Multiphysics Finite Element Analysis Research Articles

Seismic assessment of corroded concrete bridges using incremental modal pushover analysis

An efficient yet accurate procedure was developed for the seismic assessment of reinforced concrete (RC) bridges subject to chloride-induced corrosion. The procedure involves using incremental modal pushover analysis to assess corroded bridges as an alternative and less computationally demanding approach to non-linear dynamic analysis. A multi-physics finite-element analysis is performed to evaluate the effects of chloride-induced corrosion on bridge columns. In doing so, chloride ingress in concrete is numerically simulated as a diffusion process by considering the effects of temperature, humidity, corrosion-induced cover cracking and concrete aging. The estimated chloride concentration is then employed to evaluate the corrosion current density, from which the effects of corrosion on reinforcement, cracked cover concrete, confinement and plastic hinge length can be determined for subsequent non-linear static analysis. A case study of a typical bridge structure is presented. The proposed procedure can be used to assess the seismic performance of irregular RC bridges exposed to severe corrosive environments.

Anisotropic frontal polymerization in a model resin-copper composite.

This work investigates experimentally and numerically frontal polymerization in a thermally anisotropic system with parallel copper strips embedded in 1,6-hexanediol diacrylate resin. Both experiments and multiphysics finite element analyses reveal that the front propagation in the thermally anisotropic system is orientation-dependent, leading to variations in the front shape and the front velocity due to the different front-metal strip interaction mechanisms along and across the metal strips. The parameters entering the cure kinetics model used in this work are chosen to capture the key characteristics of the polymerization front, i.e., the front temperature and velocity. Numerical parametric analyses demonstrate that the front velocity in the directions parallel and perpendicular to the metal strips increases as the system size decreases and approaches the analytical prediction for homogenized systems. A two-dimensional homogenized model for anisotropic frontal polymerization in the metal-resin system is proposed.

Trends in Acoustic Metamaterials Analysis and Application Development

Computational engineering has made great progress in terms of both numerical meshods and numerical computing environment. COMSOL Multiphysics®, as a mathematical modeling tool, can automate general-purpose multiphysics finite-element analysis, not only modeling process but also can create and distribute applications, that is, it can provide a ubiquitous CAE environment (U-CAE) that enables analysis for "anyone,anytime, anywhere". In this paper, we apply the U-CAE environment to the design of acoustic metasurface and demonstrate the effectiveness of the application in understanding the generalized Snell's law, which is the basis of the metasurface, and achieved quick implementation of the latest theory including numerical study to U-CAE. As a result, one of the difficult problems in computational engineering is the work of interpretation from theory to numerical model in the process of implementing the latest theory to CAE environment. It is recommended for theorist to write papers with consideration of numerical computation.

Numerical analysis of the stressed state of composite plates with a core layer made of tetrachiral honeycombs under static bending

The present work considers three-layer composite plates with solid face layers and a honeycomb core layer of the tetrachiral type. Under static bending conditions, the effects of discretization (the number of unit cells), relative density and thickness of tetrachiral honeycombs on the stressed state of composite plates are studied. Two sets of numerical experiments have been conducted: within the first one, the thicknesses of layers of composite plates have been remained constant with the variation in the volume of solid body of honeycombs, and in the second case, the volume of solid body of honeycombs is constant under the variation in the thickness of the honeycomb structures. Numerical modeling has been carried out within the framework of the theory of elasticity using the Comsol Multiphysics finite element analysis software, as well as with help of the finite element algorithms for solving the plane problem of the theory of elasticity. Based on the results of the analysis, diagrams of the honeycomb core relative density and thickness dependence of the maximal stresses in the layers of composite plates are presented, respectively, for the first and second formulation of numerical experiments. It has been shown that the discretization of tetrachiral honeycombs provides a significant effect on the strength of the honeycombs. Variation in the honeycombs thickness via changing the relative density under the constant volume of honeycombs solid body also has a significant effect on the strength of the composites.

