3D FEM Simulation Research Articles

Development of differential hall sensors for Pulsed Eddy Current Testing using Gaussian pulse excitation

This study presents the use of differential Hall sensors in Pulsed Eddy Current Testing with Gaussian pulse excitation. This method was selected for its ability to effectively distribute energy across the frequency spectrum, thereby enhancing inspection depth and precision compared to the conventional rectangular pulses. The design of the differential Hall sensors, which includes two Hall sensors, greatly minimizes interference from the primary magnetic field, resulting in improved accuracy in detecting defects, particularly corrosion, across varying lift-off distances. 3D-FEM simulations and experimental results demonstrate that differential Hall sensors outperform traditional single Hall sensors in reducing noise and maintaining corrosion signal. Compared to traditional single Hall sensors, the differential Hall sensors exhibit a significantly improved signal-to-noise ratio, particularly at larger lift-off distances. Additionally, the study employs the Full Width at Half Maximum method to accurately estimate the size of corrosion, offering a precise and non-invasive approach to assessing structural integrity.

Integrating parametric HFGMC and isogeometric RZT[formula omitted] for multiscale damage modeling of composite structures: A numerical and experimental study

In this research effort, a novel multiscale analysis scheme is proposed for damage modeling of composite laminates, sandwich structures, and stiffened plates relying on capabilities of the parametric HFGMC and isogeometric RZT{3,2} formulations. The Ramberg Osgood (RO) model is incorporated into the micromechanics model to reflect polymer matrix material nonlinearities on the overall homogenized composite behavior. Carbon fibers are assumed to behave in a linear transversely isotropic manner. The higher order RZT{3,2} theory employed at the macro level facilitates efficient applicability of the model to thick composite laminates and soft core sandwiches. On the other hand, it generates all three-dimensional stress components and thus ensures dimensional consistency between micro and macro levels. Numerical discretization and prediction of RZT{3,2} kinematic variables are enabled by performing NURBS based isogeometric analysis (IGA) thereby enhancing modeling efficacy to a significant degree. Soft core plasticity and failure in the composite are evaluated at the macro level through the RO model and Hashin criteria, respectively. Applicability of the method is presented for thin and thick flat composite and sandwich laminates; and further extended to stiffened plates via developing a multipatch formulation. A comprehensive validation of our analysis is conducted by comparing the results with established benchmarks from the literature, experimental data, and three-dimensional finite element method (3D-FEM) simulations. Initially, a moderately thick, simply supported square laminate under transverse loading is examined, a common verification benchmark. Then, results from standard mechanical tests, including tensile, shear, and four-point bending tests on thin laminates, followed by experiments on moderately thick sandwich structures subjected to four-point bending, are presented. Finally, the analysis is extended to a stiffened plate under uniform pressure, demonstrating the method’s accuracy and applicability across diverse structural configurations.

A novel measurement‐protection‐integrated current transformer based on hybrid core and magnetic field sensor

AbstractCurrent transformers (CTs) are widely used for energy metering, relay protection, condition monitoring and control circuits. However, CT saturation may lead to non‐negligible measurement errors and relay malfunctions, posing a threat to the stability and security of the power grid. In order to address the problem of CT saturation, a novel measurement‐protection‐integrated current transformer (MPICT) is proposed. First, the working states of the MPICT are summarised and the approximate expressions for the steady‐state measuring characteristics, the transient response characteristics, and the measurement errors are derived from the equivalent circuit model. Then, the feasibility of the MPICT and the theoretical analyses are verified by the 3D FEM simulation imitating the presented MPICT excited by diverse currents. Finally, a down‐scale prototype is fabricated and a series of tests are conducted in the laboratory to validate the effectiveness of the equipment. The simulation and experimental results suggest that the output of the MPICT can accurately reconstruct the primary current waveform, even if the primary current contains decaying or constant DC component.

