3D simulation of deflection basin of pavements under high-speed moving loads

In this study, the characteristics of a strain wave gear (SWG) with a double-circular-arc with a common tangent (DCACT) profile were simulated using two-dimensional (2D) and three-dimensional (3D) finite element analysis (FEA). First, theoretically generated tooth profiles for the flexible spline (FS) and circular spline (CS) of an SWG were developed according to the theory of gearing. An automated mesh-generating computer program was developed in Visual C++ to establish 2D and 3D finite element models of the SWG based on its derived geometry. An FEA was then performed to explore the meshing characteristics, including the stress distribution, torsional angle, torsional stiffness, and number of engaged teeth, of the SWG. Continuous meshing of multiple tooth pairs between the FS and CS from the 2D FEA verified the conjugation of tooth profiles. The coning effect on the FS during assembly of the SWG was also predicted and discussed from the 3D FEA results. The 3D FEA produced more accurate and practical results than the 2D FEA did. Additionally, 3D FEAs of a modified (with longitudinal crowning) and unmodified (without longitudinal crowning) FS were performed and compared. Finally, a 3D FEA of a modified FS was successfully conducted to predict cyclic contact stress, root stress, and transmission error.

Several well-known equations for estimating the crack length in the single-edge notched bending (SE(B)) specimens from the normalized crack mouth opening displacement (CMOD) compliance are evaluated based on two-dimensional (2D) and three-dimensional (3D) finite element analyses (FEAs). Two-dimensional FEAs are first carried out to verify the reported accuracy and applicable ranges for each equation based on the plane strain models with six different crack lengths. Three-dimensional FEAs are then carried out to estimate the errors of prediction of equations that evaluate the crack length from the plane stress- and plane strain-based CMOD compliances. Both plane-sided and side-grooved models are included in 3D FEAs and have seven different thickness-to-width ratios. The error of prediction of a given equation is largely impacted by the thickness-to-width ratio, the crack length, the presence of side grooves, and the use of the plane stress- or plane strain-normalized CMOD compliance. Based on the errors of prediction, the relevance of the actual state of stress in the ligament of the SE(B) specimens to the plane strain condition or the plane stress condition is inferred. Knowledge of the relevance of the plane stress condition or the plane strain condition can be used to select the corresponding CMOD compliance in crack length-CMOD equations, and, therefore, the corresponding predictive accuracy can be improved.

Thermal buckling of steel tube using finite element method

The study goal was to compare simple two-dimensional (2D) analyses of bone strength using dual energy x-ray absorptiometry (DXA) data to more sophisticated three-dimensional (3D) finite element analyses using quantitative computed tomography (QCT) data. DXA- and QCT-derived femoral neck geometry, simple strength indices, and strength estimates were well correlated. Simple 2D analyses of bone strength can be done with DXA data and applied to large data sets. We compared 2D analyses to 3D finite element analyses (FEA) based on QCT data. Two hundred thirteen women participating in the Study of Women's Health Across the Nation (SWAN) received hip DXA and QCT scans. DXA BMD and femoral neck diameter and axis length were used to estimate geometry for composite bending (BSI) and compressive strength (CSI) indices. These and comparable indices computed by Hip Structure Analysis (HSA) on the same DXA data were compared to indices using QCT geometry. Simple 2D engineering simulations of a fall impacting on the greater trochanter were generated using HSA and QCT femoral neck geometry; these estimates were benchmarked to a 3D FEA of fall impact. DXA-derived CSI and BSI computed from BMD and by HSA correlated well with each other (R=0.92 and 0.70) and with QCT-derived indices (R=0.83-0.85 and 0.65-0.72). The 2D strength estimate using HSA geometry correlated well with that from QCT (R=0.76) and with the 3D FEA estimate (R=0.56). Femoral neck geometry computed by HSA from DXA data corresponds well enough to that from QCT for an analysis of load stress in the larger SWAN data set. Geometry derived from BMD data performed nearly as well. Proximal femur breaking strength estimated from 2D DXA data is not as well correlated with that derived by a 3D FEA using QCT data.

