Conventional Finite Element Analysis Research Articles

PMSM Design for Achieving a Target Torque-Speed-Efficiency Map

During the last years, the requirements for a fast and reliable design of electrical machines by applying optimization methods using finite element analysis (FEA), has become a subject of study. Due to their capabilities, permanent magnet synchronous machines (PMSMs) have become the preference choice for many applications, including electric vehicles (EVs) propulsion, water-pumping, robotics, or renewable power generation among others. This paper presents a novel methodology for designing and optimizing PMSMs using the torque-speed-efficiency map. The design-optimization algorithm requires as input, the torque-speed-efficiency map of the target motor, to define the required performance for the given application. The objective is to find the motor geometry which better approximates the target torque-speed-efficiency map. The PMSM is evaluated by using magneto-static FEA combined with direct-quadrature (d-q) electrical modeling, thus greatly reducing the computational burden when compared to conventional time-dependent FEA methods. The magneto-static FEA method calculates iron losses taking into account the magnetic flux density harmonic content by applying a time-space conversion approach. The design-optimization process takes into account the control strategy as well as losses separation, which is validated by using the public experimental data of the Toyota Prius and Camry PMSMs.

Guided Wave Inspection of Bars in Reinforced-Concrete Beams Using Surface-Mounted Vibration Sensors

Steel reinforcement bars (rebars) in concrete structures are inaccessible and not conducive to many inspection methods. This paper proposes a non-invasive technique based on guided waves for detecting localised abnormalities in rebars embedded in concrete beams. The technique is predicated on previously published observations that guided waves are strongly reflected by discontinuities at the frequency at which they begin to propagate, i.e., at cut-on. The reflection coefficient at cut-on is estimated using a simple wave decomposition in which a near-zero wavenumber value is assumed. A simulated study is first carried out to evaluate the technique on a concrete beam featuring four rebars. The wave finite element approach is adopted to model two uniform beams which are coupled via a short, damaged section modelled in conventional finite element analysis. Estimated reflection coefficients arising from the discontinuity are close to the true values at cut-on and independent of frequency elsewhere, so that no prior knowledge of cut-on frequencies is required. Three steel-reinforced concrete beams were fabricated—one uniform and two with localised rebar damage—and reflection coefficients were estimated from measured transfer functions. As predicted, abrupt deviations in the reflection coefficient occurred at cut-on frequencies for both damaged beams.

Three-Dimensional Modeling and Finite Element Analysis of an Ankle External Fixator

External fixator has played an important role in repairing fractured ankle bone. This surgery is done due to the several factors which are the bone is not normal position or has broken into several pieces. The external fixator will help the broken bone to grow and remodel back to the original appearance. However, there are some issues regarding to the stability of this fixation. Improper design and material are the major factor that decreased the stability since it is related to the deformation of the external fixator to hold the bone fracture area. This study aims to design a stable structure for constructing delta frame ankle external fixator to increase the stability of the fixation. There are two designs of external fixator with two types of material used in this present study. Both external fixators with different materials are analyzed in terms of von Mises stress and deformation by using a conventional Finite Element Analysis software; ANSYS Workbench V15. The result obtained shows the Model 1 with stainless steel has less stress and deformation distributions compared to the Model 2. Hence, by using Model 1 as the external fixator, the stability of the fixation can be increased.

DEM Analysis of Track Ballast for Track Ballast–Wheel Interaction Simulation

This study aims to suggest a rational analysis method for a track ballast–wheel interaction that could be further developed to model the interaction in a train-derailment event, based on the discrete-element method (DEM). Track ballast is filled with gravel to form the trackbed. Although finite-element analysis (FEA) is widely applied in structural analysis, track ballast cannot be analyzed using conventional FEA because this approach does not allow separation of elements that share nodes. The DEM has been developed to analyze the dynamic behavior of separable objects, assuming that the objects are rigid. Therefore, track ballast can be modeled as separable rigid pieces of gravel, and its dynamic behavior can be analyzed using a rational contact model. In this study, a rational numerical strategy for track ballast–wheel interaction was investigated using the DEM approach. The suggested analysis method was validated through comparison with the experimental results of a drop test. In addition, case studies were conducted to investigate the effects of the contact-model parameters on the simulation result.

