Proposed Finite Element Method Model Research Articles

Flexural performance of Metal-Reinforced glass Beams: Numerical and analytical investigation

Reinforced glass beam (RG beam) is a promising but under-researched structural typology. Existing analytical models for RG beams have provided unsafe residual resistance predictions, indicating the need for better theoretical methods.As a basis for the theoretical model, this paper conducts a numerical study and validates the applied finite element method (FEM) with previous experiments. To improve computational efficiency, a simplified 2D modelling method is proposed that applies equivalent material models for both laminated glass and adhesive layers, for in-plane flexural behaviour. The applied 2D finite element (FE) model is verified against experimental data.The effects of reinforcement ratio, reinforcement material, adhesive performance, and shear span to depth ratio on the in-plane flexural performance of the RG beam are then extensively investigated using the proposed FEM model. Numerical results help understanding the failure mechanisms of different failure modes, with an emphasis on the significance of adhesive behaviour.Adopting the composite beam theory, an analytical method is proposed to address different limit states of the RG beams and is validated against the FEM and experimantal results.

Design, application and investigation of the system for generation of fast changing, rotating magnetic field causing hyperthermic effect in magnetic liquids

The paper presents and discusses the results of research aimed at developing the optimal System for Generation of the fast-changing Rotating Magnetic Field (SGRMF) that causes the hyperthermic effect in magnetic liquids. In the calculations and design of the SGRMF, the three-dimensional (3D), original approach of the Finite Element Method (FEM) has been used. The FEM software prepared by the authors is based on the Ω-T0 formulation with nodal values of the scalar potential Ω to describe the magnetic field, and edge values of the electric vector potential T0 to define currents in windings. In the prepared model of the SGRMF, the relations describing the conversion of electromagnetic energy into thermal energy in magnetic fluids have been taken into consideration. The results of the proposed FEM model and elaborated software are presented and compared with the results obtained from the measurements on the specialized test stand. The prototype of the SGRMF system has been designed and built. Finally, the application of this prototype in the investigations of the hyper-thermal effect in a selected magnetic fluid of APG 513 type is given and discussed.

Simulation of residual stress in thick thermal barrier coating (TTBC) during thermal shock: A response surface-finite element modeling

The current study demonstrates a well-designed response surface methodology (RSM), based on the generated dataset of finite element method (FEM) to establish an integrated model for simulation of residual stress distribution in a thick thermal barrier coating (TTBC). In this study, typical TTBCs were applied on Hastelloy X Nickel-based superalloy using air plasma spray technique followed by thermal cycling. The recorded stress data of Raman spectroscopy was employed to verify the proposed FEM model. A relatively good agreement was obtained between predicted residual stresses and measured ones. Verified FEM model was used to carry out the parametric studies to evaluate the effects of such various parameters as interface amplitude, wavelength, thermally grown oxide thickness and preheating temperature on the stress distribution in the TTBC during the thermal cycling. The computed data were subsequently used for the development of RSM model. In conclusion, experimentally verified numerical data was used to construct a statistical model based on RSM and successfully used to predict the residual stress distribution field in TTBC during thermal cycling. The obtained results of hybrid FEM- RSM model were in acceptable conformity with Raman spectroscopy measurements.

Finite element method modeling of temperature gradient-induced Cu atomic thermomigration in Cu/Sn/Cu micro solder joint

Predicting the growth of interfacial intermetallic compounds (IMCs) under temperature gradient (TG)-induced atomic thermomigration (TM) in micro solder joint is an important aspect for improving the reliability of packaged devices. In this paper, we propose a new model based on finite element method (FEM) to simulate the Cu concentration distribution and the diffusion flux for the cold end IMC formation in Cu/Sn/Cu micro solder joints under TG with different preferred β-Sn grain orientation. It is confirmed that the orientation of β-Sn grains had a great effect on the growth rate of the cold end IMC. Meanwhile, the orientation of β-Sn grains also affected the time when the Cu concentration distribution reached a steady state, but not the final Cu concentration values at the same positions after reaching the steady state. By comparing the simulation results with the experimental data from literature, the proposed FEM model was proved to be reliable for analyzing the atomic concentration field and the diffusion flux for IMC formation in Sn-based micro solder joint under TG.

