Displaying publications 21 - 40 of 141 in total

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  1. Azim Azahari, Zuhaila Ismail, Normazni Abdullah
    MATEMATIKA, 2018;34(1):87-102.
    MyJurnal
    Numerical simulation of the behaviour of blood flow through a stenosed bifurcated
    artery with the presence of single mild stenosis at parent artery is investigated. The
    flow analysis applies the incompressible, steady, three-dimensional Navier-Stokes equations
    for non-Newtonian generalized power law fluids. Behaviour of blood flow is simulated
    numerically using COMSOL Multiphysicsthat based on finite element method.The
    results showthe effect of severity of stenosis on flow characteristics such as axial velocity
    and its exhibit flow recirculation zone for analysis on streamlines pattern.
    Matched MeSH terms: Finite Element Analysis
  2. Ahmad S, Badshah S, Ul Haq I, Abdullah Malik S, Amjad M, Nasir Tamin M
    Materials (Basel), 2019 Oct 23;12(21).
    PMID: 31652687 DOI: 10.3390/ma12213463
    Wire ropes undergo a fretting fatigue condition when subjected to axial and bending loads. The fretting behavior of wires are classified as line contact and trellis point of contact. The experimental study on the fatigue of wire ropes indicates that most of the failure occurs due to high localized stresses at trellis point of contact. A continuum damage mechanics approach was previously proposed to estimate the fatigue life estimation of wire ropes. The approach majorly depends on the high value of localized stresses as well as the micro-slippage occurs at the contact region. Finite element approach has been used to study radial and axial distribution of stresses and displacement in order to clearly understand the evolution of stresses and existence of relative displacements between neighboring wires under various loading and frictional conditions. The relative movements of contacting wires are more when friction is not considered. In the presence of friction, the relative movement occurs at the boundaries of the contact region. The location of microslip in the presence of friction is backed by the experimental observation stating the crack is initiated at or the outer boundary of the contact spot. The existence of slip is due to different displacement of outer and central wires.
    Matched MeSH terms: Finite Element Analysis
  3. Yidris N, Isham NH, Gires E, Mutafi A
    Materials (Basel), 2020 Mar 21;13(6).
    PMID: 32245266 DOI: 10.3390/ma13061441
    The compressive behaviour of column members can be considerably affected by local buckling, material yielding and local end conditions. In this paper, the effects of the loading conditions at the ends of plain channel section columns subjected to uniformly compressed loading, and fixed conditions at the column ends with respect to global rotations, was examined. Finite element simulation was employed to look at the post-buckled response of thin-walled, plain channel section columns that covered the complete loading history of the compression columns from the onset of elastic local buckling through the nonlinear elastic and elastoplastic post-buckling phases of behaviour to final collapse and unloading. Two types of loading conditions were considered: the first was one that has been used practically in tests whereby one end is loaded with a moving top platen while the other end is fixed at the lower platen, but, for the second loading condition, both ends were loaded with equally moving top and lower platens. These two conditions were shown to lead to quite different characteristic interactive responses of the columns due to mode jumping in the buckling mode for the locally rotationally constrained case.
    Matched MeSH terms: Finite Element Analysis
  4. Yanliang Shang, Shouji Du, Biao Shao, Tongyin Han
    Sains Malaysiana, 2017;46:2091-2099.
    A large number of shallow buried tunnels are built in the city nowadays and the special strata such as large upper-soft and lower-hard ground often encountered. Deformation control of strata is the focus issue related to the construction safety. Based on Dalian metro Hing Street station with the classical geological condition of upper-soft and lower-hard ground, this paper fully used a combined control method including six different support measures to control the deformation of surrounding rock. 3D finite element model was setup to analyze the construction effect of combined control measures and the monitoring in-site was carried out to verify the deformation control effect of combined control method. It shows that the maximum surface subsidence value is gradually reduced with the support measures gradually increasing. In the case of various supports the maximum sedimentation value is 2.67 cm, which is 42. 1% lower than that of not using control method and the control effect is obvious. In addition, it can be seen that the two-layer initial support and additional large arch foot have the best effect on controlling the ground surface settlement with reduction of 11.7% and 20.2%, respectively. The research results can provide practical experience for the construction of such tunnels, and guide the design and construction of the tunnel in the future.
