Search results for: flat plate

Authors: Ch. Ramreddy, P. Naveen, D. Srinivasacharya

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The objective of the present study is to investigate the effect of nonlinear temperature and concentration on the mixed convective flow of micropolar fluid over an inclined flat plate in a non-Darcy porous medium in the presence of convective boundary condition. In order to analyze all the essential features, the transformed nonlinear conservation equations are worked out numerically by spectral method. By insisting the comparison between vertical, horizontal and inclined plates, the physical quantities of the flow and its characteristics are exhibited graphically and quantitatively with various parameters. An increase in the coupling number and inclination of angle tend to decrease the skin friction, mass transfer rate and the reverse change is there in wall couple stress and heat transfer rate. The nominal effect on the wall couple stress and skin friction is encountered whereas the significant effect on the local heat and mass transfer rates are found for high enough values of Biot number.

Keywords: convective boundary condition, micropolar fluid, non-darcy porous medium, non-linear convection, spectral method

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Authors: Y. C. Khoo, W. T. Lai

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The single orifice hydraulic flat spray nozzle was evaluated with two global imaging techniques to characterize various aspects of the resulting spray. The two techniques were high resolution flow visualization and Particle Image Velocimetry (PIV). A CCD camera with 29 million pixels was used to capture shadowgraph images to realize ligament formation and collapse as well as droplet interaction. Quantitative analysis was performed to give the sizing information of the droplets and ligaments. This camera was then applied with a PIV system to evaluate the overall velocity field of the spray, from nozzle exit to droplet discharge. PIV images were further post-processed to determine the inclusion angle of the spray. The results from those investigations provided significant quantitative understanding of the spray structure. Based on the quantitative results, detailed understanding of the spray behavior was achieved.

Keywords: spray, flow visualization, PIV, shadowgraph, quantitative sizing, velocity field

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Authors: Syukri Himran, Erwin Eka Putra, Nanang Roni

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This study explains the natural convection of viscous fluid flowing on semi-infinite vertical plate. A set of the governing equations describing the continuity, momentum and energy, have been reduced to dimensionless forms by introducing the references variables. To solve the problems, the equations are formulated by explicit finite-difference in time dependent form and computations are performed by Fortran program. The results describe velocity, temperature profiles both in transient and steady state conditions. An approximate value of heat transfer coefficient and the effects of Pr on convection flow are also presented.

Keywords: natural convection, vertical plate, velocity and temperature profiles, steady and unsteady

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Authors: Seyyed Abbas Mojtabavi, Mojtaba Fatzaneh Moghadam, Masoud Mahdavi

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Steel Metal Shear Wall is one of the most common and widely used energy dissipation systems in structures, which is used today as a damping system due to the increase in the construction of metal structures. In the present study, the shear wall of the steel plate with dimensions of 5×3 m and thickness of 0.024 m was modeled with 2 floors of total height from the base level with finite element method in Abaqus software. The loading is done as a concentrated load at the upper point of the shear wall on the second floor based on step type buckle. The mesh in the model is applied in two directions of length and width of the shear wall, equal to 0.02 and 0.033, respectively, and the mesh in the models is of sweep type. Finally, it was found that the steel plate shear wall with cavity (CSPSW) compared to the SPSW model, S (Mises), Smax (In-Plane Principal), Smax (In-Plane Principal-ABS), Smax (Min Principal) increased by 53%, 70%, 68% and 43%, respectively. The presence of cavities has led to an increase in the estimated stresses, but their presence has caused critical stresses and critical deformations created to be removed from the inner surface of the shear wall and transferred to the desired sections (regular cavities) which can be suggested as a solution in seismic design and improvement of the structure to transfer possible damage during the earthquake and storm to the desired and pre-designed location in the structure.

