3D FEM Simulation Research Articles

Enhancement in structure stability of gold micro-cantilever by constrained fixed-end in MEMS devices

This paper reports effects of the constraint condition at fixed end of the Ti/Au-layered micro-cantilever on the structure stability. Two types of constraint at the fixed end were used. One was constraining only bottom surface of the fixed end, and the other was constraining both top and bottom surfaces of the fixed end. The evaluation was conducted by observing the deformation by a 3D optical microscope and FEM simulation using the COMSOL Multiphysics software. From optical microscope observations, the top and bottom constrained micro-cantilevers showed a lower deflection at the tip, and the average deformation was also lowered. The FEM simulation revealed similar results as the optical microscope results. The fixed end was found to deform along as the body of the micro-cantilever deformed from the FEM simulation. Hence, the constraint condition at the fixed end contributes greatly to the overall structure stability of the Ti/Au micro-cantilevers.

Influence of the worn tool affected by built-up edge (BUE) on micro end-milling process performance: A 3D finite element modeling investigation

Micro milling process has been utilized for several decades due to the flexibility of the process in producing complex components. The small size of the process makes the comprehension of cutting phenomenon details more difficult. This study presents a 3D finite element modeling (3D FEM) approach for the micro end-milling process of Aluminum material (Al6082-T6). 3D FEM simulations are carried out in full slot micro end-milling and contour up milling. The model first implements the actual tool geometry and then the effect of typical built-up edge (BUE) on the milling tool. The influence of BUE on the process performance is investigated by comparing the predicted 3d chip flow shape, burr formation and cutting forces with experiments conducted on an ultra-high precision micro milling center. Simulations indicate that BUE has significant impact on the chip shape and chip load for different teeth engagements. Results prove that also burr height is negatively affected by the presence of BUE. The predicted micro milling cutting forces resulted affected by BUE with different teeth engagements. Analysis of experimental measured forces indicates comparable results in respect to simulated profiles confirming the usefulness of the develop 3D FE modelling approach.

Correlation of design parameters with performance for electrostatic precipitator. Part II. Design of experiment based on 3D FEM simulation

The performance of electrostatic precipitators (ESP) depends on their geometrical and operational parameters. The first part of a two-paper series developed and validated a three-dimensional model describing corona discharge, turbulent flow, and particle charging and tracking in the ESP. Based on the model developed in Part I, this paper correlates the design parameters with ESP performance by applying the design of experiment (DOE) approach. Through a full factorial two-level DOE, both individual and interactive effects of design parameters on ESP performance are studied. Five design parameters are investigated, including wire radius, collecting plate length, plate–plate spacing, applied voltage, and particle diameter. The strength of these effects is quantified with sensitivity factors, based on which the parameters and their interactions are ranked. The ranking changes with the extent of its variation from the nominal value. This analysis can be extended to other design factors and different types of ESPs.

Effect of wafer-level silicon cap packaging on BiCMOS embedded RF-MEMS switch performance

Abstract In this paper, the effect of silicon (Si) cap packaging on the BiCMOS embedded RF-MEMS switch performance is studied. The RF-MEMS switches are designed and fabricated in a 0.25μm SiGe BiCMOS technology for K-band (18 – 27 GHz) applications. The packaging is done based on a wafer-to-wafer bonding technique and the RF-MEMS switches are electrically characterized before and after the Si cap packaging. The experimental data shows the effect of the wafer-level Si cap package on the C-V and S-parameter measurements. The performed 3D FEM simulations prove that the low resistive Si cap, specifically 1 Ω·cm, results in a significant RF performance degradation of the RF-MEMS switch in terms of insertion loss.

3D FEM simulations and experimental validation of plastic deformation of pure aluminum deformed by ECAP and combination of ECAP and direct extrusion

Rigid-viscoplastic 3D finite element simulations (3D FEM) of the equal channel angular pressing (ECAP), the combination of ECAP + extrusion with different extrusion ratios, and direct extrusion of pure aluminum were performed and analyzed. The 3D FEM simulations were carried out to investigate the load–displacement behavior, the plastic deformation characteristics and the effective plastic strain homogeneity of Al-1080 deformed by different forming processes. The simulation results were validated by microstructure observations, microhardness distribution maps and the correlation between the effective plastic strain and the microhardness values. The 3D FEM simulations were performed successfully with a good agreement with the experimental results. The load–displacement curves and the peak load values of the 3D FEM simulations and the experimental results were close from each other. The microhardness distribution maps were in a good conformity with the effective plastic strain contours and verifying the 3D FEM simulations results. The ECAP workpiece has a higher degree of deformation homogeneity than the other deformation processes. The microhardness values were calculated based on the average effective plastic strain. The predicted microhardness values fitted the experimental results well. The microstructure observations in the longitudinal and transverse directions support the 3D FEM effective plastic strain and microhardness distributions result in different forming processes.