    Matched MeSH terms: Finite Element Analysis
  5. Rahimian Koloor SS, Karimzadeh A, Yidris N, Petrů M, Ayatollahi MR, Tamin MN
    Polymers (Basel), 2020 Jan 07;12(1).
    PMID: 31936184 DOI: 10.3390/polym12010157
    Composite structures are made of multidirectional (MD) fiber-reinforced polymer (FRP) composite laminates, which fail due to multiple damages in matrix, interface, and fiber constituents at different scales. The yield point of a unidirectional FRP composite is assumed as the lamina strength limit representing the damage initiation phenomena, while yielding of MD composites in structural applications are not quantified due to the complexity of the sequence of damage evolutions in different laminas dependent on their angle and specification. This paper proposes a new method to identify the yield point of MD composite structures based on the evolution of the damage dissipation energy (DDE). Such a characteristic evolution curve is computed using a validated finite element model with a mesoscale damage-based constitutive model that accounts for different matrix and fiber failure modes in angle lamina. The yield point of composite structures is identified to correspond to a 5% increase in the initial slope of the DDE evolution curve. The yield points of three antisymmetric MD FRP composite structures under flexural loading conditions are established based on Hashin unidirectional (UD) criteria and the energy-based criterion. It is shown that the new energy concept provides a significantly larger safe limit of yield for MD composite structures compared to UD criteria, in which the accumulation of energy dissipated due to all damage modes is less than 5% of the fracture energy required for the structural rupture.
    Matched MeSH terms: Finite Element Analysis
  6. Ahmad AF, Abbas Z, Obaiys SJ, Ibrahim N, Hashim M, Khaleel H
    PLoS One, 2015;10(10):e0140505.
    PMID: 26474301 DOI: 10.1371/journal.pone.0140505
    Bio-composites of oil palm empty fruit bunch (OPEFB) fibres and polycaprolactones (PCL) with a thickness of 1 mm were prepared and characterized. The composites produced from these materials are low in density, inexpensive, environmentally friendly, and possess good dielectric characteristics. The magnitudes of the reflection and transmission coefficients of OPEFB fibre-reinforced PCL composites with different percentages of filler were measured using a rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in the X-band frequency range. In contrast to the effective medium theory, which states that polymer-based composites with a high dielectric constant can be obtained by doping a filler with a high dielectric constant into a host material with a low dielectric constant, this paper demonstrates that the use of a low filler percentage (12.2%OPEFB) and a high matrix percentage (87.8%PCL) provides excellent results for the dielectric constant and loss factor, whereas 63.8% filler material with 36.2% host material results in lower values for both the dielectric constant and loss factor. The open-ended probe technique (OEC), connected with the Agilent vector network analyzer (VNA), is used to determine the dielectric properties of the materials under investigation. The comparative approach indicates that the mean relative error of FEM is smaller than that of NRW in terms of the corresponding S21 magnitude. The present calculation of the matrix/filler percentages endorses the exact amounts of substrate utilized in various physics applications.
    Matched MeSH terms: Finite Element Analysis*
  7. Ridzwan MIZ, Sukjamsri C, Pal B, van Arkel RJ, Bell A, Khanna M, et al.
    J Orthop Res, 2018 03;36(3):993-1001.
