Proposed FE Model Research Articles

동시 이중주파수를 이용한 기어 열처리의 열·전자기 연성 해석

In this paper, Finite Element Analysis (FEA) for gear heat treatment using simultaneous dual frequency (SDF) induction heating is conducted. To do this, thermal-electromagnetic coupled FE model is built. A two dimensional FE model of gear and heater is introduced to reduce computation time. For more time-efficient analysis, harmonic analysis for electromagnetic model is adopted and transient analysis model, for heat transfer model. Through the coupled analysis, it can be found that the proposed FE model can solve for SDF induction heating of gear and heat treatment parameters can also be determined.

Numerical analysis of the mechanical behaviour of reinforced thermoplastic pipes under combined external pressure and bending

Reinforced thermoplastic pipes (RTPs) are promising design solutions for deep-water riser applications due to their light weight, high performance and good spoolability. For such applications, RTPs experience significant ambient pressure and sustain bending and/or tension loads during the installation and operation phases. Normally an RTP is composed of an inner Polyethylene (PE) liner, reinforced layers made from fibre-reinforced PE composites and an outer PE cover. The mechanical behaviour of such an RTP when it has been subjected to combined external pressure and bending has been studied through finite-element analysis (FEA). The nonlinear mechanical behaviour of both PE and the fibre-reinforced PE composites has been modelled by developing numerical algorithms that reflect the strain-dependent mechanical characteristics of PE. These algorithms are implemented in the analysis tool used, Abaqus/Standard, with the user subroutine, UMAT. The proposed FE model could accurately simulate the buckling and post-buckling response of the RTP and predict its failures under the combined external pressure and bending. Rotation-pressure interaction collapse envelopes of the RTP in different loading paths are generated. Additionally, the effects of ply angles, loading paths and diameter-to-thickness (D/t) ratios on the performance of the RTP under this loading case are investigated. The results obtained could be used to improve the design of RTPs for deep-water riser applications in the offshore oil and gas industry.

Seismic retrofitting of an HV circuit breaker using base isolation with wire ropes. Part 2: Shaking-table test validation

This paper addresses the experimental characterisation of a base-isolation system for the seismic qualification, of High Voltage (HV) ceramic circuit breakers, in accordance with the European standard CEI EN 62271-207. The adopted solution is based on an innovative application of wire rope isolators. The results of a preliminary investigation of an HV circuit breaker, which was base-isolated with wire ropes, were previously illustrated in a companion paper in which the effectiveness of this isolation system was analytically demonstrated. To validate these results, a shake table test campaign has been performed that includes the performance analysis of two optimal isolation system configurations. The results, which are illustrated in this paper, show both the effectiveness of this isolation system and the reliability of the proposed FE model.

Modeling the Effects of Myocardial Fiber Architecture and Material Properties on the Left Ventricle Mechanics during Rapid Filling Phase

The objective of this research is to study the effects of myofiber volume fraction and fiber orientation on the deformation mechanics of left ventricular (LV) during diastole. The human LV was simulated by three-dimensional finite element (3D-FE) model. The LV geometrical model was represented as a thick-walled ellipsoid truncated at two thirds of major axis. 3D Fiber network, with parallel myofiber bundles to reproduce the globally anisotropic behavior of cardiac tissue, were embedded within the LV model. The LV wall thickness in the reference unstressed state (at hypothetical zero pressure applied inside the LV internal cavity) is divided into n different concentric thin layers (n = 3, 5, 7 and 9 layers). The presence of blood (incompressible fluid) inside the LV cavity was also simulated. Fourschememodelsoffiberangledefinition(onesymmetric, twoasymmetricand onecomplex pattern)wereusedthroughout this study. Complex pattern of fiber-structures are derived from diffusion tensor magnetic resonance imaging (DT-MRI) data. Simulation results have shown that the proposed FE model was able to reproduce experimental ventricular volume during the rapid filling phase and that the complex fiber orientations are in good agreement with the measurements.

