Finite Element Method Simulation Model Research Articles

Support vector regression-assisted finite element method for mode I-II fatigue crack growth path prediction

Most of failures in mechanical components in engineering are caused by fatigue crack growth (FCG), especially mode I-II cracks. Accurately and fast predict of crack growth paths of mode I-II in structures is important in academic research and engineering applications. Finite element method (FEM) simulation of FCG can be accurately performed for engineering applications. However, the commercial FEM simulation software, e.g., ABAQUS combined with FRANC3D is generally time-consuming. Therefore, an accurately and fast mode I-II crack growth path prediction method is developed by support vector regression (SVR)-assisted FEM analysis. Firstly, the initial location data of FCG path and stress intensity factor (SIFs) are collected by FEM simulations. The SVR model is trained using initial location data and the corresponding FCG path will be predicted for several growth steps. Secondly, the predicted crack results are input into the FEM simulation model to obtain the several other growth steps. Finally, the two procedures are repeat alternately to obtain the full FCG path. The numerical case is given to validate the performance of the present method using the double-hole plates with mode I-II crack growths. Comparisons show that the performance of the present method are superior to those of FEM simulation and SVR alone.

Validation of inductively coupled plasma simulation model by laser Thomson scattering experiment

To comprehensively study the physical properties of inductively coupled plasma (ICP), a finite element method (FEM) simulation model of ICP is developed using the well-established COMSOL software. To benchmark the validation of the FEM model, two key physical parameters, the electron density and the electron temperature of the ICP plasma, are precisely measured by the state-of-the-art laser Thomson scattering diagnostic approach. For low-pressure plasma such as ICP, the local pressure in the generator tube is difficult to measure directly. The local gas pressure in the ICP tube has been calibrated by comparing the experimental and simulation results of the maximum electron density. And on this basis, the electron density and electron temperature of ICP under the same gas pressure and absorbed power have been compared by experiments and simulations. The good agreement between the experimental and simulation data of these two key physical parameters fully verifies the validity of the ICP FEM simulation model. The experimental verification of the ICP FEM simulation model lays a foundation for further study of the distribution of various physical quantities and their variation with pressure and absorption power, which is beneficial for improving the level of ICP-related processes.

Influence of the Rotor Geometry on Efficiency and Torque Ripple of Switched Reluctance Motor Controlled by Optimized Torque Sharing Functions

Torque sharing function (TSF)-based switched reluctance motor (SRM) control is an effective approach to minimize torque ripple and maximize efficiency. This study investigated the influence of the rotor geometry to overcome the inherent torque and current tracking error of used TSFs. Parameters of the TSF were optimized according to several objectives. A finite element method simulation model of the motor was built and verified to evaluate the objective functions. The optimization result is a set of functions that calculate optimal values of the start angle and overlap angle of the sinusoidal TSF for every operating point of the motor. Different objectives, including efficiency and a torque ripple, lead to different functions for calculating start and overlap angles. The research showed that if efficiency is the most important objective, it is possible to determine a suitable rotor pole geometry. For other criteria, the choice of rotor geometry is not so clear-cut and requires consideration of the SRM operating modes.

Electromagnetic Modeling Strategy Supporting the Fabrication of Inkjet-Printed Chipless RFID Sensors

Inkjet printing fabrication techniques can be used for the manufacturing process of chipless radio-frequency identification RFID sensors. With respect to traditional silicon-based fabrication, flexible electronics induce the possibility to experiment new substrates and conductive materials. With the development of high-conductive nano-inks the low sintering temperature required to process them results compatible with a large variety of substrates. However, the requirements for the conductivity of the metallized printed patterns are particularly stringent for applications where the working frequency is high, like in the case of common chipless RFID tags working in the frequency range 3-10GHz. In chipless RFID systems, the higher the conductivity of the conductive parts and the better the signal response of the tag. However, in printed chipless RFIDs the conductivity can only give a partial indication of the goodness of the tag. The tag response is dependent on the sheet resistance, which is not only related to the conductivity of the ink but also to the thickness of the printed pattern. Therefore, if a sufficiently high-conductive nano-ink is selected, the signal efficiency of the printed tag can be further improved by making an evaluation based on the thickness of the patterns. The objective of this study is to propose a strategy for evaluating the signal response efficiency in inkjet-printed chipless tags by means of a first quantification of the average thickness of the printed layer, which is used to feed a finite element method simulation model to give the manufacturer an idea of the optimal number of layers to be printed in order to have a strong signal response.

