3D Finite Element Method Model Research Articles

Analysis of Peak Electromagnetic Torque Characteristics for Superconducting DC Induction Heaters

The efficiency of novel superconducting direct current (DC) induction heaters can be up to 80-90%. This is much higher than the 40-50% of conventional alternating current induction heaters. Induction heaters are used to preheat aluminum billets in extrusion pressing. Such devices use a driving motor to rotate the billet. A peak in the electromagnetic torque appears at low rotation speeds (of the motor). Therefore, this peak electromagnetic torque is of particular interest when designing the driving system, which is one of the main challenges for megawatt-class superconducting DC induction heaters. In this paper, the peak electromagnetic torque characteristics of different sized billets were analyzed. A numerical 3D finite element method model was built to analyze the peak electromagnetic torque and resistive heating power behavior of aluminum billets. The results obtained from simulations and experiments match well. The effect of the following five relative parameters, on electromagnetic torque and resistive heating power, were studied: billet diameter, billet length, magnetic flux density, billet material, and electrical conductivity. The peak electromagnetic torque increases nonlinearly with increasing billet diameter, up to 640 mm. The time elapsed between the peak to stable torque decreases nonlinearly with increasing magnetic flux density. The effects of billet material (copper, titanium alloy and stainless steel) on torque were analyzed and compared. These results are likely to guide more cost-effective and practical designs for the billet driving system of superconducting DC induction heaters.

Novel array ECT probe with three-phase excitation for steam generator tube inspection

Eddy current testing (ECT) is commonly used in steam generator tube inspection. Among multiple probes applied in this area, array probe shows the merit of the capability of obtaining a C-scan image in a simple linear scan. In this work, a novel array ECT probe with three-phase excitation is proposed. The probe consists of two rows of excitation coils and a row of pickup coils. The induced eddy current shifts electrically in the testing sample so that the necessity of multiplexer is eliminated, resulting in advantages of lower cost, less noise and faster inspection speed. Theoretical analysis indicates that the background signal of the array sensor would be small. A 3D finite element method (FEM) model is developed to study the operating principle and to predict the inspection performance of the probe. A prototype probe has been developed and tested, by which a steam generator tube sample with different kinds of defects was inspected. The experiment results validate the simulation model and further demonstrate the feasibility of the sensor.

Evaluating the Performance of Warm Mix Asphalt Incorporating Recycled Asphalt Pavement Treated Bases

The use of warm mix asphalt (WMA) partially mixed with recycled asphalt pavement (RAP) as a base course or a sub-base course is continually gaining interest all over the world, particularly in Europe and North America. The progressive interest and preference of WMA-RAP over hot mixed asphalt (HMA) resides in the exceptional benefits WMA-RAP offers. Those benefits include health benefit to workers, economic benefits, and paving benefits in cold weather condition. Although WMA partially mixed with RAP was originally created to overcome the environmental challenges and the shortages of natural resources, the fact remains that it has shortcomings in performing well against rutting failure, and moisture damage. Therefore, this paper aims to evaluate and to understand the mechanical performances of WMA partially mixed with RAP in terms of fatigue cracking and rutting damage. In order to achieve the aim of this study, the indirect tensile strength test was conducted. Thereafter, the results obtained were used as input data to model the flexible pavement. Furthermore, various scenarios of structural flexible pavements subjected to the effect of load were analysed and modeled using the 3D finite element method (FEM) in ABAQUS and the layered elastic analysis (LEA) as a control. The Results showed that the HMA and the WMA were in close proximity, as the percentage difference between the horizontal strain at the bottom of the asphalt layers 3.7% for the 3D FEM Model and the compressive vertical strain on the top of the sub-grade 1%, which imply that the WMA can perform more or less as the HMA. Overall, the RAP can be incorporated successfully in the WMA which can be applied to new construction and rehabilitation of low to medium traffic volume roads.

