Translator Eccentricity Analysis in Tubular Linear Machines Using Quasi-3-D Finite Element Method Modeling

Translator Eccentricity Analysis in Tubular Linear Machines using Quasi-3D Finite Element Method Modeling

Damping modeling is important for the accurate evaluation of the seismic response of structures. Our group previously reported a damping modeling method using element Rayleigh damping and evaluated the effectiveness using a simple lumped-mass model with multiple damping properties; however, the effectiveness of the method was not evaluated for three-dimensional (3D) finite element method (FEM) models with multiple damping properties. Moreover, further studies showed that the method needed to be improved to be applied to 3D FEM models. Therefore, the method has been improved to enable application to the seismic analysis of 3D FEM models, and the effectiveness of the method has been evaluated. The proposed method uses a weighted least-squares method to automatically determine the coefficients of element Rayleigh damping. The weighted least-squares method minimizes the differences between the modal damping ratios to be modeled and those given by element Rayleigh damping. Although all modal damping ratios in a simple lumped-mass model were used for damping modeling in our previous study, obtaining them for 3D FEM models is impractical because these models have more natural modes than simple lumped-mass models. Therefore, we used modal damping ratios below a cut-off frequency. The effectiveness of the proposed method was evaluated by comparing it with conventional methods in terms of the modeling errors related to the modal damping ratios and the maximum absolute acceleration. The proposed method tended to have lower errors than the conventional methods and is concluded to be more effective for the seismic analysis of 3D FEM models with multiple damping properties. The proposed method can automatically determine the coefficients of element Rayleigh damping and can more accurately model the damping properties of analysis models, indicating that the proposed method is a powerful tool for the seismic analysis of 3D FEM models with multiple damping properties.

The thermal conductivity of emulsion-polymerized styrene–butadiene rubber (ESBR) composites filled with carbon nanotubes (CNTs), zinc oxide (ZnO) and alumina (Al2O3) was predicted using the finite element method (FEM). Two-dimensional (2D) FEM models, which involved the effects of aspect ratio (AR), shape, orientation and thermal conductivity anisotropy (TCA) of the CNTs, and interfacial thermal resistance (ITR), were used to simulate the microstructure of CNT filled ESBR composites. Also, 2D and three-dimensional (3D) FEM models were developed to simulate the microstructure of Al2O3 or ZnO filled ESBR composites. An increase in the thermal conductivity with increasing Al2O3 or ZnO loadings was predicted by the FEM. The orientation angle (OA) of the CNTs and the ITR strongly affect the thermal conductivity as predicted by the FEM. The TCA of the CNTs also has a prominent effect on the thermal conductivity when CNTs have a relatively small OA. At a given filler loading, the thermal conductivity increased with the increasing intrinsic thermal conductivity of the filler over a certain range for a particular shape of filler. The thermal conductivities predicted by the FEM were compared with those predicted by Agari's models and the experimental results. The trends of the thermal conductivity predicted by the FEM agreed with the experimental data. The thermal conductivity of the ESBR composites predicted by 2D and 3D spherical particle filler (SPF) FEM models as a function of ZnO and Al2O3 loading showed that the 3D SPF FEM model agreed well with the experimental results at low loadings (not higher than 20 phr), while the 2D SPF FEM model agreed well with the experimental results at high loadings (higher than 80 phr). In addition to being used for the analysis of existing composites, the proposed FEM models are useful for the design and optimization of new composite materials, and are expected to provide a more insightful understanding into the thermal conductivity of polymeric composites.

There are two main beneficial characteristics that doubly salient permanent magnet (PM) electrical machines present for aircraft applications: armature windings and PMs excitation sources placed on the stator side (maintenance and thermal management), and having a clear-cut rotor without PMs or excitation windings (vulnerable at high speeds due to associated centripetal mechanical stresses). Within this framework, a doubly salient permanent magnet (DSPM) generator was conceived by optimizing the stator size and rotor structure to minimize the torque ripple and maximize the root-mean-square (RMS) voltage value per turn of each generator phase. Firstly, a comparison between the 2D and 3D finite element method (FEM) models is made considering the results of 3D finite element analysis (FEA) as our benchmark in order to understand the accuracy of the 2D results against our benchmark model, the 3D one. A multi-objective design strategy based on a 2D FEA is made, it is set to have characteristics closest to optimal for a Boeing 767 turbine, that is, the necessary electromotive force for a required power of 90 kW at 3000 rpm, feeding a simplified Boeing 767 electrical power distribution system. The results show that the machine could not deliver the required power at 3000 rpm since the 2D FEA demonstrates that the 2D model gives optimistic results when compared with the 3D FEM model. However, with a 3D FEA of the machine feeding the aircraft load, it was seen that the machine’s efficiency is 92%, suggesting that this machine can be a plausible solution.