Numerical study of confinement in short concrete filled steel tube columns

This study presents a numerical investigation into the behaviour of short concrete filled steel tubular (CFST) columns. Three Dimensional Nonlinear finite element analysis of the compression process is performed using commercial software ABAQUS v6.9 (2009). Steel tubes of different geometries and in-filled with different grades of concrete are chosen for modelling from literature. The proposed FE model is validated by comparing its results with those of the corresponding experimental specimens. The model is further used to study the variation of radial confining pressure f cp provided by the steel tube to the concrete core. It is observed that the value of f cp varies widely throughout the length of the CFST, with the values in the area adjacent to top and bottom platens being markedly higher than the values in-between due to the end restraint provided by the machine platens. This is in contrast to the present confined concrete model which uses a uniform value of confining pressure throughout the height. Effect of effective length of column and interfacial friction present between the platen and specimen are found to be negligible on behaviour of short CFST column.

Finite element modeling of microstructural changes in dry and cryogenic cutting of Ti6Al4V alloy

This paper presents a customized FE model for describing the microstructural changes during dry and cryogenic cutting of Ti6Al4V. It addresses the importance to modify the material behavior taking into account the microstructural changes and the cooling/lubrication effects during the cutting process. With this aim, a user subroutine is implemented in the FE code to describe the surface and subsurface modifications taking place during the cutting process and to implement them in order to properly modify the material flow stress. Thus, the material flow stress is continuously updated during the simulation according to the new microstructure characteristics. The proposed FE model is calibrated and validated by comparison with experimental results.

Penetration of cutting tool into cortical bone: Experimental and numerical investigation of anisotropic mechanical behaviour

An anisotropic mechanical behaviour of cortical bone and its intrinsic hierarchical microstructure act as protective mechanisms to prevent catastrophic failure due to natural loading conditions; however, they increase the extent of complexity of a penetration process in the case of orthopaedic surgery. Experimental results available in literature provide only limited information about processes in the vicinity of a tool–bone interaction zone. Also, available numerical models the bone-cutting process do not account for material anisotropy or the effect of damage mechanisms. In this study, both experimental and numerical studies were conducted to address these issues and to elucidate the effect of anisotropic mechanical behaviour of cortical bone tissue on penetration of a sharp cutting tool. First, a set of tool-penetration experiments was performed in directions parallel and perpendicular to bone axis. Also, these experiments included bone samples cut from four different cortices to evaluate the effect of spatial variability and material anisotropy on the penetration processes. Distinct deformation and damage mechanisms linked to different microstructure orientations were captured using a micro-lens high-speed camera. Then, a novel hybrid FE model employing a smoothed-particle-hydrodynamic domain embedded into a continuum FE one was developed based on the experimental configuration to characterise the anisotropic deformation and damage behaviour of cortical bone under a penetration process. The results of our study revealed a clear anisotropic material behaviour of the studied cortical bone tissue and the influence of the underlying microstructure. The proposed FE model reflected adequately the experimental results and demonstrated the need for the use of the anisotropic and damage material model to analyse cutting of the cortical-bone tissue.

Finite element verification on constitutive law of AZ31 magnesium alloy at 400 °C

A constitutive law is offered for an AZ31B-H24 Mg alloy within a strain rate range of 10−5−10−2 s−1 at a temperature of 400 °C. The constitutive law, which is developed by curve fitting the tensile tests data, is expressed as a flow stress function of strain and strain rate. Furthermore, the constitutive law is embedded into a proper FE model to simulate the tensile experiments for the purpose of verifying reliability, where the incremental stress-strain relationships are calculated by an elastic-plastic theory in the finite element analysis (FEA). The results show that the stress-strain characteristics and the final deformed shapes in the FEA agree well with the experiments. In addition, the predicting analysis of constant-velocity stretch conditions and the verification of a free bulge forming experiment show that the proposed FE model is practicable for mechanical analysis on superplastic forming problems. A selective numerical method is offered for advanced superplastic analysis on AZ31 Mg alloys.

Numerical Analysis of High Strength Steel Endplate Connections at Ambient and Elevated Temperatures

This paper deals with the behaviour of high strength steel (HSS) endplate connections at ambient and elevated temperatures using ABAQUS. The detailed FE model considers material and geometric non-linear effects, large deformations and contact interactions. This paper highlights the main challenges in modelling endplate connections. Validation against experimental results shows that the proposed FE model can reproduce the behaviour of mild steel endplate connections with reasonable accuracy. Using HSS instead of mild steel as endplate material, this model is able to predict the performances of HSS endplate connections both at ambient temperature and under fire condition. By a parametric study, it is found that a thinner HSS endplate enhances the ductility of connection both at normal condition and under fire condition, and achieves the same load-bearing capacity with mild steel endplate connection. This finding is promising for further investigations on improving the robustness of endplate connections in fire.

