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This paper is the first that proposes an extended hybrid analytical method (HAM) based on a two-dimensional (2-D) coupling between the semi-analytical Maxwell-Fourier analysis and finite-element method (FEM) in polar coordinates. The proposed model is applied to any rotating electrical machines. The main objective of this paper is to establish the magnetic field solution in the whole machine by coupling an exact analytical model (AM), proposed for all regions having relative magnetic permeability equal to unity, with a FEM in ferromagnetic regions. The AM and FEM are coupled in both directions (r , θ) in the edge separating teeth regions and all its adjacent regions by applied boundary conditions (BCs). The developed HAM gives accurate results on the magnetic flux density distribution and the cogging torque whatever the operating conditions, the magnetic or geometric parameters. All results obtained give very satisfactory agreement with 2-D finite-element analysis (FEA). [ABSTRACT FROM AUTHOR]

Classical numerical techniques remain very computationally expensive to model the magnetization of twisted multifilamentary superconductors in three dimensions because they require solving a large system of equations. In this paper, a reduced model is proposed to approximate the ac losses of these types of wires. It is established through the projection of the physical problem in a helical Frenet basis and the use of periodic boundary conditions on a slice of the wire. The reduced model on the slice leads to systems of more reasonable size leading to smaller and faster simulations than when the whole wire is modeled. Simulation results show that the proposed method leads to computed losses similar to those obtained on a whole wire. Several simulation cases are proposed to prove the validity of the proposed model, and a comparison to some ac loss measurements is proposed to show the effectiveness of the proposed approach. The implementation relies on the H-formulation and is solved with the open-source solver, Getdp. [ABSTRACT FROM AUTHOR]

When designing steel members with nonsymmetric cross sections, it is essential to consider twisting effects when performing stability checks via second-order analysis according to the ANSI/AISC 360-22. Existing line-element formulations for nonsymmetric sections are mostly derived based on thin-walled assumptions, leading to an overestimation of member strength due to the inaccurate prediction of member behavior, especially when the cross sections have moderate wall thickness. This paper proposes an efficient line-element method for second-order analysis of steel members with nonsymmetric thick-walled sections considering the warping degree of freedom (DOF) and the twisting effects along with the transverse shear deformations. Additionally, a two-dimensional (2D) finite-element cross section analysis method employing the constant strain triangle (CST) element is developed to calculate the section properties for arbitrary cross sections, including the Wagner and the shear coefficients. The proposed method is implemented in the educational structural analysis software MASTAN2 and verified through two sets of examples. [ABSTRACT FROM AUTHOR]

Metro systems provide an efficient, convenient, and expeditious way to travel around crowded routes. Because these systems are established in cities, residential buildings close to metro viaducts are significantly affected by structure-borne noise (SBN). Although most previous studies developed SBN prediction with a focus on the accuracy and computational efficiency of a specific bridge type, only limited studies on parameters for the SBN on bridges were carried out. Thus, eliminating SBN is still a challenging task for both the design and operation phases of bridge design. Therefore, this study integrates simplified experiments with numerical analyses to evaluate the influential parameters on the structure-borne noise level (SBNL) for two types of bridge girders, that is, the double-box pre-stressed concrete girder and the double-box steel girder. The present study also proposes an optimization method for reducing the SBNL in the bridge design and operation phases and identifies the sources of SBN for these two types of bridges. In this paper, the solutions to mitigating SBN are first reviewed and briefly introduced. Theories associated with SBN are then derived and experimentally verified using a concrete or steel plate with a unit area. A hybrid evaluation method is developed to integrate transient finite-element simulation with experimental results, and the main sources (e.g., plate thickness, train speed, fastener stiffness, and track irregularity) that induce SBN are examined by this hybrid method. Consequently, the approach to resolving the SBN problem can be optimally determined. As demonstrated in the results from the hybrid evaluation method, the track condition dominates the SBNL for both types of bridges, and the relationship between train speed and plate eigenfrequency should be carefully investigated to avoid the effect of plate resonance. The pre-stressed concrete box girder is the recommended bridge type for use in urban areas from the viewpoint of minimizing the SBNL. [ABSTRACT FROM AUTHOR]

Optical current transducers (OCTs) have clear advantages over conventional current transformers. To better understand the OCT performance, a basic OCT model is developed using finite-element analysis. To model an open-core OCT, the Faraday rotation and detection is implemented in the COMSOL Multiphysics. This paper introduces two experimental setups, which can be used for studying OCT performances under ac and dc excitations. The measured data agree with simulation results and validate the proposed model. The presented model can be developed to study different nonideal effects, in order to identify and mitigate noise sources in OCTs. [ABSTRACT FROM PUBLISHER]