This paper presents a novel method for early detection of hematomas using highly sensitive optical fNIR imaging methods based on broadband photon migration. The NIR experimental measurements of inhomogeneous multi-layer phantoms representing human head are compared to 3D numerical modeling over broadband frequencies of 30–1000 MHz. A finite element method (FEM) simulation of the head phantom are compared to measurements of insertion loss and phase using custom-designed broadband free space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 670 nm, 795 nm, 850 nm, though results of 670 nm are discussed here. Standard error is used to compute error between 3D FEM modeling and experimental measurements by fitting experimental data to the asqrt {frequency} + b . Error results are shown at narrowband and broadband frequency modulation in order to have confidence in 3D numerical modeling. A novel method is established here to identify presence of hematoma based on first and second derivatives of changes in insertion loss and phase (∆IL and ∆IP), where frequency modulated photons sensitive to different sizes of hematoma is identified for wavelength of 670 nm. The high accuracy of this comparison provides confidence in optical bio-imaging and its eventual application to TBI detection.

Analysis of the thermo-mechanical behaviour of the DEMO Water-Cooled Lithium Lead breeding blanket module under normal operation steady state conditions

Linear machines are currently considered as viable candidates for direct-drive wave and free-piston energy converters. This paper is devoted to an approach based on a magnetic equivalent circuit (MEC), which is also called lumped circuit, dedicated to the modeling and sizing of a tubular linear permanent-magnet synchronous machine (T-LPMSM). The proposed approach considers, in a first step, the cancelation of the end-effect phenomenon. To do so, a dedicated design procedure, consisting in 1) achieving a $2\pi/3$ -shift between the armature phase flux linkages by selecting a fractional ratio of the stator pole pitch to the mover one and 2) balancing the amplitudes of the phase flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions, is firmly applied on two basic T-LPMSM topologies using a dedicated MEC. Then, an investigation of the influent sizing parameters on the force production capability of the initial concept is carried out. The MEC-based prediction of the force requires the incorporation of the mover displacement, yielding the so-called “position varying MEC” on one hand and the armature magnetic reaction on the other hand. The finite-element analysis of the armature phase flux linkages and the developed force enable the validation of the results yielded by the established MECs.

This paper presents a new analytical model for both magnetic flux density and thrust force in a linear direct-drive machine. The model is then used to design a tubular linear direct drive machine (TLDDM) by optimizing its effective parameters. Although the machine has many applications when it works as a motor, but the same design can be used when it works as a generator, where it has applications in renewable energy and sustainable systems. Two-dimensional finite element method (FEM) is used for numerical analysis. Magnetic flux density and thrust force computed numerically shows a good agreement with the values resulted from proposed analytical model. This research, investigates the effect of some geometrical dimensions of Tubular Linear Direct-Drive Machine (TLDDM). The sensitivity analysis of parameters by response surface method (RSM) highlights the influence of effective parameters and their interactions. Permanent magnet (PM) radius, PM length, air gap, coil thickness, and current density of phases are effective factors on Mover’s acceleration. It is found that lower air gap, higher coil thickness and longer PM cause higher ratio of maximum thrust force to mover’s mass. It is shown that RSM can predict the optimum acceleration with error of 6%. The general shape of thrust force in different current densities is also confirmed by experimental results.

The performance of a gear set is strongly influenced by the manufacturing and assembly quality. Therefore, detailed analyses at the design stage, where the effects of expected assembly and manufacturing errors can be simulated, are crucial. At an early design stage, when contact conditions are addressed, the widely used finite element method (FEM) may still result in unwanted computing time. The paper presents an Express model developed to serve as a fast design tool offering fine simulation and a high precision level. The model establishes load sharing, fillet stresses and pressure distribution along the contacting surfaces of meshing helical gear teeth. The calculations combine the finite strip method with a pseudo-three-dimensional (3D) model of the tooth base solved with finite differences to calculate tooth bending deflexion and fillet stresses. The accuracy of the procedure is demonstrated through 3D FEM models. A contact cell discretization completes the model. This very fast and accurate approach gives the contact pressure distributions resulting from the roll-slide motion of mating teeth. An analysis of a helical gear set in two different assembly positions reveals the effects of edge contact, and exhibits the influence of tooth stiffness reduction near tooth corners.