Keywords: steel plate shear wall, abacus software, finite element method, , boundary element, seismic structural improvement, von misses stress

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Authors: Zhi Zhang, Liling Cao, Seyedbabak Momenzadeh, Lisa Davey

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Reinforced concrete (RC) flat slab-column systems are commonly used in residential or office buildings, as the flat slab provides efficient clearance resulting in more stories at a given height than regular reinforced concrete beam-slab system. Punching shear of slab-column joints is a critical component of two-way reinforced concrete flat slab design. The unbalanced moment at the joint is transferred via slab moment and shear forces. ACI 318 provides an equation to evaluate the punching shear under the design load. It is important to note that the design code considers gravity and environmental load when considering the design load combinations, while it does not consider the effect from differential foundation settlement, which may be a governing load condition for the slab design. This paper describes how prestressed reinforced concrete slab punching shear is evaluated based on ACI 318 provisions and finite element analysis. A prestressed reinforced concrete slab under differential settlements is studied using the finite element modeling methodology. The punching shear check equation is explained. The methodology to extract data for punching shear check from the finite element model is described and correlated with the corresponding code provisions. The study indicates that the finite element analysis results should be carefully reviewed and processed in order to perform accurate punching shear evaluation. Conclusions are made based on the case studies to help engineers understand the punching shear behavior in prestressed and non-prestressed reinforced concrete slabs.

Keywords: differential settlement, finite element model, prestressed reinforced concrete slab, punching shear

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Authors: Masoud Mahdavi, Mojtaba Farzaneh Moghadam

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The seismic forces caused by the waves created in the depths of the earth during the earthquake hit the structure and cause the building to vibrate. Creating large seismic forces will cause low-strength sections in the structure to suffer extensive surface damage. The use of new steel shear walls in steel structures has caused the strength of the building and its main members (columns) to increase due to the reduction and depreciation of seismic forces during earthquakes. In the present study, an attempt was made to evaluate a type of steel shear wall that has regular holes in the inner sheet by modeling the finite element model with Abacus software. The shear wall of the steel plate, measuring 6000 × 3000 mm (one floor) and 3 mm thickness, was modeled with four different pores with a cross-sectional area. The shear wall was dynamically subjected to a time history of 5 seconds by three accelerators, El Centro, Imperial Valley and Kobe. The results showed that increasing the distance between the geometric center of the hole and the geometric center of the inner plate in the steel shear wall (increasing the R_CS index) caused the total maximum acceleration to be transferred from the perimeter of the hole to horizontal and vertical beams. The results also show that there is no direct relationship between R_CS index and total acceleration in steel shear wall and R_CS index is separate from the peak ground acceleration value of earthquake.

Keywords: hollow steel plate shear wall, time history analysis, finite element method, abaqus software

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Authors: C. S. Paglia

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The deformation and the crystallization in a 7075-T651 friction stir weld, in particular for regions directly in contact with the mechanical action of the rotating probe, have been investigated by means of optical microscopy. The investigation enabled to identify regions of the weld differently affected by the deformation caused by the welding process. The highly deformed grains in the horizontal direction close to the plate margin were indicative of shear movements along the horizontal plane, while highly deformed grains along the plate margin in the vertical direction were indicative of vertical shear movements of opposite directions, which superimposed the shear movement along the horizontal plane. The vertical shear movements were not homogeneous through the plate thickness. The microstructure indicated that after the probe passes, the grain growth may take place under static conditions. The small grains microstructure of the nugget region, formed after the main dynamic recrystallization process, develops to an equiaxed microstructure. A material transport influenced by the rotating shoulder was also observed from the trailing to the advancing side of the weld.

Keywords: AA7075-T651, friction stir welding, deformation, crystallization

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Authors: K. Khaerunnisa, D. Ryangga, S. A. Pawiro

