Coupled Field Finite Element Analysis Research Articles

Fourier-Based Vibration Model of Electrical Machines Considering Nonideal Orthogonality Between Electromagnetic Forces and Structural Modes

This paper proposes a Fourier-based model of vibration synthesis, improving both precision and speed. For the first time, the nonideal orthogonality between electromagnetic (EM) forces and structural modes is theoretically proposed and modelled by spatial harmonics. Different from the discrete vectors used in previous literature, the proposed method achieves a one-dimension (1-D) continuous model of EM forces and modes. On the basis, the vectors of modes and forces on tooth surfaces are decomposed by fast Fourier transform (FFT), so that the vibration response is synthesized based on Fourier coefficients. Further, the proposed model is applied to a 12-slot/10-pole (12s/10p) interior permanent-magnet (IPM) machine. The spatial harmonics of mode vectors are elaborated to identify the key orders of EM forces before the vibration response is completed. Then, the proposed model is compared with the coupled-field finite element analysis (FEA). The advantages are verified in terms of computational accuracy, speed, and sensitivity to mesh quality. Finally, the feasibility of the proposed model is verified by both coupled-field finite element analysis (FEA) and experiment.

Introduction of a recurrent neural network constitutive description within an implicit gradient enhanced damage framework

The contribution at hand presents a method for the application of Recurrent neural network based constitutive models within a coupled field Finite Element Analysis. Thereby, an additional scalar field is coupled to the displacement field and evolved by a scalar variable at the integration points. By employing implicit gradient enhancement as regularization framework, the representation of softening material behavior is possible without the generation of localization phenomena. The feasibility of this approach is shown for an anisotropic constitutive description based on the microplane model, by employing a self-adversarial training scheme for enhanced robustness which was proposed to work for arbitrary inelastic materials. Its capabilities and limitations during application in Finite Element Analysis are evaluated and discussed for two numerical simulations.

Thermal bowing of reinforced concrete sandwich panels using time-domain coupled-field finite element analysis

Thermal bowing in concrete sandwich panels (CSPs), which is an undesirable deflection due to temperature differentials between inner and outer surfaces, has not been studied sufficiently and its effects are still not well understood. In this study, a transient thermal-mechanical finite element technique in ANSYS software, featuring two separate but interrelated time-domain simulations, a heat transfer and a non-linear structural, has been developed to study the bowing phenomenon in CSPs. The model predictions were validated by comparing with experimental data from full-scale panels in the literature subjected to heating on one wythe that produced an increasing temperature differential up to 30 °C. Validation included thermal bowing, slip and temperatures gradient. The structural component of the model was also validated by comparing with panels tested under flexural loads. The coupled model was then used to study the effects of several key variables that were not examined in the experiments, including cooling load, degree of composite action (kp), and wind loading combined with thermal loading. Results showed that very cold temperatures can result in bowing that exceeds serviceability limits and can cause compression failure in connectors. Bowing increased by 129% when kp increased from zero to 85%. Up to 50% increase in bowing was observed when adding wind effects to thermally determined bowing for the thermal range investigated in the parametric study.

Numerical Investigation on Crack Detection Technique for Electric Connector with Joule Heating Effect

Using the electro-thermo-structural coupled-field finite element analysis, the crack detection technique with the Joule heating effect for the electric connector is studied and discussed. The physical behavior of the electric connector with an edge crack is investigated numerically. The electric current density, Joule heating temperature and structural deformation are obtained. As a result, the electric current concentration and Joule heating effect can induce a local hot spot or hot band region around the crack tip. Furthermore, the crack tip location can be determined according to the temperature distribution. For the accurate crack detection, two better electric loading conditions are found as follows: (a) shorter electric operating time (tp), (b) larger electric current (I0). The optimal condition , I0 = 100 A and tp = 0.001 s, is found for this crack detection research.

Numerical simulation for health monitoring of thin simply supported plate using PZT transducers

PZT (Lead Zirconate Titanate) sensors are primarily used due to their important role in structural condition monitoring mainly in nondestructive evaluation. The electromechanical impedance (EMI) strategy is being developed as a successful tool for basic Damage identification. Local damages and flaws in the structure are characterized by variations in the electromechanical impedance signature pattern of the piezoelectric transducer that is attached to the structure. On Basing EMI techniques, numerical simulations are performed using coupled field finite element analysis on a PZT transducer bonded at various location on homogenous plate simply supported with damage in the center of plate, by inducing stiffness reduction, in ANSYS to obtain admittance signatures. RMSD is used for calculation of damage index among damaged and undamaged states. A parametric investigation of the structural stiffness and position of the PZT provides a detailed understanding of admittance signature analysis.

