Three-dimensional Finite Element Analysis Research Articles

A reverse identification of the friction coefficient operating within crack lips through a complete elastoplastic simulation of 3D fretting fatigue cracks

This study investigates the fretting fatigue cracking process for wires made of aluminum alloy through elastic and elastoplastic simulations of former tests where both crack arrest and crack growth until failure were observed. A three-dimensional finite element analysis (FEA), incorporating 3D cracks within the contact, is conducted to replicate the experiments in the conditions of these former results. The present study demonstrates that an elastic assumption fails to capture the threshold crack extension, which would result in systematically underestimated lengths for crack arrest. When considering elastoplastic behavior of the aluminum strands, instead of elastic behavior, the SIF values evolve consistently with experimental observations. By this way, it is now possible to carry out a sounded FEA so as to account for friction in the crack lips in the presence of plasticity. First, this model clarifies the role of friction in crack arrest. Secondly, a reverse analysis is proposed to assess the associated coefficient of friction between crack lips, yielding a value consistent with measurements obtained from gross slip fretting experiments.

Formation of plate-like high-strain region in polycrystalline α-titanium and its relation to high-strain bands on surface

The investigation of heterogeneous deformation mechanisms in materials is important for understanding fracture mechanisms. In this study, uniaxial tensile deformation of polycrystalline α-titanium was numerically reproduced by three-dimensional crystal plasticity finite element analysis, and the following were revealed for the first time: (i) plate-like high-strain regions form inside the specimen, which are typically observed as band-like high-strain regions (high-strain bands: HSBs) on the surface of and cross-sections in α-titanium specimen, and (ii) the formation of HSBs also affects the work-hardening rate near the yielding point. The reasons for the difference in the formation mechanism of HSBs between the surface and inside were also discussed. The results obtained showed that active slip systems that contribute to the formation of HSBs may differ between the surface and inside of specimen, and strain in HSBs on the specimen surface is higher than that inside. The distributions of HSBs at the surface of and inside the specimen are determined by distributions of resolved shear stress. These results are important for understanding the differences in the fracture mechanisms between the surface and interior of materials.

Analysis of prefabricated myofunctional appliances with different overjet and bumper designs: a three-dimensional finite element analysis

BackgroundPrefabricated myofunctional appliance can guide tooth eruption, improve dentition alignment, correct myofunctional disorders and harmful oral habits. However, its application to skeletal discrepancy may result in unsatisfactory tooth inclination. This study aimed to construct a novel appliance with overjet design to avoid this side effect and investigated its shape and mechanical changes under occlusion using three-dimensional finite element method.MethodsWe established three samples of prefabricated myofunctional appliances. The first one was edge to edge without overjet, and the outer shield of both jaws were flattened. The second one was 3 mm overjet with stepped the outer shield. The last one was 3 mm overjet, and the outer shield of both jaws were flatted, which meant the front wall of lower jaw was strengthened with bumper, termed as lower bumper. A complete dentition model was applied to the study. 150 N occlusal force was applied to each type of appliance and the deformation displacement and the changes in stress was recorded.ResultsThe deformation was significant in the incisors regions, especially in the vertical and lateral dimensions. The maximum displacements of 3 mm overjet with step shield group were 7.08 mm (vertical), 3.99 mm (lateral), and 2.90 mm (sagittal), while it decreased to 3.92 mm(vertical), 1.94 mm (lateral), and 1.55 mm (sagittal) in overjet with bumper group. Moreover, the upper molar regions exhibited higher vertical and sagittal displacement in 3 mm overjet with step shield group, which were 3.03 mm (vertical) and 1.99 mm (sagittal), and the bumper design could decrease the maximum displacement to 1.72 mm (vertical) and 0.72 mm (sagittal). In addition, the Von Mises stress of appliances was analyzed, and results indicated that 3 mm overjet with step shield generated higher stress than other groups, with the maximum Von Mises stress was 0.9387 MP, which were 0.5858 and 0.5657 MP in edge to edge group and 3 mm overjet with lower bumper group, respectively.ConclusionThe prefabricated myofunctional appliances may cause deformation during occlusion. Compared to step shield group, the application of lower bumper exhibited better resistance to occlusal force.

Three-dimensional finite element analysis of the biomechanical properties of different material implants for replacing missing teeth.