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Over the past few decades, film dosimetry has become a tool which is used in various radiotherapy modalities, either for clinical quality assurance (QA) or dose verification. The response of the film to irradiation is usually expressed in optical density (OD) or net optical density (netOD). While the film's response to radiation is not linear, then the use of film as a dosimeter must go through a calibration process. This study aimed to compare the function of the calibration curve of various measurement methods with various densitometer, using a flat bad scanner, point densitometer and spectrophotometer. For every response function, a radichromic film calibration curve is generated from each method by performing accuracy, precision and sensitivity analysis. netOD is obtained by measuring changes in the optical density (OD) of the film before irradiation and after irradiation when using a film scanner if it uses ImageJ to extract the pixel value of the film on the red channel of three channels (RGB), calculate the change in OD before and after irradiation when using a point densitometer, and calculate changes in absorbance before and after irradiation when using a spectrophotometer. the results showed that the three calibration methods gave readings with a netOD precision of doses below 3% for the uncertainty value of 1σ (one sigma). while the sensitivity of all three methods has the same trend in responding to film readings against radiation, it has a different magnitude of sensitivity. while the accuracy of the three methods provides readings below 3% for doses above 100 cGy and 200 cGy, but for doses below 100 cGy found above 3% when using point densitometers and spectrophotometers. when all three methods are used for clinical implementation, the results of the study show accuracy and precision below 2% for the use of scanners and spectrophotometers and above 3% for precision and accuracy when using point densitometers.

Keywords: Callibration Methods, Film Dosimetry EBT3, Flat Bad Scanner, Densitomete, Spectrophotometer

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Authors: Thulodin Mat Lazim, Aminuddin Saat, Ammar Fakhir Abdulwahid, Zaid Sattar Kareem

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Film cooling is one of the cooling systems investigated for the application to gas turbine blades. Gas turbines use film cooling in addition to turbulence internal cooling to protect the blades outer surface from hot gases. The present study concentrates on the numerical investigation of film cooling performance for a row of twisted cylindrical holes in modern turbine blade. The adiabatic film effectiveness and the heat transfer coefficient are determined numerical on a flat plate downstream of a row of inclined different cross section area hole exit by using Computational Fluid Dynamics (CFD). The swirling motion of the film coolant was induced the twisted angle of film cooling holes, which inclined an angle of α toward the vertical direction and surface of blade turbine. The holes angle α of the impingement mainstream was changed from 90°, 65°, 45°, 30° and 20°. The film cooling effectiveness on surface of blade turbine wall was measured by using 3D Computational Fluid Dynamics (CFD). Results showed that the effectiveness of rectangular twisted hole has the effectiveness among other cross section area of the hole at blowing ratio (0.5, 1, 1.5 and 2).

Keywords: turbine blade cooling, film cooling, geometry shape of hole, turbulent flow

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Authors: M. Tawfik, X. Tonnellier, C. Sansom

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The Lens-Lens Beam Generator (LLBG) is a Fresnel-based optical concentrating technique which provides flexibility in selecting the solar receiver location compared to conventional techniques through generating a powerful concentrated collimated solar beam. In order to achieve that, two successive lenses are used and followed by a flat mirror. Hence the generated beam emerging from the LLBG has a high power flux which impinges on the target receiver, it is important to determine the precision of the system output. In this present work, mathematical investigation of different parameters affecting the precision of the output beam is carried out. These parameters include: Deflection in sun-facing lens and its holding arm, delay in updating the solar tracking system, and the flat mirror surface flatness. Moreover, relationships that describe the power lost due to the effect of each parameter are derived in this study.

Keywords: Fresnel lens, LLBG, solar concentrator, solar tracking

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Authors: Lewis J. Woollin, Robert I. Davidson, Paul Watson, Philip J. Hyde