Shack–Hartmann wavefront sensing: A new approach to time-resolved measurement of the stress intensity factor during dynamic fracture

The stress intensity factor describes the stress state around a crack tip in a solid material and is important for understanding crack initiation and propagation. Because stresses cannot be measured directly, the characterization of the stress intensity factor relies on the measurement of deformation around a crack tip. Such measurements are challenging for dynamic fracture of brittle materials where the deformation is small and the crack tip velocity can be high. Digital gradient sensing (DGS) is capable of full-field measurement of surface deformation with a sub-micrometer sensitivity and a sub-microsecond temporal resolution, but it has only been demonstrated on centimeter-scale specimens with a spatial resolution of ∼ 1 mm. This makes it challenging to measure deformations close to the crack tip. Here, we demonstrate the potential of Shack–Hartmann wavefront sensing (SHWFS), as an alternative to DGS, for measuring surface deformation during dynamic brittle fracture of millimeter-scale specimens. Using an opaque commercial glass ceramic as an example material, we demonstrate the capability of SHWFS to measure the surface slope evolution induced by a propagating crack with a micrometer spatial resolution and a sub-microsecond temporal resolution. The SHWFS apparatus has the additional advantage of being physically more compact than a typical DGS apparatus. We interpret our SHWFS measurements of the surface slope by comparing them with 2D analytical predictions and phase-field simulations as well as 3D linear-elastic FEM simulations, based on which we discuss the relevance of 3D effects around the crack tip. Then, we introduce our procedure for extracting the apparent stress intensity factor associated with the propagating crack tip using SHWFS measurements. We conclude by discussing potential future enhancements of this technique and how its compactness could enable the integration of SHWFS with other characterization techniques including x-ray phase-contrast imaging (XPCI) for multi-modal characterization of dynamic fracture.

Surface microstructuring by Ultrasonic Vibration Assisted Deformational Machining (UVADM) – Simulation and experimental results

Polymer-metal hybrids are a lightweight solution for many industrial applications, especially in the automotive or aircraft sector. However, due to their poor chemical bonding the manufacturing of such compounds requires the use of adhesive layers or the conditioning of the metallic surface to achieve form closure and high joint strength. Ultrasonic Vibration Assisted Deformational Machining (UVADM) is a novel process that generates functional microstructures with high production rates, aiming to form defined burr structures with undercuts, that have a significant impact on the interlaminar strength of polymer-metal hybrids (PMH). A 3D FEM simulation using Abaqus/Explicit software was applied to design and analyze process conditions including tool geometry. Material deformation was described by the Johnson-Cook model. Simulation results were validated experimentally using two different MCD tools. For the UVADM experiments, specimens of the aluminum alloy EN AW-6082 were used. In the tests, a constant ultrasonic frequency (20.42 kHz), machining speed (100 m/min and 200 m/min), and peak-to-peak amplitude (7 µm) were used. Geometrical surface properties were analyzed by optical methods and SEM. The study demonstrates a conformity between simulated and experimental results, highlighting the potential of UVADM for an increased productivity in the surface conditioning for polymer-metal hybrids.

Heat-Distribution Approximation of Cylindrical Wire Carrying an Alternating Current

This article presents a new approach for calculating the heat distribution of a cylindrical wire carrying an alternating current. It is an approximation method that uses the skin-depth factor to distribute the heat flow into two different directions. The main objective of this method is to develop a relatively simple heat equation to calculate the temperature in cylindrical wire without using Basel functions. First, a Fourier heat equation for direct current is shown and compared with 2D FEM simulation results. Then the approximation formula will be derived from the Fourier heat equation for the case of alternating current (AC). A 2D FEM simulation is also performed for this case to validate the results of the approximation formula. The results show that the approximation formula is very suitable for most applications.