Nonlinear analysis of concrete-filled single and double skin steel tubular tapered columns under axial loading

In this study, the structural response of concrete-filled single and double skin steel tubular (CFST and CFDST) composite tapered columns was investigated through the finite element method (FEM). In the development of the FEM model, the concentric axial loading condition and circular section were adopted. Experimental results available in the literature were used to verify the proposed FEM model. In addition, a parametric study was performed to visualize the effectiveness of tapered angle and material strengths on the ultimate capacity of CFST and CFDST tapered columns. To this aim, a total of 60 tapered column samples (including 30 CFST and 30 CFDST columns) were modeled by taking into consideration five tapered angles, two steel tube yield strengths, and three concrete cube compressive strengths. The verification of the FEM model revealed that the developed model has a reliable and trustable assessment capability. It was noticed that the tapered angle was the most crucial parameter, influencing significantly the ultimate axial strength and stiffness of both CFST and CFDST composite tapered columns. As well, it was overtly beheld from the study that CFST composite tapered column specimens had better ultimate axial strength values than CFDST composite tapered column specimens with the same sectional and material properties.

Extraction of winding parameters for 33/11 kV, 30 MVA transformer based on finite element method for frequency response modelling.

This paper proposes an alternative approach to extract transformer’s winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.

Nonlinear finite element analysis of double skin composite columns subjected to axial loading

The study aimed to simulate the behavior of the concrete-filled double skin steel tubular (CFDST) composite columns having a circular hollow section using the finite element method (FEM). To indicate the accuracy and the reliability of the model, the proposed FEM model was verified by the experimental test results available in the literature. Moreover, the code-based formulas (ACI, AISC, and Eurocode 4) and some empirical models suggested by the previous researchers for predicting the axial capacity of CFDST columns were used in this study to compare their results with the proposed FEM model. Furthermore, to visualize the effectiveness of sectional properties and infilled concrete compressive strength on the ultimate axial strength of double skin composite columns, a parametric study was conducted. For this, 72 test specimens were modeled considering two outer and inner steel tube diameters, three outer and inner steel tube thicknesses, and two different concrete cylinder strengths. All results were statistically evaluated. It was observed that the proposed FEM model had a good prediction performance. As well, the FEM model results indicated that the sectional properties, in particular, the diameter of the outer steel tube and concrete compressive strength, had remarkable effects on the load-carrying capacity of CFDST columns.

Finite element modelling of a historic church structure in the context of a masonry damage analysis

The paper includes a case study of modelling a real historic church using the finite element method (FEM) based on laser scans of its geometry. The main goal of the study was the analysis of the causes of cracking and crushing of masonry walls. An FEM model of the structure has been defined in ABAQUS. A non-linear dynamic explicit analysis with material model including damage plasticity has been performed. A homogenization procedure has been applied to obtain the material parameters used in the modelling of masonry. In the numerical analysis, the interactions between the church structure, the foundations and the ground were taken into account.The obtained results match well with the damaged area of the entire structure from the in situ survey, and it should be highlighted that the proposed FEM model allows for a rather precise identification of the causes and effects of cracking walls in a qualitative sense. Also a brief research summary is presented.

