Finite Element Analysis Values Research Articles

Investigation of Circular Hollow Concrete Columns Reinforced with GFRP Bars and Spirals

Glass fiber-reinforced polymer (GFRP) reinforcements are useful alternatives to traditional steel bars in concrete structures, particularly in vertical structural elements such as columns, as they are less prone to corrosion, and impart increasing strength and endurance of buildings. There is limited research on the finite element analysis (FEA) of the structural behavior of hollow glass fiber-reinforced polymer reinforced concrete (GFRPRC) columns. The hollow portion can be used for the service duct and for reducing the self-weight of the members. Numerical analysis of the compressive response of circular hollow concrete columns reinforced with GFRP bars and spirals is performed in this study. This article aims to investigate the axial behavior of hollow GFRP concrete columns and compare it with that of solid steel reinforced concrete (RC) columns as well as hollow steel RC columns. The Abaqus software is used to construct finite element models. After calibration of modeling using an experimental test result as a control model, a parametric study is conducted. The columns with the same geometry, loading, and boundary conditions are analyzed in the parametric study. It is resulted that the hollow GFRP concrete columns provide a greater confinement effect than the solid steel RC columns. The average variation in the ultimate axial load-carrying capacities of the experimental results, from that of the FEA values, is noted to be only 3.87%, while the average difference in the corresponding deformations is 7.08%. Moreover, the hollow GFRP concrete columns possess greater axial load and deformation capacities compared with the solid steel RC columns.

Mechanical properties prediction of composite laminate with FEA and machine learning coupled method

In order to predict mechanical properties of composite laminate, a method coupling finite element analysis (FEA) and machine learning is established to analyze three examples of composite laminates, such as failure factor of Puck theory under random stress state, failure factor and critical buckling eigenvalues of open-hole laminate. By writing Abaqus script, parametric FEA models of composite laminates are built and large samples are generated. Artificial neural network (ANN) model and random forest (RF) model are set up to learn these virtual samples to predict their corresponding mechanical properties for these examples. By analyzing predicted results and FEA values of these mechanical parameters, predicted data are well consistent with the curves of FEA values and the calculated root-mean-square errors are much smaller, which proves this FEA and machine learning coupled method is effective. Even if these errors predicted by ANN model are smaller than RF model, and the learning processes of RF model take less time, these methods with ANN model and RF model are all appropriate to predict mechanical properties of composite laminates.

Research on the line-arc-line constant-torque flexure hinge (LAL-CTFH) based on improved pseudo-rigid-body model (PRBM)

In order to enlarge the proportion of constant-torque output, a new type of constant-torque flexure hinge based on line-arc-line segment (LAL-CTFH) is designed. The LAL-CTFH has the characteristics of good constant-torque output performance, simple structure and easy manufacturing. The improved pseudo-rigid-body model (PRBM) method named four-bar linkage PRBM (FB-PRBM) for the LAL-CTFH is proposed to analyze the torque-angle characteristics of LAL-CTFH. The method is verified by finite element analysis (FEA). Furthermore, the constant-torque output characteristics of LAL-CTFH are optimized. Theoretical analysis, FEA, physical prototype production and experimental test of the optimized model are carried out respectively. The results show that in the range of 0–40°, the proportion of constant-torque output can reach more than 65%, the error between theoretical value and FEA value is less than 1%, and the average error between theoretical value and test value is less than 5%, which verifies the feasibility of the design scheme and the validity of the theoretical analysis.

马铃薯碰撞加速度试验测试与有限元分析

To analyze the maximum acceleration (amax) of a potato colliding with different objects, both experimental test and finite element analysis (FEA) methods were used. Results showed that when potatoes were collided with the single rod, the steel plate and the double rods, the average discrepancies of FEA and experimental test values were 5.3%, 3.95% and 5.04%. The maximum acceleration increased with the increase of potato drop height, and decreased with the increase of potato mass. Under the same conditions, the maximum acceleration decreased in turn when the potatoes were collided with the steel plate, the single rod and the double rods. The FEA results showed that the maximum acceleration in collision with the steel plate was 60.78% to 96.29% higher than that with the double rods. The maximum acceleration in collision with the steel plate was 53.89% to 83.27% higher than that with the double rods. The maximum acceleration in collision with the single rod covered with soil was 37.65% and 31.54% lower than that without soil. The research methods and conclusions of this article provided a basis for the analysis of impact mechanics and damage mechanism of potatoes, and contributed to further researches related to solid-like agricultural and food products.