COST EFFECTIVE METHOD FOR THE STUDY OF THE SHORT-CIRCUIT BEHAVIOUR OF AN ELECTRICAL RESISTOR

Electrical resistors for power lines are used worldwide as Neutral Earthing Resistors for short-circuit current reduction in power grids, and also as Filtering Resistors in combination with capacitors and inductances. The manufacturers of such resistors must certificate that they withstand the mechanical and thermal stresses imposed by the external loads, in accordance with IEC 62001 standard. Although this certification can be achieved by means of testing the resistor under working conditions, this process is both expensive and time-consuming. In this paper it is proposed a methodology for simulating the thermal and mechanical behavior of an electrical resistor, based on Multiphysics Finite Element Analysis. The methodology has been applied for the analysis of a filtering resistor for the Ethiopia-Kenia Power Systems Interconnection. Keywords: Earthing and Filtering Resistor, Multiphysics Finite Element Analysis, IEC 62001 short-circuit behavior.

Electromagnetic Force and Vibration Study of Dual-Stator Consequent-Pole Hybrid Excitation Motor for Electric Vehicles

This paper investigates the electromagnetic force and vibration characteristics of a dual-stator consequent-pole hybrid excitation (DSCPHE) motor for electric vehicles. Firstly, the topology and operation principle of the DSCPHE motor are introduced. Subsequently, the temporal and spatial harmonic characteristics of airgap flux and electromagnetic force are derived and analyzed theoretically. The influences of circumferential-segmented winding, consequent-pole rotor, and excitation modes on radial force harmonics are investigated by finite element analysis (FEA). The vibration behaviors of the DSCPHE motor are investigated by the multi-physics FEA model based on mode superposition method. The radial force harmonics that dominate the motor vibration are analyzed. Finally, the DSCPHE motor prototype is built and tested. The motor vibration behaviors are experimentally measured and compared with an interior permanent-magnet synchronous motor (IPMSM) to validate the theoretical results. This work will contribute to the vibration suppression and optimization of the DSCPHE motor.

Numerical simulation on the noise reduction of underwater pile-driving using a bubble curtain

Aiming at the problem of heavy noise pollution caused by underwater piling operation and, to protect the marine ecosystem near the construction site, this paper discusses the attenuation effect of bubble curtain system on underwater noise generated by piling operations, basing on the previous research on underwater bubble sound attenuation and the attenuation characteristics of sound propagation of different media. Using COMSOL Multiphysics finite element analysis software, the noise field of underwater piling and the model of underwater bubble curtain are established to study the influence of the bubble curtain on the pressure peak values at different depths generated by the same noise source, and the attenuation effect of the bubble curtain on underwater noise is discussed. The results show that the peak sound pressure level of underwater noise can be attenuated by about 8 dB using the bubble curtain.

Infrared and UV Imaging Characteristics of Insulator Strings Containing a Zero‐Value Insulator Based on Experiment and Multi‐Physics Simulation

To study the effectiveness of infrared and UV imaging technology to detect zero‐value insulators, the infrared thermal images and UV videos of zero‐value insulators at different positions on insulator strings were collected at different humidities and levels of pollution. The heat and discharge characteristics of the insulator strings were analyzed. The thermal‐electric multi‐physics simulation models were established with COMSOL Multiphysics finite element analysis software. The temperature and electric field distributions of the insulator string under different conditions were verified. The study shows that, under conditions of dry pollution, the insulator strings did not easily discharge, thus the UV imaging method cannot effectively detect a zero‐value insulator. The infrared thermal image shows that the temperature rise in a normal insulator is significantly higher than that in a zero‐value insulator; zero‐value insulators can thus be detected using infrared imaging. In the case of wet pollution, infrared and UV imaging may return erroneous results due to heavy pollution of high conductivity and unevenness of pollution owing to moisture. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

An experimental validation of a new shape optimization technique for piezoelectric harvesting cantilever beams

