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Anticipating local flaps closed-form solution on 3D face models using finite element method

Kwan Z, Khairu Najhan NN, Yau YH, Luximon Y, M Nor F

Int J Numer Method Biomed Eng, 2020 11;36(11):e3390.
PMID: 32735083 DOI: 10.1002/cnm.3390

A realistic three-dimensional (3D) computational model of skin flap closures using Asian-like head templates from two different genders, male and female, has been developed. The current study aimed to understand the biomechanics of the local flap designs along with the effect of wound closures on the respective genders. Two Asian head templates from opposite genders were obtained to use as base models. A third-order Yeoh hyperelastic model was adapted to characterize as skin material properties. A single layer composed of combined epidermis and dermis was considered, and the models were thickened according to respective anatomical positions. Each model gender was excised with a fixed defect size which was consequently covered by three different local flap designs, namely advancement, rotation, and rhomboid flaps. Post-operative simulation presented various scenarios of skin flap closures. Rotation and rhomboid flaps demonstrated maximal tension at the apex of the flap for both genders as well as advancement flap in the female face model. However, advancement flap closure in the male face model was presented otherwise. Yet, the deformation patterns and the peak tension of the discussed flaps were consistent with conventional local flap surgery. Moreover, male face models generated higher stresses compared to the female face models with a 70.34% mean difference. Overall, the skin flap operations were executed manually, and the designed surgery model met the objectives successfully while acknowledging the study limitations. NOVELTY FILE: 3D head templates were considered to address the gap as 3D face models were uncommonly employed in understanding the biomechanics of the local flaps realistically. Most of the existing studies focus on the 2D and 3D planar geometry in their models. As gender comparison has yet to be addressed, we intended to fill this gap by exploring the stress contours of the local flap designs in different genders. Create a 3D face model from two opposite genders which is capable of simulating closure of wounds using local flaps with a focus on advancement, rotation, and rhomboid flaps.

Matched MeSH terms: Finite Element Analysis
Selection of suitable pedicle screw for degenerated cortical and cancellous bone of human lumbar spine: A finite element study

Jain P, Sing Ngie DC, Lim SF, Lim BH

Int J Artif Organs, 2020 Oct 13.
PMID: 33045876 DOI: 10.1177/0391398820964483

Pedicular arthrodesis is the traditional procedure in terms of increase in the biomechanical stability with higher fixation rate. The current work aims to identify the effect of three spinal pedicle screws considering cortical and cancellous degeneracy condition. Lumbar section L2-L3 is utilized and various load and moment conditions were applied to depict the various biomechanical parameters for selection of suitable screw. Three dimensional model is considered in finite element analysis to identify the various responses of pedicle screw at bone screw juncture. Computed tomography (CT) images of a healthy male were considered to generate the finite element vertebral model. Generated intact model was further utilized to develop the other implanted models of degenerated cortical and cancellous bone models. The three fused instrumented models with different cortical and cancellous degeneracy conditions were analyzed in finite element analysis. The results were obtained as stress pattern at bone screw boundary and intervertebral disc stress. FE simulated results represents significant changes in the von Mises stress due to various load and moment conditions on degenerated bones during different body movement conditions. Results have shown that among all pedicle screws, the 6.0 mm diameter screw reflects very less stress values at the juncture. Multiple results on biomechanical aspects obtained during the FE study can be considered to design a new stabilization device and may be helpful to plan surgery of critical sections.

Matched MeSH terms: Finite Element Analysis
Fulltext Shear Response of Glass Fibre Reinforced Polymer (GFRP) Built-Up Hollow and Lightweight Concrete Filled Beams: An Experimental and Numerical Study