Abstract 16111: Clinical Application of Deep Learning for Stress Analysis of Ascending Thoracic Aortic Aneurysms

Introduction: Current guidelines for elective surgery of ascending thoracic aortic aneurysms (aTAAs) use aneurysm size as primary determinant for risk stratification of adverse events. Biomechanically, dissection may occur when wall stress exceeds wall strength. A widespread method for stress analysis is structural finite-element analysis (FEA). Patient-specific aortic geometries are easily obtainable and stress distributions can potentially predict risk of dissection. However, FEA is a time-consuming and difficult procedure. To bypass this issue, a recent study has developed the first deep learning (DL) approach for a fast and accurate estimation of aortic wall stress distributions. Hypothesis: In this study, we assessed the hypothesis that this deep learning approach can be applied to a large clinical dataset. Model performance was measured by comparing FEA and DL stress predictions in parallel. Methods: Patients with aTAA (n = 169) were studied. Patient-specific aneurysm geometries were obtained from ECG-gated computed tomography. Shapes were represented by hexahedral meshes with 9648 nodes and 6336 solid elements. FEA peak wall stresses and stress distributions were determined using LS-DYNA software with user-defined fiber-embedded material models under systolic pressure. The DL model was implemented in Julia and consisted of unsupervised and supervised learning algorithms. Training was performed on a training set of 152 shapes and testing set of 17 shapes with 10-fold cross-validation. Mean absolute error (MAE) and absolute error of peak stress values (APE) were used to compare DL model predictions with FEA values considered to be ground truth. Results: Average stress values predicted by our DL model were 175.64 ± 4.17 kPa and 95.69 ± 2.15 kPa in the circumferential and longitudinal direction, respectively. We computed a MAE of 5.06 ± 1.08 kPa and APE of 2.58 ± 1.39 kPa in the circumferential direction and MAE of 4.51 ± 0.98 kPa and APE of 2.32 ± 1.84 kPa in the longitudinal direction. Conclusions: DL model trained exclusively on clinical data was able to accurately predict stress distributions on complex aortic geometries. Fast and accurate stress predictions will facilitate real-time clinical applications for the risk assessment of aTAAs.

Influence of Misfit on the Occurrence of Porcelain Veneer Fractures in Implant-Supported Metal-Ceramic Fixed Dental Prostheses. Part 2: A Three-Dimensional Finite Element Analysis.

To investigate the impact of different extents of misfit between a restoration and the supporting implant on veneer fractures in screw-retained implant-supported metal-ceramic fixed dental prostheses (FDPs). A finite element analysis (FEA) model of a five-unit screw-retained metal-ceramic FDP supported by three implants was constructed, replicating a previous in vitro study. Eight different gap configurations at the single terminal implant, ranging from 0 to 150 μm, were tested. All setups were tested after clamping and with a load of 200 N applied. Maximum stress within the FDP was calculated. The stress increased with each increase in misfit size above 30 μm, with the relationship between gap size and stress being linear up to 100-μm misfit. Above 100 μm, the stress increase accelerated. The stress pattern within the FDP changed with increasing gap size, confirming the findings of a previously conducted in vitro experiment for a misfit of 150 μm. The results of the FEA were in agreement with in vitro observations, validating the predictive value of FEA for technical complications. A misfit between an FDP and a supporting implant implies an increased risk of veneer fracture. Above a misfit of 30 μm, the stress levels are likely to be high enough to cause veneer fracture, and the risk increases disproportionately for misfit above 100 μm.

Design, Fabrication and Experiment of Double U-Beam MEMS Vibration Ring Gyroscope.

This study presents a new microelectromechanical system, a vibration ring gyroscope with a double U-beam (DUVRG), which was designed using a combination of mathematical analysis and the finite element method. First, a ring vibration resonator with eight double U-beam structures was developed, and 24 capacitive electrodes were designed for drive and sense according to the advantageous characteristics of a thin-shell vibrating gyroscope. Then, based on the elastic mechanics and thin-shell theory, a mathematical stiffness model of the double U-beam was established. The maximum mode resonant frequency error calculated by the DUVRG stiffness model, finite element analysis (FEA) and experiments was 0.04%. DUVRG structures were manufactured by an efficient fabrication process using silicon-on-glass (SOG) and deep reactive ion etching (DRIE), and the FEA value and theoretical calculation had differences of 5.33% and 5.36% with the measured resonant frequency value, respectively. Finally, the static and dynamic performance of the fabricated DUVRG was tested, and the bias instability and angular random walk were less than 8.86 (°)/h and 0.776 (°)/√h, respectively.

Dynamic analysis of a flexure-based compliant stage

This paper presents the dynamic analysis of a flexure-based compliant stage. The dynamic model is first obtained, after which the equivalent masses of the flexure hinge, including the axial equivalent mass, the bending equivalent mass, and the shear equivalent mass, are derived. According to this method, the equivalent mass components of the proposed stage are derived by accumulating those of the output platform, input platform, and flexure hinges. Finally, to verify the validity of the proposed method, the first two resonant frequencies and the corresponding mode shapes are analyzed by using finite element analysis (FEA). An experimental platform is fabricated, and experimental results and FEA values appear to be in accordance with the theoretical calculations. This result demonstrates that the dynamic model and equivalent mass are accurate. The dynamic model provides an effective method for calculating equivalent masses, and dynamic characteristics can be precisely estimated from the corresponding analytical models.