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Introduction: In-vitro testing of arthroplasty materials is of paramount importance when ensuring that they can withstand the performance requirements encountered in-vivo. One common machine used for in-vitro testing is a pin-on-plate tribometer, an early stage screening device that generates data on the wear characteristics of arthroplasty bearing materials. These devices test vertically loaded rotating cylindrical pins acting against reciprocating plates, representing the bearing surfaces. In this study, a pin-on-plate machine has been developed that provides several improvements over current technology, thereby progressing arthroplasty bearing research. Historically, pin-on-plate tribometers have been used to investigate the performance of arthroplasty bearing materials under conditions commonly encountered during a standard gait cycle; nominal operating pressures of 2-6 MPa and an operating frequency of 1 Hz are typical. There has been increased interest in using pin-on-plate machines to test more representative in-vivo conditions, due to the drive to test 'beyond compliance', as well as their testing speed and economic advantages over hip simulators. Current pin-on-plate machines do not accommodate the increased performance requirements associated with more extreme kinematic conditions, therefore a next-generation pin-on-plate tribometer has been developed to bridge the gap between current technology and future research requirements. Methodology: The design was driven by several physiologically relevant requirements. Firstly, an increased loading capacity was essential to replicate the peak pressures that occur in the natural hip joint during running and chair-rising, as well as increasing the understanding of wear rates in obese patients. Secondly, the introduction of mid-cycle load variation was of paramount importance, as this allows for an approximation of the loads present in a gait cycle to be applied and to test the fatigue properties of materials. Finally, the rig must be validated against previous-generation pin-on-plate and arthroplasty wear data. Results: The resulting machine is a twelve station device that is split into three sets of four stations, providing an increased testing capacity compared to most current pin-on-plate tribometers. The loading of the pins is generated using a pneumatic system, which can produce contact pressures of up to 201 MPa on a 3.2 mm² round pin face. This greatly exceeds currently achievable contact pressures in literature and opens new research avenues such as testing rim wear of mal-positioned hip implants. Additionally, the contact pressure of each set can be changed independently of the others, allowing multiple loading conditions to be tested simultaneously. Using pneumatics also allows the applied pressure to be switched ON/OFF mid-cycle, another feature not currently reported elsewhere, which allows for investigation into intermittent loading and material fatigue. The device is currently undergoing a series of validation tests using Ultra-High-Molecular-Weight-Polyethylene pins and 316L Stainless Steel Plates (polished to a Ra < 0.05 µm). The operating pressures will be between 2-6 MPa, operating at 1 Hz, allowing for validation of the machine against results reported previously in the literature. The successful production of this next-generation pin-on-plate tribometer will, following its validation, unlock multiple previously unavailable research avenues.

Keywords: arthroplasty, mechanical design, pin-on-plate, total joint replacement, wear testing

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Authors: Bartosz Olszanski, Zbigniew Nosal, Jacek Rokicki

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An experimental study of cold-jet (nitrogen) reaction control jet system has been carried out to investigate the flow control efficiency for low to moderate jet pressure ratios (total jet pressure p0jet over free stream static pressure in the wind tunnel p∞) and different angles of attack for infinite Mach number equal to 2. An investigation of jet influence was conducted on a flat plate geometry placed in the test section of intermittent supersonic wind tunnel of Department of Aerodynamics, WUT. Various convergent jet nozzle geometries to obtain different jet momentum ratios were tested on the same test model geometry. Surface static pressure measurements, Schlieren flow visualizations (using continuous and photoflash light source), load cell measurements gave insight into the supersonic crossflow interaction for different jet pressure and jet momentum ratios and their influence on the efficiency of side jet control as described by the amplification factor (actual to theoretical net force generated by the control nozzle). Moreover, the quasi-steady numerical simulations of flow through the same wind tunnel geometry (convergent-divergent nozzle plus test section) were performed using ANSYS Fluent basing on Reynolds-Averaged Navier-Stokes (RANS) solver incorporated with k-ω Shear Stress Transport (SST) turbulence model to assess the possible spurious influence of test section walls over the jet exit near field area of interest. The strong bow shock, barrel shock, and Mach disk as well as lambda separation region in front of nozzle were observed as images taken by high-speed camera examine the interaction of the jet and the free stream. In addition, the development of large-scale vortex structures (counter-rotating vortex pair) was detected. The history of complex static pressure pattern on the plate was recorded and compared to the force measurement data as well as numerical simulation data. The analysis of the obtained results, especially in the wake of the jet showed important features of the interaction mechanisms between the lateral jet and the flow field.

Keywords: flow visualization techniques, pressure measurements, reaction control jet, supersonic cross flow

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Authors: Mohamed Hassan Gundu, Jaeseung Lee, Muhammad Faizan Chinannai, Hyunchul Ju

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In this study, we present the effects of bipolar plate design to control the temperature of the cell and ensure effective water management under an excessive amount of air flow and low humidification conditions in the proton exchange membrane fuel cell (PEMFC). The PEMFC model developed and applied to consider a three type of bipolar plate that is defined by ratio of inlet channel width to outlet channel width. Simulation results show that the design which has narrow gas inlet channel and wide gas outlet channel width (wide coolant inlet channel and narrow coolant outlet channel width) make the relative humidity and water concentration increase in the channel and the catalyst layer. Therefore, this study clearly demonstrates that the dehydration phenomenon can be decreased by using design of bipolar plate with narrow gas inlet channel and wide gas outlet channel width (wide coolant inlet channel and narrow coolant outlet channel width).