Torsional Effects on Wind Turbine Blades and Impact on Field Damages

The purpose of this paper is to present the importance of torsional loads when understanding the significant increase in structural damages on large wind turbine blades. By comparing the stress state of two blades of different length, it is shown that torsional loads grow with an exponent of four (4). Thereby, a function of the length of the blades leading to a new range of challenges that are not met by the current process for design, testing and certification.The paper presents the study of these new challenges in detail, based upon:- An experimental perspective, with results from large-scale cyclic loading tests on two blade cut-outs conducted under controlled laboratory conditions in. Both blades were tested to failure.- A numerical perspective, non-linear geometrical 3D FEM simulations has been performed to study the impact of torsional loads on relevant current structural failure modes on large wind turbine blades.The conclusion is that the larger torsional loads may explain shear-web disbond, as well as sandwich skin debonding in both the transition zone and in the max chord area of wind turbine blades. In view of the findings, the paper includes proposals for remedies that are expected to mitigate some of the significant failures currently seen in the field.

A new chevron electromagnetic acoustic transducer design for generating shear horizontal guided wave

Guided wave electromagnetic acoustic transducers (EMATs) have a significant role in non-destructive testing and structural health monitoring. It can generate horizontally polarized shear waves propagating axially or circumferentially to characterize the shape and orientation of pipeline defects. This work proposes a new Chevron pattern-like coil structure design with a periodic permanent magnet (PPM) EMAT configuration. This specific design of the EMAT coil can generate a bi-directional shear horizontal wave (SH-wave) and reduce the side lobes. An optimal Chevron angle of coil wires assists in generating orthogonal propagatingwaveforms. These phenomena lead to the constructive interference of propagating waves and develop a resulting wave along the horizontal direction. A 3D FEM modeling and simulation have been carried out and validated with experimental results. The proposed EMAT results are compared with the conventional racetrack PPM EMAT model, which shows a significant improvement over conventional EMATs. A prototype of this proposed EMAT has been developed. It can be used to inspect surface defects in applications such as fuel transportation pipelines.

Modelling and analysis of electromagnetic vibration in long sheet secondary tubular linear induction motors

AbstractThis paper aims to clarify the behaviour and mechanism of electromagnetic vibration in long sheet secondary tubular linear induction motors (LSS‐TLIMs). Firstly, the spatial and temporal characteristics of electromagnetic force acting in the stator are analysed. Secondly, based on the wave propagation method, an analytical model is established to calculate the vibration response of the stator, which is simplified as a finite cylindrical shell. The accuracy of the proposed model, as well as the rationality of the simplification, are verified by 3D FEM simulation. It is indicated that the electromagnetic vibration response of LSS‐TLIMs mainly depends on the “axial breathing mode” (ABM) and corresponding “modal participation factor”. Moreover, the influences of the spatial distribution of electromagnetic force and the structural dimensions on the vibration are investigated. Finally, the “static vibration test” is performed to validate the above analysis. It is concluded that, compared with a rotary motor, the low‐frequency vibration of LSS‐TLIMs can be easily controlled since the natural frequency of ABMs tends to be much higher than that of the circumferential mode.

Investigation of Underpass and Railway Track Settlements Induced by Shield Tunneling Through In Situ Test and 3D FEM Simulation

Investigation of Underpass and Railway Track Settlements Induced by Shield Tunneling Through In Situ Test and 3D FEM Simulation

A new insight into wormhole propagation prediction in carbonate matrix acidizing based on experimental approaches