Design procedure of coreless stator PM axial field synchronous machine for small-scale wind applications

Axial field machines are available in a wide range of configurations. It has flexible design restrictions. Several research efforts were performed to discover machine performance and design horizons. However, the common design process of axial field machines depends on numerical field analysis, due to the lack of trusted and generalized analytical and/or empirical formulas especially for field distribution. This paper aims to present the essential analytic formulation for dimension selection. In addition, it provides the normalized relations between dimensions and airgap flux density using 3D-FEM as an alternative for empirical formulas. The paper describes a design procedure for coreless stator axial flux permanent magnet synchronous machine. Definite equations are derived to help the designer select the proper number of PM poles and concentrated coils to get balanced multi-phase voltage out of the generator. Moreover, the paper defines the necessary limitations of the span of the concentrated coil for a certain pole pitch to reduce the harmonic content of the output voltage waveform. The paper proposes a new approach for selecting the dimensions of the magnetic circuit using proposed data curves instead of struggling with the 3D-FEM along with its high time consumption and the need for high computational power. The loss calculations and the armature reaction are also investigated as a performance analysis criteria for the designed generator. The paper investigates the design for small-scale wind applications. The design procedure is validated using both 3D-FEM simulations and experimental results. The results show the consistency of the proposed procedure. The procedure is described and applied for a certain configuration and materials. However, it is solely extendable to several other configurations.

Coupled 3D Transient Magneto-Mechanical FEM Simulation of a Short Circuit Test on a Mock-up of a 570 MVA Transformer Unit

Large generator step-up (GSU) transformer units are particularly important components of the power generation network. In order to ensure a reliable functioning of the power network, GSU transformers have to be able to withstand a wide variety of stresses, of which Lorentz forces generated during an external short-circuit can be potentially dangerous for the transformer. In this case, a reference mock-up unit designed to withstand similar mechanical stress underwent the actual short circuit testing. Upon the demonstration of short-circuit withstand capability of the mock-up unit, a destructive test was undertaken in order to demonstrate the safety margin of the design. This was achieved by gradually increasing the current until mechanical deformations occurred. This paper describes the process of model generation, calculation, numerical behaviour and the results of a 3D transient magneto-mechanical FEM simulation of the winding assembly of the mock-up transformer unit. This unit underwent short circuit testing with the standard short circuit test currents. This type of simulation allows for a deeper insight into the actual generation and distribution of the magnetic forces and the resulting mechanical stresses during a short circuit which cannot be achieved by presently used simulation and calculation methods used in the calculation of the short circuit withstand capability of power transformer.

A study of multi-coils ECT system for SG tubes of FBR using 3D FEM simulations and experimental measurements

A study of multi-coils ECT system for SG tubes of FBR using 3D FEM simulations and experimental measurements

Buckling collapse of HDPE liners: Experimental set-up and FEM simulations

The purpose of this work is to provide a more complete framework for the development of short-term thermoplastic models to improve the design of liners subjected to external pressure. A device to perform short-term physical collapse buckling tests on HDPE liners to emulate in-service behavior under controlled conditions was designed and constructed. Tests were performed to explore the effect of temperature (in the range of 0–60°C) on the buckling parameters of a HDPE pipe confined in a steel host pipe. The constitutive model for this material was calibrated from compression and tensile tests, performed at various strain rates and temperatures. The Three Network viscoplastic material constitutive model was adopted to reproduce material behavior. Full 3D FEM simulations of collapse buckling tests were conducted and validated against experimental data. Once the 3D full FE model was verified a simplified 2D model was generated to perform an intensive parametric study considering many temperatures and pipe aspect ratios. With data arising from the parametric study a predictive Glock’s type function was derived, which takes into account the effect of temperature and the viscoplastic constitutive behavior of HDPE.

Optimization of unipolar magnetic couplers for EV wireless power chargers

In order to improve the coupling coefficient of EV wireless power chargers, it's important to optimize the magnetic couplers. To improve the coupling coefficient, the relationship between coupling coefficient and efficiency is derived, and the expression of coupling coefficient based on magnetic circuit is deduced, which provide the basis for optimizing the couplers. By 3D FEM simulation, the optimal core structure and coils are designed for unipolar circular couplers. Experiments are designed to verify the correctness of the optimization results, and compared with previous coupler, the transmission efficiency is improved and weight is reduced.