Research on bearing capacity of cross-type truss boom with variable cross-section of Crawler cranes

The web crossed truss boom is one of the commonly used truss boom structures of crawler cranes. However, the existing calculations fail to consider the limiting effect of the web members' bending resistance on the chord members, and cannot give full play to the load-bearing capacity of the existing structure. This paper takes the top section of the Crawler crane truss boom as the research object. The single-span truss theoretical model is established according to Timoshenko's elastic stability theory. And the theoretical critical load of the variable cross-section boom is obtained with full consideration of the limitation of the web member's bending resistance on the chord members. The finite element method simulation model is compared and verified. Compared with a large number of simulation experiments and theoretical calculations, it can be concluded that the theoretical calculations in this article are highly consistent with the simulation results, verified the assumptions that the web members' bending resistance help to improve the bending resistance of the chord members, and this will provide certain reference to the engineering designers.

Fabrication of grooved LGS resonators based high temperature SAW sensors and analysis with FEM simulation

Langasite (LGS) based surface acoustic wave (SAW) sensors are widely used in high temperature circumstances due to their advantages of being passive and wireless. In this research, the platinum electrodes are deposited into the grooves of the LGS instead of on the surface to further improve the acoustic properties and prolong the lifetime of the resonators at high temperature. Proper MEMS fabrication techniques are proposed to fabricate such structures. The result of every step is evaluated, and the corresponding process parameters are optimized. With the optimal processes, two types of resonators with different Euler angles of (0∘, 22∘, 30∘) and (0∘, 22∘, 90∘) are fabricated on the LGS substrate. Furthermore, the process-influenced structure parameters such as metal ratio and sidewall angle are well investigated via a weak form nonlinear finite element method simulation model. The temperature dependence of the resonance frequency is measured, and the recorded thermal behaviors match well with the prediction of the simulation. In addition, the further endurance test shows that the devices could work at 1000 ∘C for 12 h. This research proves the validity of the grooved resonator structure and the prominent role of the simulation model in further optimizing the LGS-based SAW devices design.

Study on the Mechanism of Rootstock Damage during Clamping in Watermelon Grafting

Rootstock has a soft tissue that should be held carefully to avoid mechanical damage. Holding the rootstock stem is a significant factor in the grafting process, with direct consequences on the survival rate of grafting. To analyze the damage mechanism of clamping rootstock, a finite element model of the clamping mechanism was established, and different clamping velocities and silicone rubber thicknesses were then studied in this study using the finite element method (FEM). The density and elasticity modulus of the rootstock stem and silicone rubber were determined experimentally using standard methods. The results show that as the clamping velocity increased, the contact force on the rootstock stem increased, and the clamping velocity should be lower than the critical velocity to reduce the probability of damage occurrence on the stem. The increase in silicone rubber thickness would decrease the force on the stem, while also resulting in the instability of the rootstock clamping. A silicone rubber thickness of 4 mm was confirmed as an appropriate thickness for this device. The simulation results were compared with the experimental results, and the mean error was 7.01% within the allowable range, which indicated that the FEM simulation model was reliable.

Structural Parameters Optimization for a Proportional Solenoid

This paper presents an optimization method for the structural parameters of a proportional solenoid. The 3D finite element method simulation model for performance analyse of proportional solenoid was validated by force-displacement characteristic experiment. Parameter sensitivity analysis results showed that the displacement of the armature, the length of the armature, the radius of the armature, the width of the first half of the sleeve and the angle of the magnetic-isolated ring have significant effects on the electromagnetic force. Key structural parameters were optimized according to the simulation results. Experiments results showed the average electromagnetic force was increased by 20.1 % and the effective stroke was extended to 2.1 mm.

