric multi-layer structures including dilatational motion

Condensed models act as useful tools to reduce the computational time in the finite element simulations by describing the dynamic behaviour of the multi-layer structure with only one equivalent homogeneous layer. Many condensed plate models in the literature assume constant velocity through the thickness which allows only anti-symmetric motions like bending and shear, but do not include symmetric motions like dilatational or compressional behaviour. The recently developed condensed model by Marchetti et al. (2021) overcomes this setback by including the symmetric motion through three dynamic intrinsic parameters of the multi-layer structure: a dynamic bending stiffness and two dynamic mass densities. This paper presents a finite element scheme to compute vibro-acoustic quantities from the condensed layer with these three dynamic parameters. It is further showed that the proposed scheme has high computational gain over the conventional full three-dimensional finite element approach.

An efficient numerical approach for simulating soil-pipe interaction behaviour under cyclic loading

Understanding soil-pipe interaction during cyclic axial displacement is essential for the design and evaluation of buried pipeline systems. This study introduces an efficient and practical numerical approach using beam-spring-interface elements to simulate soil-pipe interaction behaviour. Numerical predictions of the evolution of shear and normal stress distributions around the pipe are validated against full-scale experimental results for steel and high-density polyethylene pipes buried in sandy soils. Three different backfill cover depths and soil densities ranging between loose and dense were considered to allow a rigorous comparison between the numerical predictions and the experimental results. The results show that the proposed approach provides a high-fidelity representation of the complex soil-pipe interaction behaviour at the interface zones, including stress cyclic degradation, hardening and softening, cyclic accumulative contraction and stabilization. This numerical framework provides accurate predictions for a fraction of the computational cost of a full three-dimensional finite element analysis.

3D Finite Element Simulation of Processing of Generalized Newtonian Fluids in Counter-rotating and Tangential TSE and Die Combination

Abstract A full three-dimensional finite element analysis of the nonisothermal flow of generalized non-Newtonian fluids in counter-rotating tangential twin screw extruder is presented. Previous studies of the simulation of processing in tangential twin screw extruders have focused solely on the twin screw extruder, whereas here the coupled flow and heat transfer occurring in the integrated geometry of the extruder, connected to a die are considered. The FEM based numerical simulation of the coupled momentum-mass-energy conservation equations allowed the determination of the effects of some of the important system parameters, including the power law index and the staggering angle of the screws, on the pumping and pressurization capability of the extruder and the associated degree of fill in the extruder.

Enhanced ballistic resistance of multilayered cross-ply UHMWPE laminated plates

Multilayered cross-ply ultra-high molecular weight polyethylene (UHMWPE) laminated plates were envisioned and their ballistic performance explored, both experimentally and numerically. High velocity impacts were performed on both monolithic and multilayered targets with identical areal density. Ballistic data were obtained, together with dynamic deformation features and failure modes for both target types. Full three-dimensional finite element (FE) simulations were carried out to calculate the dynamic response of each target and explore the underlying mechanisms. Good agreement was achieved between FE simulations and experimental measurements. The results revealed that multi-layering the target could relieve fiber tensile stresses on its rear face and generate a more significant pull-in effect at the edges, resulting in larger back-face deflection and enhanced ballistic resistance.

Seismic stability assessment of the portal of a hydraulic tunnel under obliquely incident P waves

Tunnel portals are one of the most vulnerable sections that suffer the risk of instability during earthquakes because they are generally located in poor geological conditions. What makes this case studied in this work even more special are the oblique incident seismic waves and the large amounts of water in the hydraulic tunnel, both of which are believed to cause more complex mechanical behaviors and larger seismic response of hydraulic tunnels. In this paper, a full three-dimensional finite element model that takes the oblique incident seismic waves and hydrodynamic pressure into account is established to evaluate the stability of the tunnel portal under different incident angles of seismic waves. The numerical results indicate that: (1) the stress and displacement responses induced by oblique incident P waves are much larger than that by horizontal and vertical incident P waves; (2) the closer to the tunnel portal, the larger seismic response of the tunnel; (3) tunnel portal is where damage occurs first and suffers severe damage; (4) both oblique incident seismic waves and hydrodynamic pressure are likely to cause larger damage zone and more severe damage.

Modal Analysis of a Thin-Walled Box-Girder Bridge and Railway Track Using Finite Element Framework

Modal analysis has received widespread acceptance in past few decades for a wide range of applications. Bridges and buildings are two of the most popular structures that use this application in the context of civil engineering. The current study aims to apply finite element technique to estimate the free vibration characteristics of a railway track and a box-girder bridge. The curved bridge is numerically modeled using thin-walled box-beam finite elements that take into account torsional warping, distortion, and distortional warping, all of which are important characteristics of thin-walled box-girders. A commercially available finite element software ANSYS is used to simulate the railway track in three dimensions. The study is restricted to the initial design stage of a thin-walled box-girder bridge decks, in which a full three-dimensional finite element model is not required. For the thin-walled box-girder bridge, a MATLAB code has been built that yields the corresponding modal parameter results, whilst the modal parameters of the railway track system are acquired using ANSYS software.