Although nondestructive ultrasonic technologies have been applied in laboratory and field tests in the field of heritage conservation, few studies have quantified the relationship among the real microstructures, micromechanical properties, and macroscopic acoustic responses of earthen-site soils. This paper develops a micromechanics-based multiscale model for quantitatively exploring the ultrasonic propagation characteristics of elastic waves in untreated and consolidated earthen-site soils. Scanning electron microscope images and image processing technology are integrated into the finite-element simulation. The effects of microstructure and wave features on the acoustic characteristics of soils are quantitatively investigated under pulsive loading. The simulation results of untreated and consolidated soils are efficiently compared to ultrasonic test data. It is demonstrated that the integration of microstructure image processing and multiscale modeling can predict the ultrasonic pulse velocity well, which improves the accuracy of laboratory testing and field monitoring and better serves the evaluation and implementation of engineering practice in the field of heritage conservation. [ABSTRACT FROM AUTHOR]

The permanent magnet vernier synchronous machine (PMVSM) has the characteristics of high torque density and high power density and has advantages in the field of low-speed and high-torque applications. The PMVSM utilizes rich harmonics for torque enhancement, but it can also cause an increase in radial electromagnetic force and vibration noise. In this paper, we take a 12-slot 10-pole PMVSM as an example to analyze the source of radial electromagnetic force, vibration and noise. The electromagnetic finite-element model and structural finite-element model of the PMVSM are established for calculation. Through the analysis and calculation of two-dimensional electromagnetic fields, the radial electromagnetic force distribution of the PMVSM is obtained. We derive the radial electromagnetic force formula of the PMVSM and verify the correctness of the formula through harmonic analysis of the radial electromagnetic force. The sources of radial electromagnetic forces at various orders and frequencies within the PMVSM are analyzed and summarized by coupling the radial electromagnetic force obtained from the electromagnetic finite-element model to the structural finite-element model and conducting electromagnetic vibration harmonic response analysis on the PMVSM. The measured acceleration spectrum of the prototype is compared with the finite-element method (FEM) results, verifying the correctness of the finite-element simulation results for electromagnetic vibration. [ABSTRACT FROM AUTHOR]

An assembled floor system is a main step in the industrialization of construction in civil engineering, where the stiffness and anti-crack properties under designed loads and its self-weight are the main concerns. This paper presents a new type of assembled integral composite floor system, which is composed of precast ribbed bottom slab, lightweight infills, cast-in-situ upper slab and joints. Through the couplers for squeezing and splicing of longitudinal bars, shear keys and cast-in-situ joints between the precast panels and cast-in-situ upper part, the whole hollow floor system could not only exhibit satisfactory mechanical performance, but also lower the self-weight and shorten the construction time. To study its flexural behaviors, a full-scale specimen sized 9.2 m × 9.2 m was designed and tested under static area load. With the load increased to the designed loads of Chinese design code GB50010-2010, mechanical performance (i.e., crack distribution, deformation and stress distribution) were analyzed. To further study its load-carrying capacity and working mechanism, an effective finite element model was established in ABAQUS and compared with experimental and simulation results. It was found that the deflection of the floor under the normal service load and the crack width met the needs of normal use, and the finite element model could serve as a reliable method for the load-carrying capacity calculation. [ABSTRACT FROM AUTHOR]

Deep excavations in soft clays often demand heavy shoring supports. Closely spaced struts are known to impede construction within an excavation, resulting in longer construction time. This paper presents a novel strut-free retaining wall constructed by deep cement mixing (DCM). A new U-shaped DCM system (UDCM) was developed to support a 6.5-m-deep, 16-m-wide excavation in newly reclaimed land. Field measurements involving inclinometers and surface movement markers were interpreted using a fully coupled three-dimensional finite-element model. Results indicated a rotational deformation mechanism in the DCM wall. The mechanism was triggered by stress relief and basal heave. Due to the rigidity of the UDCM, the occurrence of basal heave caused the DCM walls to deflect outward toward the retained side. Such a mechanism is not typical in conventional retaining wall systems in which lateral props are installed after certain depths of excavation. The present UDCM possesses a distinctive characteristic, which is the capability to implement and activate props prior to excavation. It also is unique in that basal heave is used to regulate the rotation of the wall, thereby limiting lateral displacements during an excavation. This study includes a design chart developed for the prediction of lateral displacements with varying treatment geometries. [ABSTRACT FROM AUTHOR]

This paper presents a method for the treatment of multiply connected regions within the semi-explicit time-domain discontinuous Galerkin (DG) eddy current solver based on the ${H}$ – $\Phi $ field formulation. The suggested method utilizes a multivalued magnetic scalar potential over a cutting surface that divides a multiply connected domain into two simply connected regions. The multivalued magnetic scalar potential in the nonconductive domain ($\Phi $ -domain) is regularly updated after a sequence of time steps of the explicit vector DG-finite element method solver in the electrically conductive domain (${H}$ -domain) yielding an accurate time-domain solution of the magnetic field in the multiply connected space surrounding the eddy current region. The efficiency and accuracy of the method are demonstrated by a 3-D example and the obtained results are verified by comparison against the corresponding frequency-domain solution. [ABSTRACT FROM AUTHOR]