Damage minimised ball spinning process design

Ball spinning is an incremental forming process for tubes and rods. The deformation of this process is limited by surface cracking. A closer look pointed out the dependence of some process parameters. The most influencing parameters are the workpiece diameter ratio D1/D2, the tool diameter ratio D1/d and the axial feed rate v. A vast number of experiments would be necessary to study all interactions between these parameters and a 3D FEM simulation would have limitations in the computing time. Hence, this investigation proposes a 2D FEM model to predict the damage during ball spinning and gives a detailed view into a statistical design of experiments. The results show a trend to increase the axial feed rate for a damage minimised process design.

Structure stability of high aspect ratio Ti/Au two-layer cantilevers for applications in MEMS accelerometers

This paper reports the structure stability of Ti/Au two-layer micro-cantilevers with various aspect ratios based on the results obtained from a 3D optical microscope and FEM simulation. The cantilevers were fabricated by MEMS fabrication process. The movable structure stability was investigated by observing the shape of the Ti/Au two-layer micro-cantilevers with the Ti layer thickness of 0.1μm, and the Au layer thicknesses of 3μm, 10μm and 12μm. The length was varied from 100 to 1000μm. The results of the tip deflection observed from the 3D optical microscope were similar to those of the FEM simulation. The experimental results of the micro-cantilevers with the Au thickness of 12μm indicated the highest structure stability. In conclusion, these results revealed that the Ti/Au two-layer structure can enhance the stability and reliability of the movable structure.

MFL 비파괴 검사 시스템에서 다중 결함에 의한 신호 왜곡과 신호 보정에 관한 연구

Dept. of Electrical and Computer Engineering, Pusan National University, Busan 46241, Korea(Received 15 January 2016, Received in final form 22 February 2016, Accepted 23 February 2016)MFL (Magnetic flux leakage) type nondestructive testing has been used for inspection of underground gas pipelines to find metaldefects by detecting magnetic leakage signal. Because the underground gas pipeline is exposed by environment such as high pressurewith great humidity, external defects are easily formed on the surface of pipelines and they are being grouped respectively. Theseadjacent defects cause the signal distortion of leakage flux so that it is hard to estimate the shape information of defects. In this paper,we performed to study of the signal distortion and compensating method for multiple defects in MFL type nondestructive testingsystem by using 3D FEM simulation. This paper proposes the basic algorithm of defect signal analysis on multiple defects on thesurface of 30 inch diameter pipeline.Keywords: magnetic flux leakage testing, nondestructive testing, pipeline, multiple defects, finite elements method

Experimental and Numerical Analysis of Residual Stress Change Caused by Thermal Loads During Grinding

A realistic modelling and simulation of the resulting surface integrity e.g residual stresses caused by grinding is limited due to the lack of knowledge to estimate the amount of thermal load affecting the workpiece. This paper deals with the inverse determination of the heat partitioning during grinding and the prediction of the resulting residual stress state due to the thermal impact by using 2D FEM-simulation without phase transformations. Grinding tests have been performed and the temperatures beneath the contact zone have been measured. For the first time, the concept of Process Signatures is applied on a machining process, providing basic functional relationships for process quantities, internal material loads and material modifications for predominantly thermal loads.

One sensor acoustic emission localization in plates

Acoustic emissions are elastic waves accompanying damage processes and are therefore used for monitoring the health state of structures. Most of the traditional acoustic emission techniques use a trilateration approach requiring at least three sensors on a 2D domain in order to localize sources of acoustic emission events. In this paper, we present a new approach which requires only a single sensor to identify and localize the source of acoustic emissions in a finite plate. The method proposed makes use of the time reversal principle and the dispersive nature of the flexural wave mode in a suitable frequency band. The signal shape of the transverse velocity response contains information about the propagated paths of the incoming elastic waves. This information is made accessible by a numerical time reversal simulation. The effect of dispersion is reversed and the original shape of the flexural wave is restored at the origin of the acoustic emission. The time reversal process is analyzed first for an infinite Mindlin plate, then by a 3D FEM simulation which in combination results in a novel acoustic emission localization process. The process is experimentally verified for different aluminum plates for artificially generated acoustic emissions (Hsu–Nielsen source). Good and reliable localization was achieved for a homogeneous quadratic aluminum plate with only one measurement.

