scholarly journals Axisymmetric Finite Element Modelling of the Human Lens Complex under Cataract Surgery

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 696
Author(s):  
M. T. Cardoso ◽  
B. Feijóo ◽  
A. P. G. Castro ◽  
F. J. Ribeiro ◽  
P. R. Fernandes
Keyword(s):  
Finite Element ◽  
Cataract Surgery ◽  
Complete Removal ◽  
Human Lens ◽  
Fe Model ◽  
Fe Modelling ◽  
Crystalline Complex ◽  
Blurred Vision ◽  
Operative Complications ◽  
Iol Dislocation

Cataract is a disease opacifying the crystalline, leading to a blurred vision and ultimately to blindness. With an aging population, the incidence of cataract is increasing, as well as the number of treatments. The solution available is its complete removal, followed by an implant of an intraocular lens (IOL). Although the post-operative complications on cataract surgeries have been decreasing in general, the bag-IOL complex dislocation is still an issue, probably being the most serious complication under this procedure. In this work, an axisymmetric Finite Element (FE) modelling strategy of the crystalline complex during the process of accommodation under cataract surgery is proposed. The goal was to understand the influence of biomechanical alterations promoted by the IOL on bag-IOL dislocation after surgery. An increase of force and stress in the zonules was verified in the pseudophakic eye compared to the complete eye, which could explain why zonules break years after surgery, leading to the bag-IOL dislocation. The axisymmetric FE model proposed in this work is innovative in this field, which still lacks detailed research, and can be an important complement for the clinical and biomechanical work on the crystalline complex.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

scholarly journals Finite Element Modelling and Updating of Welded Thin-Walled Beam

2018 ◽  
Vol 15 (4) ◽  
pp. 5874-5889 ◽  
Author(s):  
M. S. M. Fouzi ◽  
K. M. Jelani ◽  
N. A. Nazri ◽  
Mohd Shahrir Mohd Sani
Keyword(s):  
Finite Element ◽  
Model Updating ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Modal Parameters ◽  
Fe Model ◽  
Fe Modelling ◽  
Welded Structure ◽  
Thin Walled ◽  
Fe Model Updating

This article concentrates on the finite element (FE) modelling approach to model welded thin-walled beam and the adoption of model updating technique to enhance the dynamic characteristic of the FE model. Four different types of element connectors which are RBE2, CBAR, CBEAM and CELAS format are used to construct the FE model of welded structure. Normal mode analysis is performed using finite element analysis (FEA) software, MSC Patran/Nastran to extract the modal parameters (natural frequency and mode shape) of the FE model. The precision of predicted modal parameters obtained from the four models of welded structure are compared with the measured counterparts. The dynamic characteristics of a measured counterpart is obtained through experimental modal analysis (EMA) using impact hammer method with roving accelerometer under free-free boundary conditions. In correlation process, the CBAR model has been selected for updating purposes due to its accuracy in prediction with measured counterparts and contains updating parameters compared to the others. Ahead of the updating process, sensitivity analysis is made to select the most sensitive parameter for updating purpose. Optimization algorithm in MSC Nastran is used in FE model updating process. As a result, the discrepancy between EMA and FEA is managed to be reduced. It shows the percentage of error for updated CBAR model shrinks from 7.85 % to 2.07 % when compared with measured counterpart. Hence, it is found that using FE model updating process provides an efficient and systemic way to perform a feasible FE model in replicating the real structure.

scholarly journals Moisture Induced Deformations in Glulam Members - Experiments and 3-D Finite Element Model

2017 ◽  
Vol 36 (2) ◽  
pp. 35-45
Author(s):  
Henry M. Kiwelu
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Solid Wood ◽  
Average Moisture Content ◽  
Fe Model ◽  
Fe Modelling ◽  
Average Value ◽  
Hybrid Buildings ◽  
External Shape

Experiments were performed on scaled glue laminated bending specimens to observetime dependent development of deformations during drying and wetting. Measurementsdetermined changes in the average moisture content and external shape and dimensionsbetween when specimens were placed into constant or variable climates. Alterations inthe external shape and dimensions reflected changes in the average value anddistribution of moisture and mechanosorptive creep in the glulam. The results are beingused to develop a sequentially-coupled three-dimensional hygrothermal Finite Element(FE) model for predicting temporally varying internal strains and external deformationsof drying or wetting solid wood structural components. The model implies temporallyvarying, and eventual steady, state internal stress distributions in members based onelastic and creep compliances that represent wood within glulam as a continuousorthotropic homogenised material. Thus, predictions are consistent with smearedengineering stress analysis methods rather than being a physically correct analogue ofhow solid wood behaves. This paper discusses limitations of and intended improvementsto the FE modelling. Complementary investigations are underway to address otheraspects of the hygrothermal behaviour of structural members of wood and othermaterials (e.g. reinforced concrete) embedded within superstructure frameworks ofmulti-storey hybrid buildings.