Strain analysis and bending properties of quasi-isotropic superconducting strand based on laminate theory

• The study of bending properties has important significance for nuclear fusion and superconducting magnets. • Laminated beam theory can accurately calculate strain distribution through finite element method (FEM) simulation. • A FEM simulation model is established to analyze the critical bending radius of Q-IS strand, and samples are made for testing. • According to the built model, the critical bending radius of Q-IS strand is simulated when bended along different angles. The study of the mechanical properties of superconducting strands plays a very important role in its application in engineering. In this paper, a 3D model based on laminate theory is proposed to study the bending properties of REBCO tape and quasi-isotropic superconducting (Q-IS) strand. Laminated beam theory can not only simplify REBCO tape and superconducting strand to qualitatively analyze strain distribution, but also accurately calculate strain distribution through finite element method (FEM) simulation. A FEM simulation model is established to analyze the critical bending radius of Q-IS strand, and samples are made for testing. According to the built model, the critical bending radius of Q-IS strand is simulated when bended along different angles. The study of bending properties has important significance for the application of superconducting strand in the applications of power transmission, nuclear fusion and superconducting magnets.

Design and Performance Analysis of a Saturated Iron-Core Superconducting Fault Current Limiter for DC Power Systems

A saturated iron-core superconducting fault current limiter (SI-SFCL) can significantly limit the magnitude of the fault current and reduce the stress on circuit breakers in direct current (DC) power systems. The SI-SFCL consists of three main parts: one magnetic iron-core, one normal conductive primary coil (CPC), and one superconducting secondary coil (SSC). This paper deals with the design options for the coil system of the SI-SFCL and confirms their operating characteristics through a physical experiment. The electromagnetic characteristics and operational features of the SI-SFCL was analyzed by a 3D finite element method simulation model. The design of the SSC was based on shape, wire types, required fault current limit and protection aspects. In the CPC, the bobbin was designed based on material selection, cost, structural design, and the effects of the SI-SFCL on the fault current limit. Based on these simulation results, a laboratory-scale SI-SFCL was developed, specifically fabricated to operate on a 500 V, 50 A direct current (DC) power system. In the experiment, the operating characteristics of each coil were analyzed, and the fault current limit of the SI-SFCL according to the operating currents of the SSC and bobbin design of the CPC were confirmed. Finally, the cost analysis of the SI-SFCL with the proposed design options of the coil system was implemented. The results obtained through this study can be effectively used to large-scale SI-SFCL development studies for high-voltage direct current (HVDC) power systems.

Improving the Efficiency of NFC Systems Through Optimizing the Sintered Ferrite Sheet Thickness Selection

The reduction of embedded portable devices involves a magnetic field interference problem when it integrates near field communication (NFC) due to the presence of conductive surfaces, such as ground planes, batteries, or metallic enclosures. Flexible sintered ferrite sheets (FSFS) represent an interesting shielding solution to prevent electromagnetic interferences problems related to NFC, thanks to their ability to control the magnetic flux. The characterization of FSFS effectiveness is analyzed as a function of the sheet thickness in this contribution. This is performed with the aim of determining which is the optimum thickness value to retune an NFC antenna to its original operation frequency value (13.56 MHz) when it is affected by a near conductive surface. A finite element method simulation model is designed and corroborated with the experimental results to evaluate the performance of different FSFS thicknesses in terms of resonant frequency shift, magnetic field strength, and communication distance. An electromagnetic scanner is also used to determine the ability of the best FSFS thickness to shield an NFC transmitter antenna when a battery is set under it, emulating a usual problem. The results obtained show that the magnetic field strength is significantly attenuated and the communication distance is highly shorted. Therefore, besides selecting a material that provides high reflection and low losses at 13.56 MHz, thickness must be considered to ensure the greatest communication effectiveness. Consequently, the use of a wrong FSFS thickness could lead to shifting the resonance frequency to lower values than expected, detuning the communication.

Development of a three-dimensional finite element method simulation model to predict modified flow drilling tool performance

Flow drilling is a relatively unexplored manufacturing process in which the tool penetrates the workpiece with a defined force or defined feed along its rotational axis. This paper presents a developed three-dimensional (3D)-finite element method (FEM) simulation model to predict the performance of modified flow drilling tools. To validate the simulation model, the flow drilling of AlSi10Mg with a non-pre-heated (Tinitial = 20 °C) and pre-heated (Tinfluenced = 200 °C) tool was investigated. Thereby, the comparison of measured and simulated values of temperature, force and torques showed a good agreement. The comparison of the forces and torques concluded in almost identical maximum values. Nevertheless, the pre-heated tool was found to have a significantly more continuous heat distribution and higher bore quality than non-pre-heated flow drills, which can be attributed to the better formability of the cast aluminum alloy at elevated temperatures. Since the results of the simulation showed a good agreement with the experimental values, the three-dimensional model was used to predict the process behavior of a modified flow drilling tool, which could contribute to the optimization of the process. The result show, that the process time could be reduced by half, while the occurring temperatures, forces and torques remained acceptable.