3D FEM simulation of chip breakage in metal cutting

In metal cutting, unbroken chips may scratch the machined surface and hinder an efficient chip removal. Despite its relevance, the established methodologies of tool/process design with regard to chip breakage are still dominated by expensive empirical approaches. Valid predictive modeling helps to reduce the experimental effort and safe costs. Chip breakage initiates with ductile material fracture on the chip free surface. The fracture strain is influenced by the temperature and stress state, which is defined by the stress triaxiality and Lode angle. An introduction of fracture models considering these combined impacts to the finite element (FE) simulation of chip breakage is not available. In this work, a new model of final ductile fracture is proposed, calibrated, and applied for the 3D FE simulation of chip breakage in turning processes of AISI 1045 (C45E+N). The calculation of the fracture strain considers the stress triaxiality, Lode angle, and temperature. A new non-iterative calibration procedure is proposed, which describes the relationships between the chip geometry at breakage and the thermomechanical state variables on the chip free surface. By implementing experimentally obtained chip geometries into this methodology, the combinations of strain, stress triaxiality, Lode angle, and temperature are determined under which ductile fracture was observed in the cutting tests. Finally, a regression analysis delivers all material constants. The fracture model is implemented into a FE-chip formation model. The predicted locations of fracture are compared to high-speed videos of turning experiments while the direction of crack propagation is validated by scanning electron microscopical images of experimental chips.

Plasmon resonances of Ag capped Si nanopillars fabricated using mask-less lithography.

Localized surface plasmon resonances (LSPR) and plasmon couplings in Ag capped Si Nanopillar (Ag NP) structures are studied using 3D FEM simulations and dark-field scattering microscopy. Simulations show that a standalone Ag NP supports two LSPR modes, i.e. the particle mode and the cavity mode. The LSPR peak position of the particle mode can be tuned by changing the size of the Ag cap, and can be hybridized by leaning of pillars. The resonance position of the cavity resonance mode can be tuned primarily via the diameter of the Si pillar, and cannot be tuned via leaning of Ag NPs. The presence of a substrate dramatically changes the intensity of these two LSPR modes by introducing constructive and destructive interference patterns with incident and reflected fields. Experimental scattering spectra can be interpreted using theoretical simulations. The Ag NP substrate displays a broad plasmonic resonance band due to the contribution from both the hybridized particle LSPR and the cavity LSPR modes.

Producing hollow drive shafts by rotary compression

The paper presents the numerical and experimental results of producing hollow parts by a new method of rotary compression. First, the most popular methods for producing axisymmetric hollow parts are described. Next, the paper examines the forming of such parts by rotary compression. With the method, a hollow billet is shaped by tools that both rotate and translate relative to the axis of the billet. In order to estimate the technological viability of rotary compression, we numerically model the rotary compression process for a drive shaft by the finite element method. The 3D FEM simulations are performed using the Simufact Forming software suit. Thermal phenomena are investigated. The numerical results are then verified under laboratory conditions. The experimental results show a good agreement with the FEM results, which confirms that hollow parts such as stepped axes and shafts can be produced by rotary compression.

Multi-objective Optimal Design of a Five-Phase Fault-Tolerant Axial Flux PM Motor

Electric motors used for traction purposes in electric vehicles (EVs) must meet several requirements, including high efficiency, high power density and faulttolerance. Among them, permanent magnet synchronous motors (PMSMs) highlight. Especially, five-phase axial flux permanent magnet (AFPM) synchronous motors are particularly suitable for in-wheel applications with enhanced fault-tolerant capabilities. This paper is devoted to optimally design an AFPM for in-wheel applications. The main geometric, electric and mechanical parameters of the designed AFPM are calculated by applying an iterative method based on a set of analytical equations, which is assisted by means of a reduced number of three-dimensional finite element method (3D-FEM) simulations to limit the computational burden. To optimally design the AFPM, a constrained multi-objective optimization process based on a genetic algorithm is applied, in which two objective functions are considered, i.e. the power density and the efficiency. Several fault-tolerance constraints are settled during the optimization process to ensure enhanced fault-tolerance in the resulting motor design. The accuracy of the best solution attained is validated by means of 3D-FEM simulations.

Optimization of field grading for a 1000 KV wide-band voltage divider

Abstract An HVDC reference voltage divider has been designed for high accuracy and wide-band measurements up to 1000 kV. To maintain wide-band characteristics, field distribution must be optimized in order to minimize the response time of the divider. To compensate the stray capacitance, a capacitive path that surrounds the resistive reference divider is added to function as a shield. Optimal capacitance values producing a matched distribution are obtained using 3D FEM simulations. Factors affecting the performance of the divider are assessed by simulating multiple scenarios representing different practical considerations in real-life applications.