Carbonate acidizing is a common practice for production/injection enhancement in damaged oil/gas wells by creating conductive flow tunnels called wormholes. Previous linear acid flood studies are mostly performed on core plugs limited to the Darcy scale with a strong dependency on lab results for upscaling techniques. In this study, a novel scale-free approach of wormhole propagation inside linear porous media for small to very large core diameters is introduced. The model associates the wormhole tip velocity and wall fluid loss to the injection rate using novel flow correlations in terms of core diameter and wormhole geometries (wormhole density, length and diameter). These correlations are constructed based on the results obtained from a large number of 3D-FEM (Finite Element Method) simulations of water flow utilizing the porous rock with predefined dominant cylindrical wormholes. The application of the model is easy and quick without complex or time-consuming calculations even for large rock diameters up to 28 in (71 cm) which simultaneously predicts the acid response curve by matching with the acid coreflood experiments on specific acid/rock systems. Also, the output matching parameters for each acid/rock system can be directly used for larger core diameters without extra-large scale acid flood experiments. In the experimental parts of this study, acid flooding is performed on various rock types of four Iranian carbonate reservoir layers to find their corresponding acid response curves and optimum flow conditions required to design stimulation programs. Besides, the collected data bank could help to enrich the data pool required to validate the developed model practically. The proposed model is validated by literature model results and also experimental data obtained in our laboratory and those presented in the literature and the results showed that good agreement is obtained in regression analysis with R2 = 0.953, MSE = 0.046452, RMSE = 0.215528 and MAPE = 24.11357.

Online monitoring method based on magnetic field for stator insulation lifetime tests

In this paper, an online monitoring method of insulation faults based on the stator magnetic field for insulation life tests is developed. In recent years, a trend towards higher operating voltages, higher switching frequencies, and shorter voltage rise times has been observed for low-voltage motors, mainly driven by increasing electromobility. An insulation system must withstand these requirements over the entire operating range and the required service life. Significant over-dimensioning of the insulation is not justifiable, since this has a negative impact on the utilization or the efficiency of the machine. Lifetime tests are therefore required for dimensioning the insulation. For this purpose, end-of-life (EOL) tests are usually carried out. Here, different damage patterns occur, which are distinguished during the analysis. In addition to the EOL test, insulation faults can be detected by monitoring the magnetic field of a stator during the operating time (“online”). An early shutdown often prevents the drive from further damage. In this paper, five methods to evaluate the magnetic field are presented. The operation is investigated using a 2D FEM simulation (sinus excitation) and a network simulation (PWM excitation) and evaluated through measurements on a 4 kW PM external rotor stator. Subsequently, an application of the method on a test rig setup with continuous monitoring of the insulation system is presented. The test setup serves as a basis for future investigations on the influence of voltage rise time, switching frequency, and DC link voltage on insulation faults to estimate the lifetime of insulation systems of electrical machines.

Evaluation of Tunnel Elastic and Elasto-Plastic Deformations with Approximations Obtained from 3D-FEM Simulations

Nowadays, there are computer tools designed to simulate engineering problems. Numerical simulations in three dimensions (3D) are the closest to reality, but they require a significant amount of time and experience. In this paper, the aim is to present formulae and graphs obtained from numerical simulations using the finite element method (FEM). Their application decreases the time required to obtain deformations in the periphery of different tunnel sections and further serves to evaluate them for different excavation lengths in the face of unexpected geotechnical changes during drilling. Using the RS2 and RS3 software, 3D analyses were carried out according to the Mohr-Coulomb (MC) model, considering elastic and elasto-plastic perfect behaviors as well as isotropic and anisotropic conditions. The graphs presented herein allow obtaining displacements from an axisymmetric model to infer the 3D displacements horseshoe tunnels, and the polynomial expressions aid in determining the displacements of an established excavation length. Finally, comparisons between the displacements reported by other authors and those obtained with the polynomial expressions are presented as a means of validation for this research.

3D FEM Simulation of Titanium Alloy (Ti6Al4V) Machining with Harmonic Endmill Tools