Optimal PZT transducer location for effective damage identification in thin fixed plate

ABSTRACT In the recent advance, the employment of piezoelectric ceramic lead zirconate titanate (PZT) transducers has been widely increased because of its noticeable role in the domain of structural health monitoring (SHM) particularly in non-destructive evaluation. PZT-based electro-mechanical impedance (EMI) technique has been successfully applied to evaluate the inhomogeneities in the structure due to local damages and flaws. A numerical simulation based on EMI technique has been done using the coupled field finite element analysis on a homogenous fixed metallic plate bonded with PZT patches at different locations, to investigate the effect of damage at the fixed end and the centre of the span, induced by local reduction of stiffness, on the admittance signature pattern in ANSYSTM. The observations are discussed using RMSD as damage index computed between the states of pristine and damaged. The parametric study of PZT location and structure stiffness gives better insight into the analysis of admittance signatures, which is vital in SHM applications.

Performance of PZT8 Versus PZT4 Piezoceramic Materials in Ultrasonic Transducers

PZT8 and PZT4 are the common “hard” piezoceramic materials used in power ultrasonic transducers (e.g., welding, cutting, sonar, etc.). PZT8 is perceived as the better choice for resonant devices, primarily due to its higher mechanical quality factor Qm. PZT8 is also considered a “harder” material compared to PZT4, since it has better stability at higher preloads and drive levels. Many transducer designers never consider PZT4 for their applications, even though it has clear advantages such as higher output (i.e., higher d33). Even the perceived advantage of PZT8 regarding Qm may not be significant for most Langevin, bolted stack type transducers if the mechanical joint losses dominate. This research is a case study on the performance of identical ultrasonic transducers used for semiconductor wire bonding, assembled with either PZT8 or PZT4 materials. The main purpose of the study is to establish rule-of-thumb transducer design guidelines for the selection of PZT8 versus PZT4 materials. Several metrics are investigated such as impedance, frequency, capacitance, dielectric loss, Qm, heating, displacement gain, and electro-mechanical coupling factor. The experimental and theoretical research methods include Bode plots, thermal IR camera imaging, scanning laser vibrometry and coupled-field finite element analysis.

E/M impedance modeling and experimentation for the piezoelectric wafer active sensor

This study aimed to develop theoretical models to accurately predict the in-plane (longitudinal) and out-of-plane (thickness-wise) modes of the electromechanical impedance spectroscopy (EMIS) of a piezoelectric wafer active sensor (PWAS). Two main electrical assumptions are applied for both in-plane and thickness mode PWAS-EMIS in one-dimensional simplified analytical models. These assumptions are 1) constant electrical field assumption and 2) constant electrical displacement assumption. The analytical models with two assumptions are compared with one another to understand the prediction accuracy of the models in different vibration modes. Coupled field finite element analysis (CF-FEA) is also conducted with 2D PWAS model under stress-free boundary conditions. The simulations of the simplified analytical models for free PWAS-EMIS under these two assumptions are carried out. The analytical models are validated by corresponding finite element simulations as well as experimental measurements.

Advanced Bode Plot Techniques for Ultrasonic Transducers

The Bode plot, displayed as either impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes or impedance, but quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistence. In-process testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult. This research investigates the use of advanced Bode plot techniques to compare ultrasonic transducers with known “good” and known “bad” process performance, with the goal of a-priori process assessment. These advanced techniques expand from the basic constant voltage versus frequency sweep to include constant current and constant velocity interrogated locally on transducer or tool; they also include up and down directional frequency sweeps to quantify hysteresis effects like jumping and dropping phenomena. The investigation focuses solely on the common PZT8 piezoelectric material used with welding transducers for semiconductor wire bonding. Several metrics are investigated such as impedance, displacement/current gain, velocity/current gain, displacement/voltage gain and velocity/voltage gain. The experimental and theoretical research methods include Bode plots, admittance loops, laser vibrometry and coupled-field finite element analysis.

Coupled field finite element analysis of pin-and-cap disk type insulator assembly

Extensive research has been done throughout the world on the performance of outdoor insulators and insulator assembly, in the area of structural, thermal and electrical analysis. These effects, i.e., structural, thermal and electric have been studied on individual basis only. That is only one effect is considered, however in the real field these effects should be considered simultaneously for the complete analysis of insulator and insulator assembly since these three effects are present at the same time. In this paper, coupled field structural-thermal-electrical finite element simulations are carried out by using a commercially available software package, which allow quantifying the effects of insulator assembly on when structural, thermal and electrical load distribution are considered simultaneously. The structural, thermal and electrical results are obtained for a single 11 kV cap-and-pin type ceramic disc type insulator assembly are analysed and presented. It is observed that under normal working conditions of an insulator assembly the structural, thermal and electrical loads are found mutually coupled, but not going to affect the structural, thermal and electrical characteristics of an insulator assembly and its components.