Effects of proppant distribution in fracture networks on horizontal well performance

In this paper, we presented a coupled 3D finite element method model for the simulation of proppant transport in fracture networks and its effects on horizontal well performance. We used a mixture model, which have advantages to deal with two-phase flow containing a dispersed phase like solid particles, to simulate the proppant transport process in fracture networks. Then a tight oil reservoir model was established to evaluate the effect of the proppant distribution on the horizontal well performance. The effects of several factors, such as the proppant physical properties and injection parameters, were analyzed. The calculated results show that, in the fracture network, proppant accumulates at the intersections of cracks. Height of the proppant packed bed in natural fracture was about 30% smaller than that in the main hydraulic fracture, and the communication between hydraulic fractures leads to a larger proppant dune and higher conductivity. Besides, in a tight oil reservoir, the proppant distribution has a significant influence on the well performance. When the reservoir permeability is reduced to 0.05 mD, the productivity index fold of increase calculated including the proppant uneven distribution can be 47.7% larger than that calculated with idealized proppant distribution. Furthermore, the proppant physical properties and injection parameters are found to be correlated with the fracture network conductivity. Based on this analysis, optimum proppant injection conditions can be identified.

Tailored heating of forging billets using induction and conduction heating approaches

Purpose This paper aims to deal with different induction and conduction heating approaches to realize a tailored heating of round billets for hot forming processes. In particular, this work examines the limits in which tailor-made temperature profiles can be achieved in the billet. In this way, a flow stress distribution based on the temperature field in the material can be set in a targeted manner, which is decisive for forming processes. Design/methodology/approach For the heating of round billets by induction, the rotationally symmetric arrangement is used and a parameterized 2D finite element method model is created. The harmonic electromagnetic solution is coupled with the transient thermal solution. For heating by means of conduction, the same procedure is used only with the use of a 3D model. Findings First results have shown that both methods can achieve very good results for billets with small diameters (d < 30 mm). For larger diameters, an adapted control of the heating process is necessary to ensure through heating of the material. Further investigations are carried out. Practical implications Using tailored heating for forging billets, several forming steps can be achieved in one step. Among other things, higher energy efficiency and throughput rates can be achieved. Originality/value The peculiarity of the tailored heating approach is that, in contrast to inhomogeneous heating, where only partial areas are heated, the entire component is heated to the target.

Nonlinear Numerical Model of Post-Tensioned Elastic Rocking Panels for Application in Building Structural Analysis

This paper presents a new 4-node finite element model, developed from a 2-node rocking beam element that can predict the rocking behavior of post-tensioned panels and columns. The stiffness matrix of the 2-node beam element was derived from the flexibility method. Then, the stiffness matrix of the 4-node beam element was obtained through the use of transformation matrices. The 4-node element model allows for the prediction of not only the global behavior of the rocking element (e.g., nodal displacements and nodal loads) but also the local behavior (e.g., the contact length, the vertical displacement, and the strain and stress at the rocking interface). The numerical results from the 4-node element model were compared to that from 3D finite element method (FEM) models in MATLAB 2016 and ABAQUS programs and showed a high accuracy. Moreover, the 4-node element model can be combined with the other types of elements in order to analyze building structures at a global level, especially for mid-rise and tall buildings where the nodal displacements at panel corners are vital to correctly predict the behavior of the other structural elements (e.g., light-frame shear wall elements). An example of a six-story building that included a hybrid system of post-tensioned cross-laminated timber (CLT) walls and light-frame wood shear walls was presented.

Mechanical resistance of stepped lamination defects in a welded section of oil and gas pipeline: a finite element analysis

The mechanical resistance of API 5L X52 steel with stepping lamination in the base metal (BM), heat affected zone (HAZ) and welding bead (WB) was studied by using the finite element method (FEM) in the present work. Both internal working pressure in the pipelines and internal pressure in the stepping laminations were studied to analyze the mechanical behavior of the pipelines. 3D FEM models and kinematic hardening were activated in the software used, while tests for the mechanical properties (true stress–strain curve) of BM, HAZ and WB were also conducted. The results demonstrated that stepping laminations in the BM–HAZ–WB zone reduced the ability to support internal pressure; therefore, the failure pressure (Pf) is also reduced. Pipeline failures occurred when the Von Mises stresses reached or exceeded the ultimate tensile stress (σUTS) of the material in the outer and inner wall and the stepping lamination sizes were too large. Failure in pipelines with stepping laminations occurred on the left side of the crack on the outer wall of the BM–HAZ zone; on the inner right side of the stepping laminations, the failure takes place on the inner wall in the WB.