AbstractUsually, end milling operations have been carried out using conventional uniform helix tools with fixed helix angles. Thus, many studies have been conducted to study the effects of these tools on the thermomechanical properties of a milling process. Recently, there have been works that point to the benefits of using harmonic endmills. Harmonic endmills consist of cutting edge profiles that have continuously harmonically varying helix angles. The variation is described using a harmonic function of axial position (elevation) of points on the cutting edge. In this work, a 3D finite element simulation using ABAQUS, is carried out for the complex milling process of Titanium alloy Ti6Al4V. The envelope of the harmonic tool is first generated using a set of MATLAB codes and stored in a Standard Triangle Language (.stl) format. The machine tool is introduced into an FEM program which has been designed to provide for dynamic effects, thermo‐mechanical coupling, material damage law and the criterion for contact associated with the milling process. A Johnson‐Cook material constitutive equation which combines the effects of strain hardening, strain softening, and temperature softening is used. To account for the chip separation criterion, the Johnson Cook damage evolution equation is used. The milling process simulation for Ti6Al4V is then carried out. In the end, the stress distribution and the cutting forces are obtained.

Simulation of Dynamic Resistance and Total Loss of HTS CORC Cables

In some high temperature superconducting (HTS) applications, HTS coated conductors carry DC current under external AC magnetic fields. Dynamic resistance occurs when the amplitude of the magnetic field is greater than the threshold magnetic field of the coated conductors. The resulting AC loss, termed as total loss, consists of dynamic loss due to dynamic resistance and magnetization loss due to the shielding currents caused by the AC magnetic field. Conductor on round core (CORC) cables wound with HTS coated conductors have attracted broad attention due to their large current-carrying capability and mechanical flexibility for coil applications. However, there has been no report on dynamic resistance and total loss in CORC cables. In this work, we present 3D FEM simulation results on the dynamic resistance and total loss of a spiral tape and three CORC cables, based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\boldsymbol{T-A}}$ </tex-math></inline-formula> formulation. The number of layers of the CORC cables, the amplitude of the AC magnetic field and transport DC current levels have been varied to study the impact of those parameters on dynamic resistance and total loss of the three CORC cables. The simulation results show that magnetization loss without current in a spiral tape can be analytically estimated by Brandt and Indenbom’s theoretical equation for a superconducting strip under perpendicular AC magnetic field with a geometric coefficient 2/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> . Furthermore, dynamic resistance of the spiral tape and each tape in a single-layer cable can be predicted by the analytical equation for a strip carrying DC current under perpendicular AC magnetic field, also taking into account the geometric coefficient 2/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> . The simulation results also show that the difference of total loss values in the three CORC cables depends on the shielding effect: the more layers of CORC cables, the lower each loss component. The two-layer Cable with each tape in the outer layer sitting on top of the tape in the inner layer has the lowest loss and the highest threshold magnetic field.

Finite Element Simulation of the process combination Hammering Turning

In the process combination of Hammering Turning, the workpiece surface is microtextured during machining by means of a multi-axis superimposed oscillation of the cutting tool. These microtextures are formed by plastic deformation of the surface layer in a process phase without material removal. In this paper, the formation of the microtexture in the originally three-dimensional process is investigated in simplified analogue 2D FEM simulations. This therefore only represents the processes and mechanisms directly below the cutting edge. The influence of the tool orientation on the plastic material flow and the formation of the microtexture as well as the residual stresses in the surface layer is investigated.

Experimental Validation of Ultra-Shortened 3D Finite Element Models for Frequency-Domain Analyses of Three-Core Armored Cables

Recently, large offshore wind power plants have been installed far from the shore, using long HVAC three-core armored cables to export power. Its high capacitance may contribute to the appearance of unwanted phenomena, such as overvoltages or resonances at low frequencies. To adequately assess these problems, detailed and reliable cable models are required to develop time-domain/frequency-domain analyses on this type of cables. This paper presents, for the first time in the literature, an assessment on the performance of 3D finite element method-based (3D-FEM) models for developing frequency-domain analyses on three-core armored cables, confronting simulation results with experimental measurements found in the literature for three real cables. To this aim, a simplified ultra-shortened 3D-FEM model is proposed to reduce the simulation time during frequency sweeps, through which relevant aspects never analyzed before with frequency-domain 3D-FEM simulations are addressed, such as total losses, induced sheath current, magnetic field around the power cable, positive and zero sequence harmonic impedances, as well as resonant frequencies. Also, a time-domain example derived from the frequency-domain analysis is provided. Remarkable results are obtained when comparing computed values and measurements, presenting the simplified ultra-shortened 3D-FEM model as a valuable tool for the frequency-domain analysis of these cables.