The purpose of this study was to analyze the biomechanical properties of implants made of different materials to replace missing teeth by using three-dimensional finite element analysis and provide a theoretic basis for clinical application. CBCT data was imported into the Mimics and 3-Matic to construct the three-dimensional finite element model of a missing tooth restored by an implant. Then, the model was imported into the Marc Mentat. Based on the variations of the implant materials(titanium, titanium-zirconia, zirconia and poly (ether-ether-ketone) (PEEK))and bone densities (high and low),a total of eight models were created. An axial load of 150N was applied to the crown of the implant to simulate the actual occlusal situation. Both the maximum values of stresses in the cortical bone and implant were observed in the Zr-low model. The maximum displacements of the implants were also within the normal range except for the PEEK models. The cancellous bone strains were mainly distributed in the apical area of the implant, and the maximum value (3225μstrain) was found in PEEK-low model. Under the premise of the same implant material, the relevant data from various indices in low-density bone models were larger than that in high-density bone models. From the biomechanical point of view, zirconia, titanium and titanium-zirconia were all acceptable implant materials for replacing missing teeth and possessed excellent mechanical properties, while the application of PEEK material needs to be further optimized and modified.

Nonlinear coupled multi-physics field analysis of permanent magnet synchronous motor combining finite element analysis with optimized meshless method

Aiming at significant disadvantages of finite element analysis (FEA) performed in coupled multiphysics field calculation, including high computing cost and strong dependency on meshing quality. Taking a high-speed permanent magnet synchronous motor (P MSM) as an example, an approach combining FEA with optimized meshless method is proposed to solve the heat transfer problem. Firstly, electromagnetic losses under rated and 1.2 times overloaded operation conditions are calculated using FEA respectively. Secondly, three-dimensional FEA flow models considering the influence of viscosity varying with temperature are established. Thirdly, convective heat transfer coefficients are calculated as the boundary condition, after which the electromagnetic losses as heat sources are mapped to the threedimensional steady-state temperature field calculations using FEA and conventional meshless method respectively. Applying the above two methods, a singular boundary method (SBM) is employed to replace the temporal derivative term of the transient calculation equation. Finally, to mitigate the illconditioned matrix appearing in the conventional meshless method coupled with FEA, an optimized meshless method is proposed to recalculate the heat transfer equation. After that, the calculation results of the above methods are compared with experimental results. This research is beneficial for the multiphysical coupling analysis of electrical equipment with complex structures considering nonlinear factors.

Finite Element Analysis of Combined Bearing Characteristics of Pile–Soil Interaction in Composite Foundation

Composite foundations have been widely used and promoted in practical engineering applications. However, research on the joint-bearing mechanism of piles and soil within composite foundations is still not comprehensive enough. This paper proposes a method for calculating the additional internal forces of piles and soil within composite foundations. Based on a three-dimensional finite element analysis, this study investigates the variation patterns of the stress, displacement, and additional internal forces of piles and soil in the depth direction under the action of upper loads when using friction piles and end-bearing piles. This research aims to reveal the bearing performance of piles and soil. The results showed that, under the same conditions and due to the presence of end-bearing effects, the internal forces experienced by the entire pile body of the end-bearing piles were more uniform, exhibiting significant advantages in resisting deformation and being able to withstand larger loads. Additionally, the diffusion mechanism of the vertical forces, stresses, and displacements of piles and soil is discussed. Due to the negative frictional resistance of soil and the influence of pile end-bearing effects, the distribution of internal forces and the displacements of piles and soil exhibited different characteristics. This study provides a scientific reference for the theoretical analysis and design of composite foundations.

Holding capacity of a novel hybrid helical-skirted foundation of offshore wind turbines

A novel hybrid foundation consisting of a helical pile and a peripheral skirt was introduced in this study. This hybrid foundation exploits both the helical pile and the skirted foundation. This study focused on evaluating the undrained vertical holding capacity of this hybrid foundation in clay using three-dimensional finite element analysis. Their capacities and failure mechanisms were examined and compared. The analysis results showed that a significant increase in the vertical holding capacity was achieved compared to that of an individual component, which is attributed to the enhanced soil mobilization mechanism.

Performance of unequal piled raft under vertical loading in cohesionless medium

The performance of piled rafts with unequal pile lengths in cohesionless soil under vertical loading was investigated in the present study through experimental and numerical analysis. A pattern function is used to define the pile length arrangement. The motivation for considering such a function is to ensure that the varying pile lengths follow a suitable geometric pattern, and it does not obstruct the construction practice in field applications. The piles at different locations within the raft were equipped with strain gauges to observe the strain distribution along their lengths during the static load test. Load sharing was evaluated by placing an earth pressure cell beneath the raft. A three-dimensional finite element analysis was used to simulate the experimental results aimed at assessing the load settlement and load-sharing responses. A comparison was conducted to verify the reliability of the tests. Subsequently, a detailed parametric study was conducted in accordance with different pattern functions, pile spacing, and pile locations in the piled rafts. The load settlement, load sharing, and bending moment of the raft were evaluated. An understanding of the pile behavior at different locations within the group will be helpful in selecting the suitable pile geometry during actual construction in the field. A foundation designed by considering the optimized pile length will be helpful in developing a more economical and resilient foundation system.