Novel Array Eddy Current Sensor With Three-Phase Excitation

Array eddy current testing (AECT) sensor is capable of inspecting a large area in a single probe pass resulting in a C-scan image, which is beneficial for customizing the profile of the part being inspected. This paper presents a novel AECT sensor with three-phase excitation. The sensor has two rows of excitation coils and a row of pickup coils. The excitation coils are driven by three-phase currents that are 120° apart in phase. The induced eddy current in the conductive sample shifts electrically along the phase variation direction of the excitation currents. As a result, the sensor does not need multiplexer resulting in advantages of lower cost, less noise and faster inspection speed. The background signal measured by the sensor is small if there is no defect in the sample. Therefore, the sensor has high relative sensitivity to the presence of defect. A 3D finite element method (FEM) model is utilized to study the operating principle of the sensor. A prototype sensor has been developed and tested, with which aluminum sample and carbon fiber reinforced polymer (CFRP) sample with machined defects are inspected. The experiment results demonstrate the feasibility of the sensor for fast imaging of conductive materials.

Three-dimensional stress-transfer mechanism and soil arching evolution induced by shield tunneling in sandy ground

Tunnel excavation inevitably causes variations in stress and displacement fields in soil, which could affect the serviceability and safety of the adjacent underground structures. Change of the earth pressure acting on the existing structures is closely related to soil arching effect caused by a new tunnel excavation, but it is still lack of full understanding. In this study, a finite element method (FEM) model was first verified by field measurements based on a case history of Metro Line 2 construction in Changsha, China. Then, a series of simplified three-dimensional (3D) FEM models were established to investigate the stress redistribution and the soil arching evolution induced by earth pressure balance shield (EPBS) tunneling. The changes of the earth pressure, the coefficient of lateral earth pressure, and the settlement of soil mass above the tunnel during tunneling were analyzed and the soil arching zone was determined. 3D stress-transfer mechanism in soil arching zone during tunneling was revealed. In addition, the influences of shield-driving parameters (i.e. support pressure, grouting pressure) on soil arching evolution were also investigated. The results show that the loosened zone extends to nearly 0.73D (D = tunnel diameter) above the tunnel crown in vertical direction. The height of the arch zone above the loosened zone is about 1.27D. The horizontal soil arching in front of EPBS occurs near the ground surface. With EPBS advancing, the horizontal soil arching gradually transforms into the vertical soil arching. After the installation of lining, the earth pressure is finally mainly transferred by vertical soil arching in the transverse section. The proper combination of shield-driving parameters for controlling the expansion of the loosened zone is support pressure of 0.6P1 − 2.2P1 and grouting pressure of 1.0P2 − 1.8P2, where P1 is initial horizontal stress at the tunnel axis and P2 = 1.2P1.

Modelling Cell Origami via a Tensegrity Model of the Cytoskeleton in Adherent Cells.

Cell origami has been widely used in the field of three-dimensional (3D) cell-populated microstructures due to their multiple advantages, including high biocompatibility, the lack of special requirements for substrate materials, and the lack of damage to cells. A 3D finite element method (FEM) model of an adherent cell based on the tensegrity structure is constructed to describe cell origami by using the principle of the origami folding technique and cell traction forces. Adherent cell models contain a cytoskeleton (CSK), which is primarily composed of microtubules (MTs), microfilaments (MFs), intermediate filaments (IFs), and a nucleoskeleton (NSK), which is mainly made up of the nuclear lamina and chromatin. The microplate is assumed to be an isotropic linear-elastic solid material with a flexible joint that is connected to the cell tensegrity structure model by spring elements representing focal adhesion complexes (FACs). To investigate the effects of the degree of complexity of the tensegrity structure and NSK on the folding angle of the microplate, four models are established in the study. The results demonstrate that the inclusion of the NSK can increase the folding angle of the microplate, indicating that the cell is closer to its physiological environment, while increased complexity can reduce the folding angle of the microplate since the folding angle is depended on the cell types. The proposed adherent cell FEM models are validated by comparisons with reported results. These findings can provide theoretical guidance for the application of biotechnology and the analysis of 3D structures of cells and have profound implications for the self-assembly of cell-based microscale medical devices.

