Dimensional Finite Element Analysis Research Articles

Cogging Torque Reduction of Sandwiched Stator Axial Flux Permanent Magnet Brushless DC Motor using Magnet Notching Technique

Cogging torque reduction of axial flux permanent magnet brushless dc (PMBLDC) motor is an important issue which demands attention of machine designers during design process. This paper presents magnet notching technique to reduce cogging torque of axial flux PMBLDC motor designed for electric vehicle application. Reference axial flux PMBLDC motor of 250 W, 150 rpm is designed with 48 stator slots and 16 rotor poles of NdFeb type permanent magnet without notching. Three dimensional finite element modeling and analysis is performed to obtain cogging torque profile of initially designed reference machine. Notches are created on permanent magnets and its influence on cogging torque is analyzed with 3-D finite element modeling and analysis. It is analyzed that magnet notching is an effective technique to reduce cogging torque of axial flux PMBLDC motor.

Effect of Tunnel Progress on the Settlement of Existing Piled Foundation

Abstract Tunnel construction below or adjacent to piles will affect the performance and eventually the stability of piles due to ground deformation resulting in the movement of piles and changes in the axial force distribution along the piles. A three dimensional finite element analysis using PLAXIS 3D (2013) was performed to study the behaviour of a single pile and 3 x 3 piles group during the advancement of shield tunnelling in ground. The 10-node tetrahedral elements were used to model both the soil and the tunnel lining. The Hardening Soil (HS) model was used to simulate the soil structure interaction at the tunnel-soil interface. An isotropic elastic model was used for the pile, piles cap, tunnel lining and tunnel boring machine shield (TBM). Several parametric studies were attempted including the longitudinal, lateral, and vertical tunnel location relative to pile embedded in different types of soil (clay or sand). The results showed that the pile head settlement increases during the tunnelling advancement in larger values than that for ground surface settlement. A zone of influence was determined in the range of twice the tunnel diameter in the longitudinal direction (forward and backward of the pile), and transverse direction (left and right of the tunnel centreline). If the tunnel boring is kept off this zone then there is no fear of pile collapse.

Effect of the aspect ratio of the pre-existing rectangular adhesion failure on the structural integrity of the adhesively bonded single lap joint

Non-linear three dimensional (3-D) finite element analyses (FEA) of the single lap joints (SLJs) having pre-existing rectangular adhesion failure in the interface of the strap adherend and the adhesive have been carried out. The effect of the size, the shape and the aspect ratio of the pre-existing rectangular adhesion failure on (i) the strength, (ii) the interfacial stresses and (iii) the strain energy release rates (SERRs) in the vicinity of the adhesion failure front have been presented in this research work. The SLJ is subjected to uniformly applied tensile load. The adherends are made with very high strength steels and the adhesive is a commercially available AV119. The analyses of the adhesion failure propagation have been carried out by sequentially releasing the constraints of the nodes ahead of the pre-existing adhesion failure front in finite element model. The SERR values in the vicinity of the adhesion failure fronts are computed using the virtual crack closure technique (VCCT) for assessment of the structural integrity of the SLJ. The strength of the SLJ, the interfacial stresses, and the three modes of strain energy release rates (SERRs) have been found to be significantly affected by the shape and size of adhesion failures. The SERRs and interfacial stresses along the rectangular adhesion failure front are compared with the corresponding values around the circular adhesion failure front of same area, pre-existing in the SLJ. It is observed that the circular and rectangular adhesion failures of the same area will have dissimilar growth rate and the mode II is the dominant failure mode. The total strain energy release rate and the failure strength, computed from the 3-D FEA of the SLJ is in good agreement with the experimental fracture toughness of the AV119 adhesive and the experimentally obtained failure loads, respectively.