Assessment of Building Response Supported on Shallow Foundation Due to Tunnelling in Cohesionless Soil

The depth of foundations significantly influences the building response due to tunnelling-induced ground movement. The present study investigates the responses caused by tunnelling on buildings supported on isolated footings. The response of buildings supported on shallow foundation systems due to progressive tunnelling is investigated through experimental and numerical methods. A three-dimensional finite element analysis (3D FEM) has been developed to evaluate the response of an existing reinforced cement concrete (RCC) building underpasses a circular-shaped tunnel in cohesionless soil. The model includes soil strata, footings, super-structure, and tunnel. Different parametric studies, i.e., C/D ratios, tunnel volume losses, and eccentricity of the building, have been considered in the present study. A scale-down model of the tunnel and building is prepared in the laboratory. The scale-down model simulates the volume loss during tunnelling and evaluates the response on surface and building components due to tunnelling. The surface settlement, total and differential settlement of the foundation, and induced strain on lining and building elementals are estimated. The numerical model is benchmarked with the experimental study conducted in the laboratory. It is observed that the numerical method agrees well with the experimental investigation. The responses of buildings supported on shallow footings are compared with available literature. The findings of the present study will be useful for the hazard estimation of existing buildings situated along/adjacent to a proposed alignment of the tunnel.

Seismic response of tripod suction bucket foundation for offshore wind turbine considering multidirectional earthquake loads

Tripod suction buckets offer several advantages as offshore wind turbine (OWT) foundations, including cost-effective installation, high stability, and resistance to overturning. In seismically active regions, OWTs experience horizontal and vertical directions seismic excitations. This study employed an advanced three-dimensional nonlinear finite element analysis to investigate the influence of vertical seismic motions on the dynamic behavior of tripod bucket foundations installed in nonhomogeneous clay deposits. By adopting a simple kinematic hardening model to capture the foundation-soil nonlinear dynamic interaction, parametric analyses were conducted to study the effect of vertical seismic motions, considering several earthquake types and undrained shear strengths of the clay deposit. The results show that the influence of the vertical seismic motion on the dynamic response and deformation of the nacelle depends on the dominant frequency of the vertical seismic motion and the overturning resistance capacity of the OWT in different horizontal directions. The deformation mechanisms of an OWT vary with the strengths of the clay deposits. Based on these analyses, this study offers insights into the influence of vertical seismic motions on the dynamic response of tripod suction bucket foundations.

The pull-out capacity of torpedo anchor in clay considering the full opening cavity

Torpedo anchors are increasingly being considered for mooring floating facilities in deep waters owing to their efficient and economical installation. The anchor was released from a specified height above the seabed to allow it to gain velocity as it fell freely into the water before penetrating the seabed. A cavity was formed above the anchor shaft after the anchor installation. The formation of this post-installation cavity is largely dependent on the soil strength conditions and affects the anchor capacity after installation. However, there is a lack of understanding regarding the formation mechanisms of the cavity and its effect on the bearing capacity of a torpedo anchor. Thus, this study focuses on the effects of the post-installation cavity on the bearing capacity of the torpedo anchor. The impact of a fully open post-penetration cavity on both the vertical and inclined bearing capacity of a torpedo anchor without fins was investigated using the Coupled Eulerian–Lagrangian (CEL) method in ABAQUS with three-dimensional large deformation finite element (LDFE) analysis. A method for evaluating the vertical bearing capacity of a torpedo anchor, considering the effect of a post-installation cavity, was proposed. This study provides insight into the installation effect on the bearing capacity of torpedo anchors.

Effect of Second and Third Molar Eruption Stages on First Molar and Maxillary Arch Distalization With Modified Palatal Anchorage Plate and Beneslider: A 3D Finite Element Analysis.

To analyze the effects of the maxillary second molar and third molar eruption stages on the distalization of first molars with a modified palatal anchorage plate (MPAP) and Beneslider using three-dimensional (3D) finite element analysis. Six finite element models (FEMs) of individual maxillary molar distalization and six FEM models of en-masse maxillary arch distalization (EMAD) at different stages of the maxillary molar eruption were created from cone-beam computed tomography (CBCT) images of the maxillary complex, and 3D displacements of the maxillary first and second molars were evaluated with MPAP and Beneslider. On individual molar distalization, Beneslider showed first molar distal translation during the second and third molar follicular stages, while MPAP showed distal tipping of the first molar. With EMAD, either of the appliances showed distal tipping of the first molars. There was palatal rolling and extrusion of the first molars. The second molar showed buccal drifting with intrusion, and the incisors showed palatal displacementalong withextrusion. Second and third molar eruption stages had no adverse influence on first molar and en-masse maxillary arch distalization. Beneslider showed distal translation of the first molar, while distal tipping was seen with MPAP.