    PMID: 28762563 DOI: 10.1002/jor.23669
    Proximal femoral fractures can be categorized into two main types: Neck and intertrochanteric fractures accounting for 53% and 43% of all proximal femoral fractures, respectively. The possibility to predict the type of fracture a specific patient is predisposed to would allow drug and exercise therapies, hip protector design, and prophylactic surgery to be better targeted for this patient rendering fracture preventing strategies more effective. This study hypothesized that the type of fracture is closely related to the patient-specific femoral structure and predictable by finite element (FE) methods. Fourteen femora were DXA scanned, CT scanned, and mechanically tested to fracture. FE-predicted fracture patterns were compared to experimentally observed fracture patterns. Measurements of strain patterns to explain neck and intertrochanteric fracture patterns were performed using a digital volume correlation (DVC) technique and compared to FE-predicted strains and experimentally observed fracture patterns. Although loaded identically, the femora exhibited different fracture types (six neck and eight intertrochanteric fractures). CT-based FE models matched the experimental observations well (86%) demonstrating that the fracture type can be predicted. DVC-measured and FE-predicted strains showed obvious consistency. Neither DXA-based BMD nor any morphologic characteristics such as neck diameter, femoral neck length, or neck shaft angle were associated with fracture type. In conclusion, patient-specific femoral structure correlates with fracture type and FE analyses were able to predict these fracture types. Also, the demonstration of FE and DVC as metrics of the strains in bones may be of substantial clinical value, informing treatment strategies and device selection and design. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:993-1001, 2018.
    Matched MeSH terms: Finite Element Analysis*
  8. Jahanshahi P, Ghomeishi M, Adikan FR
    ScientificWorldJournal, 2014;2014:503749.
    PMID: 24616635 DOI: 10.1155/2014/503749
    The most common permittivity function models are compared and identifying the best model for further studies is desired. For this study, simulations using several different models and an analytical analysis on a practical surface Plasmon structure were done with an accuracy of ∼ 94.4% with respect to experimental data. Finite element method, combined with dielectric properties extracted from the Brendel-Bormann function model, was utilized, the latter being chosen from a comparative study on four available models.
    Matched MeSH terms: Finite Element Analysis
  9. Modi R, Kohli S, Rajeshwari K, Bhatia S
    Eur J Dent, 2015 6 4;9(2):255-261.
    PMID: 26038660 DOI: 10.4103/1305-7456.156847
    OBJECTIVE: The aim of the study is to evaluate the stress distribution in tooth supported 5-unit fixed partial denture (FPD) having tooth as pier abutment using rigid and nonrigid connectors respectively, under simultaneous and progressive loading.

    MATERIAL AND METHODS: The three-dimensional (3D) finite element program (ANSYS software) was used to construct the mathematical model. Two 5-unit FPD'S were simulated, one with rigid connector and another one with nonrigid connector. For analysis, each of these models were subjected to axial and oblique forces under progressive loading (180, 180, 120, 120, 80 N force on first and second molars, premolars and canine respectively) and simultaneous loading (100, 100, 100, 100, 100 N force on first and second molars, premolars and canine respectively).

    RESULTS: The rigid and nonrigid connector design have effect on stress distribution in 5-unit FPDs with pier abutments.

    CONCLUSION: Oblique forces produce more stresses than vertical forces. Nonrigid connector resulted in decrease in stress at the level of prosthesis and increase in stress at the level of alveolar crest.

    Matched MeSH terms: Finite Element Analysis
  10. Ahad Javanmardi, Zainab Ibrahim, Khaled Gheadi, Mohammed Jameel, Usman Hanif, Gordan, Meisam
    Scientific Research Journal, 2018;15(1):1-14.
    MyJurnal
    Nowadays, development of cable-stayed bridges is increasing around the world. The mitigation of seismic forces to these bridges are obligatory to prevent damages or failure of its structural members. Herein, this paper aimed to determine the near-fault ground motion effect on an existing cablestayed bridge equipped with lead-rubber bearing. In this context, Shipshaw cable-stayed bridge is selected as the case study. The selected bridge has a span of 183.2 m composite deck and 43 m height of steel tower. 2D finite element models of the non-isolated and base isolated bridges are modelled by using SAP2000. Three different near-fault ground motions which are Tabas 1978, Cape Mendocino 1992 and Kobe 1995 were subjected to the 2D FEM models in order to determine the seismic behaviour of the bridge. The near-fault ground motions were applied to the bridge in the longitudinal direction. Nonlinear dynamic analysis was performed to determine the dynamic responses of the bridge. Comparison of dynamic response of nonisolated and base isolated bridge under three different near-fault ground motions were conducted. The results obtained from numerical analyses of the bridge showed that the isolation system lengthened the period of bridge and minimised deck displacement, base shear and base moment of the bridge. It is concluded that the isolation system significantly reduced the destructive effects of near-fault ground motions on the bridge.
