Finite Element Analysis Tool Research Articles

Fluxball magnetic field analysis using a hybrid analytical/FEM/BEM with equivalent currents

In this paper, a fluxball electric machine is analyzed concerning the magnetic flux, force and torque. A novel method is proposed based in a special hybrid FEM/BEM (Finite Element Method/Boundary Element Method) with equivalent currents by using an analytical treatment for the source field determination. The method can be applied to evaluate the magnetic field in axisymmetric problems, in the presence of several magnetic materials. Same results obtained by a commercial Finite Element Analysis tool are presented for validation purposes with the proposed method.

박판판재 경화를 고려한 다이 캠 드라이브의 구조해석 최적화에 대한연구

프레스 가공에서 포밍이나 굽힘 등의 변형에 따라 판재는 가공경화를 발생하게 되며, 판재 경화와 가스 스프링 반력에 의한 캠 성형 과정에서 캠 및 판재의 변형과 미 성형이 발생하게 된다. 본 연구는 알루미늄 판재 성형 과정에서 판재경화를 고려한 응력, 변형이 주어진 판재 물성치와 캠 성형 압력에 맞게 입력 값으로 처리하였다. 그리고 유한요소 해석툴인 Hyperstudy와 Abaqus 연동으로 캠 형상을 비선형적으로 형상 최적화 해석을 수행 했다. 그 결과 판재의 변형이 제거 되면서 허용되는 최대, 최소 응력 범위와 최소 변형을 갖는 조건하에서 캠 형상을 최적화 하였다. 따라서 해석 결과를 통해 응력-변형 곡선과 응력-두께의 정규 분포도를 얻을 수 있었고, 또한 Iteration 처리로 판재 경화와 가스 스프링 반력을 고려한 다이캠 두께에 맞는 응력과 변형에 대한 최적화 형상을 얻을 수 있었다. According to the forming or bending deformation in the press die, the thin plate occurs a work-hardening, the sheet hardening and cam unit's deformation causes incomplete forming during the cam molding process by the reacting spring forces. This study treated the input parameters of the stress and strain as given properties and also used Cam forming pressure considering the sheet hardening in the forming process of the aluminum sheet. The Hyperstudy are operated be linked with the Abaqus of the finite element analysis tool and the shape of Cam were carried out with non-linear shape optimization analysis. As a result removing the deformation of plate, the cam shape were optimized under conditions reduced deformation, having a minimum stress range and the minimum deformation. Therefore, a stress-strain curve and a normal distribution of stress-thickness can be obtained and optimization could be obtained for the shape of the stress and strain on the die plate hardened cam considering the thickness and reaction force of gas spring as iteration process.

Magnetic Properties of Electroformed Ni and Ni-Fe for Micromagnetic MEMS Applications

This paper reports a new technique which is based on electroforming process for high permeability Ni and Ni-Fe alloy. The magnetic properties of Ni and Ni-Fe alloy are investigated as a function of plating current density via scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and vibrating sample magnetometer (VSM). Concentration-dependent kinetics is used to formulate the deposition rate and also the same is verified by using finite element analysis tool COMSOL Multiphysics. Several experiments are performed to derive the relation between electroplating parameters and magnetic properties. The process conditions are optimized to develop high permeability (∼16000) Ni-Fe alloy (85.71–14.29 %). The higher current density shows a monotonically increasing behavior of relative permeability (μ r ). In addition, the B-H curves indicate that the saturation magnetization (B s a t ) increases and coercivity decreases with increasing plating current density. Our experimental data confirms that the higher current density increase the softness of Ni. The observed properties of Ni and Ni-Fe based on experimental results can be used to study the magnetic behavior of micromagnetic sensors and large force actuators.