Kong SY, Wong LS, Paul SC, Miah MJ

Polymers (Basel), 2020 Oct 02;12(10).
PMID: 33023168 DOI: 10.3390/polym12102270

This paper investigated the static behaviour of glass fibre reinforced polymer (GFRP) built-up hollow and concrete filled built-up beams tested under four-point bending with a span-to-depth ratio of 1.67, therefore focusing their shear performance. Two parameters considered for hollow sections were longitudinal web stiffener and strengthening at the web-flange junction. The experimental results indicated that the GFRP hollow beams failed by web crushing at supports; therefore, the longitudinal web stiffener has an insignificant effect on improving the maximum load. Strengthening web-flange junctions using rectangular hollow sections increased the maximum load by 47%. Concrete infill could effectively prevent the web crushing, and it demonstrated the highest load increment of 162%. The concrete filled GFRP composite beam failed by diagonal tension in the lightweight concrete core. The finite element models adopting Hashin damage criteria yielded are in good agreement with the experimental results in terms of maximum load and failure mode. Based on the numerical study, the longitudinal web stiffener could prevent the web buckling of the slender GFRP beam and improved the maximum load by 136%. The maximum load may be further improved by increasing the thickness of the GFRP section and the size of rectangular hollow sections used for strengthening. It was found that the bond-slip at the concrete-GFRP interface affected the shear resistance of concrete-GFRP composite beam.

Matched MeSH terms: Finite Element Analysis
Fulltext Investigation on the Curvature Correction Factor of Extension Spring

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
Fulltext A novel design, analysis and 3D printing of Ti-6Al-4V alloy bio-inspired porous femoral stem

Mehboob H, Tarlochan F, Mehboob A, Chang SH, Ramesh S, Harun WSW, et al.

J Mater Sci Mater Med, 2020 Aug 20;31(9):78.
PMID: 32816091 DOI: 10.1007/s10856-020-06420-7

The current study is proposing a design envelope for porous Ti-6Al-4V alloy femoral stems to survive under fatigue loads. Numerical computational analysis of these stems with a body-centered-cube (BCC) structure is conducted in ABAQUS. Femoral stems without shell and with various outer dense shell thicknesses (0.5, 1.0, 1.5, and 2 mm) and inner cores (porosities of 90, 77, 63, 47, 30, and 18%) are analyzed. A design space (envelope) is derived by using stem stiffnesses close to that of the femur bone, maximum fatigue stresses of 0.3σys in the porous part, and endurance limits of the dense part of the stems. The Soderberg approach is successfully employed to compute the factor of safety Nf > 1.1. Fully porous stems without dense shells are concluded to fail under fatigue load. It is thus safe to use the porous stems with a shell thickness of 1.5 and 2 mm for all porosities (18-90%), 1 mm shell with 18 and 30% porosities, and 0.5 mm shell with 18% porosity. The reduction in stress shielding was achieved by 28%. Porous stems incorporated BCC structures with dense shells and beads were successfully printed.

Matched MeSH terms: Finite Element Analysis
Stress Distributions and Micromovement of Fragment Bone of Pilon Fracture Treated With External Fixator: A Finite Element Analysis

Ramlee MH, Gan HS, Daud SA, Abdul Wahab A, Abdul Kadir MR

J Foot Ankle Surg, 2020 7 1;59(4):664-672.
PMID: 32600559 DOI: 10.1053/j.jfas.2019.09.006

Osteoporosis and osteoarthritis are common pathological problems of the human bone tissue. There are some cases of pilon fractures associated with these 2 pathological conditions. In terms of treatment, for a normal and healthy bone with pilon fracture, the use of the Delta external fixator is a favorable option because it can allow early mobilization for patients and provide stability for the healing process. However, the stability of the external fixator differs when there is low bone stiffness, which has not been previously investigated. Therefore, this study was conducted to determine the stability of the external fixator to treat pilon fracture associated with osteoporosis and osteoarthritis, particularly to differentiate the stress distribution and micromovement of fracture fragment. Three-dimensional finite element models of the ankle and foot bones were reconstructed based on the computed tomography datasets. The bones consisted of 5 metatarsal, 3 cuneiform, and 1 each of cuboid, navicular, calcaneus, talus, fibula, and tibia bones. They were assigned with linear isotropic behavior. The ankle joint consisted of ligament and cartilage, and they were assigned with the use of linear links and the Mooney-Rivlin model, respectively. During simulation of the gait cycle, 70 N and 350 N were applied axially to the tibia bone to represent the swing and stance phases, respectively. The metatarsal and calcaneus bones were fixed to prevent any movement of the rigid body. The study found that the greatest von Mises stress value was observed at the pin-bone interface for the osteoporosis (108 MPa) model, followed by the osteoarthritis (87 MPa) and normal (44 MPa) models, during the stance phase. For micromovement, the osteoporosis model had the largest value at 0.26 mm, followed by the osteoarthritis (0.09 mm) and normal (0.03 mm) models. In conclusion, the greatest magnitudes of stress and micromovement were observed for the osteoporosis bone and extra care should be taken to treat pilon fracture associated with this pathological condition.