A multimodal hybrid energy harvester based on piezoelectric-electromagnetic mechanisms for low-frequency ambient vibrations

In this paper, we proposed and experimentally validated a vibration-based multimodal hybrid piezoelectric–electromagnetic energy harvester having multiple mechanical degrees-of-freedom. This multimodal hybrid energy harvester (MHEH) has a unique design, which helps it to achieve multiple close resonant modes of vibration in a certain frequency range. Using a low-spring-stiffness material (polyacrylate) as a substrate assists MHEH in reducing the higher resonant frequencies into a low frequency range. The two combined conversion mechanisms (piezoelectric–electromagnetic) are exploited to obtain higher output power from low input accelerations at ambient vibrations. The finite element method simulation model is employed to predict and optimize the mode shapes of the proposed MHEH for different vibration modes. The simulation and experimental result imply that the proposed MHEH can operate at four resonant modes of vibration in the range of 12–22 Hz, which are concentrated around 12, 15, 17, and 22 Hz. An MHEH prototype is fabricated, where four lead-zirconate-titanate elements are used as piezoelectric materials, and NdFeB magnets with conductive coils are used as electromagnetic parts in the same system. Here, a single piezoelectric generator can produce a maximum of 250.23 µW of power across an optimum load of 90 KΩ at the 3rd resonant mode (17 Hz) under 0.4 g (3.92 ms−2) acceleration. On the other hand, a single electromagnetic generator can deliver a maximum power of 244.17 µW to a 10 Ω optimum load under the same conditions. Meanwhile, all eight generators of the MHEH operate simultaneously at their respective resonant frequencies.

Performance evaluation and experimental analysis of a novel single‐phase brushless PM motor

In order to equip the single‐phase brushless permanent magnet (PM) motor with self‐starting capability without a complex structure, we present a new kind of asymmetric air‐gap topology which can lead to the d‐, q‐axis magnetic circuit asymmetry of the motor. The field‐circuit‐coupling finite element method simulation model of the proposed motor controlled with a constant V/f control is built by using the 2D Maxwell software. The geometric parameters of the motor are also optimized by changing pole arc ratio of the PM (αp) and its eccentricity (e), and the operational characteristic is investigated. Finally, an experimental platform of the prototype and its control system are set up. Performance comparison of the experimental results and simulation results of the proposed motor running in various operating modes is reported. All the results show that the asymmetric air‐gap single‐phase brushless PM motor has potential to be used in the household appliances. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Design and Analysis of a High-Speed Permanent Magnet Compensated Pulsed Alternator

Compensated pulsed alternator (CPA, Compulsator) is a pulsed power supply with high power density and energy density. The principles of electromagnetic shielding and magnetic flux compression are used to provide a huge pulse current to the load. In order to reduce the mass or volume of the alternator and increase the storage density, high-strength composite materials are used in the air-core CPA. They are the preferred sources of modern electromagnetic weapon systems because of their merits. A high-speed air-core permanent magnet CPA (PMCPA) was presented in this paper with Halbach array PM topology of the rotor. The heavy external excitation source was not needed, so the volume and mass of the entire discharge system was reduced. Due to the special topology of air-core PMCPA, the parameters of the PMCPA were designed based on the theory of electromagnetic field analysis, numerical, and analytical methods. The finite element method simulation model is built based on the dimension parameters of CPA. The discharge process is simulated by Ansys Maxwell to optimize the performance of PMCPA.

Different boost voltage effects on the dynamic response and energy losses of high-speed solenoid valves

In the present investigation, a simulation of the dynamic characteristics of a high-speed solenoid valve (HSV) was performed using the finite-element method (FEM). The interrelation between power losses and the dynamic response of the HSV was investigated based on the FEM simulation model. The relationship between the boost voltage, dynamic response, and power losses was established according to the energy conversion at the HSV system. The simulation results indicated that as the boost voltage increases, the rising rate of the driving current at the solenoid valve increases sharply, which favors the quick opening of the solenoid, while the power losses caused by the eddy current at the iron core increase rapidly. The rapid increase in the energy loss of the eddy current was the main factor that limited the effectiveness of reducing the opening response time of the solenoid valve by increasing the boost voltage. Regarding the energy utilization, an optimal boost voltage existed, where the solenoid valve reached the highest energy utilization efficiency.