Comparative Study of Advance Smart Strain Approximation Method Using Levenberg-Marquardt and Bayesian Regularization Backpropagation Algorithm

Abstract This study aimed to develop a smart model prediction of strain calculation using fiber optic sensors and neural network. Optical parameters are obtained experimentally on a cantilever beam structure, under static loading conditions. Five variations are used by creating external damage to study strain variations on healthy, single damage and multiple damage beam structures. The strain values were correlated to the set of phase difference and change in intensities by using feed-forward back propagation neural network approach. The strain values using optical parameters were verified with conventional strain gauge measurement and finite element analysis. The neural network simulation provides advance and more accurate correlation results with strain gauge and FEA analysis.

Comparison of Moments for Pile-Cap Design

This paper discusses the comparative study of design moments for pile cap with conventional methods and finite element analysis. If a detailed finite element analysis is adopted, flexibility of the pile cap is considered. When a pile cap is designed by truss analogy, 80% of the tension reinforcement is concentrated in the region where the cap is supported on piles and at the column, which depends on design moments. It is observed that the difference in the design moments was considerable and should be taken into account for calculation and placing of reinforcement.

A finite element analysis-computational fluid dynamics coupled analysis on thermal-mechanical fatigue of cylinder head of a turbo-charged diesel engine

A finite element analysis-computational fluid dynamics coupled analysis on the thermo-mechanical fatigue of cylinder head of a turbo-charged diesel engine was performed, and the complete simulation process is illustrated in this paper. In-cylinder combustion analysis and water jacket coolant flow analysis were conducted to provide heat transfer boundary conditions to the temperature field calculation of the cylinder head. Comparing with the conventional finite element analysis of cylinder head by which the heat transfer boundary conditions of the combustion and coolant sides are estimated, the present method coupled the three-dimensional combustion computational fluid dynamics and coolant computational fluid dynamics with the finite element analysis. Both computational fluid dynamics and finite element analysis obtain more accurate boundary conditions on their interface from each other, and thus, the present method improves accuracy of thermo-mechanical fatigue prediction. Based on the measured material performance parameters such as stress–strain curve under different temperatures and E–N curve, creep, and oxidation data material performance, the cylinder head–gasket–cylinder block finite element transient stress–strain field was calculated using ABAQUS. The thermo-mechanical fatigue analysis of cylinder head submodel was performed by using FEMFAT software that is based on the Sehitoglu model to predict the thermo-mechanical fatigue life of cylinder head. By comparing the measured and predicted temperatures of cylinder head, the temperature results showed a good agreement, and the error is less than 10%.

Thermo‐hydro‐mechanical modeling of unsaturated soils using isogeometric analysis: Model development and application to strain localization simulation

SummaryThis study presents a thermo‐hydro‐mechanical (THM) model of unsaturated soils using isogeometric analysis (IGA). The framework employs Bézier extraction to connect IGA to the conventional finite element analysis (FEA), featuring the current study as one of the first attempts to develop an IGA‐FEA framework for solving THM problems in unsaturated soils. IGA offers higher levels of interelement continuity making it an attractive method for solving highly nonlinear problems. The governing equations of linear momentum, mass, and energy balance are coupled based on the averaging procedure within the hybrid mixture theory. The Drucker‐Prager yield surface is used to limit the modified effective stress where the model follows small strain, quasi‐static loading conditions. Temperature dependency of the surface tension is implemented in the soil‐water retention curve. Nonuniform rational B‐splines (NURBS) basis functions are used in the standard Galerkin method and weak formulations of the balance equations. Displacement, capillary pressure, gas pressure, and temperature are four independent quantities that are approximated by NURBS in spatial discretization. The framework is used to simulate strain localization in an undrained dense sand subjected to plane strain biaxial compression under different temperatures and displacement velocities. Results show that an increase in the displacement rate leads to reduction in the equivalent plastic strain while an increase in the temperature leads to an increase in the equivalent plastic strain. The findings suggest that the proposed IGA‐based framework offers a viable alternative for solving THM problems in unsaturated soils.

Bayesian inference for damage identification based on analytical probabilistic model of scattering coefficient estimators and ultrafast wave scattering simulation scheme