Matched MeSH terms: Finite Element Analysis
Numerical Three-dimensional Finite Element Modeling of Cavity Shape and Optimal Material Selection by Analysis of Stress Distribution on Class V Cavities of Mandibular Premolars

Pai S, Bhat V, Patil V, Naik N, Awasthi S, Nayak N

J Int Soc Prev Community Dent, 2020 06 15;10(3):279-285.
PMID: 32802773 DOI: 10.4103/jispcd.JISPCD_75_20

Aim: Adhesive restoration does not depend primarily on the configuration of the shape of the cavity. Under varying loading conditions, it is essential to know the stress concentration and load transfer mechanism for distinct cavity shapes. The aim of this study was to evaluate and compare the biomechanical characteristics of various cavity shapes, namely oval, elliptical, trapezoidal, and rectangular shapes of class V cavities on mandibular premolars restored with amalgam, glass ionomer cement, and Cention N using three-dimensional (3D) finite element analysis.
Materials and Methods: A 3D prototype of a mandibular premolar was generated by Digital Imaging and Communications in Medicine (DICOM) images obtained from the cone beam computed tomography and imported to 3D modeling software tool, SpaceClaim. The four distinct load magnitudes of 100, 150, 200, and 250N were applied as a pressure load perpendicular to the lingual plane of the lingual cusp of the occlusal surface (normal load) and at 45° to same (oblique load). The stress distribution patterns and the maximum von Mises stresses were analyzed and compared.
Results: The occlusal stresses were distributed from the force loading point in an approximate actinomorphic pattern, and when the force load was close to the margin, the stress was much greater.
Conclusion: Ovoid cavity showed lesser stress concentration and deformation for each of the tested restorative material.

Matched MeSH terms: Finite Element Analysis
In silico study of glenoid perforation during total shoulder arthroplasty: the effects on stress & micromotion

Wahab AHA, Saad APM, Syahrom A, Kadir MRA

Comput Methods Biomech Biomed Engin, 2020 Apr;23(5):182-190.
PMID: 31910663 DOI: 10.1080/10255842.2019.1709828

Glenoid perforation is not the intended consequence of the surgery and must be avoided. The analysis on biomechanical aspect of glenoid vault perforation remains unknown. The purpose of this study is to determine the impact of glenoid perforation towards stress distribution and micromotion at the interfaces. Eight glenoid implant models had been constructed with various size, number and type of fixation. A load of 750 N was applied to centre, superior-anterior and superior-posterior area. Implant perforation had minimal impact on stress distribution and micromotion at the interfaces. However, cement survival rate for implant without perforation was the highest with a difference of up to 37% compared to other perforated models. Besides that, implant fixation and high stresses at the implant had more of an impact on implant instability than implant perforation. As a conclusion, glenoid perforation did not influence the stress distribution and micromotion, but, it reduced cement survival rate and increase the stress critical volume.

Matched MeSH terms: Finite Element Analysis
Fulltext The Effects of Loading Conditions on the Behaviour of Fixed-Ended Plain Channel Columns

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
Analytical and computational sliding wear prediction in a novel knee implant: a case study

Hussin MS, Fernandez J, Ramezani M, Kumar P, Kelly PA

Comput Methods Biomech Biomed Engin, 2020 Mar;23(4):143-154.
PMID: 31928215 DOI: 10.1080/10255842.2019.1709118

Osteoarthritis (OA) is a commonly occurring cartilage degenerative disease. The end stage treatment is Total Knee Arthroplasty (TKA), which can be costly in terms of initial surgery, but also in terms of revision knee arthroplasty, which is quite often required. A novel conceptual knee implant has been proposed to function as a reducer of stress across the joint surface, to extend the period of time before TKA becomes necessary. The objective of this paper is to develop a computational model which can be used to assess the wear arising at the implant articulating surfaces. Experimental wear coefficients were determined from physical testing, the results of which were verified using a semi-analytical model. Experimental results were incorporated into an anatomically correct computational model of the knee and implant. The wear-rate predicted for the implant was 27.74 mm3 per million cycles (MC) and the wear depth predicted was 1.085 mm/MC. Whereas the wear-rate is comparable to that seen in conventional knee implants, the wear depth is significantly higher than for conventional knee prostheses, and indicates that, in order to be viable, wear-rates should be reduced in some way, perhaps by using low-wear polymers.