3D FEM Simulation of Milling Force in Corner Machining Process

To optimize milling force and machining accuracy quality in corner milling process, the changing law of milling force is revealed by Finite Element Method(FEM). Based on DEFORM software a serial of 3D FEM models for corner milling process are devloped. Tool curved trajectory is achieved by establishing accurate relationship of tool location with milling time. Adaptive remeshing technique and iterative algorithm are adopted to ensure convergence of FEM model. Component force characteristics are revealed by analyzing FEM simulation results. It indicates that the milling force in Y direction becomes negative comparing with forces in X and Z direction. Magnitude of forces in three directions decreases with increase of spindle speed, while it increases with increase of milling feedrate. The simulation results for cutting force are in good agreement with those obtained from experiment. The FEM simulation model is first successfully established for corner milling process in this study, and the results provide a guide for optimizing cutting parameters in cutting process.

Modelling and characterization of the roof tile-shaped modes of AlN-based cantilever resonators in liquid media

In this work, roof tile-shaped modes of MEMS (micro electro-mechanical systems) cantilever resonators with various geometries and mode orders are analysed. These modes can be efficiently excited by a thin piezoelectric film and a properly designed top electrode. The electrical and optical characterization of the resonators are performed in liquid media and the device performance is evaluated in terms of quality factor, resonant frequency and motional conductance. A quality factor as high as 165 was measured in isopropanol for a cantilever oscillating in the seventh order roof tile-shaped mode at 2 MHz. To support the results of the experimental characterization, a 2D finite element method simulation model is presented and studied. An analytical model for the estimation of the motional conductance was also developed and validated with the experimental measurements.

Channel Modeling of Miniaturized Battery-Powered Capacitive Human Body Communication Systems.

The purpose of this contribution is to estimate the path loss of capacitive human body communication (HBC) systems under practical conditions. Most prior work utilizes large grounded instruments to perform path loss measurements, resulting in overly optimistic path loss estimates for wearable HBC devices. In this paper, small battery-powered transmitter and receiver devices are implemented to measure path loss under realistic assumptions. A hybrid electrostatic finite element method simulation model is presented that validates measurements and enables rapid and accurate characterization of future capacitive HBC systems. Measurements from form-factor-accurate prototypes reveal path loss results between 31.7 and 42.2 dB from 20 to 150 MHz. Simulation results matched measurements within 2.5 dB. Comeasurements using large grounded benchtop vector network analyzer (VNA) and large battery-powered spectrum analyzer (SA) underestimate path loss by up to 33.6 and 8.2 dB, respectively. Measurements utilizing a VNA with baluns, or large battery-powered SAs with baluns still underestimate path loss by up to 24.3 and 6.7 dB, respectively. Measurements of path loss in capacitive HBC systems strongly depend on instrumentation configurations. It is thus imperative to simulate or measure path loss in capacitive HBC systems utilizing realistic geometries and grounding configurations. HBC has a great potential for many emerging wearable devices and applications; accurate path loss estimation will improve system-level design leading to viable products.

Integrated procedure for vibration characterization of a magnetic bearing supported rotor delevitation system

This paper considers an integrated procedure to verify and validate (V&V) the rotordynamic analyses of a magnetic bearing supported rotor delevitation system (RDS). Rotor-AMB (active magnetic bearing) systems in general have complex geometries which make accurate modelling thereof a difficult task. For this purpose, simple rotordynamic analyses methods, practical measurements, and finite element method (FEM) models are applied in an integrated framework to characterize the natural vibration frequencies of the system. First, a numerical model (Rayleigh’s energy method) and an experimental modal analysis of the rotor-only are utilized to V&V the bending natural frequency estimates of a rotor FEM simulation model. Thereafter, an analytical model (two degree of freedom method) and a modal analysis of the integrated rotor-AMB system are employed to V&V the rigid body natural frequency estimates of a rotor-AMB FEM simulation model. Adjustments of the FEM models are realized using feedback to fine-tune the geometric, material, and operating properties of the discs, the rotor, and the AMBs. A practical case study of a RDS successfully demonstrates application of the integrated procedure, which ultimately facilitates improved correlation between FEM simulation and experimental results.