Ultrasonic Guided Waves (GW) actuated by piezoelectric transducers installed on structures have proven to be sensitive to small structural defects, with acquired scattering signatures being dependent on the damage type. This study presents a generic framework for probabilistic damage characterization within complex structures, based on physics-rich information on ultrasound wave interaction with existent damage. To this end, the probabilistic model of wave scattering properties estimated from measured GWs is inferred based on absolute complex-valued ratio statistics. Based on the probabilistic model, the likelihood function connecting the scattering properties predicted by a computational model containing the damage parametric description and the scattering estimates is formulated within a Bayesian system identification framework to account for measurement noise and modelling errors. The Transitional Monte Carlo Markov Chain (TMCMC) is finally employed to sample the posterior probability density function of the updated parameters. However, the solution of a Bayesian inference problem often requires repeated runs of “expensive-to-evaluate” Finite Element (FE) simulations, making the inversion procedure firmly demanding in terms of runtime and computational resources. To overcome the computational challenges of repeated likelihood evaluations, a cheap and fast Kriging surrogate model built and based on a set of training points generated with an experiment design strategy in tandem with a hybrid Wave and Finite Element (WFE) computational scheme is proposed in this study. In each “numerical experiment”, the training outputs (i.e. ultrasound scattering properties) are efficiently computed using the hybrid WFE scheme which combines conventional FE analysis with periodic structure theory. By establishing the relationship between the training outputs and damage characterization parameters statistically, the surrogate model further enhances the computational efficiency of the exhibited scheme. Two case studies including one numerical example and an experimental one are presented to verify the accuracy and efficiency of the proposed algorithm.

The effect of winding patterns on the mechanical behavior of filament-wound cylinder shells

Purpose The purpose of this paper is to present a finite element analysis (FEA) of filament-wound composites, as well as application of these materials. Design/methodology/approach In this paper, a new finite element method of filament-wound composite is presented. The stress and strain fields in the composite cylinders are analyzed using the ABAQUS software packages for considering the filament undulation and crossover. The paper presented results of buckling load of composite cylinders with different types of filament-winding patterns. Findings The result of the example shows that the stress distributions are uniform along the cylinder length and around the circumference when the analytical approach is based on the conventional FEA. The stress distributions are not uniform along the cylinder length and around the circumference for considering the filament undulation and crossover. The stress units are arranged in a regular geometric pattern around circumference and along the axis of rotation. The analysis of the effect of filament-winding mosaic patterns on the mechanical characteristics of composite cylindrical is presented in the paper. Originality/value The stress and strain fields in the composite cylinders were analyzed for considering the filament undulation and crossover. The buckling load of composite cylinders with different types of filament-winding patterns was presented in this paper.

Comparison between finite element and hybrid finite element results to test data for the vibration of a production car body

The Hybrid Finite Element Analysis (Hybrid FEA) method is based on combining conventional Finite Element Analysis (FEA) with analytical solutions and energy methods for mid-frequency computations. The method is appropriate for computing the vibration of structures which comprises stiff load bearing components and flexible panels attached to them and for considering structure-borne loadings with the excitations applied on the load bearing members. In such situations, the difficulty in using conventional FEA at higher frequencies originates from requiring a very large number of elements in order to capture the flexible wavelength of the panel members which are present in a structure. In this presentation a three-way comparison will be offered for the vibration of a production vehicle body in the frequency range 200 Hz–1000 Hz. Six different excitation locations are utilized (one at a time); for each excitation the mobility of five reference body points on the load bearing members, and the mobility of eight flexible vehicle panels is measured and the measurements are compared with both conventional FEA results and with Hybrid FEA computations. Discussion about the development of the Hybrid FEA model and the correlation of both numerical solutions to the test data will be presented.The Hybrid Finite Element Analysis (Hybrid FEA) method is based on combining conventional Finite Element Analysis (FEA) with analytical solutions and energy methods for mid-frequency computations. The method is appropriate for computing the vibration of structures which comprises stiff load bearing components and flexible panels attached to them and for considering structure-borne loadings with the excitations applied on the load bearing members. In such situations, the difficulty in using conventional FEA at higher frequencies originates from requiring a very large number of elements in order to capture the flexible wavelength of the panel members which are present in a structure. In this presentation a three-way comparison will be offered for the vibration of a production vehicle body in the frequency range 200 Hz–1000 Hz. Six different excitation locations are utilized (one at a time); for each excitation the mobility of five reference body points on the load bearing members, and the mobility of eight ...

Structure-borne Noise at PWM Excitation using an Extended Field Reconstruction Method and Modal Decomposition

Pulse-Width Modulation (PWM) represents a carrier-frequency-dependent structural excitation. The PWM’s excitation harmonics are also reflected in the air gap’s electromagnetic forces, the vibration response and the resulting structure-borne noise. The last of these can be numerically predicted with a multiphysics finite-element-analysis (FEA) containing electronic, electromagnetic, mechanical and acoustic field problems. The multiphysics FEA are precise, but computationally inefficient and consequently inadequate for parametric studies. This paper introduces a method for a fast structure-borne noise prediction at PWM excitation. The presented approach contains the Extended Field Reconstruction Method (EFRM) to handle the magnetic saturation and slotting effects in magnetics, and the modal decomposition to couple the electromagnetic and mechanical domains. Finally, the structure-borne sound power level is calculated via the vibration-velocity response. Indeed, this approach demands a pre-calculation of the basis functions and modal parameters from the FEA, but afterwards the effect of the different PWM excitation cases can be evaluated in a few seconds. The proposed method can calculate the structure-borne noise at PWM excitation accurately and is more than 104 times faster than the conventional multiphysics FEA approach.