Matched MeSH terms: Finite Element Analysis
Effect of different implant configurations on biomechanical behavior of full-arch implant-supported mandibular monolithic zirconia fixed prostheses

Zhong J, Guazzato M, Chen J, Zhang Z, Sun G, Huo X, et al.

J Mech Behav Biomed Mater, 2020 02;102:103490.
PMID: 31877512 DOI: 10.1016/j.jmbbm.2019.103490

Mechanical failure of zirconia-based full-arch implant-supported fixed dental prostheses (FAFDPs) remains a critical issue in prosthetic dentistry. The option of full-arch implant treatment and the biomechanical behaviour within a sophisticated screw-retained prosthetic structure have stimulated considerable interest in fundamental and clinical research. This study aimed to analyse the biomechanical responses of zirconia-based FAFDPs with different implant configurations (numbers and distributions), thereby predicting the possible failure sites and the optimum configuration from biomechanical aspect by using finite element method (FEM). Five 3D finite element (FE) models were constructed with patient-specific heterogeneous material properties of mandibular bone. The results were reported using volume-averaged von-Mises stresses (σVMVA) to eliminate numerical singularities. It was found that wider placement of multi-unit copings was preferred as it reduces the cantilever effect on denture. Within the limited areas of implant insertion, the adoption of angled multi-unit abutments allowed the insertion of oblique implants in the bone and wider distribution of the multi-unit copings in the prosthesis, leading to lower stress concentration on both mandibular bone and prosthetic components. Increasing the number of supporting implants in a FAFDPs reduced loading on each implant, although it may not necessarily reduce the stress concentration in the most posterior locations significantly. Overall, the 6-implant configuration was a preferable configuration as it provided the most balanced mechanical performance in this patient-specific case.

Matched MeSH terms: Finite Element Analysis
Shape-shifting thermal coagulation zone during saline-infused radiofrequency ablation: A computational study on the effects of different infusion location

Kho ASK, Foo JJ, Ooi ET, Ooi EH

Comput Methods Programs Biomed, 2020 Feb;184:105289.
PMID: 31891903 DOI: 10.1016/j.cmpb.2019.105289

BACKGROUND AND OBJECTIVE: The majority of the studies on radiofrequency ablation (RFA) have focused on enlarging the size of the coagulation zone. An aspect that is crucial but often overlooked is the shape of the coagulation zone. The shape is crucial because the majority of tumours are irregularly-shaped. In this paper, the ability to manipulate the shape of the coagulation zone following saline-infused RFA by altering the location of saline infusion is explored.
METHODS: A 3D model of the liver tissue was developed. Saline infusion was described using the dual porosity model, while RFA was described using the electrostatic and bioheat transfer equations. Three infusion locations were investigated, namely at the proximal end, the middle and the distal end of the electrode. Investigations were carried out numerically using the finite element method.
RESULTS: Results indicated that greater thermal coagulation was found in the region of tissue occupied by the saline bolus. Infusion at the middle of the electrode led to the largest coagulation volume followed by infusion at the proximal and distal ends. It was also found that the ability to delay roll-off, as commonly associated with saline-infused RFA, was true only for the case when infusion is carried out at the middle. When infused at the proximal and distal ends, the occurrence of roll-off was advanced. This may be due to the rapid and more intense heating experienced by the tissue when infusion is carried out at the electrode ends where Joule heating is dominant.
CONCLUSION: Altering the location of saline infusion can influence the shape of the coagulation zone following saline-infused RFA. The ability to 'shift' the coagulation zone to a desired location opens up great opportunities for the development of more precise saline-infused RFA treatment that targets specific regions within the tissue.

Matched MeSH terms: Finite Element Analysis
Fulltext An Energy-Based Concept for Yielding of Multidirectional FRP Composite Structures Using a Mesoscale Lamina Damage Model

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
Fulltext Extraction of winding parameters for 33/11 kV, 30 MVA transformer based on finite element method for frequency response modelling

Srikanta Murthy A, Azis N, Jasni J, Othman ML, Mohd Yousof MF, Talib MA

PLoS One, 2020;15(8):e0236409.
PMID: 32853253 DOI: 10.1371/journal.pone.0236409

This paper proposes an alternative approach to extract transformer's winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.