For testing a conductive pipeline, remote field eddy current testing (RFECT) is used, which is composed of solenoidal exciter coil and receiving sensor coils. In RFECT, there is remote field zone where the eddy current distributions are concentrated on the external surface of the pipe wall. Therefore, it is possible to detect a defect that occurs on the external surface of the pipe wall even if the receiving coils are located inside the pipe. From the measured coil signals, it is necessary to decompose background offset and predict the pattern of defect signal in order to estimate the defect size for the maintenance of underground pipelines eventually. In the process, the amplitude variations of the induced magnetic field at sensor coils are closely related to defect depth. Therefore, it is important to analyze and eliminate distortions of measured RFECT signals. This paper analyzes the effects of the induced magnetic field on the sensing signals with respect to different depth sizes in the RFECT system. The amplitude and the distribution pattern of defect signals are computed by a 3-D finite-element method and the method to eliminate the signal distortions caused by induced magnetic fields are presented. Simulated results in this paper agreed well with measuring ones. [ABSTRACT FROM AUTHOR]

Phononic crystals are a kind of artificial acoustic metamaterial whose mass density and elastic modulus are periodically arranged. The precise and efficient design of phononic crystals with specific bandgap characteristics has attracted increasing attention in past decades. In this paper, an improved adaptive genetic algorithm is proposed for the reverse customization of two-dimensional phononic crystals designed to maximize the relative bandwidth at low frequencies. The energy band dispersion relation and transmission loss of the optimal structure are calculated by the finite-element method, and the effective wave-attenuation effect in the bandgap range is verified. This provides a solution for the custom-made design of acoustic metamaterials with excellent low-frequency bandgap sound insulation or other engineering applications. [ABSTRACT FROM AUTHOR]

Vibration analysis of bridges induced by train loads is a crucial aspect of railway design, particularly considering the complexity of vehicle components such as bogie-suspension systems. Consequently, railway engineers have endeavored to improve the computational efficiency and applicability of train models using the finite-element method. This paper introduces a toolbox implemented in ABAQUS through a user-defined element (UEL) subroutine, which incorporates the vehicle–bridge interaction (VBI) element theory. This toolbox effectively handles diverse vehicle–bridge interaction systems. In the proposed theory, the wheel-track contact force is derived based on the bridge response, eliminating the need for an iterative process and significantly reducing computational workload compared to classical physics-based analysis. The presented approach is validated through a moving sprung mass model and a moving rigid bar model. Furthermore, a case study is conducted on a three-dimensional finite-element model of a high-speed railway bridge in China, based on a design sketch, to showcase the capabilities of the developed scheme. The study demonstrates the practical application of the proposed methodology in analyzing vehicle–bridge structures with high complexity. [ABSTRACT FROM AUTHOR]

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Zeroth mode of vibration is investigated in low-speed high-torque surface-mounted permanent magnet (PM) machines with non-overlapping concentrated windings. Magnetic field distribution in the air gap is computed using time-stepping finite-element analysis, and Maxwell stress tensor is then employed to calculate the radial force density. Based on the time variation of the mean value of the radial force density spatial distribution, the zeroth-order radial forces are studied. Simple structural equations are used to compare the stator deformations for the machines under investigation. Contribution of the zeroth mode to produce vibration is analyzed and compared with the lowest non-zero mode. The influence of pole and slot combinations and the effect of rectifier load are discussed. This paper is carried out to investigate whether or not the zeroth-order radial forces can be of importance in the presented surface-mounted PM machines that are not connected to pulsewidth modulation (PWM) converters. [ABSTRACT FROM PUBLISHER]

This paper presents the design of cryogenic induction motor submerged in liquefied natural gas (LNG) for operating LNG spray pump. In cryogenic environment of −163 °C, the torque characteristics of induction motor differ greatly from the operating conditions at room temperature. So, in order to obtain the operating characteristics corresponded with design specifications of the induction motor in cryogenic environment, it is necessary to redesign motor dimensions from the result of conventional design by reflecting the changes of material properties under the very low temperature (VLT). This paper focused on the design of cryogenic induction motor considering the variation of resistivity for the stator windings and rotor bars. Also, the distribution of magnetic flux density and magnetic saturation effect on the steel core are analyzed by using 2-D finite-element method for ac sinusoidal time varying excitations under the VLT. The result of proposed method considered the magnetic and electric characteristics of matters in VLT successfully, so that the motor performances at the cryogenic temperature fit well with expected. The designed motor was fabricated and torque performance measured in VLT agreed well with design goals. [ABSTRACT FROM AUTHOR]