Purpose The aim of the paper is to find the simple and accurate model for the analysis of a drive with a tubular linear permanent magnet machine (TLPMM). Attention is paid to the models that take into account the saturation effects and is useful in the calculations of electromagnetic forces. Design/methodology/approach A circuit model and a field-circuit model (FCM) are considered. The FCM includes finite element (FE) formulation for the axisymmetric electromagnetic field, equations which define the connections of windings and converter elements, and expressions that describe the control system. The FE method is used to determine the parameters of the circuit model. In order to simplify the circuit model, saturation effects caused by armature reaction are ignored. The electromagnetic force calculation is based on the virtual work principle and uses an approximate expression for the derivative of system co-energy. The results obtained for the proposed models have been compared. Findings The proposed FE method of force calculation conforms with the applied method of movement simulation. For the rotor position when the cogging force is equal to zero the calculated cogging force is “almost” zero within seven-decimal-place accuracy. The effects of armature reaction on the performance of a TLPMM machine are similar to those which occur in a classical DC machine; in particular the demagnetising effect caused by saturation is observed. Originality/value The paper shows the influence of the saturation effects on the electromagnetic force of a TLPMM. In the case of “strong saturation”, the classical circuit model may be inappropriate for engineering calculations.

In electromagnetic machines, ferromagnetic material is one of the key components that affect the magnetic field and thus the output performance significantly. The objective of this paper is to study the influence of ferromagnetic material on magnetic field distribution of tubular electromagnetic linear machines. Generic magnetic field models are obtained for linear machines with various structure designs based on magnetic vector potential and Bessel functions. The magnetic field model is validated with numerical results from finite element calculations. The comparison between them shows that the flux model fits closely with the numerical computation. The obtained analytical model can be employed to study the flux density distribution of machine designs with single-sided, double-sided, and non back irons. It shows that the use of back iron, especially for the internal side, helps to greatly enhance the radial component of magnetic field. This component contributes to the axial force generation of tubular linear machines. The study could be useful for the design optimization of permanent-magnet linear machines.

Linear machines are widely employed in robotics, transportation and manufacturing industries because complex rotation-to-translation conversion mechanism is no longer required. This paper proposed a novel tubular linear machine with dual permanent magnet (PM) Halbach arrays to achieve high force output performance. Based on Lorentz force law, the magnetic force output and force ripple for three-phase winding linear machine is formulated in analytical way. By taking advantage of the analytical models, the force output is simulated with respect to the motion of the mover. Numerical result is then obtained to validate the analytical force models. In addition, based on the technology of non-dimensionalization, the mathematical force models are employed to analyze the influence among the structure parameters on the force output and force ripple for design purpose of the tubular linear machines. The study in this paper could contribute to the design analysis and optimization of electromagnetic linear machines with similar poles patterns.

A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.

Titanium alloys are used for the manufacturing of femoral heads for orthopaedic implants. Poor machinability of these materials, especially at high speeds, creates the need for more detailed investigations on this subject. The at hand study analyzes the construction of 3D Finite Element Method (FEM) models pertaining to the manufacturing of femoral heads made from Ti-6Al-4V. For this purpose a commercial FEM programme is employed, specialising in machining modelling, namely AdvantEdge. The validation of the model is provided through experiments on actual femoral heads cut in a CNC lathe at high cutting speeds. Comparison between experimental and numerical results on cutting forces and chip morphology exhibits a good agreement, indicating the success of the proposed models. These 3D models can be used for realistically estimating the influence of cutting conditions on the final product, without performing time and money consuming experiments.

Double stator (DS) linear-rotary actuators (LiRAs) are mainly used in machining applications with high force and torque demands, such as milling or turning. The mover of a typical DS LiRA contains two sets of permanent magnets, one arranged as in radial-flux rotating machines and the other as in tubular linear machines. A back iron is sandwiched between these two sets of permanent magnets, rendering the mover heavy and bulky. Consequently, DS LiRAs are not suitable for applications with high dynamics, such as pick-and-place robots in the packaging and semiconductor industries. In order to increase the dynamics of DS LiRAs, two different ironless mover layouts are proposed in this work. The achievable forces and torques are calculated using finite element method (FEM) simulations and compared to the standard DS LiRA. Manufacturing limitations of the proposed mover layouts and their influence on the performance are considered. Moreover, cogging force and cogging torque of the standard and proposed LiRAs are compared. To verify the FEM models used in the analysis, a simplified test setup with a flat mover is presented. The flux linkage is measured and a good agreement with FEM simulations is demonstrated.