Numerical investigation of spudcan penetration in sand with interbedded clay

Jack-up units are extensively utilized in offshore geotechnical investigations and the recent installation of wind turbine foundations. Engineers require accurate predictions of spudcan penetration resistance to assess its final penetration depth and identify potential risks, e.g., punch-through, ensuring safety during the installation of jack-up units. Notably, for seabed stratigraphy comprising sand with interbedded clay layers, a significant discrepancy exists between the penetration resistance calculated using current industry guidelines and actual measured results. In this study, three-dimensional (3D) large deformation finite-element (LDFE) analyses were performed to model the spudcan penetration response in a seabed consisting of a sand–clay–sand soil profile. A comprehensive parametric study was conducted to examine the influence of soil strength and layer thickness on penetration resistance. The variations of the soil failure mechanisms are demonstrated and associated with the varying penetration resistance, which form the basis of the new calculation method developed for the sand seabed with interbedded clay.

Probabilistic three-dimensional finite element analysis of geosynthetic-reinforced pile-supported embankments

The current study focuses on a probabilistic three-dimensional finite element analysis of geosynthetic-reinforced pile-supported embankments. The probabilistic analysis utilizes a finite element technique and was executed using Python scripting in Abaqus. A deterministic model is established for both unreinforced and geosynthetic-reinforced pile-supported embankments, employing a basic linear elastic perfectly plastic Mohr-Coulomb constitutive model. This numerical model adopted a simplified methodology that eliminates the need to simulate actual piles and subsoil. The results are validated across different embankment heights and mesh sizes. Based on results from Monte-Carlo simulations, we aimed to show how results can vary even by considering only one random variable. Probability density functions for various parameters, including pile efficacy, maximum differential settlement, and maximum strain in the reinforcement, are shown. The findings illustrate the ability of probabilistic approaches to predict the most likely occurrences for different governing parameters of geosynthetic-reinforced pile-supported embankments. They also highlight the potential of probabilistic approaches to expand further into a full-scale comprehensive study which can offer deeper insights into the stability of these embankments considering various sources of uncertainties.

Biomechanical behavior of all-on-4 concept and alternative designs under different occlusal load configurations for completely edentulous mandible: a 3-D finite element analysis

The aim of this study was to evaluate the effect of the All-on-4 design and 4 alternative implant-supported fixed prosthesis designs on stress distribution in implants, peri-implant bone, and prosthetic framework in the edentulous mandible under different loading conditions using three-dimensional finite element analysis (3D-FEA).Five different experimental finite element models (Model A (unsplinted 6), Model B (splinted 6), Model C (All-on-4), Model D (axial; 2 anterior, 2 posterior), and Model E (4 interforaminal)) were created. Three different loading conditions were applied (canine loading, unilateral I-loading, and unilateral II-loading). The highest minimum (Pmin) and the maximum (Pmax) principal stress values were acquired for cortical and trabecular bones; the highest von Mises (mvM) stress values were obtained for implants and metal frameworks. Model B and Model D showed the most favorable stress distribution. The All-on-4 design (Model C) also showed acceptable stress values close to those of Model B and Model D in the cortical and trabecular bones. In accordance with the stress values in the bone structure, the lowest stress values were measured in the implants and Co-Cr framework in Model B and Model D. The highest stress values in all structures were measured for unilateral loading- II, while the lowest values were found for canine loading. It was concluded that Model B and Model D experimental models showed better biomechanical performance in all structures. Furthermore, the use of a splinted framework, avoiding cantilevers, results in lower stress transmission. On the other hand, canine loading and unilateral loading-I exhibited the best loading conditions.