Design optimization for cogging torque mitigation in brushless DC motor using multi-objective particle swarm optimization algorithm

Purpose– The purpose of this paper is to propose a multi-objective particle swarm optimization (MOPSO) algorithm based design optimization of Brushless DC (BLDC) motor with a view to mitigate cogging torque and enhance the efficiency.Design/methodology/approach– The suitability of MOPSO algorithm is tested on a 120 W BLDC motor considering magnet axial length, stator slot opening and air gap length as the design variables. It avails the use of MagNet 7.5.1, a Finite Element Analysis tool, to account for the geometry and the non-linearity of material for assuaging an improved design framework and operates through the boundaries of generalized regression neural network (GRNN) to advocate the optimum design. The results of MOPSO are compared with Multi-Objective Genetic Algorithm and Non-dominated Sorting Genetic Algorithm-II based formulations for claiming its place in real world applications.Findings– A MOPSO design optimization procedure has been enlivened to escalate the performance of the BLDC motor. The optimality in design has been out reached through minimizing the cogging torque, maximizing the average torque and reducing the total losses to claim an increase in the efficiency. The results have been fortified in well-distributed Pareto-optimal planes to arrive at trade-off solutions between different objectives.Research limitations/implications– The rhetoric theory of multi objective formulations has been reinforced to provide a decisive solution with regard to the choice of the design obtained from Pareto-optimal planes.Practical implications– The incorporation of a larger number of design variables together with an orientation to thermal and vibration analysis will still go a long way in bringing on board new dimensions to the fold of optimality in the design of BLDC motors.Originality/value– The proposal offers a new perspective to the design of BLDC motor in the sense it be-hives the facility of a swarm based approach to optimize the parameters in order that it serves to improve its performance. The results of a 120 W motor in terms of lowering the losses, minimizing the cogging torque and maximizing the average torque emphasize the benefits of the GRNN based multi-objective formulation and establish its viability for use in practical applications.

Low Frequency Noise Characterization and Signal-to-Noise Ratio Optimization for Silicon Hall Cross Sensors

In this paper, silicon-based Hall cross sensors with different device dimensions and carrier densities are designed and fabricated. Low frequency noise behavior regarding to the device dimension and carrier density of the Hall cross sensors has been successfully characterized. Based on the measured $1/f$ -dependent low frequency noise spectral density and the theoretically calculated geometrical factors using a finite-element analysis tool, the noise voltage is calculated and Hooge's constant is reliably extracted. The signal-to-noise ratio is thus calculated and experimentally verified. This paper provides a guidance for the optimal design of Hall cross sensors.

A New Design Tool for Tire Braking Performance Evaluations

The objective of this study is to understand the influence of high frequency tire vibrations induced due to road disturbances and brake torque cycling due to anti-lock braking system (ABS) on braking performance. Under these conditions, transient dynamics of the tire play a crucial role in the generation of braking force. To implement this, a dynamic tire model was developed using a rigid ring tire and a tandem elliptical cam design for the enveloping model. This tire model is validated using experimental data obtained from high-speed cleat tests on a fixed axle. The validated tire model is then integrated with a quarter vehicle and a commercial grade rule-based ABS model to evaluate braking performance with and without a road cleat, which can provide a high frequency disturbance. Simulation results show that the presence of a 1 cm cleat causes large variations in wheel slip, consequently increasing the braking distance. The developed tool will help both tire and vehicle manufactures for quick and early evaluation of braking performance without computationally intensive finite element analysis (FEA) tools.

Non-linear inverse problems and optimal design of MEMS

Purpose – Fostered by the development of new technologies, micro-electro-mechanical systems (MEMS) are massively present on board of vehicles, within information equipment, as well as in medical and healthcare equipment. The purpose of this paper is to approach here the shape design of MEMS in terms of the optimization of a vector objective function, subject to a set of constraints. Objectives and constraints are non-linear, dependent on the unknown device shape. When multiple objective functions should be optimized simultaneously, the set of solutions minimizing the degree of conflict (Pareto front) can be searched for. Design/methodology/approach – This paper proposes an automated optimal design method based on connecting the MATLAB surrogate modeling (SUMO) toolbox with COMSOL Multiphysics finite element analysis tool, and the evolutionary algorithm NSGA-II as well. Findings – The efficiency of the optimization method proposed is approximately doubled in terms of runtime (5 vs 10 h for the referred pla...