Since the events of September 11, 2001, the engineering community has devoted increased attention to evaluating the vulnerability of multistory buildings to disproportionate collapse, including substantial research and standards development. This paper reviews recent research conducted by the NIST on the robustness of RC buildings, including experimental validation of both high-fidelity and reduced-order modeling approaches using measurements from subsystems and an entire building tested under column removal scenarios. A robustness index was developed using pushdown analysis of a structure with initial damage to allow an evaluation and comparison of the disproportionate collapse potential of various structural systems using the validated modeling approaches. It is shown that the robustness index is sensitive to differences in the strength and detailing of the structural system, providing higher values for buildings with more stringent design requirements. Further, the paper presents a novel approach for enhancing the robustness of RC beams through local debonding of tensile reinforcing bars at the joints, where significant cracking occurs after a column loss. Experimental and computational studies were conducted to demonstrate the efficacy of this approach. It is shown that debonding of the bottom bars for a length of two beam depths on each side of a central column results in an improvement of more than 30% in the peak vertical load-carrying capacity under a column removal scenario. [ABSTRACT FROM AUTHOR]

An asphalt pavement with gravel base (AP-GB) is used to alleviate the occurrence of reflective cracks. However, its interlaminar stability is affected by the gravel base's looseness and interlaminar complex contact form. In this situation, a viscoelastic model-cohesive zone model-random aggregate model (VM-CZM-RAM) composite structure model of AP-GB is proposed to describe the interlaminar complex contact form through the finite-element method. Meanwhile, the influences of gravel embedded in AP-GB interlamination stability are considered. Then based on this model, the effects of vertical load, horizontal shear speed, and interlaminar asphalt spraying dosage on interlaminar stability are investigated systematically. Results show that the interlaminar shear strength is positively correlated with the vertical load and shear speed under the model with the optimal interlaminar gravel embedded rate (5%). The best shear strength is obtained when the interlaminar asphalt spraying dosage is 0.8 L/m2. Finally, a no-demolding specimen and its shear test method were designed to verify the feasibility of the model. The conclusions of this paper can highly help the structural design and application of the AP-GB. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of an algorithm for the prediction of transformer core deformation, using a fully coupled magneto-mechanical approach. An imposed magnetic flux method coupled with finite-element modeling is employed for the magnetic resolution. The constitutive law of the material is considered with a simplified multi-scale model describing both magnetic and magnetostrictive anisotropies. Magnetostriction is introduced as an input free strain of a mechanical problem to get the deformation and displacement fields. A 3-D estimation of acoustic power is carried out to evaluate the global core deformation and acoustic noise level. The numerical process is applied to a three-phase transformer made of grain-oriented FeSi core, leading to a set of noise estimation for different flux excitations and core geometries. [ABSTRACT FROM PUBLISHER]

Defects occur in laser powder bed fusion (L-PBF) such as the keyholing, lack of fusion, and the balling depending on the laser power (P) and the scan speed (V). The figure shows that the occupied regions of each defect are the process window and are essentially important to fabricate a high-quality part. This paper is a study of process window generation using single-track experiments and finite-element method simulation of thermal conduction for Inconel738LC alloy. A series of single-track experiments were conducted varying the range of P and V and the results were classified into keyholing, lack of fusion, balling, and good track. A series of simulations were conducted and validated by comparison with the experiments. To quantitively identify the balling, the isolines from the contour map generated by the results of simulations and the balling criteria of the ratio of melt pool length and the depth (L/D) of 7.69 were determined considering the past theoretical studies. The lack of fusion criteria: the ratio of the overlap depth in fabrication using multi-scan (Dov) and powder layer thickness (t) of 0.1 was obtained. Using the criteria obtained from the experiments and simulation, the process window was generated. [ABSTRACT FROM AUTHOR]

In this paper, an element-based deep learning approach named DeepFEM for solving nonlinear partial differential equations (PDEs) in solid mechanics is developed to reduce the number of sampling points required for training the deep neural network. Shape functions are introduced into deep learning to approximate the displacement field within the element. A general scheme for training the deep neural network based on derivatives computed from the shape functions is proposed. For the sake of demonstrations, the nonlinear vibration, nonlinear bending, and cohesive fracture problems are solved, and the results are compared with those from the existing methods to evaluate the performance of the present method. The results demonstrate that DeepFEM can effectively approximate the solution of the nonlinear mechanics problems with high accuracy, while the shape functions can significantly improve the computational efficiency. Moreover, with the trained DeepFEM model, the solutions of nonlinear problems with different geometric or material properties can be obtained instantly without retraining. Finally, the proposed DeepFEM is employed in the identification of material parameters of composite plate. The results show that the longitudinal and transverse elastic moduli of the ply in the composite plates can be accurately predicted based on the nonlinear mechanical response of plates. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results from a transverse flux generator with a modified structure. The new transverse flux generator enjoys a coreless rotor leading to a reduction in manufacturing complexity, as well as a decrease in the mass of the rotor, which in turn results in a better active power density. On the other hand, the number of permanent magnets used in the proposed machine is half of that utilized in a conventional transverse flux generator, which reduces the construction cost, especially in large-scale transverse flux generators. Moreover, in the proposed machine, the leakage flux originating from the inactive magnets would considerably be less than that in conventional machines. Besides, this paper demonstrates an analytical model based on the magnetic equivalent circuit for calculation of the proposed generator parameters. Finally, a transverse flux generator is prototyped and tested. [ABSTRACT FROM AUTHOR]