A new approach to quickly edit geometries and estimate stresses and displacements of implants in real-time

Abstract Although osteosynthesis plates rarely break, such cases still occur. Since the construction of these plates is mainly focussing on the best fit for anatomical structures, they may not provide optimal mechanical stability. It should be considered whether they might be changed in terms of e.g. hole size and number. Finite element analysis can help to estimate whether the plates will withstand loads or break. However, these analyses can be very time-consuming. To counteract this problem, a new software solution (ANSYS Discovery Live) has been established for estimation of stresses in real time. In this study the accuracy of the new software was compared to a conventional finite element analysis software solution to investigate whether this software solution provides appropriate accuracy to be used for medical applications.

An experimental assessment of rotor superconducting stack demagnetization in a liquid nitrogen environment

Stacks of high-temperature superconducting tape have proved to trap in laboratory conditions levels of magnetic flux density one order of magnitude above actual state-of-the-art permanent magnets. Their simple manufacturing, high mechanical properties and intrinsic resistance to sudden quench greatly facilitate their utilization in industrial applications, amongst them, as a source of magnetic flux density in the rotor of electrical machines. For this to happen, the currents induced in the superconducting layers of the stack must not be disturbed during operation. This work studies in experimental conditions the demagnetization of a stack rotating in the airgap of an electrical motor under slot and winding-induced cross-field components, whose values are estimated via conventional 2D finite element analysis. The results are congruent with previous laboratory studies and show small long-term demagnetization rates that may allow operation for time spans longer than initially established.

An investigation of ballistic response of reinforced and sandwich concrete panels using computational techniques

Structural performance of nuclear containment structures and power plant facilities is of critical importance for public safety. The performance of concrete in a high-speed hard projectile impact is a complex problem due to a combination of multiple failure modes including brittle tensile fracture, crushing, and spalling. In this study, reinforced concrete (RC) and steel-concrete-steel sandwich (SCSS) panels are investigated under high-speed hard projectile impact. Two modeling techniques, smoothed particle hydrodynamics (SPH) and conventional finite element (FE) analysis with element erosion are used. Penetration depth and global deformation are compared between doubly RC and SCSS panels in order to identify the advantages of the presence of steel plates over the reinforcement layers. A parametric analysis of the front and rear plate thicknesses of the SCSS configuration showed that the SCSS panel with a thick front plate has the best performance in controlling the hard projectile. While a thick rear plate is effective in the case of a large and soft projectile as the plate reduces the rear deformation. The effects of the impact angle and impact velocity are also considered. It was observed that the impact angle for the flat nose missile is critical and the front steel plate is effective in minimizing penetration depth.

Large elastic deformation of micromorphic shells. Part II. Isogeometric analysis

In Part I of this study, a variational formulation was presented for the large elastic deformation problem of micromorphic shells. Using the novel matrix-vector format presented for the kinematic model, constitutive relations, and energy functions, an isogeometric analysis (IGA)-based solution strategy is developed, which appropriately estimates the macro- and micro-deformation field components. Due to the capability of constructing exact geometries and the powerful mesh refinement tools, IGA can be successfully applied to solve the equilibrium equations with dominant nonlinear terms. It is known that different types of locking phenomena take place in the conventional finite element analysis of thin shells based on low-order elements. Non-standard finite element models with mixed interpolation schemes and additional degrees of freedom (DOFs) or the ones used the high-order Lagrangian shell elements which require high computational costs, are the available solutions to tackle locking issues. The present 16-DOFs IGA is found to be efficient because of possessing a good rate of convergence and providing locking-free stable responses for micromorphic shells. Such a conclusion is found from several comparative studies with available data in the well-known macro-scale benchmark problems based on the classical elasticity as well as the corresponding numerical examples studied in nano-scale beam-, plate-, cylindrical shell- and spherical shell-type structures on the basis of the micromorphic continuum theory.