Finite Element Analysis for Shock Resistance Evaluation of Cushion-Packaged Multifunction Printer Considering Internal Modules

Failures in IT electronics are often caused by falling or external shocks during transportation. These failures cause customers to mistrust the reliability of the products. Many manufacturers of IT electronics have not only used cushioning materials but also increased the shock resistance of their products for failure prevention. Especially in case of printer products, the design of the packaging and the product robustness are extremely important because of their substantial weight and the fragility of the internal modules. For product design, it is essential to understand the impact failure mechanism of the products. In this study, a compression test, a drop impact test, and a finite element analysis (FEA) were performed to analyze the dynamic behaviors of a packaged multifunction printer (MFP). The mechanical properties of a cushioning material were measured by compression tests. The FE models of the cushion packaging and the MFP included the physical characteristics of the internal modules, and their dynamic behaviors were obtained using the commercial software ls-dyna3d. Simulation results were also compared with drop test results to verify the proposed FE models. The shock resistance of the MFP was assessed by stress analysis and strength evaluation. We also expect our FE models will be useful for evaluating the fragility of the internal modules because the models can numerically estimate the shock acceleration profiles of the internal modules, which are difficult to measure experimentally.

마찰 접촉을 고려한 현수교 PPWS용 소켓의 거동 해석

현수교 주케이블용 평행강선 스트랜드(PPWS) 소켓의 엄밀한 수치해석을 위한 유한요소해석 모델을 제안하였고, 제안된 해석 모델을 이용하여 소켓의 거동을 분석하였다. 개별 강선과 소켓 내부 주입 합금재의 영향을 고려한 직교 이방성 재료 모델을 적용하였고, Coulomb 마찰 및 표면접촉 모델을 도입하여 소켓 내면과 주입 합금재 표면의 접촉 상태를 구현하였다. 인장 실험으로부터 측정된 소켓 외면의 변형율과 유한요소 해석 결과를 비교하여 제안된 유한요소 해석 모델의 타당성을 검증하였고, 마찰계수의 변화에 따른 소켓의 거동을 해석하였다. 해석 결과, 소켓 내면과 주입 합금재 표면의 마찰은 소켓과 주입 합금재에 발생하는 응력 집중을 크게 완화 시켰으며, 소켓 설계법에서 정의된 수직응력식은 소켓 내면과 주입 합금재 표면의 접촉응력 분포에서 상하부 사분위값의 평균을 대표하는 것으로 나타났다. A sophisticated finite element model is illustrated to analyze the behavior of Prefabricated Parallel Wire Strand(PPWS) sockets for main cables of suspension bridges. An orthotropic model is proposed for the casting material by considering both effects of individual wires and a casting alloy, and the contact between surfaces of a socket and a casting alloy is idealized by using the Coulomb friction and the surface-based contact model. The proposed FE model is verified by comparing the strain distributions obtained from the tensile test and FE analysis. The mechanical behavior of a socket is investigated with respect to the variation of the frictional coefficient. The result shows that the friction between surfaces significantly diminishes the stress concentration of a socket and a casting alloy, and the normal stress from the design equation represents the averaged value of the upper and lower quartiles in the distribution of contact stresses between a socket and a casting alloy.

