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finite-element-analysis
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Dynamic performance of concrete slabs reinforced with steel and GFRP bars under impact loading
, Article Engineering Structures ; Volume 191 , 2019 , Pages 62-81 ; 01410296 (ISSN) ; Khaloo, A ; Soltani, H ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar's material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs,...
Subject-specific loads on the lumbar spine in detailed finite element models scaled geometrically and kinematic-driven by radiography images
, Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 35, Issue 4 , 2019 ; 20407939 (ISSN) ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
Wiley-Blackwell
2019
Abstract
Traditional load-control musculoskeletal and finite element (FE) models of the spine fail to accurately predict in vivo intervertebral joint loads due mainly to the simplifications and assumptions when estimating redundant trunk muscle forces. An alternative powerful protocol that bypasses the calculation of muscle forces is to drive the detailed FE models by image-based in vivo displacements. Development of subject-specific models, however, both involves the risk of extensive radiation exposures while imaging in supine and upright postures and is time consuming in terms of the reconstruction of the vertebrae, discs, ligaments, and facets geometries. This study therefore aimed to introduce a...
In silico study of patient-specific magnetic drug targeting for a coronary LAD atherosclerotic plaque
, Article International Journal of Pharmaceutics ; Volume 559 , 2019 , Pages 113-129 ; 03785173 (ISSN) ; Amani, A ; Forouzandehmehr, M ; Ghoytasi, I ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Coronary artery disease is the first cause of death across the world. Targeted delivery of therapeutics through controlled release of micro- and nano-particles remains a very capable approach to develop new strategies in treating restenosis and atherosclerotic plaques. In this research, to produce the arterial geometry, an image-processing was done using CT-scan images of a LAD coronary artery. After implementing the finite element mesh, the Fluid-Structure Interaction (FSI) simulation based on physiological boundary conditions was performed. Next, a Lagrangian description of particles dynamics in a non-Newtonian blood flow considering momentum equation of motion for each particle and the...
3D simulation of solutes concentration in urinary concentration mechanism in rat renal medulla
, Article Mathematical Biosciences ; Volume 308 , 2019 , Pages 59-69 ; 00255564 (ISSN) ; Abdekhodaie, M. J ; Farhadi, F ; Shafiee, M. A ; Sharif University of Technology
Elsevier Inc
2019
Abstract
In this work, a mathematical model was developed to simulate the urinary concentration mechanism. A 3-D geometry was derived based on the detail physiological pictures of rat kidney. The approximate region of each tubule was obtained from the volume distribution of structures based on Walter Pfaller's monograph and Layton's region-based model. Mass and momentum balances were applied to solve for the change in solutes concentration and osmolality. The osmolality of short and long descending nephrons at the end of the outer medulla was obtained to be 530 mOsmol/kgH2O and 802 mOsmol/kgH2O, respectively, which were in acceptable agreement with experimental data. The fluid osmolality of the short...
Subject-specific regression equations to estimate lower spinal loads during symmetric and asymmetric static lifting
, Article Journal of Biomechanics ; Volume 102 , 2020 ; Shirazi Adl, A ; El Ouaaid, Z ; Plamondon, A ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Workplace safety assessment, personalized treatment design and back pain prevention programs require accurate subject-specific estimation of spinal loads. Since no noninvasive method can directly estimate spinal loads, easy-to-use regression equations that are constructed based on the results of complex musculoskeletal models appear as viable alternatives. Thus, we aim to develop subject-specific regression equations of L4-L5 and L5-S1 shear and compression forces during various symmetric/asymmetric tasks using a nonlinear personalized finite element musculoskeletal trunk model. Kinematics and electromyography (EMG) activities of 19 young healthy subjects were collected during 64 different...
Development of a shell superelement for large deformation and free vibration analysis of composite spherical shells
, Article Engineering with Computers ; 2020 ; Hosseinzadeh, A ; Movahhedy, M. R ; Sharif University of Technology
Springer
2020
Abstract
Finite element analysis of huge and/or complicated structures often requires long times and large computational expenses. Superelements are huge elements that exploit the deformation theory of a specific problem to provide the capability of discretizing the problem with minimum number of elements. They are employed to reduce the computational cost while retaining the accuracy of results in FEM analysis of engineering problems. In this research, a new shell superelement is presented to study linear/nonlinear static and free vibration analysis of spherical structures with partial or full spherical geometries that exist in many industrial applications. Furthermore, this study investigates the...