Keywords: PEMFC, air-cooling, relative humidity, water management, water concentration, oxygen concentration

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Authors: Carlos H. Cuadra, Nobuhiro Shimoi

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Application of piezoelectric sensors to detect structural damage due to seismic action on building structures is investigated. Plate-type piezoelectric sensor was developed and proposed for this task. A film-type piezoelectric sheet was attached on a steel plate and covered by a layer of glass. A special glue is used to fix the glass. This glue is a silicone that requires the application of ultraviolet rays for its hardening. Then, the steel plate was set up at a steel column-beam joint of a test specimen that was subjected to bending moment when test specimen is subjected to monotonic load and cyclic load. The structural behavior of test specimen during cyclic loading was verified using a finite element model, and it was found good agreement between both results on load-displacement characteristics. The cross section of steel elements (beam and column) is a box section of 100 mm×100 mm with a thin of 6 mm. This steel section is specified by the Japanese Industrial Standards as carbon steel square tube for general structure (STKR400). The column and beam elements are jointed perpendicularly using a fillet welding. The resulting test specimen has a T shape. When large deformation occurs the glass plate of the sensor device cracks and at that instant, the piezoelectric material emits a voltage signal which would be the indicator of a certain level of deformation or damage. Applicability of this piezoelectric sensor to detect structural damages was verified; however, additional analysis and experimental tests are required to establish standard parameters of the sensor system.

Keywords: piezoelectric sensor, static cyclic test, steel structure, seismic damages

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Authors: Katarzyna Falkowicz

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The work focused on the original concept of a thin-walled plate element with a cut-out, for use as a spring or load-bearing element. The subject of the study were rectangular plates with a cut-out with variable geometrical parameters and with a variable angle of fiber arrangement, made of a carbon-epoxy composite with high strength properties in an asymmetrical arrangement, subjected to uniform compression. The influence of geometrical parameters of the cut-out and the angle of fiber arrangement on the value of critical load of the structure and buckling form was investigated. Uniform thin plates are relatively cheap to manufacture, however due to their low bending stiffness; they can carry relatively small loads. The lowest form of loss of plate stability, which is the bending form, leads to its rapid destruction due to high deflection increases, with a slight increase in compressive load - low rigidity of the structure. However, the stiffness characteristics of the structure change significantly when the work of plate is forcing according to the higher flexural-torsional form of buckling. The plate is able to carry a much higher compressive load while maintaining much stiffer work characteristics in the post-critical range. The calculations carried out earlier show that plates with forced higher form of buckling are characterized by stable, progressive paths of post-critical equilibrium, enabling their use as elastic elements. The characteristics of such elements can be designed in a wide range by changing the geometrical parameters of the cut-out, i.e. height and width as well as by changing the angle of fiber arrangement The commercial ABAQUS program using the finite element method was used to develop the discrete model and perform numerical calculations. The obtained results are of significant practical importance in the design of structures with elastic elements, allowing to achieve the required maintenance characteristics of the device.

Keywords: buckling mode, numerical method, unsymmetrical laminates, thin-walled elastic elements

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Authors: Rasha Saad, Jean Frederic Weber, Fatimah Bebe, Sadia Sultan