In this paper, a novel modular linear double-stator biased flux (LDSBF) machine is proposed for wave power generation. The operation principle based on flux path analysis is presented. And stator/rotor pole number combinations are discussed by using coil flux analysis. The modular LDSBF machine has better flux path distribution than its counterpart, namely, linear biased flux permanent magnetic machine. More than that, the topology of the modular LDSBF machine makes it feasible to modular design and easy assembly. The electromagnetic characteristics of four types of linear machines are analyzed and compared by using time-stepping finite-element method. The comparative study shows that modular LDSBF machine with improved performance is a good potential design for wave power generation. [ABSTRACT FROM AUTHOR]

Considering that SF6 is a potent greenhouse gas, SF6/N2 gas mixtures are preferred to serve as the insulating gas for its environmental friendliness and good insulation. Since heat transfer analysis is very useful for ascertaining the appropriate temperature rise range, which can ensure the safe operation and extension of remaining useful life of GIL, it is essential to study the thermal properties of SF6/N2 gas mixtures. Nevertheless, very few studies investigate on the temperature field of SF6/N2 gas mixtures under ideal conditions. To reflect the heat transfer characteristics accurately, in this paper, by using the finite-element method and multi-physics coupling, the heat transfer properties in the GIL is analyzed by using a three-dimensional (3-D) axisymmetric GIL model. By varying the SF6/N2 mixing ratio and observing the corresponding heat transfer characteristics, the mapping between SF6/N2 mixing ratio and the temperature rise is obtained by using the model. Furthermore, the mappings are studied under different gas pressures, line currents and ambient temperatures, which correspond to different real-life operating conditions. The proposed strategies can effectively give guidance of choosing proper SF6/N2 mixing ratio for desired temperature rise, and thus having great values of practical applications. [ABSTRACT FROM AUTHOR]

A freeform imaging telescope (FIT) can achieve a large field of view, high resolution, light weight, and small volume at the same time. Single-point diamond turning (SPDT) is usually used to fabricate FITs, which is made entirely of aluminum alloy. Compared with a traditional telescope, whose reflector is made of glass and whose structure is aluminum, the coefficient of thermal expansion (CTE) of the structure and reflector of which is non-conforming, the CTE of the structure and reflector in an all-aluminum FIT is identical. Therefore, it was expected to theoretically have athermalization properties. In this paper, an all-aluminum off-axis three-mirror FIT was verified. The opto-mechanical–thermal coupling analysis of the FIT at −20 °C was carried out, including data processing and coordinate transformation. The reflector node deformation data of the global coordinates obtained from the finite-element analysis were converted into XY polynomial coefficients of the local coordinate system in ZEMAX. The results showed that the modulation transfer function (MTF) of the FIT at −20 °C~+40 °C still reached the diffraction limit. Moreover, the MTF of the FIT at −20 °C was 0.291 through a thermal environmental test, which was almost the same as the MTF at 22 °C. These results showed that the all-aluminum FIT could achieve athermalization properties. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) interconnection technology based on glass through vias (TGVs) has been used to integrate passive devices, and optoelectronic devices due to its superior electrical qualities, outstanding mechanical stability, and lower cost. Nevertheless, the performance and reliability of the device will be impacted by the thermal stress brought on by the mismatch of the coefficient of thermal expansion among multi-material structures and the complicated structure of TGV. This paper focuses on thermal stress evolution in different geometric and material parameters and the development of a controlled method for filling polymers in TGV interconnected structures. In addition, a numerical study based on the finite element (FE) model has been conducted to analyze the stress distribution of the different thicknesses of TGV-Cu. Additionally, a TGV interconnected structure model with a polymer buffer layer is given to solve the crack problem appearing at the edge of RDL. Meanwhile, after practical verification, in comparison to the experimental results, the FE model was shown to be highly effective and accurate for predicting the evolution of stress, and several recommendations were made to alleviate stress-related reliability concerns. An improved manufacturing process flow for the TGV interconnected structure was proposed and verified as feasible to address the RDL crack issue based on the aforementioned research. It provides helpful information for the creation of highly reliable TGV connection structures. [ABSTRACT FROM AUTHOR]

Induction motors were traditionally used in industrial applications ranging from a fraction of horse-power up to several Megawatts due to their substantial benfits. Induction drives with more than three phases are superior to the 3-phase induction drives in terms of overall volume, torque fluctuations, current passing each stator-winding, ohmic loss, efficiency, and reliability in the case of stator-windings open-circuit fault. These benfits are particularly more attractive in variable speed drivers due to the reduced capacity of power-electronic switches. This paper aims to develop an optimal electromagnetic-thermal design procedure of a high-power seven-phase induction motor suitable for variable-speed applications. In this multi-objective design approach, the objective function is defined aiming to increase the efficiency, power-factor, power-toweight ratio, and starting-torque as well as reduce the starting-current. Furthermore, the electrical, mechanical, dimensional, magnetic, and thermal limitations are included in this optimization study in order to ensure practical realization of the designed machine. The coupled-circuit method is employed for nonlinear electromagnetic modeling, while the current displacement phenomenon is considered in calculations of rotor parameters. A lumped-parameter-thermal model is established for calculating heat rises of different parts at each iteration of optimization study. Finally, the performance characteristics of the optimally designed 1-MW 4-pole motor are verified based on 2D FE analyses. [ABSTRACT FROM AUTHOR]