Matched MeSH terms: Finite Element Analysis*
Fulltext Finite element modelling and simulation for lower limb of human bone: a review

Muhammad Hanif Ramlee

Malaysian Journal of Medicine and Health Sciences, 2020;16(3):262-271.
MyJurnal

Most orthopaedic cases that involved with bone fracture are normally treated with medical implants. To be noticed that some precautions in terms of biomechanical and biomaterial properties are necessary for a successful post-sur- gery process. The biomechanical evaluation of implants could be carried out using computing and engineering technologies. However, in the computer simulation, some assumptions are needed as the limitations on computer resources and data input. This review focuses on the current method of developing the finite element model for patients with specific values of material properties for lower limb part such as hip, knee and ankle joint. Previous literature was reviewed from which keywords and search engines were identified. In this review, inclusion and exclusion criteria were used to limit the literature search. We reviewed the state-of-the-art in this area and provide recommendations for future research. In conclusion, the previous published reports illustrated different methods to develop numerical models.

Matched MeSH terms: Finite Element Analysis
Fulltext Thermal profiling Analysis for Asymmetrically Embedded Tumour with Different Breast Densities

Laila Fadhillah Ulta Delestri, Kenshiro Ito, Gan Hong Seng, Muhammad Faiz Md Shakhih, Asnida Abdul Wahab

Malaysian Journal of Medicine and Health Sciences, 2020;16(108):6-12.
MyJurnal

Introduction: Detecting breast cancer at earlier stage is crucial to increase the survival rate. Mammography as the golden screening tool has shown to be less effective for younger women due to denser breast tissue. Infrared Ther- mography has been touted as an adjunct modality to mammography. Further investigation of thermal distribution in breast cancer patient is important prior to its clinical interpretation. Therefore, thermal profiling using 3D compu- tational simulation was carried out to understand the effect of changes in size and location of tumour embedded in breast to the surface temperature distribution at different breast densities. Methods: Extremely dense (ED) and pre- dominantly fatty dense (PF) breast models were developed and simulated using finite element analysis (FEA). Pennes’ bioheat equation was adapted to show the heat transfer mechanism by providing appropriate thermophysical prop- erties in each tissue layer. 20 case studies with various tumour size embedded at two asymmetrical positions in the breast models were analysed. Quantitative and qualitative analyses were performed by recording the temperature values along the arc of breast, calculating of temperature difference at the peaks and comparing multiple thermal images. Results: Bigger size of tumour demands a larger increase in breast surface temperatures. As tumour is located far from the centre of the breast or near to the edge, there was a greater shift of temperature peak. Conclusion: Size and location of tumour in various levels of breast density should be considered as a notable factor to thermal profile on breast when using thermography for early breast cancer detection.

Matched MeSH terms: Finite Element Analysis
Fulltext Dataset on microstructural characteristics and mechanical performance of homogeneous and functionally graded fibrous scaffolds

Khoo W, Chung SM, Lim SC, Low CY, Shapiro JM, Koh CT

Data Brief, 2019 Dec;27:104718.
PMID: 31763388 DOI: 10.1016/j.dib.2019.104718

Data in this article are supplementary to the corresponding research article [1]. Morphological features of homogeneous and graded nanofibrous electrospun gelatin scaffolds were observed using scanning electron microscopy. Microstructural properties including fiber diameter and pore size were determined via image analysis, using ImageJ. Uniaxial tensile and fracture tests were performed on both homogeneous and graded scaffolds using a universal testing machine. Stress-strain curves of all scaffolds are presented. Computing software, MATLAB, was used to design fibrous networks with thickness-dependent density and alignment gradients (DAG). Finite element analysis software, Abaqus, was used to determine the effect of the number of layers on the fracture properties of DAG multilayer scaffolds.

Matched MeSH terms: Finite Element Analysis
Low-cost low-tech obstacle pushing/gliding wheelchair accessory

Jalal Abdullah S, Shaikh Mohammed J

Disabil Rehabil Assist Technol, 2019 11;14(8):849-858.
PMID: 30556753 DOI: 10.1080/17483107.2018.1539130