Finite element modeling of living cells for AFM indentation-based biomechanical characterization

Mechanotransduction—the process living cells sense and respond to forces—is essential for maintenance of normal cell, tissue, and organ functioning. To promote the knowledge of mechanotransduction, atomic force microscope (AFM) force-indentation has been broadly used to quantify the mechanical properties of living cells. However, most studies treated the cells as a homogeneous elastic or viscoelastic material, which is far from the real structure of cells, and the quantified mechanical properties cannot be used to investigate the inner working mechanism of mechanotransduction, such as internal force distribution/transduction. Therefore, a new viscoelastic finite element method (FEM) model is proposed in this study to simulate the force response of living cells during AFM force-indentation measurement by accounting for both the cell elasticity and viscoelasticity. The cell is modeled as a multi-layered structure with different mechanical characteristics of each layer to account for the depth-dependent mechanical behavior of living cells. This FEM model was validated by comparing the simulated force-indentation curves with the AFM experimental data on living NIH/3T3 cells, and the simulation error was less than 10% with respect to the experiment results. Therefore, the proposed FEM model can accurately simulate the force response of living cells and has a potential to be utilized to study and predict the intracellular force transduction and distribution.

Numerical simulation of the shear capacity of bolted side-plated RC beams

A numerical model was developed using the finite element method (FEM) software OpenSees to simulate the shear behavior of bolted side-plated (BSP) reinforced concrete (RC) beams. The multi-layer shell elements, truss elements, flat shell elements, and coupled zero-length elements were employed to model the concrete, reinforcement, steel plates, and bolt connection. Good agreement between the numerical results and the testing in literature indicates that the proposed FEM model can simulate the shear behavior of BSP beams. A parametric study was then conducted to reveal the variation of the shear performance with different factors, including the depth, thickness and yield strength of the bolted steel plates, the diameter, horizontal spacing, and number of rows of the anchor bolts, as well as the shear span ratio. By incorporating the piecewise transverse slip profile and improving the hypotheses in the shear-compression failure model of BSP beams, a semi-empirical design formula was derived based on the force equilibrium of the beam segment outside the main diagonal crack, thus the shear capacity of BSP beams can be evaluated. The accuracy of this theoretical model was then validated by comparing the prediction with the experimental and numerical results.

Parametric study for optimal design of an air plasma sprayed thermal barrier coating system with respect to thermal stress

The use of thermal barrier coatings (TBCs) is expected to become more popular in various gas turbines because these coatings provide excellent thermal insulation and damage protection. However, unexpectedly early failure has often discouraged the full use of TBC, resulting in a shortening of the life span of gas turbines because these substrates are directly exposed to harsh operation conditions. The general mechanics of TBC and its complex inner phenomena, mainly related to failure, have been investigated to prolong the lifetime of TBC. However, our understanding is limited because TBC has various specifications and operating conditions, and complex interplays between many factors. The primary goal of this study is to construct an extensive finite element method (FEM) model to evaluate thermal stress of an air plasma sprayed TBC under its operating conditions by considering various inner phenomena, including thermal grown oxide, undulating topology of coating interface, aluminum depletion, creep effect, and elastoplastic deformation. With the proposed FEM model, a parametric study has been conducted with respect to a variety of material properties, as well as the thickness of bond coat and of top coat. The influence of each design factor on thermal stress and the other parameters is fully discussed. Finally, this work leads to optimal design criteria for minimizing thermal stress across a wide range of TBC systems.

Numerical analysis of fibers tensions in the Siro-spinning triangle using finite element method

Siro-spinning is a new kind of modified ring spinning method and achieved by feeding two rovings simultaneously, which have three spinning triangles including two primary spinning triangles and one final spinning triangle. In this paper, by using finite element method (FEM), the quantitative relationships between the fiber tension in the Siro-spinning triangle and some chosen important spinning parameters are investigated. The constituent fibers in the Siro-spinning triangle are considered as three-dimensional elastic beam elements with tensile, compressive, torsion, and bending capabilities. Then, the finite element model of Siro-spinning triangle is constructed under the assumption that the ends of all fibers gripped in the front roller nip distribute evenly, and the initial strain of the central fiber in each primary triangle is set as zero. Finally, the effects of some more important parameters of the Siro-spinning triangle, including the spinning yarn count, spinning tension, yarn twist, the distance between two feeding bell mouths on fiber tension distributions, are numerically examined and their quantitative relationships are discussed in detail. The accuracy of the proposed FEM model in calculating the fiber tension distribution of the Siro-spinning triangle has been validated by comparing it with our earlier theoretical models. Furthermore, the spinning experiments with different progress parameters were made, and the properties of spun yarns were evaluated and analyzed.