Development of new improved plastic collapse moment equations of pressurized different angled pipe bends under bending moments

In a piping system, pipe bends are more flexible than straight pipes because of their curved geometry, supplemented by higher stress and strain concentration, leading to one of the crucial components in piping industries. Therefore, safe design of pipe bends is essential for smooth running of the piping system, and plastic collapse moment is one of its criteria. This paper utilizes three-dimensional finite element analyses to model empirical solutions for the plastic collapse moment for different angled pipe bends subjected to combined pressure and in-plane closing, in-plane opening, and out-of-plane bending moments. Plastic collapse moments for 30∘ to 180∘ pipe bends are determined for elastic perfectly plastic and strain hardening materials, employing large geometry change option and internal pressure effect. It is observed from results that pressure effect is more prominent in thinner pipe bends of larger bend angle under all bending cases. For in-plane opening and out-of-plane bending moments, collapse moment increases and then decreases with increase in pressure intensity for all sizes of pipe bend. However, for in-plane opening bending moment, collapse moments keep on decreasing for thicker ([Formula: see text] = 11.33) pipe bends. Finally, the study presents new improved plastic collapse moment solutions for different angled pipe bends under bending moment and internal pressure, derived from the finite element results of elastic perfectly plastic and strain hardening material models.

Performance of Pile–Wall System Adjacent to Footings

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall’s performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing.

Effect of cross wall on the strut forces for braced excavations in clays

This study evaluates and estimates the effect of cross walls on the strut force for braced excavation in clays by using three-dimensional finite element analysis. A well-documented case history of a braced excavation with cross walls was utilized to validate the numerical analysis. Furthermore, a series of parametric studies were conducted to evaluate the distribution of strut force by considering different schematics of cross walls. The results revealed that implementing cross walls inside the excavation could significantly reduce the wall deformation and strut force along the wall section, particularly for the location near cross walls. In addition, a new empirical method was proposed to estimate the maximum strut force based on the apparent earth pressure for braced excavation with cross walls, which was verified through case histories. Finally, this study concluded that the existence of cross walls in braced excavations could ensure a safer bracing system and excavation design.

Development of dynamic centrifuge models for measurement and visualization of deformation mechanisms in liquefiable soils

Recent advancements in geotechnical physical modeling have enabled visualization and analysis of deformation mechanisms in soil sections through the integration of Particle Image Velocimetry (PIV) in dynamic centrifuge modeling. PIV requires a rigid wall container. In this paper, we summarize the design considerations that enable reliable measurement and visualization of soil deformation mechanisms at the University of Colorado (CU) Boulder’s 400 g-ton, 5.5 m radius centrifuge facility. The primary objective of this system is to investigate the response of complex and stratigraphically variable, saturated granular soil deposits beneath shallow-founded structures, though it can also be used for other configurations that benefit from advanced visualization in the centrifuge. The setup aims to enable quantification and visualization of different deformation mechanisms, including shear, volumetric, and soil ejecta formation, near and away from structures. The paper provides detailed design considerations for the system components, including a rigid container with a transparent Perspex wall and duct seal inclusions, a linear-elastic single-degree of freedom (SDOF) structure, soil texture, a potential ground improvement technique, and a high-speed camera system. Through fully-coupled, three-dimensional (3D) nonlinear finite element analyses, we investigate the influence of container type, domain size, and duct seal geometry on boundary effects, with consideration of nonlinearities within various soil profile configurations with and without the presence of a building model. The findings highlight the critical impact of proximity to lateral boundaries of the container on accelerations, excess pore pressures, foundation settlement, tilt, and shear strains, as well as the benefits of duct seal in reducing those boundary effects. The results also show that the extent of boundary effects on key performance measures depends on the properties of the container, soil layers, and ground motion. The simulations also show that surface ejecta potential within stratigraphic soil profiles is highly sensitive to the depth of the groundwater table and variations in soil permeability, which must be considered in designing experimental programs that investigate the development of soil ejecta.

Effect of padeye offset ratio on keying behaviours and capacity of square plate anchors in clay

This paper reports the effect of padeye offset ratio on the keying behaviours and capacity of square plate anchors in clay. The investigation is conducted through three-dimensional large deformation finite element analyses using the Remeshing and Interpolation Technique with Small Strain in ABAQUS. Strain rate dependency of the undrained shear strength and soil remoulding are accounted for adopting an extended Tresca model. The results from LDFE analyses are compared with existing analytical solutions, centrifuge test data, and numerical results; with reasonable agreement obtained. Parametric analyses are then carried out varying several critical factors including initial embedment depth, load eccentricity, padeye offset ratio, soil sensitivity, and soil strength heterogeneity. It is seen that the padeye offset has significant influence on the ultimate loss of embedment and capacity under vertical loading. To assess the keying behaviour of square plate anchors in clay, an equivalent soil strength incorporating strain rate dependency and remoulding is adopted. A combined factor defined as a function of the initial embedment depth and equivalent soil strength is used to estimate the ultimate loss of embedment. An equivalent ultimate bearing capacity factor is shown to be a function of the initial embedment depth, padeye offset ratio, and load eccentricity.