Finite Element Analysis of Crack Welding Process

The numerical simulation of the crack welding process is reported in this paper. The thermo-electro-structural coupled-field finite element analysis is adopted to investigate the welding process of crack surfaces. In the simulation, the pressure-dependent and temperature-dependent electrical contact conditions are considered. From the results, the crack surfaces can melt and weld together under the compressive load and electric current. The contact pressure effect must be considered in the finite element analysis to obtain more practical results. Keywords—Crack welding, contact pressure, Joule heating, finite element, coupled-field.

Study on Residual Stresses and Fatigue Properties of Friction Stir Welding Joint

Friction Stir Welding (FSW) is a new type of solid-state connection which can reduce structural weight significantly. In this paper, fatigue tests and finite element analysis were employed to study fatigue properties and residual stresses of aerial aluminum alloy 2524-T3 FSW joint. The residual stresses in FSW joint were obtained by a nonlinear direct coupled-field finite element analysis. On the basis of finite element analysis results, the fatigue life of FSW joint was estimated. It is verified that the analytic and estimated results agree with that of experiment.

Squeeze-Film Damping Characteristics of Cantilever Microresonators under Large Electrostatic Loading

A semi-analytical model of an electrostatically actuated damped cantilever microbeam is used to study the response characteristics of small amplitude motion about a statically deflected position. A Euler-beam equation, incorporating the electrostatic force terms and the squeeze-film damping terms, coupled with the linearized compressible Reynolds equation is analyzed under different ambient pressures and DC polarization conditions. The dynamic problem is simulated with the coupled field finite element analysis software ANSYS and results are compared. The applicability of the present model for the range of flow compressibility has been studied through the use of a term called compressibility ratio.

Coupled-Field Finite Element Analysis of MEMS Compound Electrostatic Actuator by Using the ANSYS Software

MEMS (Microelectromechanical Systems) electrostatic actuators have been successfully applied in a number of areas, including accelerometers, gyroscopes, pressure sensors, and optical devices. In this paper, the actuator optimization of a silicon bulk-micro machined MEMS compound electrostatic actuator of an optical device is discussed. The actuator uses folded-beam structure to enhance the electromechanical performance. The movable block is connected to the compound electrostatic actuator through unequal-height folded-beam springs. The lower-height springs connect the block with parallel plates, and can convert the descending motion of the plates into out-of-plane tilting motion of the block efficiently Additionally, the block is capable of in-plane motion by applying the driving force of the comb-drive actuator through structural connection. ANSYS FEM simulation is used to extract the device electromechanical performance and resonant frequency of the device. By gradually varying the design parameters in ANSYS simulation, the relationship between the actuator electromechanical performance and various design parameters is derived. The curves of actuator electromechanical performance versus beam length and beam height are derived and they are in good agreement with theoretical prediction. From the analysis it is concluded that the actuator behavior strongly depends upon various actuator parameters. By adjusting design parameters, desired electromechanical performance can be obtained. Based on the simulation results, a set of optimized design parameters for the compound electrostatic actuator is decided. The above-proposed MEMS compound electrostatic actuator may be used for many applications, such as optical device and micro-operating.

Soft Magnetic Composite Switched Reluctance Generator - Fabrication and Analysis

The main objective of this paper is to investigate the suitability of Soft Magnetic Composite (SMC) material SOMOLOY1000 for a Switched Reluctance Generator (SRG) through electromagnetic, thermal and vibration characteristics employing extensive Finite Element Analysis. The fabrication aspects of Soft Magnetic Composite Switched Reluctance Generator (SMC-SRG) using preform material blanks utilizing indigenous machining process have been delineated. The static and transient electromagnetic characteristics have been obtained through the electromagnetic finite element analysis software MagNet6.22.1 while the thermal and vibration aspects have been studied through coupled field Finite Element Analysis employing the multi physics software ANSYS10 while the Impulse hammers excitation - free vibration test using RT Pro Photon data acquisition system facilitated the experimental determination of vibration characteristics. The study concludes that the advantages of less weight , low torque ripple, low eddy current losses, reduction in vibration level of stator structure coupled with the ability to maintain precise mechanical dimensional tolerance may present SMC-SRG a viable candidate in standalone wind energy conversion systems meant for rural and remote area electrification scheme.