Alignment Criteria for Through-Wall Flaws in Plates and Pipes

2008 ◽  
Author(s):  
B. Bezensek ◽  
K. Miyazaki
Keyword(s):  
Finite Element ◽  
Load Capacity ◽  
Damage Model ◽  
Fe Model ◽  
Experimental Sample ◽  
Fe Modelling ◽  
Combination Rules ◽  
Single Flaw

Multiple flaws in vessels and pipes are frequently assessed as a larger single flaw in accordance with the flaw alignment and combination rules. In this paper the alignment of two through-wall flaws is examined for plates in tension and pipes in bending using detailed finite element (FE) modelling. The FE model is developed using the Gurson-Tvergaard damage model and accurately describes the flaw interaction and load capacity of a random experimental sample. Results suggests that two flaws should be aligned onto the same plane for the purpose of assessment when the separation between the parallel planes containing flaws equals the flaw length for both, plates in tension and pipes in bending.

The Application of Aeroelastic Analysis Output Load Distributions to Finite Element Models of Wind

2005 ◽  
Vol 29 (2) ◽  
pp. 153-168 ◽  
Author(s):  
Timothy J. Knill
Keyword(s):  
Finite Element ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Fe Model ◽  
Wind Turbine Blades ◽  
Fe Modelling ◽  
Load Distributions ◽  
Aeroelastic Analysis ◽  
Extreme Load ◽  
Application Techniques

The structural design of wind turbine blades is a rapidly evolving technology. Finite element (FE) modelling is used extensively by structural designers to assess the behaviour of wind turbine blades under operational and extreme load conditions. This paper develops a method of transferring aerodynamic and inertial loads from the aeroelastic analysis output to the FE model. Once a procedure is developed and verified, case studies are undertaken using an FE model of a 34m blade. Loads are applied using the newly developed method and various FE analysis results compared to the same blade analysed under more traditional load application techniques. The case study clearly demonstrates that the method of applying loads can influence some types of analysis results significantly.

Finite element analysis of intramedullary devices: The effect of the gap between the implant and the bone

2008 ◽  
Vol 222 (3) ◽  
pp. 333-345 ◽  
Author(s):  
D J Simpson ◽  
C J Brown ◽  
A L Yettram ◽  
P Procter ◽  
G J Andrew
Keyword(s):  
Finite Element ◽  
Fracture Plane ◽  
Local Geometry ◽  
Fe Model ◽  
Fe Modelling ◽  
Element Analysis ◽  
Medial Side ◽  
Intramedullary Device ◽  
Interaction Interface ◽  
Distribution Of Stress

This paper examines the interaction interface between the implant and the bone for an intramedullary femoral nailing system using a finite element (FE) model and specifically considers the hypothesis that the local geometry at the interface is significant to the resulting localized contact stress between the medial and lateral aspect of nail and endosteum. Contact mechanics algorithms are used in the FE modelling technique that can be developed to deal with any form of intramedullary device for which contact at the bone—implant interface is important. Global stiffness data from the FE model are compared with available data from an experiment carried out on a construct of the bone and the device that uses intramedullary femoral nails. Acceptable agreement is obtained. The results demonstrate that the mechanical interface between the implant and the bone is significantly affected by the gap geometry and magnitude. In particular, larger gaps lead to greater concentrations of stress on the medial side, while the distribution of stress is more uniform at the lateral contacts. Furthermore, the results show that the gap can have a marked effect on the stresses that occur on the fracture plane.

Finite element modelling of pullout testing on a soil nail in a pullout box under different overburden and grouting pressures

2011 ◽  
Vol 48 (4) ◽  
pp. 557-567 ◽  
Author(s):  
Wan-Huan Zhou ◽  
Jian-Hua Yin ◽  
Cheng-Yu Hong
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Back Analysis ◽  
Soil Mass ◽  
Friction Model ◽  
Soil Parameters ◽  
Fe Model ◽  
Fe Modelling ◽  
Soil Nail ◽  
Pullout Behaviour

In this paper, a three-dimensional (3D) finite element (FE) model is developed to simulate the pullout behaviour of a soil nail in a soil-nail pullout box under different overburden and grouting pressures. The FE model simulates all the procedures of a pullout test on a grouted soil nail in a compacted and saturated completely decomposed granite (CDG) soil. The stress–strain behaviour of the CDG soil is described by a modified Drucker–Prager/Cap model, while that of the soil–nail interface is represented by the Coulomb friction model. Triaxial experiment data are used to calibrate the soil parameters in the soil constitutive model. The interface parameters are determined from back-analysis with the laboratory soil-nail pullout data. The soil stress variations surrounding the soil nail during drilling, grouting, saturation, and pullout are all well simulated by the FE modelling and compared with available test data. The comparisons between the modelling and experimental data have shown that the established FE can well simulate the pullout behaviour of a soil nail in a soil mass. Based on this, the verified FE model has the potential to simulate the performance of a soil nail in a field soil slope.

scholarly journals Gait-Specific Optimization of Composite Footwear Midsole Systems, Facilitated through Dynamic Finite Element Modelling