Inter-model comparison of embedded-tube radiant floor models in BPS tools

Hydronic radiant floor heating and cooling can potentially reduce energy consumption in buildings. Numerous building performance simulation (BPS) tools contain models for predicting the heat transfer between embedded-tube radiant floor systems and building thermal zones. However, the accuracy, limitations, and methodologies of these models, and their implementations into BPS tools, have never been contrasted in the literature. This paper describes the approaches employed by TRNSYS, ESP-r, and EnergyPlus for modelling embedded-tube radiant floors. An inter-model comparison is then presented for test cases designed to explore model performance. The predictions from the three BPS tools are compared to each other as well as to predictions made with a transient stand-alone finite element analysis tool. Significant issues are identified with the embedded-tube radiant floor models in all three BPS tools.

Load-Displacement Relationships for Ball and Spherical Roller Bearings

Analytical relationships for calculating three rolling element bearing loads (Fx, Fy, and Fz) and two tilting moments (My and Mz) as a function of three relative race translations (dx, dy, and dz) and two relative race tilting angles (dθy and dθz) have been given in a previous paper. The previous approach was suggested for any rolling element bearing type, although it has been recognized that the assumption of a constant rolling element-race contact angle is not well supported by deep groove ball bearings (DGBB) or angular contact ball bearings (ACBB). The new approach described in this paper addresses the latter weaknesses by accounting for the variation of the contact angle on the most loaded ball and also shows that misalignment effects on spherical roller bearing (SRB) loads are negligible. Comparisons between the simplified approach (option 1) and the “enhanced” numerical approach (option 2, which requires a summation of the load components on each ball with the appropriate contact angle included) is made, showing a good correlation as long as the relative misalignment remains reasonable or occurs in the plane corresponding to maximum radial displacement. Option 2 can, however, be recommended since it is easy to program and quite accurate at any misalignment level. Other pros and cons of both options are described. As in the previous paper, a full coupling between all displacements and forces, as well as roller and raceway crown radii, are considered, meaning that Hertzian point contact stiffness is used in roller bearings at low load with a smooth transition toward Hertzian line contact as the load increases. This approach is particularly recommended for programming the rolling element bearing behavior in any finite element analysis or multibody system dynamic tool, since only two nodes are considered: one for the inner race (IR) center, usually connected to a shaft, and another node for the outer race (OR) center, connected to the housing.

Warm forming die design, Part III: Design and validation of a warm forming die

Warm forming is a sheet metal stamping process at elevated temperature that can significantly expand the forming limits of light weight alloys such as aluminum. Most of the work detailed in the literature has been based on a laboratory setting with minimal guidance on how to design warm forming dies for high-volume production. The challenges that arise when transferring this technology from the laboratory to production are generally focused on the attainment of thermal stability within the die. Thermal stability is required to both maintain the dimensions of the matched die and to provide the sheet with ample formability. Achieving a thermally stable die is a direct function of how the die is heated and insulated. When this is done properly, temperature gradients throughout the die and at the parting surface can be minimized. This work outlines the upfront design approach used for a production-level warm forming die. The die was designed utilizing analytical and thermal finite element analysis tools that were developed specifically to assist with the identification of key design characteristics, such as heater wattages and locations, thermocouple placement, insulation strategy, and overall die architecture. A three-piece warm forming die fitted with resistance heating cartridges was constructed based on the presented design approach. The performance of the die was then validated through simulation and experimental comparisons. The results confirm the performance of the die and validate the predictability of the steady-state temperature response of the parting surface by the thermal finite element software.

Nonlinear ultrasound modelling and validation of fatigue damage

Nonlinear ultrasound techniques have shown greater sensitivity to microcracks and they can be used to detect structural damages at their early stages. However, there is still a lack of numerical models available in commercial finite element analysis (FEA) tools that are able to simulate the interaction of elastic waves with the materials nonlinear behaviour. In this study, a nonlinear constitutive material model was developed to predict the structural response under continuous harmonic excitation of a fatigued isotropic sample that showed anharmonic effects. Particularly, by means of Landau׳s theory and Kelvin tensorial representation, this model provided an understanding of the elastic nonlinear phenomena such as the second harmonic generation in three-dimensional solid media. The numerical scheme was implemented and evaluated using a commercially available FEA software LS-DYNA, and it showed a good numerical characterisation of the second harmonic amplitude generated by the damaged region known as the nonlinear response area (NRA). Since this process requires only the experimental second-order nonlinear parameter and rough damage size estimation as an input, it does not need any baseline testing with the undamaged structure or any dynamic modelling of the fatigue crack growth. To validate this numerical model, the second-order nonlinear parameter was experimentally evaluated at various points over the fatigue life of an aluminium (AA6082-T6) coupon and the crack propagation was measured using an optical microscope. A good correlation was achieved between the experimental set-up and the nonlinear constitutive model.