Purpose: Some wheelchair users continue to struggle in maneuvering a wheelchair and navigating through manual doors. Several smart wheelchairs and robotic manipulators were developed to minimize such challenges facing disabled people. Disappointingly, a majority of these high-tech solutions are restricted to laboratories and are not extensively available as commercial products. Previously, a low-tech wheelchair accessory (arc-shaped with many wheels) for pushing doors was modelled and simulated. This work demonstrates the fabrication and testing of the first-generation prototype of the accessory.Materials and methods: The accessory has side portions with a straight arrangement of wheels and a front portion with a straight-arc-straight arrangement of wheels. The accessory was fabricated using conventional manufacturing, off-the-shelf components, and 3D printed ABS fasteners. Stress analysis simulations were done for the fasteners that attach the front accessory to the wheelchair frame. The proof-of-concept of the prototype installed onto a powered wheelchair was tested with a door and an obstacle, each with ∼50 N resistance force.Results: Prototype tests demonstrate the ability of the accessory along with the mechanical robustness of the 3D printed fasteners to push open doors allowing easy navigation through doors and to push/glide against obstacles. The accessory is foldable and detachable.Conclusion: The low-cost of the accessory makes it affordable to many users intending to improve their quality of life. The current study provides an engineering perspective of the accessory, and a clinical perspective is crucial. Other potential applications of the wheelchair accessory include use with scooters, walkers and stretchers.Implications for rehabilitationLow-cost, low-tech accessory is foldable and detachable.Accessory is effective for pushing doors and pushing/gliding against obstacles.Protective nature of the front accessory could prove highly beneficial to some wheelchair users.

Matched MeSH terms: Finite Element Analysis
Fulltext Assessment of Nano-Indentation Method in Mechanical Characterization of Heterogeneous Nanocomposite Materials Using Experimental and Computational Approaches

Karimzadeh A, R Koloor SS, Ayatollahi MR, Bushroa AR, Yahya MY

Sci Rep, 2019 10 31;9(1):15763.
PMID: 31673118 DOI: 10.1038/s41598-019-51904-4

This study investigates the capacity of the nano-indentation method in the mechanical characterization of a heterogeneous dental restorative nanocomposite using experimental and computational approaches. In this respect, Filtek Z350 XT was selected as a nano-particle reinforced polymer nanocomposite with a specific range of the particle size (50 nm to 4 µm), within the range of indenter contact area of the nano-indentation experiment. A Sufficient number of nano-indentation tests were performed in various locations of the nanocomposite to extract the hardness and elastic modulus properties. A hybrid computational-experimental approach was developed to examine the extracted properties by linking the internal behaviour and the global response of the nanocomposite. In the computational part, several representative models of the nanocomposite were created in a finite element environment to simulate the mechanism of elastic-plastic deformation of the nanocomposite under Berkovich indenter. Dispersed values of hardness and elastic modulus were obtained through the experiment with 26.8 and 48.5 percent average errors, respectively, in comparison to the nanocomposite properties, respectively. A disordered shape was predicted for plastic deformation of the equilateral indentation mark, representing the interaction of the particles and matrix, which caused the experiment results reflect the local behaviour of the nanocomposite instead of the real material properties.

Matched MeSH terms: Finite Element Analysis
Fulltext Thermo-mechanical contact problems and elastic behaviour of single and double sides functionally graded brake disks with temperature-dependent material properties

Bayat M, Alarifi IM, Khalili AA, El-Bagory TMAA, Nguyen HM, Asadi A

Sci Rep, 2019 Oct 25;9(1):15317.
PMID: 31653877 DOI: 10.1038/s41598-019-51450-z

A thermo-elastic contact problem of functionally graded materials (FGMs) rotating brake disk with different pure brake pad areas under temperature dependent material properties is solved by Finite Element Method (FEM). The properties of brake disk change gradually from metal to ceramic by power-law distribution along the radial direction from the inner to the outer surface. Areas of the pure pad are changing while the vertical force is constant. The ratio of brake pad thickness to FGMs brake disk thickness is assumed 0.66. Two sources of thermal loads are considered: (1) Heat generation between the pad and brake disk due to contact friction, and (2) External thermal load due to a constant temperature at inner and outer surfaces. Mechanical responses of FGMs disk are compared with several pad contact areas. The results for temperature-dependent and temperature-independent material properties are investigated and presented. The results show that the absolute value of the shear stress in temperature-dependent material can be greater than that for temperature-independent material. The radial stress for some specific grading index (n = 1.5) is compressive near the inner surface for double contact while it is tensile for a single contact. It is concluded that the radial strain for some specific value of grading index (n = 1) is lower than other FGMs and pure double side contact brake disks.

Matched MeSH terms: Finite Element Analysis

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