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Dimitris Drougkas ◽  
Evagelos Karatsis ◽  
Maria Papagiannaki ◽  
Serafeim Chatzimoisiadis ◽  
Fotini Arabatzi ◽  
...  
Keyword(s):  
Finite Element ◽  
Nonlinear Material ◽  
Fe Model ◽  
Micro Computed Tomography ◽  
Fe Modelling ◽  
Plantar Pressure Distribution ◽  
Optimization Function ◽  
Modelling Techniques ◽  
Mesh Grid

Objective. During the last century, running shoes have been subject to drastic changes with incremental however improvements as to injury prevention. This may be, among others, due to the limited insight that experimental methodologies can provide on their 3D in situ response. The objective of this study was to demonstrate the effectiveness of finite element (FE) modelling techniques, in optimizing a midsole system as to the provided cushioning capacity. Methods. A commercial running shoe was scanned by means of micro computed tomography and its gel-based midsole, reverse-engineered to a 200 μm accuracy. The resulting 3D model was subjected to biorealistic loading and boundary conditions, in terms of time-varying plantar pressure distribution and shoe-ground contact constraints. The mesh grid of the FE model was verified as to its conceptual soundness and validated against velocity-driven impact tests. Nonlinear material properties were assigned to all entities and the model subjected to a dynamic FE analysis. An optimization function (based on energy absorption criteria) was employed to determine the optimum gel volume and position, as to accommodate sequential cushioning in the rear-, mid-, and forefoot, of runner during stance phase. Results. The in situ developing stress fields suggest that the shock dissipating properties of the midsole could be significantly improved. Altering the position of the gel pads and varying their volume led to different midsole responses that could be tuned more efficiently to the specific strike and pronation pattern. Conclusions. The results suggest that midsole design can be significantly improved through biorealistic FE modelling, thus providing a new platform for the conceptual redesign and/or optimization of modern footwear.

scholarly journals Investigation of Mesh Size Effect on Dynamic Behaviour of an Assembled Structure with Bolted Joints using Finite Element Method

2018 ◽  
Vol 15 (3) ◽  
pp. 5695-5709 ◽  
Author(s):  
R. Omar ◽  
M.N Abdul Rani ◽  
M. A. Yunus ◽  
A. A. Mat Isa ◽  
W. I. I. Wan Iskandar Mirza ◽  
...  
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Total Error ◽  
Mesh Size ◽  
Bolted Joints ◽  
Fe Model ◽  
Processing Unit ◽  
Memory Usage ◽  
Fe Modelling ◽  
Selection Of

The predicted results of the finite element (FE) model of an assembled structure with different types of joints are highly dependent on the mesh size of the FE model. The complexity of the FE model has forced engineers to seek the most efficient techniques for the selection of the appropriate mesh size specifically in obtaining accurate predicted results in normal modes analysis. This paper concerns the investigation into the effects of the mesh sizes and selection technique of the appropriate mesh size in the FE modelling and analysis of the assembled structure with bolted joints. The investigation was carried out by predicting the modal parameters of the FE models with the predefined range of mesh sizes. The predicted results of the FE models were compared with the measured counterparts obtained from the experimental modal analysis (EMA). The total error obtained from the comparison between FE and EMA was recorded. Evaluations were made by comparing the number of nodes and elements of the FE models, percentage of total error, computer processing unit (CPU) elapsed time and memory usage. The outcomes of the evaluations showed that there are significant effects of the mesh sizes on the accuracy, computing time and memory usage of the FE modal analysis of the assembled structure with bolted joints. This work also demonstrated an efficient technique for the selection of the appropriate mesh size in achieving a reliable, efficient and economic FE modelling and analysis of the assembled structure with bolted joints.

scholarly journals Case Report: Diagnosis of Late Spontaneous Intraocular Lens Dislocation on Point-of-care Ultrasound

2021 ◽  
Vol 5 (3) ◽  
pp. 332-334
Author(s):  
Alexandra Pizarro ◽  
Thompson Kehrl
Keyword(s):  
Case Report ◽  
Cataract Surgery ◽  
Intraocular Lens ◽  
Vision Loss ◽  
Imaging Modality ◽  
Point Of Care ◽  
Angle Closure ◽  
Point Of Care Ultrasound ◽  
Blurred Vision ◽  
Iol Dislocation

Introduction: Spontaneous intraocular lens (IOL) dislocation is a rare, but serious, complication following cataract surgery. Case Report: We report a case of patient with a remote history of cataract surgery presenting to the emergency department with monocular blurred vision. Ocular point-of-care ultrasound (POCUS) facilitated diagnosis of a late spontaneous IOL dislocation. Discussion: Prosthetic IOL dislocations are being reported with increasing frequency. Prompt recognition of IOL dislocation is essential to prevent secondary complications, including acute angle-closure glaucoma and retinal detachment, which can result in permanent vision loss. Conclusion: Point-of-care ultrasound is a rapid, noninvasive imaging modality for early detection of IOL dislocation to help guide management, improve patient outcomes, and mitigate long-term sequelae.

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