    Matched MeSH terms: Finite Element Analysis
  11. Kashyzadeh KR, Rahimian Koloor SS, Omidi Bidgoli M, Petrů M, Amiri Asfarjani A
    Polymers (Basel), 2021 Feb 03;13(4).
    PMID: 33546387 DOI: 10.3390/polym13040483
    The main purpose of this research is to design a high-fatigue performance hoop wrapped compressed natural gas (CNG) composite cylinder. To this end, an optimization algorithm was presented as a combination of finite element simulation (FES) and response surface analysis (RSA). The geometrical model was prepared as a variable wall-thickness following the experimental measurements. Next, transient dynamic analysis was performed subjected to the refueling process, including the minimum and maximum internal pressures of 20 and 200 bar, respectively. The time histories of stress tensor components were extracted in the critical region. Furthermore, RSA was utilized to investigate the interaction effects of various polymer composite shell manufacturing process parameters (thickness and fiber angle) on the fatigue life of polymer composite CNG pressure tank (type-4). In the optimization procedure, four parameters including wall-thickness of the composite shell in three different sections of the CNG tank and fiber angle were considered as input variables. In addition, the maximum principal stress of the component was considered as the objective function. Eventually, the fatigue life of the polymer composite tank was calculated using stress-based failure criterion. The results indicated that the proposed new design (applying optimal parameters) leads to improve the fatigue life of the polymer composite tank with polyethylene liner about 2.4 times in comparison with the initial design.
    Matched MeSH terms: Finite Element Analysis
  12. Tan PS, Akhavan Farid A, Karimzadeh A, Rahimian Koloor SS, Petrů M
    Materials (Basel), 2020 Sep 21;13(18).
    PMID: 32967330 DOI: 10.3390/ma13184199
    The curvature correction factor is an important parameter in the stress calculation formulation of a helical extension spring, which describes the effect of spring wire curvature on the stress increase towards its inner radius. In this study, the parameters affecting the curvature correction factor were investigated through theoretical and numerical methods. Several finite element (FE) models of an extension spring were generated to obtain the distribution of the tensile stress in the spring. In this investigation, the hook orientation and the number of coils of the extension spring showed significant effects on the curvature correction factor. These parameters were not considered in the theoretical model for the calculation of the curvature correction factor, causing a deviation between the results of the FE model and the theoretical approach. A set of equations is proposed for the curvature correction factor, which relates both the spring index and the number of coils. These equations can be applied directly to the design of extension springs with a higher safety factor.
    Matched MeSH terms: Finite Element Analysis
  13. Norliza Mohd. Zain, Zuhaila Ismail
    MATEMATIKA, 2019;35(2):213-227.
    MyJurnal
    Blood flow through a bifurcated artery with the presence of an overlapping stenosis located at parent’s arterial lumen under the action of a uniform external magnetic field is studied in this paper. Blood is treated as an electrically conducting fluid which exhibits the Magnetohydrodynamics principle and it is characterized by a Newtonian fluid model. The governing equations are discretized using a stabilization technique of finite element known as Galerkin least-squares. The maximum velocity and pressure drop evaluated in this present study are compared with the results found in previous literature and COMSOL Multiphysics. The solutions found in a satisfactory agreement, thus verify the source code is working properly. The effects of dimensionless parameters of Hartmann and Reynolds numbers in the fluid’s velocity and pressure are examined in details with further scientific discussions.
    Matched MeSH terms: Finite Element Analysis
  14. Rahmandoust M, Ochsner A
    J Nanosci Nanotechnol, 2012 Oct;12(10):8129-36.