The right bank slope of Dagangshan hydropower station in China has complex geological conditions and is subjected to high in situ stress. Notably, microseismic activities in the right bank slope occurred during reservoir impounding. This paper describes the microseismic monitoring technology, and three-dimensional (3D) finite element analysis is used to explore the microseismic activities and damage mechanisms in the right bank slope during reservoir impounding. Based on data obtained from microseismic monitoring, a progressive microseismic damage model is proposed and implemented for 3D finite element analysis. The safety factor for the right bank slope after reservoir impoundment obtained from the 3D finite element analysis, which included the effects of progressive microseismic damage, was 1.10, indicating that the slope is stable. The microseismic monitoring system is able to capture the slope disturbance during reservoir impounding in real time and is a powerful tool for qualitatively assessing changes in slope stability over time. The proposed progressive microseismic damage model adequately simulates the changes in the slope during the impoundment process and provides a valuable tool for evaluating slope stability.

The finite element method is widely used in dental research. The decision to use two-dimensional (2D) or three-dimensional (3D) modelling is dependent on many interrelated factors. The purpose of the present study was to compare and contrast 2D and 3D finite element analysis (FEA) in investigating the mechanical behaviour of a maxillary premolar restored with a full crown under similar conditions of axial and lateral occlusal loading. The 2D analysis required modelling both a buccolingual and mesiodistal section of the restored premolar and for comparison sections of a 3D model were examined. Differences in the results for displacement and maximum principal stress distribution within the component structures and interfaces of the 2D and 3D models were, in general, attributable to differences in geometry represented in the models. Maximum principal stresses tended to be greater under lateral rather than axial occlusal loading. It was concluded that 2D FEA may find application in investigating key aspects of the mechanical behaviour of a dental restoration in a single tooth unit, but that in certain situations combinations of 2D and 3D FEA may offer the best understanding of the biomechanical behaviour of complex dental structures. Sophisticated FE models are required to better understand the mechanical behaviour of restored tooth units.

There is limited literature focused on experimentally investigating the influence of the crystalline structure of particles on the constitutive anisotropy of silica sand. This paper assesses the influence of quartz crystal structure on the constitutive response of synthetic silica cubes and natural silica sand particles using 3D x-ray diffraction (3DXRD), synchrotron micro-computed tomography (SMT), and 3D finite element (FE) analysis. The results of unconfined uniaxial compression experiments on synthetic silica cubes exposed constitutive anisotropy that was caused by the crystal structure of quartz. The 3D finite element (FE) analysis was validated to accurately model the crystal-based constitutive anisotropy in silica particles using the results of the silica cube experiments. Then 3D FE analysis was conducted to study how the change in crystal local orientation of individual sand particles can fundamentally produce anisotropy in the constitutive response of natural sand particles. Both the experiments and 3D FE analysis showed that the crystal structure of quartz essentially causes a directional anisotropy in the constitutive behavior of silica sand particles.

ABSTRACTObjectives:To assess the outcome of implant diameter and length on THE distribution of stress using a three-dimensional (3D) finite elements (FE) analysis, with immediate loading implants.Materials and Methods:This study made use of a 3D FE model of an implant encased in a chunk of bone. The LEADER/ITALIA-Fix type implant was created specifically for immediate loading. To create a solid model of the implant and bone and to carry out the FE analysis, the ANSYS V.12 programme was used.Results:The findings indicated that the neck of dental implants is the area of highest stress for all implant diameters and lengths, with an increase in implant length from 10 mm to 12 mm resulting in a slight raise in stress at the interface of implant-bone, and an increase in diameter from 3.75 mm to 4.25 mm having no appreciable impact on the value of stresses around dental implants.Conclusion:It was concluded that an increase in length has a negative effect on stress, while a diameter increase has no discernible impact on stress values.