Development and Environmental Assessment of a Phase Change Material Based Thermal Management System for Na/NiCl2 Batteries

The sodium/nickel chloride battery (Na/NiCl2) is considered an eco-friendly, long-term stable and safe alternative to other secondary battery technologies. The overall system efficiency of this high-temperature battery can be increased by optimizing the thermal management system. This paper addresses the integration of a phase change material (PCM) into the battery modules and evaluates the thermal performance and environmental impact of such a design. The module layout with PCM and heat transfer elements (HTEs) was selected based on 2D FEM simulation results and verified in a prototype Na/NiCl2 module. It was shown that the module temperatures could be kept within the operating limits during operation by the HTEs and the PCM even at high current rates. Since no critical temperature limits were reached, the usable battery capacity was higher compared to results of a reference module without PCM or HTEs. In addition, the PCM prolonged the cooling down process after discharge. In parallel with the experimental studies, the environmental performance of the battery was evaluated using a life cycle assessment (LCA). Amongst other things, it was found that the application of PCM is also beneficial from an ecological point of view.

IDeS Method Applied to an Innovative Motorbike—Applying Topology Optimization and Augmented Reality

This study is on the conception of the DS700 HYBRID project by the application of the Industrial Design Structure method (IDeS), which applies different tools sourced from engineering and style departments, including QFD and SDE, used to create the concept of a hybrid motorbike that could reach the market in the near future. SDE is an engineering approach for the design and development of industrial design projects, and it finds important applications in the automotive sector. In addition, analysis tools such as QFD, comprising benchmarking and top-flop analysis are carried out to maximize the creative process. The key characteristics of the bike and the degree of innovation are identified and outlined, the market segment is identified, and the stylistic trends that are most suitable for a naked motorbike of the future are analyzed. In the second part the styling of each superstructure and of all the components of the vehicle is carried out. Afterwards the aesthetics and engineering perspectives are accounted for to complete the project. This is achieved with modelling and computing tools such as 3D CAD, visual renderings, and FEM simulations, and virtual prototyping thanks to augmented reality (AR), and finally physical prototyping with the use of additive manufacturing (AM). The result is a product conception able to compete in the present challenging market, with a design that is technically feasible and also reaches new lightness targets for efficiency.

GaN-Based Multichip Half-Bridge Power Module Integrated on High-Voltage AlN Ceramic Substrate

Power electronic systems employing wide-bandgap GaN transistors promise high efficiency operation and power density but require minimized parasitic circuit elements and an effective cooling concept. This article presents a half-bridge module integrating two 600 V/170 mΩ gallium nitride (GaN) high-electron mobility transistors with their gate drive stages and a fraction of the dc-link capacitance on a patterned multilayer polycrystalline AlN-substrate. The high-voltage isolation at a layer distance of 10 μm and a dense chip-by-chip integration on the GaN half-bridge module enable a compact lateral commutation loop design combined with improved cooling capability of the power transistors. Consequently, the GaN half-bridge module allows for higher load currents at lower device temperature while most parasitic circuit elements are reduced compared to a conventional printed circuit board (PCB) design. The parasitic circuit elements of the GaN half-bridge module and a reference four-layer PCB half-bridge are evaluated using 3D-FEM field simulation and in-circuit measurements. Selected finite element method (FEM) simulation results are validated by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameter measurements and further used to parametrize a lumped commutation loop model. The thermal characterization of the GaN half-bridge module validates the improved cooling capability of the GaN half-bridge power module. Transient switching characteristics are studied in hard-switching mode. The device temperature and converter efficiency are evaluated in dc/dc buck-converter operation.