    PMID: 23421189
    In this study, Single-Walled and Multi-Walled Carbon Nanotubes in their perfect forms were investigated by the Finite Element Method. Details on the modeling of the structure are provided in this paper, including the appropriate elements, the element properties that should be defined based on the atomic structure of Carbon Nanotubes and the corresponding chemical bonds. Non-covalent van der Waals interactions between two neighbor atoms as well as the required approximations for the modeling of the structures with this kind of interaction are also presented. Specific attention was dedicated to the necessity of using some time- and energy-consuming steps in the simulation process. First, the effect of simulating only a single ring of the whole structure is studied to find out if it would represent the same mechanical behavior as the long structure. Results show that by applying an appropriate set of boundary conditions, the stiffness of the shortened structure is practically equal to the long perfect structure. Furthermore, Multi-Walled Carbon Nanotube structures with and without defining the van der Waals force are studied. Based on the observations, applying the van der Waals force does not significantly influence the obtained Young's modulus of the structure in the case of a uniaxial tensile test.
    Matched MeSH terms: Finite Element Analysis
  15. Ahmad A, Lajis MA, Shamsudin S, Yusuf NK
    Materials (Basel), 2018 Jun 06;11(6).
    PMID: 29882752 DOI: 10.3390/ma11060958
    Melting aluminium waste to produce a secondary bulk material is such an energy-intensive recycling technique that it also indirectly threatens the environment. Hot press forging is introduced as an alternative. Mixing the waste with another substance is a proven practice that enhances the material integrity. To cope with the technology revolution, a finite element is utilised to predict the behaviour without a practical trial. Utilising commercial software, DEFORM 3D, the conjectures were demonstrated scientifically. The flow stress of the material was modified to suit the material used in the actual experiment. It is acknowledged that the stress⁻strain had gradually increased in each step. Due to the confined forming space, the temperature decreased by ~0.5% because the heat could not simply vacate the area. A reduction of ~10% of the flesh observed in the simulation is roughly the same as in the actual experiment. Above all, the simulation abides by the standards and follows what has been done previously. Through the finite element utilisation, this study forecasted the performance of the recycled composite. The results presented may facilitate improvement of the recycling issue and conserve the environment for a better future.
    Matched MeSH terms: Finite Element Analysis
  16. Mohamed Ibrahim J. Ibrahim, Mohd Zuhri Mohamed Yusoff
    MyJurnal
    This study presents an investigation about the effect of size variation on mechanical
    performance of square core interlocking structures, by using finite element analysis
    (FEA). The material used in this study is flax fibre reinforced polypropylene (PP)
    composite. Abaqus software was used for modelling and visualizing number of six
    interlocking honeycomb structures with different cell sizes and heights. In the first
    analysis, Abaqus/standard was performed on the perfect models by applying quasistatic
    loading to identify the imperfection shape and obtaining the buckling Eigenmodes
    for the models, then the Eigen-modes from abaqus/standard were imported
    to abaqus/explicit to run post-buckling analysis and simulate the overall imperfection
    behaviour of models. The numerical results from the finite element analysis
    simulation were used to plot load-displacement curve to each model. The area under
    the load-displacement curve represents the total absorbed energy, energy absorption
    per unit mass indicates the specific energy absorption, and the highest value of
    specific energy absorption represents the optimum size. The findings demonstrated
    that the square interlocking structure exhibits good energy absorption performance
    in some geometrical cases, and also revealed that the natural fibre composites have
    unique energy absorption capability under quasi-static loads.
    Matched MeSH terms: Finite Element Analysis
  17. Leman, A.M., Fakhrurrazi Rahman, Dafit Feriyanto
    MyJurnal
    The simulation of the catalytic converter system is quite needed in order to characterize the catalyst and also
    optimizing the monolithic design for the gas emission in the catalytic converter and other related mechanism. The
    objective of this study is to obtain quantitative description of the gas emission in the catalytic converter system of
    natural powered automobile exhaust gas using ANSYS Software. This work will present a finite element calculation
    to predict and evaluate the mass transfer, energy balance and velocity of gas emission in the catalytic converter. The
    expected result for this research is to evaluate data of the gas emission obtained from the software to be compared with
    the manual experiment in order to verify the effectiveness of modified catalytic converter.