Static Voltage Sharing Design of a Sextuple-Break 363 kV Vacuum Circuit Breaker

A balanced voltage distribution for each break is required for normal operation of a multi-break vacuum circuit breaker (VCB) This paper presented a novel 363 kV/5000 A/63 kA sextuple-break VCB with a series-parallel structure. To determine the static voltage distribution of each break, a 3D finite element method (FEM) model was established to calculate the voltage distribution and the electric field of each break at the fully open state. Our results showed that the applied voltage was unevenly distributed at each break, and that the first break shared the most voltage, about 86.3%. The maximum electric field of the first break was 18.9 kV/mm, which contributed to the reduction of the breaking capacity. The distributed and stray capacitance parameters of the proposed structure were calculated based on the FEM model. According to the distributed capacitance parameters, the equivalent circuit simulation model of the static voltage distribution of this 363 kV VCB was established in PSCAD. Subsequently, the influence of the grading capacitor on the voltage distribution of each break was investigated, and the best value of the grading capacitors for the 363 kV sextuple-break VCB was confirmed to be 10 nF. Finally, the breaking tests of a single-phase unit was conducted both in a minor loop and a major loop. The 363 kV VCB prototype broke both the 63 kA and the 80 kA short circuit currents successfully, which confirmed the validity of the voltage sharing design.

Investigation of energy release rate under mode II loading in a rectangular orthotropic plate with a band crack using 3D finite element analysis

A rectangular plate containing a band crack and made of orthotropic elastic material is considered and the energy release rate (ERR) component in mode II at this crack front is investigated. It is assumed that the crack’s edge planes are parallel to the upper and lower face planes of the plate and the edge planes of the crack are loaded with uniformly distributed sliding forces. The corresponding boundary value problem is formulated within the scope of the three-dimensional linear theory of elasticity and the solution to this problem is found by employing 3D finite element method (3D FEM) modeling. Numerical results on the ERR for mode II and on the influence of the mechanical-orthotropic properties of the plate material are presented and discussed. In particular, it is established that the influence of the shear modulus in a plane which is simultaneously perpendicular to the crack’s front and crack’s plane on the ERR is more significant than that caused by the change of another modulus of the orthotropic material.

Analysis of textured silicone rubber performance under contaminated conditions

Electric field analysis around high-voltage insulators is with an extreme importance during the development of new polymeric insulators design. In this study, the authors combine the finite-element method (FEM) with the design of experiment method to investigate and describe the behaviour of textured silicone rubber insulators. First, a 3D FEM model of different silicone textured surfaces is developed. The maximum electric field is calculated taking into account various available patterns of hemispherical protuberance having different diameters. Then the design of experiment methodology is adopted to reduce the number of simulations and to give more significance to the results. Various influencing factors were considered in this stage. Finally, the analysis of variance is used to evaluate the contribution of the studied factors and their interaction on the total variation of the studied responses.

Effects of The Shell Thickness On The Directional Deformation And Buckling On The Cylindrical Steel Water Tanks Under The Kobe Earthquake Loading