This paper presents an approach for improving the process of optimal design of permanent-magnet (PM) motors. A finite-element method (FEM) combined with a dynamic dual-response-surface model (dual-RSM) is proposed to compute an objective function. The FEM is employed as a basic tool for the computation of the objective function. In order to build up the dual-RSM model, a radial basis function and a moving least-square approximation are both employed. The results that are obtained from the dual-RSM model are dynamically compared together with a preset goodness-of-fit, which determines whether the accuracies of the dual-RSM are high enough to replace the FEM computation. This strategy makes the FEM computation not always necessary at all the sample points in the optimization process and ensures the accuracy of the solution. For the purpose of showing the effectiveness of the proposed optimization methodology, the optimal design process of a dual PM-excited synchronous motor is taken as an example in this paper. [ABSTRACT FROM AUTHOR]

novel method for obtaining superior intracranial focusing field in transcranial magnetic stimulation is proposed in this paper. In order to improve stimulation intensity and focalization, a semiellipse coil pair (SEP) of special coil configuration is designed and introduced. Projected onto a plane parallel to stimulating target, the two adjacent coils are in semiellipse shapes. From the front view, the SEP is bent along a symmetrical axis at specific angles. Finite-element method is adopted to analyze the relations between the geometric structure characteristics of SEP and the three-dimensional spatial distributions of the induced electromagnetic field produced by SEP. The SEP coil is compared to a conventional figure of eight coil by the positive peak value of intracranial induced electrical field and the focusing area at a target plane located 20 mm below the scalp. Results indicate that under similar power loss, the design of SEP makes it possible to enhance the positive peak value of induced electrical field and decrease the focusing area simultaneously. A real human head modeled as homogeneous and isotropic is occupied in this paper to verify our method. [ABSTRACT FROM AUTHOR]

This paper proposes a sensitivity analysis for the shape optimization of current-carrying conductor in the dc system. The design variable for the current-carrying conductor problem is the outer boundary of the conductor, which has the homogeneous Neumann condition. The 3-D shape sensitivity formula is derived using the material derivative concept from continuum mechanics and the adjoint variable technique. The evolution of the conductor shape is expressed by using the level set method. Three numerical examples are tested to show the usefulness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper describes a highly robust and efficient hybrid parallel computing method for periodic eddy current problems considering motions. This hybrid parallel approach is composed of two levels of parallelization, with distributed memory parallel based on message passing interface at the higher level and shared memory parallel based on multi-threading at the lower level. Application examples will be presented to demonstrate the effectiveness of this method. [ABSTRACT FROM AUTHOR]

This paper presents a new topology optimization method based on basis functions for design of rotating machines. In this method, the core shape of a given rotating machine is represented by the linear combination of the basis functions. The shape is then freely deformed by changing the weighting coefficients to the basis functions to find the optimal shape. The proposed method is compared with the conventional shape optimization based on polygon morphing. The former is shown to outperform the latter in both interior permanent magnet and synchronous motor models. [ABSTRACT FROM AUTHOR]

This paper proposes an optimization method using the continuum sensitivity analysis for conductor shape design in the electrostatic system. The continuum sensitivity formula for a conductor shape is analytically derived by employing the material derivative concept from continuum mechanics and the adjoint variable technique. The geometry change of the conductor surface is determined by the velocity field from the derived sensitivity formula, and it is expressed by the level set method. Two numerical examples are tested to show the feasibility and usefulness of the proposed method. [ABSTRACT FROM AUTHOR]

The effective in-plane elastic moduli of different types of honeycomb cores with thick walls are studied using analytical and numerical approaches. Analytical equations derived in this paper take a proposed jointed rectangle into consideration. The analytical results under plane stress and plane strain conditions are also obtained. The effective in-plane elastic moduli are studied as a function of their own relative densities because of the different methods of describing the geometrical shapes of honeycomb cores. The results are quantitatively compared with the available experimental results in this paper. It indicates that the present model can better predict the elastic properties in x -direction but are less suitable in y -direction. The proposed jointed rectangle has significant effect at high relative density. Moreover, the effective in-plane modulus increases with the relative height of honeycomb cores because of the Poisson effect of the material, and the results under plane stress and plane strain conditions are the lower and upper bounds, respectively. [ABSTRACT FROM AUTHOR]