Optimization of a passive vibration absorber for a barrel using the genetic algorithm

The non-linear vibrations of a barrel, induced by the interaction with a high-speed moving projectile, negatively affect the shooting accuracy of a weapon. This study presents a new method that determines the non-linear behavior of the barrel with a passive vibration absorber and optimizes the absorber using the genetic algorithm (GA). Since both the barrel geometry and its coupling with the absorber are non-linear, a new finite element method (FEM) approximation has been developed for the interaction of barrel and projectile and combined with the classical finite element method. The final coupled equation of motion of entire system has been solved by a step by step integration, and for minimum tip deflection of the barrel, a GA has been then used in order to optimize the some parameters of the absorber. The results of analyses of the proposed FEM model were compared, and a good agreement was seen with the existing literature. In another example, the FEM–GA integrated optimization procedure was also used for the optimization of a passive vibration absorber, and a more accurate result (0.5% better) was obtained when compared to the experimental study given in literature.

An atomic interaction-based adhesive contact model for shallow nanoindentation and nanoscratch

The size effects and physical mechanisms governing small-scale mechanical behavior have important influences on the atomic force microscopy (AFM) measurement. Typically, high surface to volume ratio associated with the small-scale system leads to an appreciable surface force; such that the adhesion of AFM indenter to specimen should be taken into consideration for the nanoindentation and nanoscratch testing. In this work, a finite element method (FEM) model was developed to simulate the adhesive contact between spherical indenter and half-space, in which the adhesive stress is obtained based on the Lennard–Jones potential. Shallow indentation and scratching under different contact conditions were investigated with the proposed FEM model. For adhesion-included cases, the load drop events were found during the indent process, which is demonstrated as a manifestation of local plastic yielding caused by the adhesive stress in contact edge. Adhesion-included scratch load was found sharply increased in the beginning, and rapidly decreased once the scratch displacement reaches to a critical value. Such a predicted stick-slip behavior was interpreted as the rupture of adhesive bond with increasing of scratching distance.

FEM Model of Wraparound CNTFET With Multi-CNT and Its Capacitance Modeling

The wraparound gate carbon nanotube field-effect transistor (CNTFET) has the advantage of more accurately controlled channel than the top-gate CNTFET. A 3-D simulation is performed using the finite-element method (FEM) to model the wraparound CNTFET with multi-CNT channels. Analytical expressions to model various capacitances of the same device are also derived from capacitances for the 1-D FET with multiple cylindrical conducting channels incorporating screening effect due to multiple CNT. Various capacitances thus obtained exhibit remarkable improvement over the planar top-gate device with multiple conducting channels. This is attributed to the charge enhancement and the better charge confinement in the channel of the wraparound CNTFET with multi-CNT channels. Capacitances are also extracted from the proposed FEM model. The extracted capacitances are in excellent agreement with the capacitances obtained from the analytical model presented in this study.

Fatigue Tests of Bituminous Mixtures with Inclusion of Initial Cracks

The method of testing asphalt mixtures, including initial cracks appearing in pavements, is presented in this paper. The main aim of the study was a determination of the durability of asphalt mixtures, in regard to crack sizes. For this purpose, the four-point bending test was performed according to the technical standard PN-EN 12697-24. The test was conducted with selected asphalt mixtures under the controlled strain, and with the application of different crack sizes. Specimens with cracks were analyzed. Moreover, a model based on finite-element method (FEM) calculations was worked out, which allowed for the verification of conditions of the asphalt mixtures’ response to strains and the assessment of the state of stresses and strains at the crack tip. The wide range of studied conditions helped to determine the fatigue criterion for the “cracked” beam in the fatigue tests. The presented fatigue condition is very useful in the estimation of fatigue durability of asphalt mixtures. The results of analyses clearly showed the influence of cracks on the decrease in stiffness modulus. This effect has a nonlinear behaviour in the case of larger cracks. The proposed FEM model of beam, including cracks, is very useful in studies of stresses and tensile strains concentrated at the crack tip.