3D numerical investigation of the coupled interaction behavior between mechanized twin tunnels and groundwater – A case study: Shiraz metro line 2
, Article Tunnelling and Underground Space Technology ; Volume 103 , 2020 ; Hataf, N ; Pirastehfar, K ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Mechanized tunneling method using Tunnel Boring Machine (TBM) is being extensively employed in urban areas, especially when excavation takes place underneath the groundwater table. In this study, three-dimensional coupled Finite Element Analyses (FEA) have been performed to investigate the interaction mechanism between mechanized twin tunnels construction of Shiraz metro (line 2) and groundwater. Firstly, two soil constitutive models (Mohr-Coulomb and Modified Cam-Clay model) of Shiraz lean clay are validated against drained triaxial compression test data. Varying the permeability of the grout layer within the specified range, the base numerical model is then calibrated by the field data of...
A study on microstructural changes and mechanical properties in steel rods subjected to uniform and non-uniform cooling layout using a finite element analysis
, Article Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture ; Volume 222, Issue 12 , 2008 , Pages 1639-1649 ; 09544054 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
2008
Abstract
This paper presents a mathematical model for prediction of temperature history, final microstructures, and transformation kinetics in steel rods subjected to non-uniform cooling conditions. To achieve this goal, a mathematical model based on two-dimensional finite element method is developed to solve the governing heat conduction equation with non-uniform boundary conditions. The additivity rule is coupled with the finite element analysis to assess the kinetics of austenite decomposition during continuous cooling. The effect of decarburization during heating stage is also considered in the model employing Fick's second equation. To verify the predictions, time-temperature histories during...
Improvement of concentrated winding layouts for six-phase squirrel cage induction motors
, Article IEEE Transactions on Energy Conversion ; Volume 35, Issue 4 , 2020 , Pages 1727-1735 ; Tahami, F ; Capolino, G. A ; Vaschetto, S ; Nasiri Gheidari, Z ; Henao, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The fault-tolerant capability is a prerequisite for electrical safety-critical applications. In this regard, multi-phase induction motors are well-known actuators used to provide this feature. Compared to conventional three-phase machines with distributed windings, induction machines having concentrated windings could be more fault-tolerant because of increasing the number of phases. In addition, concentrated windings have shorter end-winding and less required copper weight which makes it a lower cost solution compared to distributed windings. However, concentrated windings adversely increase the distortion of the air gap flux density which affects motor performances. In this paper, a...
Time-dependent analysis of leaflets in mechanical aortic bileaflet heart valves in closing phase using the finite strip method
, Article Medical Engineering and Physics ; Volume 28, Issue 2 , 2006 , Pages 122-133 ; 13504533 (ISSN) ; Ahmadian, M. T ; Wan, W. K ; Sharif University of Technology
2006
Abstract
Background and aims of the study: Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this study the dynamic behaviour during the closing phase of a bileaflet MHV under normal physiological conditions has been investigated. Methods: Fluid analysis is based on the control volume with moving boundaries in the vicinity of the occluder. Unsteady continuity equation, unsteady momentum equation on the control volume and unsteady Bernoulli's equation have been used to...
The biomechanical response of the lower cervical spine post laminectomy: geometrically-parametric patient-specific finite element analyses
, Article Journal of Medical and Biological Engineering ; Volume 41, Issue 1 , 2021 , Pages 59-70 ; 16090985 (ISSN) ; Cheng, C. H ; Wang, J. L ; Niu, C. C ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Purpose: This study aimed to investigate the biomechanical impact of laminectomy on cervical intersegmental motion and load sharing using a parametric patient-specific finite element (FE) model towards providing clinicians with a viable quantitative tool for informed decision-making and improved surgical planning. Methods: Ten subject-specific nonlinear osteo-ligamentous cervical spine (C3–C7) FE models were developed using X-ray image-based algorithms. The models were used to evaluate the effect of laminectomy on lower cervical spine biomechanics for two-level (C3–C4) and three-level (C3–C5) laminectomy procedures. Results: The average cervical spine ranges of motion (ROM) for the pre-op...