Finite element model updating of a simply supported skewed PSC I-girder bridge using Hybrid Genetic Algorithm

Hybrid Genetic Algorithm (HGA) which combines the genetic algorithm as a global optimization and the simplex method as a local optimization is proposed for a finite element model updating of a real prestressed concrete bridge structure. In order to minimize the updating error between the measurement and the finite element model updating result, objective functions which are combinations of fitness functions based on the natural frequency, the mode shape and the static displacement are introduced. And an interface tool is also developed in order to utilize various element library and numerical analysis tools which are provided by commercial finite element and numerical analysis programs. A simply supported skewed PSC girder bridge which has 30 m span length is selected for the verification of the proposed FE model updating algorithm. Static vehicle loading test and forced vibration test by traveling vehicle as well as ambient vibration test were carried out to obtain the reference measurement data for numerical updating. A grillage model is used for the finite element analysis. Effect of the spring element to simulate the realistic support condition which is not perfectly free or restrained in real situation as well as that of the objective function on the updating accuracy are studied. From the result of parametric study, it is investigated that the use of spring element for support condition is effective to minimize the updating error for natural frequency and mode shape. Furthermore, including the static displacement fitness function together with those of dynamic properties may improve the global behavior of updated finite element model. It is concluded that the hybrid genetic algorithm proposed in this study is a very effective finite element model updating method to find an accurate result in updating real bridge structure based on measured data.

Modelling of corrosion-induced cover cracking in reinforced concrete by an embedded cohesive crack finite element

Corrosion of a reinforcement bar leads to expansive pressure on the surrounding concrete that provokes internal cracking and, eventually, spalling and delamination. Here, an embedded cohesive crack 2D finite element is applied for simulating the cracking process. In addition, four simplified analytical models are introduced for comparative purposes.Under some assumptions about rust properties, corrosion rate, and particularly, the accommodation of oxide products within the open cracks generated in the process, the proposed FE model is able to estimate time to surface cracking quite accurately. Moreover, emerging cracking patterns are in reasonably good agreement with expectations.As a practical case, a prototype application of the model to an actual bridge deck is reported.

Analysis of composite beams with longitudinal and transverse partial interactions using higher order beam theory

A new one dimensional finite element model based on a higher order beam theory is presented for the analysis of composite beams taking into account the effect of longitudinal as well as vertical partial interaction between the adjacent layers. The proposed method models the transverse shear deformation of the beam components in a refined manner. A third order variation of the axial displacement of the fibres over the beam depth is taken to have a parabolic variation of shear stress which is also made zero at the beam top and bottom surfaces. In the proposed FE model, there is no need of incorporating any shear correction factor and the model is free from shear locking problem. In addition to correctly predicting the global responses of the beam, the model can predict better distribution of stresses than the existing models based on Euler–Bernoulli or Timoshenko beam theory. Many new results are presented as there is no published result on the present problem based on higher order beam theory.

Analysis of composite beams with partial shear interactions using a higher order beam theory

A new finite element model based on a higher order beam theory is presented for the analysis of composite beams. The proposed model takes into account the effect of partial shear interaction between the adjacent layers as well as transverse shear deformation of the beam. A third order variation of the axial displacement of the fibres over the beam depth is taken to have a parabolic variation of shear stress which is also made zero at the beam top and bottom surfaces. In the proposed FE model, there is no need of incorporating any shear correction factor and the model is free from shear locking problem. In addition to correctly predicting the global responses of the beam, the model can predict better distribution of stresses than the existing models based on Euler–Bernoulli or Timoshenko beam theory. The proposed finite element model is validated by comparing the results with those available in literature. Many new results are presented for future references as there is no published result on composite beams based on higher order beam theory.

Evaluation of Mechanical Properties of Single-Walled Carbon Nanotubes

A micromechanical finite element model incorporated with molecular mechanics is employed to determine the mechanical properties of single-walled carbon nanotubes (SWCNT). The SWCNT is modelled as a space-frame structure. The bonds between the carbon atoms are simulated as beam members to carry the loads, while the carbon atoms are the joints of the members. The modified Morse potential is adopted to characterize the non-linear behavior of C-C bonds. In this work, the mechanical properties of SWCNT such as the Young’s modulus, ultimate strength and strain are investigated. To verify the proposed FE model and evaluate its performance, the effects of diameter and chirality on the mechanical properties of SWCNT are presented. It is found that both the Young’s modulus and ultimate strength of SWCNT increase monotonically with the increase of diameter. The Young’s modulus of armchair is larger than that of zigzag SWCNTs. These results are in good agreement with the existing numerical and experimental results.