The piezoelectric energy harvester efficiency depends on optimizing the cantilever geometry and tuning its natural frequency with vibration source frequency. Moreover, the effect of harvester parameters on natural frequency is vital in tuning the resonance frequency. So, a COMSOL Multi-physics finite element analysis, Eigen frequency study and analytical analysis using MATLAB were constructed to calculate the resonance frequencies and to analyze the harvester parameters effect. Five harvester different shapes, namely, the T-shaped, rectangular, L-shaped, variable width, and triangular cantilevers were optimized using the genetic algorithm. The simulation of the five shapes was implemented using COMSOL. The results indicated that the T- shaped cantilever produced the largest power. Due to its high power and inclusive shape, the T-shaped cantilever with variable width was optimized using the COMSOL optimization module (BOBYQA). Linking genetic algorithm and COMSOL optimization module has highly improved the output power. The COMSOL results were validated using an experimental setup of piezoelectric cantilevers. The experimental setup was employed to calculate the voltage of the base excited harvester with very low excitation frequencies from 0.5 to 10 Hz. Also, the experimental setup investigated the effect of the tip mass, length of the cantilever, and piezoelectric material volume on the output voltage.

Acoustic Modeling and Prediction of Ultrahigh-Speed Switched Reluctance Machines Based on Multiphysics Finite Element Analysis

High-speed switched reluctance machines (SRMs) have been a timely topic recently. However, for ultrahigh-speed SRMs over 100,000 rpm, the acoustic noise is a significant issue in many applications such as high speed spindles, compressors/ turbochargers, flywheels, and etc. In this article, a multiphysics acoustic modeling of ultrahigh-speed SRMs is presented based on finite element analysis (FEA). First, a three-dimensional electromagnetic FEA is conducted to calculate the radial force on the stator teeth. Then, a modal analysis and a harmonic response analysis are shown in the frequency domain to estimate the natural frequencies and vibration of the whole motor. An acoustic response analysis is done to estimate the sound pressure level (SPL) using the superposition of the surface vibration. To verify the model, experiments are done to measure and compare the natural frequencies and the SPL of a 4/2 ultrahigh-speed SRM at 100,000 rpm. The results show that the SPL of the motor is as high as 115 dB at 10 mm away from the motor, which matches the simulation result (113 dB) well. The impact of the bearing is proven to be negligible compared with the noise generated by the radial force. Finally, a parametric study example of using the proposed model to guide the design of SRMs has been conducted. It is shown that “hot dog” shaped motors have less noise than “pancake” shaped motors under the same motor volume, speed, and power.

Modeling and Fabrication of a Piezoelectric Artificial Cochlea Electrode Array With Longitudinal Coupling

In this study, inspired from human cochlea, we propose an artificial basilar membrane structure based on an array of gold electrodes microfabricated along the opposite surfaces of a piezoelectric continuum. The proposed piezoelectric continuum features an isosceles trapezoidal geometry and is situated atop an elastomer matrix with embedded electrode grooves and a duct. At first, a detailed analytical model is presented, which formulates the continuum’s planar deflection equation, governing its elastodynamic behavior. Subsequently, in order to verify the analytical outcomes, a multiphysics finite-element analysis is performed in COMSOL®. Both analytical and numerical models demonstrate desired frequency selectivity akin to the capability of a biological basilar membrane. Subsequently, a proof-of-concept model of the proposed structure is custom-fabricated through standard photo- and soft lithography techniques using Polyvinylidene Difluoride (PVDF), gold, and Polydimethylsiloxane (PDMS) materials. Finally, the fabricated artificial basilar membrane that is intended to be used as a broad band sensor, and artificial cochlea for seamless human-robot interaction is experimentally characterized using a custom-built acoustic exciter, and its effective performance is validated within the frequency range of 3 kHz to 8 kHz.

Investigation on Graphene-Coated Silver-Palladium Microelectrical Contact and Effect of Coating Thickness

This article investigates silver-palladium (AgPd) microelectrical contact coated with graphene (Gr). An analysis is carried out for 2-D, circle-rectangle microelectrical contact using COMSOL multiphysics finite element analysis (FEA) simulation software tool. Under applied force between 6 and $15~\mu \text{N}$ , mechanical performance parameters such as contact radius, depth of penetration, and contact pressure are obtained for AgPd uncoated microelectrical contact. The results are validated with the Hertz contact model. The analysis is also carried out for the AgPd microelectrical contact coated with graphene (Gr). The Gr coating thickness is varied between 5 and 10 nm, and better mechanical performance is obtained for lesser coating thickness. This result shows that Gr can be used as a coating and lubricant on AgPd for electrical contact applications.