A novel coupled musculoskeletal finite element model of the spine – Critical evaluation of trunk models in some tasks
, Article Journal of Biomechanics ; Volume 119 , 2021 ; 00219290 (ISSN) ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Spine musculoskeletal (MS) models make simplifying assumptions on the intervertebral joint degrees-of-freedom (rotational and/or translational), representation (spherical or beam-like joints), and properties (linear or nonlinear). They also generally neglect the realistic structure of the joints with disc nuclei/annuli, facets, and ligaments. We aim to develop a novel MS model where trunk muscles are incorporated into a detailed finite element (FE) model of the ligamentous T12-S1 spine thus constructing a gold standard coupled MS-FE model. Model predictions are compared under some tasks with those of our earlier spherical joints, beam joints, and hybrid (uncoupled) MS-FE models. The coupled...
A comprehensive approach for the validation of lumbar spine finite element models investigating post-fusion adjacent segment effects
, Article Journal of Biomechanics ; Volume 121 , 2021 ; 00219290 (ISSN) ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Spinal fusion surgery is usually followed by accelerated degenerative changes in the unfused segments above and below the treated segment(s), i.e., adjacent segment disease (ASD). While a number of risk factors for ASD have been suggested, its exact pathogenesis remains to be identified. Finite element (FE) models are indispensable tools to investigate mechanical effects of fusion surgeries on post-fusion changes in the adjacent segment kinematics and kinetics. Existing modeling studies validate only their intact FE model against in vitro data and subsequently simulate post-fusion in vivo conditions. The present study provides a novel approach for the comprehensive validation of a lumbar...
Novel force–displacement control passive finite element models of the spine to simulate intact and pathological conditions; comparisons with traditional passive and detailed musculoskeletal models
, Article Journal of Biomechanics ; Volume 141 , 2022 ; 00219290 (ISSN) ; Ebrahimkhani, M ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Passive finite element (FE) models of the spine are commonly used to simulate intact and various pre- and postoperative pathological conditions. Being devoid of muscles, these traditional models are driven by simplistic loading scenarios, e.g., a constant moment and compressive follower load (FL) that do not properly mimic the complex in vivo loading condition under muscle exertions. We aim to develop novel passive FE models that are driven by more realistic yet simple loading scenarios, i.e., in vivo vertebral rotations and pathological-condition dependent FLs (estimated based on detailed musculoskeletal finite element (MS-FE) models). In these novel force–displacement control FE models,...
Experimental investigation and finite element modelling of PMMA/carbon nanotube nanobiocomposites for bone cement applications
, Article Soft Matter ; Volume 18, Issue 36 , 2022 , Pages 6800-6811 ; 1744683X (ISSN) ; Khakbiz, M ; Chagami, M ; Bagheri, R ; Chashmi, F. S ; Akbari, B ; Shakibania, S ; Lee, K. B ; Sharif University of Technology
Royal Society of Chemistry
2022
Abstract
Multi-walled carbon nanotubes (MWCNTs) are one of the preferred candidates for reinforcing polymeric nanobiocomposites, such as acrylic bone type of cement. In this study, at first, bulk samples of the reinforced polymethylmethacrylate (PMMA) matrix were prepared with 0.1, 0.25, and 0.5 wt per wt% of MWCNTs by the casting method. Tensile and three-point bending tests were performed to determine the essential mechanical properties of bone cement, such as tensile and bending strengths. The tensile fracture surfaces were investigated by scanning electron microscopy (SEM). The commercial software (Abaqus) was used to conduct finite element analysis (FEA) by constructing a representative volume...