Data Interpolation and Design Optimisation of Brushless DC Motor Using Generalized Regression Neural Network

This paper proposes a generalized regression neural network (GRNN) based algorithm for data interpolation and design optimization of brushless dc (BLDC) motor. The procedure makes use of magnet length, stator slot opening and air gap length as design variables. Cogging torque and average torque are treated as performance indices. The optimal design necessitates mitigating the cogging torque and maximizing the average torque by varying design variables. The data set for interpolation and ensuing design optimisation using GRNN is obtained by modeling a standard BLDC motor using finite element analysis (FEA) tool MagNet 7.1.1. The performance indices of the standard motor obtained using FEA are validated with an experimental model and an analytical method. The optimal design is authenticated using particle swarm optimization (PSO) algorithm and the performance indices of the optimal design obtained using GRNN is validated using FEA. The results indicate the suitability of GRNN as an interpolation and design optimization tool for a BLDC motor.

Thermal Modeling of 3-D Stacked DRAM Over SiGe HBT BiCMOS CPU

We have previously evaluated the feasibility of a serial code accelerator core with 3-D DRAM stacked on the core operating at high frequencies. While operating at such high frequencies (>24 GHz), there are concerns with removing heat from the 3-D stack. We propose the use of thin diamond sheets, which have high thermal conductivity, as a heat spreader by bonding it close to the processor core substrate and memory stacks. We show, through thermal modeling using COMSOL finite-element analysis tools, the feasibility of diamond as an effective heat spreader in a processor-memory 3-D stack.

Reduction of Rotor Eddy-Current Losses for Surface PM Machines With Fractional Slot Concentrated Windings and Retaining Sleeve

High strength nonmagnetic metallic retaining sleeve is widely used in surface permanent magnet (SPM) machines for mechanical reliability, especially to high speed machines. Rotor eddy-current losses would be significantly increased in fractional slot concentrated winding (FSCW) SPM machines using sleeve. In this paper, the novel structure with copper damping rings inserted in rotor lamination is proposed. A current will be induced in the damping rings in reaction to the nonsynchronous harmonics field in the rotor, therefore, the eddy-current losses in sleeve and magnet will be reduced. FSCW SPM machines with common slot and pole combination such as 9-slot/8-pole, 12-slot/10-pole, and 24-slot/22-pole are investigated by the finite element analysis tools, and simulation results indicate that the eddy-current loss in sleeve, particularly on the single layer windings, is significantly reduced using the proposed structure.

Simulation Research for the Excavation Stability of IV Brittle Rock Based on Vault Settlement Effect

Due to the brittle rock deformation is not obvious, and the destruction process has the features of sudden and concealment, it is often neglected in the field during construction. In this paper, Brittle rock was selected as the research object. Using the vault subsidence as monitoring parameters, the excavation process was simulated in single line tunnel by the finite element analysis tool of ANSYS, we obtain the maximum displacement of brittle rock and stress variation with time. Then the subsidence effect of different buried condition were analyzed, to determine the stability period of IV Brittle surrounding rock. The research results can be used to guide the development of the monitoring standard, in underground engineering construction of the brittle rock.

Automatic Parameter Identification of Inverter-Fed Induction Motors at Standstill

As a step toward the self-commissioning of the next generation of ac drives, this work deals with an automatic procedure for the identification of the inverse- Γ equivalent circuit of inverter-fed induction motors (IM) at standstill. The algorithm, cut out for the modern microprocessors combines different test signals with the aim of extracting and mapping the magnetic model nonlinearity. As a key feature, the procedure uses the existing inverter as a precise voltage probe to get the complete parameter set usually required by the advanced control of ac drives. The theoretical investigations are supported by experimental results and are reported in the paper. A distinguishing characteristic of the proposed method among the other existing solutions is the accuracy of the results confirmed by the comparison with finite-element analysis tools and tailored to the laboratory IM prototypes.