3D FEA modelling of laminated composites in bending and their failure mechanisms

Biomechanical effect of implant design on four implants supporting mandibular full-arch fixed dentures: In vitro test and finite element analysis

The interfacial stress and its distribution affect directly the mechanical properties of polymeric blends and composites. Polymers are usually modified with rubber to improve their toughness. The three-dimensional (3D) finite element analysis (FEA) of the interfacial stress distribution between the particulate and the matrix during tensile of a rubber-modified polypropylene (PP) blend is made by means of an ANSYS software in this article, and the results are compared with those of the two-dimensional (2D) FEA simulation published earlier. The results show that the shear effect subjected in the pole zone of the rubber particle is maximal, the equator zone of the rubber particle is strongly pressed and pulled, and the tensile stress reaches the maximum. Comparatively, the stress distribution of 3D FEA is more gentle than that of 2D FEA.

Structural integrity of casings is critical for safe and economic operation of offshore wells and it can be compromised by external corrosion due to exposure to environment such as seawater. Assessing the impact of severe casing corrosion on the structural integrity of the well can be challenging due to complexities arising from local wall loss, non-uniform wall thickness, presence of holes due to severe corrosion, and non-bonded cement. Such complexities are not adequately addressed by existing codes/standards and available analytical equations. This paper presents a study that utilized a combination of a thermo-mechanical well simulator and threedimensional (3D) finite element analysis (FEA) to model severely corroded offshore well casing strings towards assessing structural integrity of the wells. The goal of the study was to determine the extent of allowable corrosion in conductor and surface casing beyond which the wells would be at risk for failure, and if topping off the cement in the annulus would be beneficial for structural integrity. A thermo-mechanical well simulator was utilized to model how corrosion wall loss evolved over time for both the conductor and surface casing, and the corresponding impact on their load capacity. In conjunction with the well simulator, full 3D FEA was conducted to model various complexities, such as the effect of corrosion holes and non-uniform corrosion. The 3D FEA helped assess the impact of remedial cementing on casing integrity and refine the critical wall thickness limit needed to withstand loads predicted by the well simulator. Compression and buckling were identified as governing failure modes and FEA results were compared with a buckled conductor in the field. The systematic, mechanics-based approach used in this study provided a basis for risk assessment where at-risk wells can be prioritized for remediation and/or abandonment.

Evaluation of mechanical and thermal stress in an endodontically treated cracked premolar with three restorative designs: 3D-finite element analysis

This study aims to evaluate the load-settlement behavior of five different piled raft foundation case studies using two-dimensional (2D) and three-dimensional (3D) finite element analyses. Hydre Park Barracks in London and Messeturm, Torhaus, Westend, and the Skyper Tower in Frankfurt are five well-instrumented and monitored buildings with piled raft foundations. Their foundation systems were modeled via PLAXIS 2D and 3D software, and the computed load settlement behavior including maximum and differential settlement along with the pile loads and bending moments were compared with the field measurements. The results indicate that 3D models predict the load settlement behavior more accurately compared with 2D models, particularly on structures with a non-symmetrical pile layout. Furthermore, it is also concluded that while 3D finite element analysis yields more accurate results in expense of complexity of model setup and computational time, 2D models provide conservative results with simplicity and faster computation.

This report describes a methodology for demand estimate through the improvement of load distribution factors in reinforced concrete flat-slab and T-beam bridges. The proposed distribution factors are supported on three-dimensional (3D) Finite Element (FE) analysis tools. The Conventional Load Rating (CLR) method currently in use by INDOT relies on a two-dimensional (2D) analysis based on beam theory. This approach may overestimate bridge demand as the result of neglecting the presence of parapets and sidewalks present in these bridges. The 3D behavior of a bridge and its response could be better modeled through a 3D computational model by including the participation of all elements. This research aims to investigate the potential effect of railings, parapets, sidewalks, and end-diaphragms on demand evaluation for purposes of rating reinforced concrete flat-slab and T-beam bridges using 3D finite element analysis. The project goal is to improve the current lateral load distribution factor by addressing the limitations resulting from the 2D analysis and ignoring the contribution of non-structural components. Through a parametric study of the slab and T-beam bridges in Indiana, the impact of selected parameters on demand estimates was estimated, and modifications to the current load distribution factors in AASHTO were proposed.