Relative performances of artificial neural network and regression mapping tools in evaluation of spinal loads and muscle forces during static lifting
, Article Journal of Biomechanics ; Volume 46, Issue 8 , 2013 , Pages 1454-1462 ; 00219290 (ISSN) ; Ekrami, O ; Shirazi Adl, A ; Plamondon, A ; Parnianpour, M ; Sharif University of Technology
2013
Abstract
Two artificial neural networks (ANNs) are constructed, trained, and tested to map inputs of a complex trunk finite element (FE) model to its outputs for spinal loads and muscle forces. Five input variables (thorax flexion angle, load magnitude, its anterior and lateral positions, load handling technique, i.e., one- or two-handed static lifting) and four model outputs (L4-L5 and L5-S1 disc compression and anterior-posterior shear forces) for spinal loads and 76 model outputs (forces in individual trunk muscles) are considered. Moreover, full quadratic regression equations mapping input-outputs of the model developed here for muscle forces and previously for spine loads are used to compare the...
Predictive equations for lumbar spine loads in load-dependent asymmetric one- and two-handed lifting activities
, Article Clinical Biomechanics ; Volume 27, Issue 6 , 2012 , Pages 537-544 ; 02680033 (ISSN) ; Plamondon, A ; Shirazi Adl, A ; Parnianpour, M ; Larivière, C ; Sharif University of Technology
2012
Abstract
Background: Asymmetric lifting activities are associated with low back pain. Methods: A finite element biomechanical model is used to estimate spinal loads during one- and two-handed asymmetric static lifting activities. Model input variables are thorax flexion angle, load magnitude as well as load sagittal and lateral positions while response variables are L4-L5 and L5-S1 disc compression and shear forces. A number of levels are considered for each input variable and all their possible combinations are introduced into the model. Robust yet user-friendly predictive equations that relate model responses to its inputs are established. Findings: Predictive equations with adequate...
Predictive equations to estimate spinal loads in symmetric lifting tasks
, Article Journal of Biomechanics ; Volume 44, Issue 1 , Jan , 2011 , Pages 84-91 ; 00219290 (ISSN) ; Plamondon, A ; Shirazi Adl, A ; Larivière, C ; Parnianpour, M ; Sharif University of Technology
2011
Abstract
Response surface methodology is used to establish robust and user-friendly predictive equations that relate responses of a complex detailed trunk finite element biomechanical model to its input variables during sagittal symmetric static lifting activities. Four input variables (thorax flexion angle, lumbar/pelvis ratio, load magnitude, and load position) and four model responses (L4-L5 and L5-S1 disc compression and anterior-posterior shear forces) are considered. Full factorial design of experiments accounting for all combinations of input levels is employed. Quadratic predictive equations for the spinal loads at the L4-S1 disc mid-heights are obtained by regression analysis with adequate...
Effect of intervertebral translational flexibilities on estimations of trunk muscle forces, kinematics, loads, and stability
, Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 18, Issue 16 , Sep , 2015 , Pages 1760-1767 ; 10255842 (ISSN) ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
Due to the complexity of the human spinal motion segments, the intervertebral joints are often simulated in the musculoskeletal trunk models as pivots thus allowing no translational degrees of freedom (DOFs). This work aims to investigate, for the first time, the effect of such widely used assumption on trunk muscle forces, spinal loads, kinematics, and stability during a number of static activities. To address this, the shear deformable beam elements used in our nonlinear finite element (OFE) musculoskeletal model of the trunk were either substantially stiffened in translational directions (SFE model) or replaced by hinge joints interconnected through rotational springs (HFE model). Results...
Dynamic analysis of laminated composite plates traversed by a moving mass based on a first-order theory
, Article Composite Structures ; Volume 92, Issue 8 , 2010 , Pages 1865-1876 ; 02638223 (ISSN) ; Asghari, M ; Sharif University of Technology
2010
Abstract
The dynamic response of angle-ply laminated composite plates traversed by a moving mass or a moving force is investigated. For this purpose, a finite element method based on the first-order shear deformation theory is used. Stationary and adaptive mesh techniques have been applied as two different meshing schemes. The adaptive mesh strategy is then used to avoid off-nodal position of moving mass. In this manner, the finite element mesh is continuously adapted to follow and comply with the path of moving mass. A Newmark direct integration method is employed to solve the equations of motion. Parametric study is directed to find out how different parameters like mass of the moving object as...