Stochastic Modeling of Reinforced Concrete Cracking due to Nonuniform Corrosion: FEM-Based Cross-Scale Analysis

Chloride-induced rebar corrosion is one primary cause of early cracking of reinforced concrete (RC). A model to accurately predict the time before steel corrosion and concrete cracking, with due consideration of the heterogeneous nature of concrete matrix, is highly desired by maintenance engineers. This paper presents the results of a research study directed at developing a stochastic numerical method to model the microstructure of concrete matrix and to predict the service life of RC in three key steps: chemical ingress, steel corrosion, and concrete cracking. The finite-element method (FEM) is employed to model the ingress of multiple chemical species into variably saturated concrete matrix. By using Faraday’s law, rebar corrosion is modeled in a mixed localized—uniform pattern and quantified as a transient displacement boundary condition for subsequent analysis of concrete cracking. The proposed FEM model is validated by using laboratory experiments and applied to predicting the corrosion-induced cracking of an RC bridge deck.

Numerical analysis of the mechanical behavior of a ring-spinning triangle using the Finite Element Method

The purpose of this study is to investigate the quantitative relationships between the mechanical performance of a ring-spinning triangle and the spinning parameters by using the Finite Element Method (FEM). The constituent fibers in the ring-spinning triangle are considered as three-dimensional elastic beam elements with tensile, compressive, torsional, and bending capabilities. The accuracy of the proposed FEM model in calculating the fiber tension distribution of the spinning triangle has been validated by comparing it with earlier models and experimental data. Compared with the earlier models, some important theoretical factors ignored previously, including the fiber torsional strain and the frictional contact of fibers with the bottom roller, are considered in the current model. With the input of various spinning parameters, some essential factors of the spinning triangle, including the fiber tension distribution and fiber torsion distribution, are numerically examined and their quantitative relationships are discussed in detail.

Dynamic Model of Giant Magnetostrictive Acceleration Sensors Including Eddy-Current Effects

Compared with other types of acceleration sensors, the rare-earth giant magnetostrictive acceleration sensors have obvious advantages. In order to analyze performance of the giant magnetostrictive acceleration sensors, this paper presents a magneto-mechanical strongly coupled dynamic model for the giant magnetostrictive acceleration sensors, which includes eddy-current effects. Using the proposed model, the time characteristic of the induced voltage for the acceleration sensors is calculated by finite element method (FED). In order to validate the presented model, an experiment of the relation between the induced voltage and time for the acceleration sensors has been done. A comparison between the calculated results and measured ones has been carried out to examine the validity of the proposed model and the FED implementation. It is found that both of them are qualitatively in an agreement. This indicates that the proposed FED model can reflect dynamic response performance of the giant magnetostrictive acceleration sensors.

Comparison of a finite element model with a multiple-scales solution for sound propagation in varying ducts with swirling flows

A multiple-scales (MS) solution is proposed to study sound propagation in slowly varying ducts with mean swirling flows. Instead of the standard linearized Euler equations, the MS method is applied to the so-called Galbrun’s equation. This equation is based on an Eulerian–Lagrangian description and corresponds to a wave equation written only in terms of the Lagrangian perturbation of the displacement. This yields simpler differential equations to solve for the MS model as well as simpler boundary conditions. In this paper, Galbrun’s equation is also solved by a mixed pressure-displacement finite element method (FEM). The proposed FEM model has already been tested in authors’ previous papers. This model is quite general and is extended here to arbitrary mean flows, including compressibility and swirling flow effects. Some MS and FEM solutions are then compared in order to validate both models.