A Short Review on Numerical Modelling Approaches for Seismic Evaluation Performance of Nuclear Power Plant Structures

Nuclear power plant (NPP) structures play a crucial role in protecting the safety of the whole plant. Overall, NPP structures have complex shapes and large dimensions. Therefore, the decision of an appropriate finite element model for seismic response analysis is important. This study presents a brief review of various numerical modelling approaches for seismic evaluation performance of NPP structures. Different conventional models, i.e. lumped-mass stick model (LMSM), full three-dimensional finite element model (3D FEM), elastic solid element model (ESM), and multi-layer shell model (MLSM), which have been applied in modelling nuclear structures, are introduced. Also, the advantages and drawbacks of those models are analysed. Furthermore, a new model namely, beam-truss model (BTM), which is recently proposed, is highlighted. It reveals that LMSM is the most simplified approach for structural modelling of NPP structures. However, it is normally used for linear analyses and not able to simulate the local behaviours and vertical responses of the complex NPP structures. Even though 3D FEM is the most sufficient method for nonlinear seismic response analyses, this approach is very time-consuming and costly computation. MLSM and BTM are recommended as practical and efficient models for nonlinear analyses of NPP structures.

Drag on a spherical particle at the air–liquid interface: Interplay between compressibility, Marangoni flow, and surface viscosities

We investigate the flow of viscous interfaces carrying an insoluble surface active material, using numerical methods to shed light on the complex interplay between Marangoni stresses, compressibility, and surface shear and dilatational viscosities. We find quantitative relations between the drag on a particle and interfacial properties as they are required in microrheology, i.e., going beyond the asymptotic limits. To this end, we move a spherical particle probe at constant tangential velocity, symmetrically immersed at either the incompressible or compressible interface, in the presence and absence of surfactants, for a wide range of system parameters. A full three-dimensional finite element calculation is used to reveal the intimate coupling between the bulk and interfacial flows and the subtle effects of the different physical effects on the mixed-type velocity field that affects the drag coefficient, both in the bulk and at the interface. For an inviscid interface, the directed motion of the particle leads to a gradient in the concentration of the surface active species, which in turn drives a Marangoni flow in the opposite direction, giving rise to a force exerted on the particle. We show that the drag coefficient at incompressible interfaces is independent of the origin of the incompressibility (dilatational viscosity, Marangoni effects or a combination of both) and that its higher value can not only be related to the Marangoni effects, as suggested earlier. In confined flows, we show how the interface shear viscosity suppresses the vortex at the interface, generates a uniform flow, and consequently increases the interface compressibility and the Marangoni force on the particle. We mention available experimental data and provide analytical approximations for the drag coefficient that can be used to extract surface viscosities.

Critical length of encased stone columns

Encased stone columns are vertical inclusions in soft soils formed by gravel wrapped usually with a geotextile. Their critical length is the one where further lengthening of the column provides a negligible improvement and it is therefore not effective to build columns longer than it. This paper aims to obtain common values of the critical length using simplified two-dimensional axisymmetric and full three-dimensional finite element analyses. A uniform soft soil layer with a linear elastic perfectly plastic behaviour is considered for the sake of simplicity. For the studied cases, the critical column length is around 1.3–2.5 times the footing diameter for encased stone columns, and slightly lower for ordinary stone columns, namely around 1.1–1.9. The critical length of the encasement is found to be slightly lower than the critical column length. The value of the critical column length is related to the extent of plastic deformation and that may be used to decide the column length in the design phase without the need of parametric analyses. As a first approximation, a general value of the critical column length of 2 and 2.5 times the footing diameter may be considered for ordinary and encased stone columns, respectively.

Efficiency of various structural modeling schemes on evaluating seismic performance and fragility of APR1400 containment building

The purpose of this study is to investigate the efficiency of various structural modeling schemes for evaluating seismic performances and fragility of the reactor containment building (RCB) structure in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). Four structural modeling schemes, i.e. lumped-mass stick model (LMSM), solid-based finite element model (Solid FEM), multi-layer shell model (MLSM), and beam-truss model (BTM), are developed to simulate the seismic behaviors of the containment structure. A full three-dimensional finite element model (full 3D FEM) is additionally constructed to verify the previous numerical models. A set of input ground motions with response spectra matching to the US NRC 1.60 design spectrum is generated to perform linear and nonlinear time-history analyses. Floor response spectra (FRS) and floor displacements are obtained at the different elevations of the structure since they are critical outputs for evaluating the seismic vulnerability of RCB and secondary components. The results show that the difference in seismic responses between linear and nonlinear analyses gets larger as an earthquake intensity increases. It is observed that the linear analysis underestimates floor displacements while it overestimates floor accelerations. Moreover, a systematic assessment of the capability and efficiency of each structural model is presented thoroughly. MLSM can be an alternative approach to a full 3D FEM, which is complicated in modeling and extremely time-consuming in dynamic analyses. Specifically, BTM is recommended as the optimal model for evaluating the nonlinear seismic performance of NPP structures. Thereafter, linear and nonlinear BTM are employed in a series of time-history analyses to develop fragility curves of RCB for different damage states. It is shown that the linear analysis underestimates the probability of damage of RCB at a given earthquake intensity when compared to the nonlinear analysis. The nonlinear analysis approach is highly suggested for assessing the vulnerability of NPP structures.