Mechanical Analysis of the Recycled Concrete Brick Masonry Wall under In-Plane Load

The purpose of this paper was to investigate the mechanical behavior and failure mode of recycled concrete brick masonry wall under cycling in-plane load. These models of masonry walls were constructed in the laboratory and experimented under in-plane cycling load. The masonry wall was made of recycled concrete bricks joined by mortar, with gypsum lining on both faces. A simulation based on the experiment was carried out using the finite element software ANSYS. In the proposed FE model, the recycling concrete bricks and joints were modeled separately, allowing for nonlinear deformation characteristics of the two materials. The results of the experiment and the finite element analysis were analyzed and compared. When the stress distributions were taken into consideration in the experiments and solutions of ANSYS, it was observed that the stress concentration occurred on two diagonals of the masonry wall. The destruction process and characteristics of the masonry wall were obtained by the experiments. The results of finite element method matched experimental results very well. The FE software ANSYS can be used in the analysis of recycling concrete brick masonry walls under in-plane cycling load and strength capacity.

Research on dynamic characteristics of giant magnetostrictive acceleration sensors

This paper studies the dynamic response performance of giant magnetostrictive acceleration sensors. A magneto- mechanical strongly coupled dynamic model is presented, which is calculated by means of the finite element method. Accor ding to the proposed model, the time characteristic of the induced voltage for the acceleration sensor built with rare earth g iant magnetostrictive alloy is calculated. A comparison between the calculated results and measured ones has been carried out to examine the validity of the proposed dynamic model and the FE implementation. It is found that they are in an agreement. This indicates that the proposed FE model can reflect dynamic resp onse performance of giant magnetostrictive acceleration sensors.

Performance‐based seismic assessment method for Taiwanese historic Dieh‐Dou timber structures

AbstractLateral force, response spectrum and step‐by‐step pushover analyses are performed and compared with the post‐earthquake survey of two Dieh‐Dou buildings seriously affected in the 1999 Chi‐Chi earthquake in Taiwan. The results show that the proposed FE model with finite translational and rotational stiffness can successfully be employed to assess the vulnerability of the frames. The fundamental period of Dieh‐Dou structures is about 1.0 s higher than that calculated by the simplified approach of the codes for regular frames; a modal analysis is, therefore, essential for this typology of structure. The elastic analysis, either lateral force or response spectrum, is shown to be reliable to assess Dieh‐Dou frames when quick results are desired. However, a non‐linear step‐by‐step pushover analysis has the advantage of greater accuracy, as it allows mapping the failure trend and indicating the critical elements. The lateral drifts are compared with the actual observed damage pattern and when the damage level is related to the peak ground acceleration on a vulnerability curve plot, it is shown that the joint failure combined with the lateral drift gives an indication of the global structural behaviour of this historic construction typology. Owing to the unique construction features of the Dieh‐Dou, the joint failure represents also a critical criterion in terms of maximum retention for conservation. Based on a damage level approach, an assessment methodology is suggested that would allow optimizing a strengthening strategy, for protection of these precious structures from future earthquakes while avoiding unnecessary interventions. Copyright © 2010 John Wiley & Sons, Ltd.

Numerical investigation of inelastic buckling of steel–concrete composite beams prestressed with external tendons

The ultimate resistance of a continuous composite beam is governed by either distortional lateral buckling or local buckling, or an interactive mode of the two which is sharply different from the torsional buckling mode in a bare steel beam. A finite element model is developed and based on the proposed FE model, inelastic finite element analysis of composite beams in negative bending is investigated, considering the initial geometric imperfection and the residual stress patterns and the FE results are found agree well with the test results. Parametrical analysis is carried out on the prestressed composite beams with external tendons in negative bending. Factors that influence load carrying performance and buckling moment resistance of prestressed composite beams are analyzed, such as initial geometric imperfection, residual stress in steel beams, force ratio, which is defined as the extent of prestressing force and negative reinforcement in the beams, as well as the slenderness ratios of web, flange, and beams. By varying cross-section parameters, 25 groups of composite beams under negative uniform bending with initial geometric imperfection, residual stress as well as different force ratios, 200 beams in total are studied by means of the FE method. The computed buckling moment ratios are drawn against the modified slenderness proposed by the authors and compared with the Chinese Codified steel column design curve. It is demonstrated that the tentative design method based on the Chinese Codified design curve can be used in assessment of buckling strength of composite beams in a term of the modified slenderness defined.