An Algorithm for Effective Design and Performance Investigation of Active Cooling System for Required Temperature and Torque of PM Traction Motor

The conventional mechanical design approach of cooling jackets serves the goal of heat dissipation to keep motor temperature below the maximum allowable limit for thermal protection. However, the desired motor performance cannot be effectively achieved by this approach since it only employs heat transfer mechanism. Therefore, a detailed algorithm is developed to provide a constructive cooling design process to achieve the desired performance of a permanent magnet (PM) traction motor. In the preprocessing stage, a two-way electromagnetic (EM) and thermal co-analysis method is developed for preinvestigation of motor temperature and torque to set the goal for the cooling requirement. In the solver, a shape and size optimization method is utilized to get the optimal cooling design for fulfilling the requirement. Further, a multiphysics finite-element analysis model is developed for structural optimization to ensure safe minimal weight of cooling design for the improvement in torque and power density. In the validation step, unlike using only computational fluid dynamics (CFD) to predict motor temperature, a two-way coupling of EM and CFD model is utilized to ensure the design goals of both torque and temperature for several operating conditions. Finally, the design optimization of a cooling jacket for an interior PM synchronous motor is conducted by implementing this algorithm.

3D numerical modelling and analysis of a magnetorheological elastomer (MRE)

Magneto rheological elastomer (MRE) is a smart material consists of a polymer matrix embedded micro/nano-sized magnetic particles. Its mechanical properties are altered by external magnetic fields. In this article, a magnetic-mechanical coupled physics is done for MRE using COMSOL multi-physics finite element analysis (FEA) software for a particle level (micro-scale). Both linear and torsional transmissibility analysis are done on MRE under influence of magnetic fields. Simulation results indicate both linear and torsional stiffness increased with magnetic field. Under the initial influence of magnetic field, it is shown that an increase of 28.75 % and 20.12 % of the stiffness in linear and torsional modes, respectively. Transmissibility curve showed shift in the natural frequency due to increase in stiffness when exposed to a magnetic field. Vibration isolation was reached by achieving a minimum transmissibility factor.

Magneto-Thermal Analysis of an Axial-Flux Permanent-Magnet-Assisted Eddy-Current Brake at High-Temperature Working Conditions

This article proposes an analytic coupled magneto-thermal analysis of an axial-flux (AF) permanent-magnet-assisted (PMA) eddy-current brake (ECB) at high-temperature working conditions. In the topology investigated, permanent magnets (PMs) are placed into stator slot openings to increase the braking torque production capability. This modification enables to control the magnet flux by altering the dc excitation current. However, the utilization of PMs will make the construction vulnerable at high operating temperatures simply because the magnet properties and the brake capability are strongly dependent on temperature. Such problems require complex coupled multiphysics finite-element analyses to obtain the actual brake performance. The proposed approach offers a simple and effective solution that consists of magnetic and thermal models, which are coupled to each other in the time domain. The nonlinear electrical, magnetic, and thermal properties are influenced by the temperature variation in time. An AF-PMA-ECB prototype is manufactured to validate the proposed coupled models and the experimental studies confirm that the proposed approach provides very practical results to determine the working conditions of the AF-PMA-ECB at high-temperature operations.

Dynamic Response of Piles under Wave Loading Based on Comsol Multiphysics

In order to simulate the action of waves on Submarine Structures, COMSOL Multiphysics Finite Element Analysis Software was used. By solving Helmholtz equation in frequency domain of given frequency and introducing artificially applied background acoustics field, considering incidence and penetration of acoustics pressure at the junction of seabed and water surface, a total acoustics field is established. Porous media was characterized by Biot’s consolidation theory to compute the displacement field and acoustics pressure fluctuation in porous media propagating porous elastic waves, considering the viscous loss of the model,so the deformation of Solid Matrix can be described. Finally, a numerical model of wave-pile-seabed was established by coupling the pressure acoustic physical field with the physical field of porous media. The influence of different wave frequencies and wave incidence angles on the displacement of piles and the influence of different wave incidence angles on the stress of piles were analyzed. Finally, the liquefaction of soil around piles was studied.