Seismic Analysis of Reinforced Concrete Pier Strengthened by Carbon Fiber Reinforced Polymers

In this vast world after an earthquake lessons are learned; many strategies have been considered in order to achieve a proper seismic strength capacity.The aim of this paper is studying the seismic behavior of a typical reinforced concrete bridge pier in Iraq and implementing a proper technique of strengthening in order to fix any damage that had happened.Structure of a full scale three-dimensional finite element model was used in order to simulate a reinforced concrete pier via the computer software ABAQUS/CAE 2017 using concrete plasticity damage model (CDP).Under the action of Halabja earthquake, which was recorded at city of Halabja in Iraq on 12 November 2017, the behavior of model was traced, analyzed and the resulted damages were managed.The finite element analysis results indicated that the proposed configuration of carbon fiber reinforced polymers laminates substantially increases the lateral load strength and deformation capacity of the bridge pier

Finite Element Modeling of Tight Elastic Knots

Abstract We present a methodology to simulate the mechanics of knots in elastic rods using geometrically nonlinear, full three-dimensional (3D) finite element analysis. We focus on the mechanical behavior of knots in tight configurations, for which the full 3D deformation must be taken into account. To setup the topology of our knotted structures, we apply a sequence of prescribed displacement steps to the centerline of an initially straight rod that is meshed with 3D solid elements. Self-contact is enforced with a normal penalty force combined with Coulomb friction. As test cases, we investigate both overhand and figure-of-eight knots. Our simulations are validated with precision model experiments, combining rod fabrication and X-ray tomography. Even if the focus is given to the methods, our results reveal that 3D deformation of tight elastic knots is central to their mechanical response. These findings contrast to a previous analysis of loose knots, for which 1D centerline-based rod theories sufficed for a predictive understanding. Our method serves as a robust framework to access complex mechanical behavior of tightly knotted structures that are not readily available through experiments nor existing reduced-order theories.

How hydrogel inclusions modulate the local mechanical response in early and fully formed post-infarcted myocardium

Expansion of myocardium after myocardial infarction (MI) has long been identified as the primary mechanism that drives adverse left ventricular (LV) remodeling towards heart failure and death. Direct injection of hydrogels into the myocardium to mechanically constrain the infarct has demonstrated promise in limiting its remodeling and expansion. Despite early successes, there remain open questions in the determination of optimal hydrogel therapies, key application characteristics for which include injected polymer volume, stiffness, and spatial placement. Addressing these questions is complicated by the substantial variations in infarct type and extent, as well as limited understanding of the underlying mechanisms. Herein, we present an investigation on how hydrogel inclusions affect the effective tissue-level stiffness and strain fields in myocardium using full three-dimensional (3D) finite element simulations at early and late post-MI time points. We calibrated our simulations to triaxial mechanical and structural measurements of cuboidal LV myocardial specimens of post-infarcted myocardium, 0 and 4 weeks post-MI, injected with a dual-crosslinking hyaluronic acid-based hydrogel. Simulations included multiple deformation modes that spanned the anticipated physiological range in order to assess the effects of variations in inclusion size, location, and modulus on tissue-level myocardial mechanics. We observed significant local stiffening in the hydrogel-injected specimens that was highly dependent on the volume and mechanical properties of the injected hydrogel. Simulations revealed that the primary effect of the injections under physiological loading was a reduction in myocardial strain. This result suggests that hydrogel injections reduce infarct expansion by limiting the peak strains over the cardiac cycle. Overall, our study indicated that modulation of local effective tissue stiffness and corresponding strain reduction are governed by the volume and stiffness of the hydrogel, but relatively insensitive to its transmural placement. These findings provide important insights into mechanisms for ameliorating post-MI remodeling, as well as guidance for the future design of post-MI therapies.

Three-Dimensional Simulation of Interaction Between Surface Buildings and Twin Tunnelling Regarding the Surface Settlement

Tunneling-induced strain and stress distribution in a soil medium is completely three dimensional. However, the issue is usually modeled in two-dimensions (2D) in order to lower the computational costs. In this study, full three-dimensional (3D) finite element (FE) analysis of twin tunnelling and surface building are carried out to compare the results with 2D ones and to find out surface settlement behavior during tunneling process considering the presence of a building on the surface. Conducting 3D FE parametric studies, a large database is created and the results are used to evaluate different aspects of 3D modeling. Based on the outcomes of this study, comparison between 2D and 3D modeling is conducted, the situations in which 3D analysis could be substituted by 2D plane strain models and the cases in which 3D modeling is necessary are defined. The effects of different parameters on surface settlement trough are assessed and a modification design graph for prediction of maximum 3D building settlement from 2D green-field analysis is suggested.