Investigating mesh sensitivity and polycrystalline RVEs in crystal plasticity finite element simulations

Crystal plasticity-finite element method (CP-FEM) is now widely used to understand the mechanical response of polycrystalline materials. However, quantitative mesh convergence tests and verification of the necessary size of polycrystalline representative volume elements (RVE) are often overlooked in CP-FEM simulations. Mesh convergence studies in CP-FEM models are more challenging compared to conventional finite element analysis (FEA) as they are not only computationally expensive but also require explicit discretization of individual grains using many finite elements. Resolving each grains within a polycrystalline domain complicates mesh convergence study since mesh convergence is strongly affected by the initial crystal orientations of grains and local loading conditions. In this work, large-scale CP-FEM simulations of single crystals and polycrystals are conducted to study mesh sensitivity in CP-FEM models. Various factors that may affect the mesh convergence in CP-FEM simulations, such as initial textures, hardening models and boundary conditions are investigated. In addition, the total number of grains required to obtain adequate RVE is investigated. This work provides a list of guidelines for mesh convergence and RVE generation in CP-FEM modeling.

PowerSynth: A Power Module Layout Generation Tool

PowerSynth is a multiobjective optimization tool for rapid design and verification of power semiconductor modules. By using reduced order models for the calculation of electrical parasitics of the layout and thermal coupling between devices, optimal trace layout and die placement can be simultaneously achieved orders of magnitude faster than conventional finite element analysis (FEA) techniques. An overview of the tool, its modeling methods, model validation, and module layout optimization are presented. The electrical and thermal models are validated against FEA simulations and physical measurements of built modules generated from the tool. The FEA comparisons are performed with FastHenry and ANSYS Icepak to evaluate electrical parasitics and thermal behavior, respectively. A sample hardware prototype based on a half-bridge circuit topology is chosen for testing. Excellent agreement between the FEA simulations, experimental measurements, and PowerSynth predictions are demonstrated. Additionally, when compared with conventional simulation runtime and workflow, PowerSynth takes considerably less computation and user time to produce several candidate layout solutions from which a designer may easily balance selected tradeoffs.

Homogenization of multi-turn coil with elliptic cross-section using complex permeability

Purpose The tensor complex permeability of a multi-turn coil with elliptic cross-section is analytically expressed. In field analysis, a multi-turn coil can be modeled by the uniform material that has the present tensor complex permeability. It is shown that the frequency characteristic of the present tensor complex permeability is in good agreement with that evaluated by finite element method applied to a unit cell of the multi-turn coil region. Design/methodology/approach The authors introduce a new method to evaluate the complex permeability of a multi-turn rectangular coil. To obtain the complex permeability of a rectangular coil in a closed form, it is approximated as an elliptic coil. Because the rectangular coil has different complex permeabilities in the vertical and horizontal directions, the complex permeability have to be defined in a tensor form. It suffices to discretize the coil region into rather coarse finite elements without considering the skin depth in contrast to the conventional finite element method. Findings The proposed method is shown to give the impedance of multi-turn coils which is in good agreement with results obtained by the conventional finite element (FE) analysis. By extending the proposed approach, the authors can easily perform 3D FE analysis without difficulty in discretization of the coil region with fairly fine finite elements. Moreover, they found that the approximation of rectangular coils as the elliptic coils is valid for analysis of quasi-static fields using this homogenization method. Originality/value The novelty of this study is in the approximation of the rectangular coils with elliptic coils, and the complex permeability for them is formulated here in a closed form. The proposed formula includes that for the round coils. Using the present method, the authors analyze the rectangular coils without fine discretization.

An equivalent model for sandwich panel with double-directional trapezoidal corrugated core

A novel sandwich panel with double-directional corrugated core is proposed in this paper. This complex-corrugated core makes the conventional detailed finite element analysis of large structures a tough work. Thus, an equivalent homogeneous method is proposed, the key of which is to obtain the equivalent property of this novel structure. The equivalent elastic modulus considering the effect of geometrical parameters is analytically derived and verified by finite element method. Besides, equivalent shear modulus and Poisson’s ratios are obtained by finite element method. Three-dimensional detailed and equivalent models are established for further validation of this equivalent homogeneous method. Results show that elastic modulus predicted by analytical formulas is in good agreement with that by finite element method no matter how geometrical parameters change. It has been proved that stretching deformation is dominating in thickness direction, and only corrugation along loading direction can bear the load. The proposed novel sandwich structure owns better mechanical property than the conventional one with single-corrugated core. The result by equivalent model agrees well with that by detailed model, which means that this equivalent homogeneous method can well predict the macroscopic property of this novel structure.