Acoustic Noise Mitigation of Switched Reluctance Machines with Windows on Stator and Rotor Poles

Switched reluctance machines (SRMs) have been studied by many researchers as an alternative to the other types of electrical machines for use in electric and hybrid vehicle applications. SRMs are fault tolerant and have wide speed operating range. However, they suffer from several disadvantages, including high vibration, acoustic noise, and torque ripple. In this article, the placement of rectangular windows in both the rotor and stator poles is proposed to reduce the vibration and acoustic noise of SRMs. An iterative optimization algorithm in a wide speed range of operation using finite-element analysis (FEA) tools provides the best position and dimension of window design parameters. Multiphysics FEA is also performed to predict the vibration and acoustic noise of the optimized design. The results of this study present that placing windows in both the stator and rotor of the SRMs can significantly reduce the acoustic noise compared with the baseline SRMs. Based on the simulation results, the optimum design has been constructed as a prototype and tested in a wide speed operating condition. The simulation and experimental test validation results prove the effectiveness of the proposed design in mitigating the acoustic noise and vibration.

Effect of magnetic field on nanofluid free convection in Conical Partially Annular Space

Natural convection of a magneto hydrodynamic nanofluid in a porous cavity in the presence of a magnetic field is investigated. The two vertical side walls are held isothermally at temperatures Th and Tc, while the horizontal walls of the outer cone are adiabatic. The governing equations obtained with the Boussinesq approximation are solved using Comsol Multiphysics finite element analysis and simulation software. Impact of Rayleigh number (Ra), Hartmann number (Ha) and nanofluid volume fraction (ϕ) are depicted. Results indicated that temperature gradient increases considerably with enhance of Ra and ϕ but it reduces with increases of Ha.

Resonance frequency selective electromagnetic actuation for high-resolution vibrotactile displays

Vibrotactile displays offer significant potential for conveying information through the sense of touch in a wide variety of applications. Spatial resolution of these displays is limited by the large size of actuators. We present a new selective electromagnetic actuation technique to control the vibrations of multiple tactile elements using a single coil based on their individual mechanical resonance frequencies. This technique allows low-cost and highly reliable implementation of many tactile elements on a smaller area. A prototype is manufactured using 3D-printed tactile elements and off-the-shelf coils to characterize the proposed technique. This prototype successfully increases the resolution by 100 % from 16 to 32 tactile pixels (taxels) on a 25 cm2 pad, without sacrificing other performance metrics such as refresh rates and power consumption. The multiphysics finite element analysis developed for this new actuation technique are experimentally validated by optical vibrometry measurements. This work demonstrates the capability of resonance-selective electromagnetic actuator in developing high-resolution low-cost vibrotactile displays.

AC Equivalent Circuit Model of an Electrochemical Accelerometer for 3D Numerical Simulation in the Low-Frequency Range

The electrochemical principles presented in this paper can be applied to the manufacture of vibration sensors for oil and gas exploration, as well as long-period vibration sensors for the observation of natural earthquakes. To facilitate the manufacture of high-volume electrochemical accelerometer (EAM), this paper presents an AC equivalent circuit model of an EAM in a low-frequency range. A 3D time-dependent numerical simulation based on finite element analysis was designed to combine a complex chemical reaction with electric circuit theory. A sensitive chip channel model was constructed by using partial differential equations and the problem caused by a designed mathematical model was solved by using multi-physics finite element analysis. When the electrochemical properties of an electrochemical vibration sensor and its design parameters as well as the parameters of the AC equivalent circuit model are considered, the abstract processing of the sensor on the equivalent circuit is better accomplished. The effectiveness of the proposed simulation model and the equivalent circuit model were verified by comparing the amplitude-frequency characteristic curve of the equivalent circuit with the amplitude-frequency characteristic curve of the single-channel simulation model of the sensitive chip. These model not only have great significance for the design guidance of an external conditioning circuit but also provide an effective method to decouple the output signal and noise of the sensor reaction cavity.