Cylindrical steel storage tanks are widely used for the storage of various liquids, industrial chemicals and firefighting waters. They have been used for cooling purposes in nuclear power plants in recent years. Liquid-storage tanks have many different configurations; however, in this study, cylindrical ground-supported liquid steel tanks were preferred because of their simplicity in design and construction as well as their efficiency in resisting hydrostatic and hydrodynamic applied loads, when compared with other configurations. If liquid steel tanks are damaged in an earthquake, they can also cause great financial and environmental damage with their hazardous chemical contents. These tanks may be exposed to some damages such as elephant-foot buckling, diamond-shape buckling, overturning and uplifting during earthquakes. Dimensions of cylindrical open-top, flat-closed and torispherical-closed top tanks were determined for 3D-finite element method (FEM) models in an ANSYS workbench software. This article focuses on the seismic-activity-resistant ground-supported cylindrical (vertical) steel storage liquid tanks. Seismic analyses were conducted under Kobe earthquake loads. The frequency values calculated with API 650 were verified with the FEM model results. Directional deformation, buckling results were presented for both impulsive and convective regions. According to API 650 standard, the tank shell thickness is 6 mm. Simulations were performed with 4 mm and 8 mm shell thickness for tanks. In this study, directional deformation and buckling were observed with simulations made by choosing the shell thickness under (4 mm) the standard and above (8 mm) the standard, unlike the approaches in the literature. As a result, it was observed that the 8 mm shell thickness determined above the standard increased the deformation in the flat-closed tank. In addition, torispherical dome-shaped tanks have been observed to lower directional deformation and buckling in any case. The differences obtained are detailed with

Study of a Hybrid Excitation Synchronous Machine: Modeling and Experimental Validation

This paper deals with a parallel hybrid excitation synchronous machine (HESM). First, an expanded literature review of hybrid/double excitation machines is provided. Then, the structural topology and principles of operation of the hybrid excitation machine are examined. With the aim of validating the double excitation principle of the topology studied in this paper, the construction of a prototype is presented. In addition, both the 3D finite element method (FEM) and 3D magnetic equivalent circuit (MEC) model are used to model the machine. The flux control capability in the open-circuit condition and results of the developed models are validated by comparison with experimental measurements. The reluctance network model is created from a mesh of the studied domain. The meshing technique aims to combine advantages of finite element modeling, i.e., genericity and expert magnetic equivalent circuit models, i.e., reduced computation time. It also allows taking the non-linear characteristics of ferromagnetic materials into consideration. The machine prototype is tested to validate the predicted results. By confronting results from both modeling techniques and measurements, it is shown that the magnetic equivalent circuit model exhibits fairly accurate results when compared to the 3D finite element method with a gain in computation time.

Temperature Effects on Damage Mechanisms of Hybrid Metal – Composite Bolted Joints Using SHM Testing Method

This paper presents the quasi-static thermo-mechanical loading effects on the progressive damage mechanisms and failure modes of the single-bolt, single-shear, hybrid metal-composite, bolted joints in aerospace applications. A three-dimensional finite element method (FEM) technique was used to model the countersunk head bolted joint in details, including geometric and frictional based contact full nonlinearities and using commercial software PATRAN as pre/post-processor. The progressive damage analysis (PDA) in laminated (CFRP/ vinyl ester epoxy) composite material including nonlinear shear behavior, Hashin-type failure criteria and strain-based continuous degradation rules for different values of temperatures was made using SOL 400 NASTRAN solver. In order to validate the numerical results and close investigation of the fracture mechanisms for metal-composite bolted joints by determining ultimate failure loads, experiments were conducted in temperature controlled chamber using SHM (Structural Health Monitoring) technique. The results show that the thermal effects are not negligible on failure mechanism in hybrid aluminum-CFRP bolted joints having strong different thermal expansion coefficients. The complex 3D FEM model using advanced linear continuum solid-shell elements proved computational efficiency and ability to accurately predict the various failure modes as bearing and shear-shear out, including the temperature effects on the failure propagation and damage mechanism of hybrid metal-composite bolted joints.

Ablation of Hepatic Tumors through the Use of a Novel Magnetic Nanocomposite Probe: Magnetic Characterization and Finite Element Method Analysis

The authors recently proposed a novel system for thermoablation—based on nanoheating—that can potentially overcome limitations associated with previously reported techniques. The aim of this study was to evaluate the therapeutic performance of the system in the ablation of hepatic tissue, the most frequently ablated. A model nanocomposite system, maghemite nanoparticle-filled polydimethylsiloxane, was prepared, and its magnetic properties were studied as a function of nanoparticle concentration. On the basis of measured magnetic properties, a 3D finite element method (FEM) model was used to explore the development of temperature and thermal damage in nonperfused and fully perfused tissue using alternating magnetic field (AMF) parameters that are acceptable for human use. The FEM model was tested for its validity using an analytical model. The saturation magnetization increased to about 9% of the value of pure maghemite nanoparticles over the range of volume fraction (vol. %) between 1 and 5%. Lesion sizes were shown to be greatly affected by tissue perfusion and time. FEM predictions showed good agreement with results obtained with an analytical model to within 7%. Probes fabricated with magnetic nanocomposite can potentially be used to achieve reasonable lesion sizes in hepatic tissues using human-safe AMF parameters.