In general, a magnetic flux leakage (MFL) pipeline inspection gauge (PIG) has been applied to nondestructive testing for investigating ferromagnetic materials, such as underground gas pipelines. Although MFL PIG is efficient to the inter-city large-scale pipelines, it is hard to apply to small-size pipelines that are usually installed in the city, because the permanent magnet for MFL PIG is too big and heavy to operate inside the small pipe. The strong adhesive magnetic force of permanent magnet to the pipe wall also prevents the usage of MFL PIG in small pipelines. In this paper, we propose a new technology of nondestructive inspection by using a differential coil, which is easy to be manufactured with lightweight, low cost, and simple structure for operating inside the underground pipelines. Comparing with the conventional permanent-magnet MFL PIG, the results of the proposed system could also maximize the detection sensitivity of defect signals and minimize the magnetic adhesive force on the pipe wall simultaneously. [ABSTRACT FROM AUTHOR]

The degrading effect of laser cutting on steel sheet material, and thus on the material's magnetic characteristics, is much less understood than that of mechanical cutting. Furthermore, the degrading influence on the magnetic properties is still difficult to determine. This paper focuses on the modeling of the degrading influence of laser cutting on the magnetic properties of electrical steel sheets. As the degradation depth and the degradation profile are still difficult to define, a method is needed, which takes the effect of laser cutting into account, but without the need of knowing the degradation profile exactly. This paper shows that a method that does not require any information on the physical phenomena that are introduced by the cutting process and that has already been verified for mechanically cut samples can also be applied to laser-cut samples, although the deterioration mechanisms and the resulting degradation profile and depths differ. Magnetic characteristics are identified for two different material zones and subsequently inserted into a finite-element model, which accounts for arbitrary geometries. The simulation results for the influence of laser cutting on the magnetic characteristics of the stator lamination stacks are verified by measurements, including three different materials and frequencies. [ABSTRACT FROM AUTHOR]

In this paper, we derive the weak form for clamped plates composed of incompressible neo-Hookean material from the uniformly valid asymptotic plate theory. By using the finite-element software COMSOL, we study the numerical solutions of the weak form. We show the accuracy and the efficiency of the weak form by comparing the numerical results for the two-dimensional weak form and a three-dimensional model. As a basis for comparison we choose numerical values of the displacement, the second Piola–Kirchhoff stress, and the Green–Lagrange strain at the bottom. The numerical simulations are performed for three different cases of thickness–span ratios, including (1) very thin plate, (2) thin plate, and (3) moderately thick plate. The results show that the uniformly valid plate theory is a reliable and implementable plate theory for even moderately thick plates with large deformations. [ABSTRACT FROM AUTHOR]

The stator coreless axial flux permanent magnet (AFPM) motor with a compact structure, low torque ripple, and high efficiency is particularly suitable as a motor for electric propulsion systems. However, it still requires great effort to design an AFPM motor with higher torque density and lower torque ripple. In this paper, a stator coreless multidisc AFPM (SCM-AFPM) motor with a three-rotor and two-stator topology is proposed. To reduce rotor mass and increase torque density, the proposed SCM-AFPM motor adopts the hybrid permanent magnets (PMs) array with Halbach PMs in the two-terminal rotor and the conventional PMs array in the middle rotor. In addition, a multi-objective optimization model combining response surface method (RSM) and genetic algorithm (GA) is proposed and applied to the proposed SCM-AFPM motor. With the help of the three-dimensional finite-element analysis (3-D FEA), it is found that the torque ripple of the optimized SCM-AFPM motor is 4.73%, while it is 6.21% for the initial motor. Its torque ripple is reduced by 23.8%. Therefore, the proposed multi-objective optimization design method can quickly and reliably obtain the optimal design of the SCM-AFPM motor. [ABSTRACT FROM AUTHOR]

This paper presents a real-time analytical space harmonic model of permanent magnet synchronous machines with shaped poles. The goal of this configuration is to produce an air-gap flux density distribution as close to sinusoidal as possible to enhance the machine performance. The analytical model is derived to predict the magnetic fields and the machine behavior by solving Maxwell’s equations and applying the superposition theorem. The digital hardware realization of the model is developed on the field-programmable gate arrays (FPGAs) in a paralleled and pipelined paradigm for an efficient hardware design. Such real-time emulation on FPGA can be used in the design procedure and the assessment of newly prototyped controllers and drive systems in the hardware-in-the-loop platform. In this paper, the analytical model of the machine is simulated in real time on 7.5 ns input FPGA clock cycles, and the achieved executive time is 1.8 \mu \texts . The captured real-time analytical results demonstrate the good accuracy of the emulator in comparison with the offline 2-D time-stepping transient finite-element solution obtained by JMAG software. [ABSTRACT FROM AUTHOR]

The objective of this study is to conduct a finite-element (FE) numerical study to assess the effect of size on the shear resistance of reinforced concrete (RC) beams strengthened in shear with externally bonded carbon fibre-reinforced polymer (EB-CFRP). Although a few experimental studies have been done, there is still a lack of FE studies that consider the size effect. Experimental tests are time-consuming and costly and cannot capture all the complex and interacting parameters. In recent years, advanced numerical models and constitutive laws have been developed to predict the response of laboratory tests, particularly for issues related to shear resistance of RC beams, namely, the brittle response of concrete in shear and the failure modes of the interface layer between concrete and EB-CFRP (debonding and delamination). Numerical models have progressed in recent years and can now capture the interfacial shear stress along the bond and the strain profile along the fibres and the normalized main diagonal shear cracks. This paper presents the results of a nonlinear FE numerical study on nine RC beams strengthened in shear using EB-CFRP composites that were tested in the laboratory under three series, each containing three sizes of geometrically similar RC beams (small, medium, and large). The results reveal that numerical studies can predict experimental results with good accuracy. They also confirm that the shear strength of concrete and the contribution of CFRP to shear resistance decrease as the size of beams increases. [ABSTRACT FROM AUTHOR]