Effect Of changing various parameters on stress distribution in mini-screws and surrounding alveolar bone: a three dimensional finite element analysis

Aim: The purpose of the study was to clarify and evaluate the effects of various force magnitudes and mini-screw length, diameter and insertion angle on the stress distribution of the mini-screw and the surrounding bone utilizing a three dimensional finite element analysis. Methods: We created a three dimensional finite element model simulating various clinical situations where mini-screws with different diameters (1.5 and 2 mm), lengths (9, 11 and 13 mm) and insertion angles (45o and 90o) were utilized under various force magnitudes (200 and 250gm). The resultant deformations and stresses from the applied loading were analyzed with a 3D FEM according to maximum values of total deformations and Von Mises stress. Results: The Von Mises stresses in both the mini-screw and the cortical bone in obliquely inserted 1.5 mm diameter screws with 200 gm and 250gm force were higher than those with 2 mm diameter screws. The Von Mises stresses in the spongy bone in both the vertically and obliquely inserted 1.5 and 2 mm diameter screws with 200gm and 250gm force were higher with the 2 mm diameter screws. The maximum compressive stress and equivalent micro-strain in cortical bone was evident with screw dimensions 13mm length and 2mm diameter under an oblique force magnitude of 250 gm. The Von Mises stresses in the spongy bone in obliquely inserted 1.5 and 2 mm diameter screws with 200gm and 250gm force were higher with the 2 mm diameter screws The maximum stress (Von Mises) generated in the miniscrew and cortical bone in all the simulated finite element models was 72.77 and 13.52 MPa respectively. Conclusion: Increase in the mini-screw diameter with both vertical and oblique insertion reduced the deformations and stresses within the mini-screw and cortical bone but increased the deformations and stresses within the spongy bone. Increase in the mini-screw length with vertical insertion had negligible effect. The deformation and stress values within the cortical bone were higher in oblique insertion than vertical insertion with both (200 and 250 gm) force

A unified approach for thermoelastic constitutive modeling of composite structures

Mechanics of structure genome (MSG) has been extended to provide a unified approach to predict the thermoelastic behaviors of composite structures. The variational statement of the MSG models has been modified to capture pointwise temperature distribution in composite structures. The effective coefficients of thermal expansions (CTEs) are predicted using the MSG solid model whose accuracy is validated using the three dimensional (3D) finite element analysis (FEA). Thermal induced stress resultants are derived based on the extended MSG plate and beam models, which are used to describe the thermoelastic behaviors of thin or slender structures. The traditional fiber reinforced laminates and complex woven composite structures subjected to distributed temperature loads are analyzed using the proposed method. The results, including both the structural responses and local 3D stress fields, are predicted and compared with the ones from direct numerical simulations (DNS) using 3D FEA.

Impedance Functions for Double-D-Shaped Caisson Foundations

Abstract This article proposes solutions for stiffness estimation of Double-D-shaped caisson foundations embedded in three different types of ground profiles (stiffness variation along the depth: homogeneous, linear, and parabolic). The approach is based on three-dimensional finite element analyses and is in line with the methodology adopted in the Eurocode 8—Part 5 (2004) lumped spring approach. The method of extraction of various stiffness values from the finite element model is described, followed by obtainment of the closed-form solutions. Parametric study revealed the nominal effect of the embedment length of Double-D caissons, and hence only the width and diameter effects are included in the suggested formulations. The obtained results are presented in terms of multiplication factors for Double-D caissons. Final impedance functions for a given width and diameter of a Double-D caisson can be conveniently estimated by multiplying the proposed functions to the circular shaft solutions available in literature. The applicability of the proposed formulations is demonstrated by considering a typical bridge pier supported by Double-D caissons. The proposed formulations require a minimum amount of input parameters and can be used during the tender design to arrive at the required geometry of such foundations.

Buckling behaviour of thin-walled laminated composite beams having open and closed sections subjected to axial and end moment loading

An efficient modelling technique based on one dimensional (1D) beam finite element analysis for buckling of thin-walled laminated composite beams having open/closed sections is proposed. The formulation derived has sufficient generality for accommodating arbitrary stacking sequences of the individual beam section walls, and includes all possible couplings between axial, shear, bending and torsional modes of deformation. The effects of transverse shear deformation of the section walls and out-of-plane warping of the beam section are considered where provision exists to restrain or allow warping deformation. The incorporation of shear deformation leads to a problem in the finite element implementation of the proposed beam kinematics, but this is successfully addressed adopting a novel modelling concept. Numerical results obtained for the sample cases of open sections I beams and closed section box beams are presented. The numerical results are benchmarked/compared to data available in open literature, and it is shown that the proposed model performs very well. Finally, a study of the effect of axial and end moment loading, acting alone or in combination, on the buckling response of thin-walled composite beams is presented.