Modeling characterization and optimization design for PZT transducer used in Near Field Acoustic Levitation

An acoustic actuator with large radiation surface has been used in a non-contact levitation system. The actuator is composed of a Langevin transducer and a disk-shape radiator. A comprehensive modeling approach has been developed to simulate electrical and mechanical characterization. A coupled-field finite element analysis has been performed considering the vibrator with flexural mode. Identical experimental conditions were used in the simulation to investigate size effect and optimize the transducer design. The stimulated results show good agreement with experimental measurements. This model may be employed to facilitate the analysis and optimization of Near Field Acoustic Levitation transducer assemblies. Moreover, this paper demonstrated the important role that modeling plays in the design, fabrication and optimization of coupled transducers.

Coupled field finite element analysis of railway block brakes

Simulation of interface pressure and temperature distribution in a railway block brake is carried out using a coupled field (structural—thermal) finite element method. Temperature is estimated using the heat generation calculated from the interface pressure. Deceleration of the wheel is simulated by applying rotations. With the use of coupled field analysis along with the simulation of deceleration, heat generation at a point on the rubbing surface is calculated from the instant value of interface pressure at that time. Present results are verified with the experimental values for temperature rise, variation in speed, and stop time.

Finite Element Analysis of Aluminum Nitride Bimorph Actuators – The Influence of Contact Geometry and Position

AbstractIn this work, the results of 3-dimensional finite element analysis (FEA) of Aluminum Nitride (AlN) homogeneous bimorphs (d31 mode) are shown. The coupled-field FEA simulations were performed using the commercially available software tool ANSYS. The effect of altering the contact geometry and position on the displacement, electric field, stress, and strain distributions for the static case is reported.Piezoelectric beams are commonly used in microelectromechanical systems (MEMS) and also have many possible applications in smart sensor and actuator systems. For example, they have been used as the active element in microfluidic and microactuator MEMS devices. In the actuator mode, they employ the converse piezoelectric effect to couple electrical energy into mechanical deformation. Aluminum Nitride (AlN) based devices have attracted much interest because AlN is a piezoelectric material with high thermal stability, high dielectric strength, a reasonable electromechanical coupling coefficient, and a perfect compatibility with standard silicon processing techniques.

Characterization of Curing Stress Effects on Fracture Behavior of FRP Laminated Composites with Embedded Delaminations

A detailed study on the effect of curing stresses on interlaminar delamination crack growth behavior in fiber-reinforced polymeric (FRP) composites is presented. At a given applied load or displacement, the strain energy release rate distribution along the delamination front with and without considering the effects of curing stresses are compared. In this analysis, results are presented for elliptical delaminations embedded between plies of different orientations in the laminate. A full three-dimensional coupled-field finite element analysis has been conducted to study the delamination crack growth behavior due to curing stress effects. A superposition procedure along with the modified crack closure integral technique based on the concepts of linear elastic fracture mechanics is employed to evaluate the individual modes of strain energy release rates during delamination propagation. It has been observed that the residual thermal stresses developed during the curing stages in manufacturing of FRP laminated composites significantly affect the onset and growth of delamination. The asymmetric behavior of interlaminar fracture energy along the delamination front is found to depend upon the stacking sequence, neighboring ply orientation, thermoelastic anisotropy, and material heterogeneity at the interface of laminated composites.

Sources of high intensity ultrasound—vols 1 and 2

PZT8 and PZT4 are the common “hard” piezoceramic materials used in power ultrasonic transducers (e.g., welding, cutting, sonar, etc.). PZT8 is perceived as the better choice for resonant devices, primarily due to its higher mechanical quality factor Qm. PZT8 is also considered a “harder” material compared to PZT4, since it has better stability at higher preloads and drive levels. Many transducer designers never consider PZT4 for their applications, even though it has clear advantages such as higher output (i.e., higher d33). Even the perceived advantage of PZT8 regarding Qm may not be significant for most Langevin, bolted stack type transducers if the mechanical joint losses dominate. This research is a case study on the performance of identical ultrasonic transducers used for semiconductor wire bonding, assembled with either PZT8 or PZT4 materials. The main purpose of the study is to establish rule-of-thumb transducer design guidelines for the selection of PZT8 versus PZT4 materials. Several metrics are investigated such as impedance, frequency, capacitance, dielectric loss, Qm, heating, displacement gain, and electro-mechanical coupling factor. The experimental and theoretical research methods include Bode plots, thermal IR camera imaging, scanning laser vibrometry and coupled-field finite element analysis.