The maximum interface sheer stress and crack density can be used as criteria for the interfacial bonding property and fracture performance, respectively. In this paper, interface stress and crack density as a function of applied strain of Zn–Zn-Al multilayer coating/304 stainless steel substrate system with different coating thicknesses were studied using uniaxial tensile tests. For comparison, Zn and Zn-Al monolayer coatings also were prepared. The saturated crack density of the Zn–Zn-Al coating was the largest, and that of the Zn-Al coating was the smallest. Furthermore, the maximum interfacial shear stress of the Zn–Zn-Al coating substrate system with 0.24-mm coating thickness was the largest. Finite-element simulation was used to analyze the development of interfacial cracks of the multilayer coating–substrate system during three-point bending. The simulation results showed that the interfacial crack was dominated by shear stress in the Zn–Zn-Al multilayer coating–substrate system with a total coating thickness of 0.32 mm, which proves the accuracy of the experiment. [ABSTRACT FROM AUTHOR]

Spiraling of conductors in a helical winding of a transformer may lead to a catastrophic failure under the action of torsional short-circuit electromagnetic forces. Torsional forces are produced by the interaction of the axial component of the short-circuit current and the radial component of the leakage magnetic flux density. In this paper, 3-D magnetostatic analysis has been performed to determine the leakage magnetic-field distribution in a 130-MVA power transformer. Torsional electromagnetic forces are calculated from the analysis to determine circumferential displacements of conductors of its low-voltage helical winding. Furthermore, mechanical stress components are computed and a factor of safety is defined, which gives an indication as to whether the winding conductors are in the elastic or plastic zone. The numerical results thus obtained by the finite-element method are verified using the first principles from mechanics. The effect of looseness in the inner support structure on the von-Mises equivalent stress and, hence, on the factor of safety has been studied. [ABSTRACT FROM PUBLISHER]

Finite-element method (FEM) has been widely used in industrial applications for many years. With the increase of finite-element model complexity and the number of elements, computation burden has become a serious issue and requires more attention. In this paper, the transmission line method (TLM) is adopted to the solution of FEM-based nonlinear axisymmetric magnetostatic problem and an equivalent finite-element network’s circuit model is given. Several methods were investigated to speed up the computation, such as Newton preconditioners, simplification of nonlinear equation solution and parallel computation. Compared with traditional Newton FEM iteration, our results show that the proposed method has more obvious advantages on computational efficiency at the same calculation accuracy. The method is applicable and valuable in the characteristic analysis and design of the magnetic device with a cylindrical structure. [ABSTRACT FROM AUTHOR]

This study focuses on the safety assessment of antiliquefaction performance of an embankment of a reservoir, which is an important infrastructure located in Shanghai, China. The performance-based design (PBD) philosophy is introduced for the assessment. In the accompanying paper, the experimental safety assessment using dynamic centrifuge model tests is presented. In this paper, an effective stress-based, fully coupled, hybrid, finite element-finite differences (FE-FD) numerical method is adopted for the numerical safety assessment. The numerical scheme is verified and validated using the dynamic centrifuge model tests reported in the accompanying paper and then applied to assess the safety of the whole embankment subjected to precautionary earthquake. The liquefiable soils are described by a well-calibrated cyclic elastoplastic constitutive model, while a Ramberg-Osgood model is adapted for the other soils. All the parameters used in the simulation are determined based on field data and element tests. The hydrodynamic pressure is also considered in the safety assessment. The seismic performances of the constructed embankment during and after an earthquake are predicted. The safety of antiliquefaction performance of the reservoir embankment is assessed based on the PBD concept. [ABSTRACT FROM AUTHOR]

In this paper, a wideband dual polarized self-complementary connected array antenna with low radar cross section (RCS) under normal and oblique incidence is presented. First, an analytical model of the multilayer structure is proposed in order to obtain a fast and reliable predimensioning tool providing an optimized design of the infinite array. The accuracy of this model is demonstrated thanks to comparative simulations with a full wave analysis software. RCS reduction compared to a perfectly conducting flat plate of at least 10 dB has been obtained over an ultrawide bandwidth of nearly 7:1 at normal incidence and 5:1 (3.8 to 19 GHz) at 60° in both polarizations. These performances are confirmed by finite element tearing and interconnecting computations of finite arrays of different sizes. Finally, the realization of a $28 \times 28$ cell prototype and measurement results are detailed. [ABSTRACT FROM PUBLISHER]