A three dimensional (3D) musculoskeletal finite element analysis of DARSN temporomandibular joint (TMJ) prosthesis for total unilateral alloplastic joint replacement

PurposeThe purpose of this study was to evaluate the strain and stress distribution for DARSN alloplastic unilateral temporomandibular joint (TMJ) prosthesis and the effects on contralateral natural joint using a finite element analysis (FEA). MethodsThe replacement of the TMJ may have complications like infection, failure of hardware, facial paralysis and perforation. The understanding of the mechanical forces exerted by muscles of mastication and jaw movement on the joint helps in identifying the regions on alloplastic TMJ with various maximum forces, which makes that area more prone for failure of hardware. A three dimensional structural FEA was applied using a validated finite element model (FEM) where the areas of stress and strain were evaluated in the alloplastic joint and the contralateral natural joint. As the pattern of stress and strain can be influenced by the materials used for alloplastic joint and geometry of the design, mechanical property of bone and the attached musculature were also considered while construction the FEM analysis. ResultsThe forces of the muscles of mastication has a vital role on the amount of stress and strain present across the alloplastic joint. Masseter and temporalis exhibited the greatest resultant force on the alloplastic as well as the natural condyle with a magnitude of 272 N and 329 N. This study assessed the maximum stress and strain on the condyle-ramus unit and fossa. ConclusionFEA shows that alloplastic DARSN TMJ prosthesis distributes stress and strain equally between the alloplastic joint site and the contralateral natural joint causing minimal adverse effects to the natural joint. FEA also evaluated the stress and strain on alloplastic component and resulted in drawing clinical implications for operating surgical team.

Ultimate bearing capacity of rock masses under square and rectangular footings

This paper investigates the ultimate bearing capacity of Hoek-Brown rock masses under square and rectangular footings using three dimensional finite element analyses. Analyses were conducted for different dimensions of footings and also for various rock mass properties.The results obtained show that the bearing capacity increases with increasing rock mass Hoek-Brown parameters. Furthermore, by increasing dimensions of the footings, total tolerable load will increase. It is also concluded that in the case of square and rectangular footings, three dimensional bearing capacity analyses should be performed, while the existing two dimensional methods result in over estimation of the bearing capacity.

Prediction of Plate Deformation by Multi-line Heating using SDB Method

The purpose of this study is to quickly and accurately predict the deformed shape of the curved plate located before and after the surface of the hull manufactured by multi line heating (or flame bending). Three dimensional thermo-elasto-plastic analysis takes long time and requires user’s guidance to simulate the deformation. To overcome these drawbacks, this study employed the SDB(Strain as Direct Boundary) method based on thermal strain rather than the three dimensional finite element analysis using solid element. The thermal strain, including material phase transformation and volumetric expansion occurred during Martensite phase transformation, is specially considered by SDB. This study calculates the temperature dependent phase portion using material chemical composition and reflects the martensite portion dependent volumetric expansion. The Heat Affected Zone(HAZ) is obtained by thermal analysis and virtual temperature substituting the heat input is assumed by the size and shape of HAZ. In order to reflect the initial deformation due to the former heating lines to the post-deformation analysis, this study predicts the deformation by multi-line heating using the plastic material properties. Thereafter, comparing the deformation of the plate with the 3D solid elasto-plastic analysis and the SDB method, this study shows the accuracy and efficiency of the SDB method. Key words: Plate deformation, Heat Affected Zone(HAZ), Strain as Direct Boundary (SDB), Line heating, Flame bending

Development of 3-D Finite Element Models for Geo-Jute Reinforced Flexible Pavement

In this study, three dimensional (3-D) finite element analysis are performed to evaluate the effect of geo-textile interlayer on the performance of flexible pavement. The main objective of this study is to evaluate the improvement in stress distribution of flexible pavement due to the application of geo-jute at three specific positions i.e., subgrade-base interface, base-asphalt layer interface, and within asphalt layers. Stress, strain and displacement values are investigated and compared for the application of geo-jute interlayer on various positions. Moreover, to better understand the mechanistic behavior of geo-jute on pavement subgrade, a separate 3-D finite element model is developed to simulate the California bearing ratio (CBR) test on geo-jute reinforced soil. Results showed that the inclusion of geo-jute on flexible pavement significantly improves the pavement performance by producing lower stress, strain, and displacement at top of the subgrade. Moreover, the bearing capacity of subgrade soil increased more than 20% due to the inclusion of geo-jute.