Simulation Research for the Excavation Stability of III Brittle Rock Based on Vault Settlement Effect

Due to the brittle rock deformation is not obvious, and the destruction process has the features of sudden and concealment, it is often neglected in the field during construction. In this paper, Brittle rock was selected as the research object. Using the vault subsidence as monitoring parameters, the excavation process was simulated in single line tunnel by the finite element analysis tool of ANSYS, we obtain the maximum displacement of brittle rock and stress variation with time. Then the subsidence effect of different buried were analyzed, to determine the stability period of III Brittle surrounding rock. The research results can be used to guide the development of the monitoring standard, in underground engineering construction of the brittle rock.

FEA-Based Model of Elliptic Coils of Rectangular Cross Section

We present a 3-D finite element analysis (FEA)-based model of elliptic coils. The type of elliptic coil addressed in this paper is the constant-turn density coil, which corresponds to practical implementations of flat or solenoid-type coils wound on an ellipse-shaped bobbin. We assume a coil model consisting of constant current density perpendicular to the cross section along the current trajectory. This model covers the dc operation and the ac applications with multistranded litz wires. The perpendicular current condition of the elliptic coil is implemented in the FEA tool by the gradient of the winding function and the vector trajectory of the currents. In addition, a frequency-dependent calculation of the resistance of the litz wire is included. Hence, electric parameters as the self-inductance or resistance of the elliptic coil can be extracted from the FEA tool as a function of the geometrical parameters. The model is applied to obtain the mutual inductance between two elliptic coils for different misalignments. Finally, a comparison between the self-inductance and winding resistance measurements obtained from a flat coil prototype in several scenarios and the simulation results is presented.

Topology optimisation of patch in Quasi-isotropic graphite-epoxy composite repair (in-plane direction) under tensile loading using Finite element analysis

This study provides the general guidance to make use of FEA (Finite Element Analysis) tool so as to optimize the patches on bonded repair (in plane direction) composite structures. The objective of repair process is to restore the original strength of the damaged structure with minimal usage of repair material in turn reducing the much geometrical property variation from the original structure. If more repair materials are used with the damaged structure considering the structural integrity, which could affect functional requirements and aerodynamic performance of the structure. Hence, an attempt has been made to design the optimised patch, through and through using FEA tool. The concept of topology optimisation has been extended to arrive the optimised patch in Quasi-isotropic graphite/epoxy composite. For this work, plate with hole problem has been considered to demonstrate the optimisation process. In order to quantify the material saving through this optimisation technique, conventional repair technique (circular patching) problem also solved using FEA and the results are compared. Through this technique, free shape optimum patch could be arrived (in plane direction ) effectively for any kind of damages (i.e. war field damages, regular cut-outs and damages due to improper handling of acerbic tools) over any kind of composite surfaces like flat, curved and wavy, as the problem is completely handled through FEA tool.

A parallel finite-element framework for large-scale gradient-based design optimization of high-performance structures

Structural optimization using gradient-based methods is a powerful design technique that is well suited for the design of high-performance structures. However, the ever-increasing complexity of finite-element models and design formulations results in a bottleneck in the computation of the gradients required for the design optimization. Furthermore, in light of current high-performance computing trends, any methods intended to address this bottleneck must efficiently utilize parallel computing resources. Therefore, there is a need for solution and gradient evaluation methods that scale well with the number of design variables, constraints, and processors. We address this need by developing an integrated parallel finite-element analysis tool for gradient-based design optimization that is designed to use specialized parallel solution methods to solve large-scale high-fidelity structural optimization problems with thousands of design variables, millions of state variables, and hundreds of load cases. We describe the most relevant details of the parallel algorithms used within the tool. We present consistent constraint formulations and aggregation techniques for both material failure and buckling constraints. To demonstrate both the solution and functional accuracy, we compare our results to an exact solution of a pressure-loaded cylinder made with either isotropic or orthotropic material. To demonstrate the parallel solution and gradient evaluation performance, we perform a structural analysis and gradient evaluation for a large transport aircraft wing with over 5.44 million unknowns. The results show near-ideal scalability of the structural solution and gradient computation with the number of design variables, constraints, and processors, which makes this framework well suited for large-scale high-fidelity structural design optimization.