    Matched MeSH terms: Finite Element Analysis
  18. Rini Asnida Abdullah, Takashi Tsutsumi
    Sains Malaysiana, 2018;47:683-689.
    The tensile strength of intact rock materials has been determined by indirect method more frequent than the direct method.
    The most commonly used indirect method is Brazilian test. Stress and deformability undergo during the test reflected by
    geometry shape of the samples with respect to the different diameter ratio. This study focuses on influence of geometry
    shape in solid and ring disk with different diameter ratio on the stress distribution and deformations within sandstone
    subjected to indirect tensile loading by Brazilian test. Then, the finite element method in RS2 software was utilised to
    simulate and gain in depth understanding the behaviour of Brazilian test. The analysis shown that the maximum tensile
    strength in a ring disk with diameter ratio of 0.1 is three times higher than in solid disk. Meanwhile, as the diameter
    ratio of ring disk increases, it produces lower tensile strength. The numerical simulation also has successfully illustrated
    the shear failure which observed near the loading platen of solid disk during Brazilian test. The finite element analysis
    utilised in this research has successfully enables the stress distribution and deformation behaviour of the rock under
    tension to be studied closely
    Matched MeSH terms: Finite Element Analysis
  19. Harith H, Schmutz B, Malekani J, Schuetz MA, Yarlagadda PK
    Med Eng Phys, 2016 Mar;38(3):280-5.
    PMID: 26739124 DOI: 10.1016/j.medengphy.2015.11.012
    Anatomically precontoured plates are commonly used to treat periarticular fractures. A well-fitting plate can be used as a tool for anatomical reduction of the fractured bone. Recent studies highlighted that some plates fit poorly for many patients due to considerable shape variations between bones of the same anatomical site. While it is impossible to design one shape that fits all, it is also burdensome for the manufacturers and hospitals to produce, store and manage multiple plate shapes without the certainty of utilization by a patient population. In this study, we investigated the number of shapes required for maximum fit within a given dataset, and if they could be obtained by manually deforming the original plate. A distal medial tibial plate was automatically positioned on 45 individual tibiae, and the optimal deformation was determined iteratively using finite element analysis simulation. Within the studied dataset, we found that: (i) 89% fit could be achieved with four shapes, (ii) 100% fit was impossible through mechanical deformation, and (iii) the deformations required to obtain the four plate shapes were safe for the stainless steel plate for further clinical use. The proposed framework is easily transferable to other orthopaedic plates.
    Matched MeSH terms: Finite Element Analysis
  20. Lim WTH, Ooi EH, Foo JJ, Ng KH, Wong JHD, Leong SS
    Ultrasonics, 2023 Aug;133:107046.
    PMID: 37247461 DOI: 10.1016/j.ultras.2023.107046
    The application of ultrasound shear wave elastography for detecting chronic kidney disease, namely renal fibrosis, has been widely studied. A good correlation between tissue Young's modulus and the degree of renal impairment has been established. However, the current limitation of this imaging modality pertains to the linear elastic assumption used in quantifying the stiffness of renal tissue in commercial shear wave elastography systems. As such, when underlying medical conditions such as acquired cystic kidney disease, which may potentially influence the viscous component of renal tissue, is present concurrently with renal fibrosis, the accuracy of the imaging modality in detecting chronic kidney disease may be affected. The findings in this study demonstrate that quantifying the stiffness of linear viscoelastic tissue using an approach similar to those implemented in commercial shear wave elastography systems led to percentage errors as high as 87%. The findings presented indicate that use of shear viscosity to detect changes in renal impairment led to a reduction in percentage error to values as low as 0.3%. For cases in which renal tissue was affected by multiple medical conditions, shear viscosity was found to be a good indicator in gauging the reliability of the Young's modulus (quantified through a shear wave dispersion analysis) in detecting chronic kidney disease. The findings show that percentage error in stiffness quantification can be reduced to as low as 0.6%. The present study demonstrates the potential use of renal shear viscosity as a biomarker to improve the detection of chronic kidney disease.
    Matched MeSH terms: Finite Element Analysis
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