Three dimensional finite element analysis of the influence of the umbrella arch on the settlements induced by shallow tunneling

This paper presents an analysis of the influence of the umbrella arch on the settlements induced by shallow tunneling, based on three-dimensional finite element simulations using CESAR-LCPC. The approach takes into account the actual geometry of the umbrella arch and the lining, and the various aspects of staged construction, notably the cycle of installation of the pipes. The results show that the influence of the umbrella arch on the settlements remains modest, at least for the range of parameters adopted in this study. Also, the results show that the numerical analysis can be carried out with a simplified geometry.

Three dimensional finite element analyses of ground settlement and structural damage caused by irrigation of desert landscapes overlying collapsible soil strata

ABSTRACT Experience in the United Arab Emirates (UAE) has revealed the settlement risk to foundations built on collapsible strata when such strata become increasingly wet due to irrigation of lawns. This paper presents a numerical analysis of ground settlement at a location in the UAE where structural damage occurred, prompting a forensic investigation that involved borehole drilling and measurement of subsidence and structural failure characteristics. MidasTM 3D finite element programme is used with field information from boreholes and irrigation specifications to simulate and predict the settlement profile for a typical pair of residential villas surveyed. Important factors are taken into account including the depths and thicknesses of the collapsible strata, the in-situ stresses, transient water flow, irrigation cycles, water table depth and the soil-structure mechanical properties. The maximum settlement of the boundary wall is predicted to be 157 mm, which agrees closely with the measured value of 165 mm. In addition, the predicted surface displacements are consistent with the observed ground and boundary wall deformation patterns.

Multiscale analysis of fatigue crack initiation life for unidirectional composite laminates

Three dimensional (3D) finite element analysis along with a damage model based on kinetic theory of fracture (KTF) are used to determine the onset of fatigue crack initiation in unidirectional carbon fiber reinforced composites. In addition, the Multicontinuum theory (MCT) and micromechanics are employed separately to enable the assessment of the stress state distribution at the length scale level of the constituents. While the MCT is implemented in the macroscale model formulation, micromechanical analysis of a representative unit cell has been also developed to capture the stress field in the micro length scale level. An ABAQUS™ user material (UMAT) subroutine has been developed and used for implementing the formulation. Numerical examples of various tests including tension, three point bending, four point bending, and short beam shear test of a unidirectional (UD) laminate are considered and the results are compared against actual test data. A detailed discussion, challenges and future plans on the applicability of the KTF are concluding this work.

Stress analysis of Al2014-T6 riveted splice joint fuselage structure using finite element analysis

This work describes about the stress of a splice joint in a medium transport aircraft. Typical splice joint panel forming part of a fuselage, consisting of skin plates are riveted is considered for the study. The calculations have been performed by considering the cabin pressurization load on the panel. Aluminium alloy 2014 - T6 material considered for structural elements of the panel. Two dimensional finite element analyses have been carried out on the splice joint panel. The distribution of fasteners loads and local stress field at rivet locations read using element analysis. The global finite element analysis linear static analysis first segment of typical fuselage will be carried out. The Global finite element analysis results will be benchmark for comparing the result from the splice joint panel analysis. Repeated finite element analysis will be carried out to get the response of the parent structure fuselage find location the maximum stress location will be identified from the analysis.

Research of an Axial Flux Stator Partition Hybrid Excitation Brushless Synchronous Generator

A vehicular generator has stringent requirements on its weight and volume. As a combination of permanent magnet and electric excitation motor, hybrid excitation machine could meet the requirements of vehicular generator, with small size, light weight, adjustable output voltage. In this paper, an axial flux stator partition hybrid excitation brushless synchronous generator (ASHG) is proposed. First, the structure and operation principle of ASHM is illustrated. Afterwards, the shape of the magnetic pole is optimized to obtain the air-gap flux density with low harmonic content. Moreover, the regulation performance of the magnetic field and output voltage are investigated by three dimensional finite element analysis (3D FEA). The result indicates that ASHG has a high performance of adjusting terminal voltage. It can improve the generator efficiency, power density and stability comparing with the conventional vehicular generator.