Static and dynamic analysis of two mechanically stabilized earth walls

The behavior of mechanically stabilized earth walls (MSEW), with vertical precast concrete facing panels and polymeric strips, was analyzed under harmonic loading to investigate dynamic wall performance. To this end, finite element method (FEM) analyses were carried out. The numerical model was based on a full-scale test of a 6 m-high wall built in Jundiai, Brazil. The wall was reinforced with polymeric strips made from high tenacity polyester and heavily-coated with low linear density polypropylene. The accuracy of the numerical model was verified first by comparing numerical and experimental results under static loading. The same 2D FEM model was then subjected to harmonic loading to analyze stress and deformation of the geostrips under dynamic loading conditions. In this case, it was found that the axial forces in the reinforcement strips deduced from the numerical analyses are less than those predicted using the American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) code under both static and harmonic loading. Under harmonic loading, and for the accelerations chosen in the simulations, the resulting active wedge was larger than for the static case.

Numerical Study on the Leakage Magnetic Field of Transverse Defect on T-Joint Fillet Weld

Abstract A 3D finite element method model is established for yoke-magnetization detection of a transverse defect on T-joint fillet weld and solved by the finite element software ANSOFT Maxwell (ANSYS, Canonsburg, PA). The leakage magnetic field around the transverse defect is obtained. The relationship between the width of transverse defect and leakage magnetic field signals is identified. The researchers found that the tangential component of magnetic flux leakage density, BX1, tends to be a parabolic distribution and reaches the maximum value near the center of the defect along the length direction. While BX1 shows a bimodal distribution, featuring two peaks near the edge of the defect and one peak valley at the center along the width direction, the normal component of magnetic flux leakage density, BZ1, is very different than that of BX1 along the width direction, presenting an approximate N-shape as a whole. The leakage magnetic field signals of the transverse defect on the fillet weld of the T joint will decay obviously when the scanning line is perpendicular to the weld surface over 0.5 mm. The results of numerical simulation can provide a theoretical foundation to detect and characterize various defects in the fillet weld.

Effect of manufacturing residual stress on the fatigue life of railway wheels for heavy-haul transportation

The present work aims to compare the effect of the residual stress from the thermal treatment process (TTP) on the estimate of fatigue life of railway wheels - class C, both with and without residual stresses field from thermal treatment process. A 3D finite element method model is used to calculate the thermal treatment process and the rolling contact between rail and wheel. With the stresses calculated in this region, the study estimates the life under fatigue until a crack arises. The crack, when propagated, can result in shelling, which is one of the types of failure with significant economic importance to railroad maintenance. The model primarily uses the elastoplastic approach, then adds residual stresses from the thermal treatment process of railway wheels. ABAQUS® software is used for the numerical processing, in parallel with specially developed techniques to reduce the computational cost without causing loss of accuracy of the results. The fatigue life of the railway wheel before crack initiation is determined by the modified Dang Van high-cycle fatigue criterion. Given the assumption that the wheel radius does not change during rolling, the elastic shakedown phenomenon occurs in a few loading cycles. The high-cycle life for the wheel is estimated using the variation in the stress field, both with and without residual stresses from the thermal treatment process. The results of the numerical simulation showed that the von Mises stresses in railway wheels with thermal residual stresses are lower than in wheels without thermal residual stresses. The elastic shakedown phenomenon happened in three load cycles in the wheel model with thermal residual stress and in four load cycles for in the wheel model without thermal residual stress. However, this small difference in cycles caused by the thermal treatment process has a significant effect on the fatigue life. The modified Dang Van’s fatigue criterion showed that railway wheels with thermal treatment have 43.2% more life than railway wheels without it.