Investigation, modeling, and experiment of an MEMS S-springs vibrating ring gyroscope

This study presents a microelectromechanical systems S-springs vibration ring gyroscope (MSVRG), which is driven by electrostatic force and detected by capacitance. First, a ring resonator structure with eight S-shaped symmetrical supporting springs is developed, and the capacitor electrodes are designed according to the vibration characteristics of the ring resonator. Then, a precise equivalent stiffness model of MSVRG is established based on the vibration mechanics and the Cassette theorem, which can be employed for any other ring gyroscope with differently shaped springs. Moreover, the mode resonant frequency error of between experiments, finite-element analysis (FEA) and theory calculation, is 10.54% and 3.76%, respectively. After that, the process of MSVRG structure is introduced and the structure is manufactured, and the theory calculation and FEA value with processed parameters have 1.19% and 4.59% difference with resonant frequency tested value, respectively. Finally, the static performance of the fabricated MSVRG is tested, and the bias instability is about 0.0119 deg/s and angle random walk is about 0.0359 deg/s1/2 at room temperature.

FEA to Measure Bone Strength: A Review

Finite element analysis (FEA) based on CT datasets of the spine or hip or on high-resolution peripheral CT datasets of the distal forearm or tibia is now widely used in research and clinical trials to estimate bone strength. Its clinical potential has recently been endorsed by the International Society of Clinical Densitometry Zysset et al. (J Clin Densitom 18(3):359–92, 2015). In vitro validation studies demonstrated the superiority of FEA over DXA for the prediction of ultimate load. In vivo studies confirmed the superiority in the spine, but data were less conclusive in the hip and forearm. Here, in addition to low bone strength the risk of falling is a major determinant of fracture risk. The next level of FEA dissemination, the integration into clinical practice, still faces a number of challenges such as access to dedicated FE software and its integration into the clinical workflow. Also compared to DXA, current FEA techniques have not shown a consistent superiority for hip fracture prediction, while hip CT is associated with a higher radiation exposure than hip DXA. For many clinicians, FEA and the direct measurement of strength instead of BMD are a novel perspective. However, the increasing use of abdominal and pelvic CT scans initially obtained for other clinical diagnosis, for the secondary use to assess osteoporosis and fracture risk (opportunistic screening), may accelerate the use of FEA. In this contribution, the basic technical aspects and limitation of FEA are discussed and the clinically relevant outcome measures are presented. Further advanced topics will broaden the understanding of the various aspects of FEA. Afterward a summary of in vivo studies using FEA for fracture prediction is given, which also includes a discussion of the clinical value of FEA for bone strength measurements.

Finite element modelling versus classic beam theory: comparing methods for stress estimation in a morphologically diverse sample of vertebrate long bones

Classic beam theory is frequently used in biomechanics to model the stress behaviour of vertebrate long bones, particularly when creating intraspecific scaling models. Although methodologically straightforward, classic beam theory requires complex irregular bones to be approximated as slender beams, and the errors associated with simplifying complex organic structures to such an extent are unknown. Alternative approaches, such as finite element analysis (FEA), while much more time-consuming to perform, require no such assumptions. This study compares the results obtained using classic beam theory with those from FEA to quantify the beam theory errors and to provide recommendations about when a full FEA is essential for reasonable biomechanical predictions. High-resolution computed tomographic scans of eight vertebrate long bones were used to calculate diaphyseal stress owing to various loading regimes. Under compression, FEA values of minimum principal stress (σ(min)) were on average 142 per cent (±28% s.e.) larger than those predicted by beam theory, with deviation between the two models correlated to shaft curvature (two-tailed p = 0.03, r(2) = 0.56). Under bending, FEA values of maximum principal stress (σ(max)) and beam theory values differed on average by 12 per cent (±4% s.e.), with deviation between the models significantly correlated to cross-sectional asymmetry at midshaft (two-tailed p = 0.02, r(2) = 0.62). In torsion, assuming maximum stress values occurred at the location of minimum cortical thickness brought beam theory and FEA values closest in line, and in this case FEA values of τ(torsion) were on average 14 per cent (±5% s.e.) higher than beam theory. Therefore, FEA is the preferred modelling solution when estimates of absolute diaphyseal stress are required, although values calculated by beam theory for bending may be acceptable in some situations.