A Computer Simulation Model for Thermal Forming of Ship and Offshore Structures

This paper presents a study on the line heating simulation process with an efficient "finite element analysis (FEA)" simulation model. The simulation model is conceived using concepts from three dimensional (3D) FEA of heat and mass transfer, plate theory and geometry, and implemented with commercially available software (Ansys*™ Mechanical APDL). The source of thermal energy is assumed to be "Gaussian" distributed heat flux, and we consider the temperature dependency of the material properties. The computer simulation model (CSM) is validated using the published experimental results. We study the discretization requirements for thick plates (>14 mm) that are commonly used in the shipbuilding processes and suggest guidelines for referential use in the industry. Also, we investigate the minimum time step size requirement during the cooling phase of the simulation process and based on the experimental numerical simulations, few efficient simulation practices have been coined, and we show that if they are followed then a noticeable gain in reduction of computational cost and time can be attained. We report extensive simulations of the estimated lines and then compare them with the target shape, and show a close agreement. Finally, our presented results are utilized to derive techniques for the improvement in existing FEA simulation models, and we show that the presented CSM is efficient for the application in ships and offshore structures for high bending of thick plates. 1. Introduction In ship and offshore building industries, geometric shapes are generated by forming of metal plates or sheets into simple or complex curvatures as demanded by the design requirements. Although, the doubly curved structures are used in offshore structures (e.g., spherical tanks and facades), in general, the offshore structures have planar, low curvature formations and developable surfaces, and the ships have a combination of developable and nondevelopable surfaces, low and high curvatures, and planar and nonplanar formations. In engineering sciences, a surface can either be "single curved (developable surface)" or "doubly curved (nondevelopable)" or a combination of them in various regions, e.g., doubly curved—bulbous bow and stern bulb, single curved—parallel middle body, combination—in the zones of transitions. In metal based industries, a single-curved surface can be manufactured with simple mechanical processes—bending, rolling, pressing, and/or a combination of them. For doubly curved surface, after the process of rolling and/or pressing, complex mechanical processes are needed:either the plate is shrunk along its longer edges using line/curve/pattern heating,or the plate is pressed against a base shape restricting its movement and then applying the high forces by pressing.

Estimation of the Load Sharing Ratio of Pre-installed Columns in Top-Down Buildings on Korean Rock

The estimation of the load sharing ratio of the pre-installed column in typical top-down method building was carried out using three dimensional finite element analysis. The main focus was on quantifying the apparent load sharing ratio of the prebored and precast pile–which is the common form of a pre-installed column – throughout the construction process. Additional parametric study was conducted based on series of numerical analysis with special attention given to the pile load sharing ratio under different pile array, pile embedded length, structure height and rock type. Moreover, the load sharing ratio of a single pile was investigated based on the relative location of the pile in the raft (footing). The numerical model was verified based on the field data of two actual construction site using the prebored and precast pile and the top-down method. Based on the analysis results, it was shown that the pre-installed columns of top-down method building is capable of supporting a notable portion of the structural load throughout the construction process. Furthermore, it was also shown that the pile near the center of the raft carried more structure load compared to the piles in the side and the corner.

Research progress of three⁃dimensional finite element analysis in unilateral maxillary defect restorations

Research progress of three⁃dimensional finite element analysis in unilateral maxillary defect restorations

Effect of (B/D) ratio on ultimate load capacity for horizontally curved box steel beam under out of plane concentrated load

The intended of this research is to prepare an analytical study to investigate the best width to depth section ratio (b/d) of horizontally curved steel box beam with constant cross-sectional area (without stiffeners) under single concentrated load at mid-span of the beam. The research adopts three – dimensional nonlinear finite element analysis of steel box -section horizontally curved beams exposed to static load. The isoparametric brick element of twenty-node has been used to represent the steel element; also, the yield criterion used to compute the stress level of plastic deformation is Von-Mises. The simulation model of the behavior of steel under tension and compression stresses is elastic-perfect plastic. A semi-circular two-span continuous horizontally curved steel box beam was fabricated and tested under two point loads at midspan of the beam, the results was compared with the results of the computer program (NFHCBSL) used in this study. In general, it is found that the adopted finite element model to predict the structural response of horizontally curved steel box beam has a good agreement with the test results concerning estimate load-deflection response.The effect of b/d ratio is considered by taken different values (20–100) % with the identical area of cross-section. Also, the effect of curvature was studied by considering different values from beam with half circle to straight beam. The results appear that the best (b/d) ratio is in between (0.3 and 0.4) at curvature between (0° and 90°) and the best (b/d) ratio is in between (0.4 and 0.5) at curvature between (90° and 180°). Also, the result showed that the decrease in carrying load capacity as the beam curvature increased is independent on the value of b/d ratio.