Differences in Stress and Total Deformation Due to Muscle Attachment to the Femur

To achieve accurate and precise results of finite element analysis (FEA) of bones, it is important to represent the load/boundary conditions as identical as possible to the human body such as the bone properties, the type and force of the muscles, the contact force of the joints, and the location of the muscle attachment. In this study, the difference in the Von-Mises stress and the total deformation was compared by classifying them into Case 1, which shows the actual anatomical form of the muscle attached to the femur when the same muscle force was applied, and Case 2, which gives a simplified representation of the attached location. An inverse dynamical musculoskeletal model was simulated using data from an actual walking experiment to complement the accuracy of the muscular force, the input value of FEA. The FEA method using the results of the muscular force that were calculated through the simulation showed that the maximum Von-Mises stress and the maximum total deformation in Case 2 were underestimated by 8.42% and 6.29%, respectively, compared to Case 1. The torsion energy and bending moment at each location of the femur occurred via the stress ingredient. Due to the geometrical/morphological feature of the femur of having a long bone shape when the stress distribution is wide, as shown in Case 1, a greater Von-Mises stress and total deformation are expected from the sum of the stress ingredients. More accurate results can be achieved only when the muscular strength and the attachment location in the FEA of the bones and the attachment form are the same as those in the actual anatomical condition under the various moving conditions of the human body. Keywords—Musculoskeletal modeling, Finite element analysis, Von-Mises stress, Deformation, Muscle attachment.

X-ray Diffraction Analysis of Residual Stress in Laminated Ceramic

The strength of ceramic was improved by lamination by suppressing the propagation of cracks with compressive residual stress in the face layer of the laminate. Hot pressed SiAlON+SiC/SiC/SiAlON+SiC laminate discs were fabricated for tailored residual stress. The residual stress in this laminate was studied by X-ray diffraction (XRD). There was considerable compressive residual stress in the face layer. A Finite Element Analysis (FEA) was performed to support the measured XRD results and to determine the stress field in the laminate. The residual stress measured by XRD had satisfactory agreement with the analytically calculated and FEA values. The measured value by XRD was ?385±20 MPa over most of the face layer. The calculated and FEA values were ?386MPa and ?371MPa, respectively. FEA also showed significantly modified stresses and the maximum tensile stress near the edge region which are possible crack generators in the presence of flaws or contact damage.

Fatigue creep damage at the cement–bone interface: An experimental and a micro-mechanical finite element study

The goal of this study was to quantify the micromechanics of the cement–bone interface under tensile fatigue loading using finite element analysis (FEA) and to understand the underlying mechanisms that play a role in the fatigue behavior of this interface. Laboratory cement–bone specimens were subjected to a tensile fatigue load, while local displacements and crack growth on the specimen's surface were monitored. FEA models were created from these specimens based upon micro-computed tomography data. To accurately model interfacial gaps at the interface between the bone and cement, a custom-written erosion algorithm was applied to the bone model. A fatigue load was simulated in the FEA models while monitoring the local displacements and crack propagation. The results showed the FEA models were able to capture the general experimental creep damage behavior and creep stages of the interface. Consistent with the experiments, the majority of the deformation took place at the contact interface. Additionally, the FEA models predicted fatigue crack patterns similar to experimental findings. Experimental surface cracks correlated moderately with FEA surface cracks ( r 2=0.43), but did not correlate with the simulated crack volume fraction ( r 2=0.06). Although there was no relationship between experimental surface cracks and experimental creep damage displacement ( r 2=0.07), there was a strong relationship between the FEA crack volume fraction and the FEA creep damage displacement ( r 2=0.76). This study shows the additional value of FEA of the cement–bone interface relative to experimental studies and can therefore be used to optimize its mechanical properties.

Modelling of fibre holding elements in silicon

The mechanical behaviour of a fibre holding system is studied analytically and by using finite element analysis (FEA). The system consists of anisotropically etched v-grooves in which optical fibres are passively aligned and fixed by flexible holding beam elements along the groove sides. The holding elements have a triangular shape and constant thickness. Three different thicknesses were studied: 3, 6 and 9 µm; with tilting angles in the range of 0 to 45°. The contact between a fibre and a typical beam element is modelled analytically, and expressions for the element-fibre contact force and the maximum element stress are derived using elementary beam theory. The corresponding quantities are also determined by finite element analysis, modelling the system as a contact problem. The results are compared for various parameter combinations and parameter ranges are established for which the validity of the analytical model is sufficient. It is found that generally one-dimensional beam theory is quite accurate for estimating the contact force and the maximum stress. This theory, however, overestimates the contact force slightly. For tilting angles up to 25°, the deviation is less than 10%. For the 3 µm elements, with tilting angles up to 25°, the maximum stress is within 10% of the FEA values. For the 9 µm elements, however, the same deviation is obtained for tilting angles up to 40°.