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The goal of study was to screen the effects of candesartan and four endophytic fungi for their potential in microbial biotransformation. In this experiment, four types of unidentified fungi with the codes of TH2L1, TH2R10, TH1P35 and TH1S46 were used in screening process by MECFUS (Microtiter plate, Elicitors, Combination, Freeze-drying, UHPLC, Statistical analysis) protocol. The experiment was carried out by using 96-well microtiter plate (MTP) with different media and elicitors. Various media with two concentrations of Potato Dextrose Broth (PDB) and elicitors used were to induce the production of secondary metabolites from the fungi as well as the biotransformation of the drug compound. After incubation, cultures were extracted by freeze drying method and finally analyzed by ultra-High performance Liquid Chromatography (uHPLC). The extracts analyzed by uHPLC followed by LC/Ms, demonstrated the presence of biotransformation products from the drug compound and elicitation of the secondary metabolism from the fungi by the occurrence of the additional peaks. From the four fungi, TH1S46 showed highly potential produced secondary metabolites as well as the biotransformation of candesartan. For other fungi, they responded when candesartan was introduced. Moreover, the additional peaks produced in uHPLC need to be further investigation by using LC-MS or NMR.

Keywords: biotransformation, candesartan, endophytes, secondary metabolites

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Authors: Rebhi A. Damseh, H. M. Duwairi, Benbella A. Shannak

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This work deals with heat and mass transfer by steady laminar boundary layer flow of a Newtonian, viscous fluid over a vertical flat plate with variable surface heat flux embedded in a fluid saturated porous medium in the presence of thermophoresis particle deposition effect. The governing partial differential equations are transformed into no-similar form by using special transformation and solved numerically by using an implicit finite difference method. Many results are obtained and a representative set is displaced graphically to illustrate the influence of the various physical parameters on the wall thermophoresis deposition velocity and concentration profiles. It is found that the increasing of thermophoresis constant or temperature differences enhances heat transfer rates from vertical surfaces and increase wall thermophoresis velocities; this is due to favourable temperature gradients or buoyancy forces. It is also found that the effect of thermophoresis phenomena is more pronounced near pure natural convection heat transfer limit; because this phenomenon is directly a temperature gradient or buoyancy forces dependent. Comparisons with previously published work in the limits are performed and the results are found to be in excellent agreement.

Keywords: thermophoresis, porous medium, variable surface heat flux, heat transfer

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Authors: Muhammad Shahrukh Saeed, Syed Ahmad Nameer, Shafiq Ur Rehman, Aisha Jillani

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Heat exchangers play a critical role in industrial applications of thermal systems. Its physical size and performance are vital parameters; therefore enhancement of heat transfer through different techniques remained a major research area for both academia and industry. This research reports the main purpose of heat exchanger with better kit design which plays a vital role during the process of heat transfer. Plate type heat exchanger mainly requires a design in which the plates can be easily be installed and removed without having any problem with the plates. For the flow of the fluid within the heat exchanger, it requires a flow should be fully developed. As natural laws allows the driving energy of the system to flow until equilibrium is achieved. As with a plate type heat exchanger heat the heat penetrates the surface which separates the hot medium with the cold one very easily. As some of the precautions should be considered while taking the heat exchanger accountable like heat should transfer from hot medium to cold, there should always be difference in temperature present and heat loss from hot body should be equal to the heat gained by the cold body regardless of the losses present to the surroundings. Aluminum plates of same grade are used in all experiments to ensure similarity. Size of all plates was 254 mm X 100 mm and thickness was taken as 5 mm.

Keywords: heat transfer coefficient, aluminium, entry length, design

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Authors: Ahmed Almurshedi, Mark Atherton, Mares Cristinel, Tadeusz Stolarski, Masaaki Miyatake

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Transportation and handling of delicate and lightweight objects is a significant issue in some industries. Two levitation prototype designs, a horn transducer design and surface-mounted piezoelectric actuator vibrating plate design, are compared. Both designs are based on the method of squeeze-film levitation (SFL) and the aim of this study is to evaluate the characteristics and performance of each. To this end, physical experiments are conducted and are demonstrated that the horn-type transducer prototype design produces better levitation performance but it design complexity and operating characteristics make it less suitable than the vibrating plate design for practical applications.

Keywords: floating, levitation, piezoelectric, squeeze-film, transducer

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Authors: Pagadaplly Girish, P. V. Manohar

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Introduction: Management of distal femur fractures is challenging. Recently, treatment has evolved towards indirect reduction and minimally invasive techniques. Objectives: To assess the fracture union and functional outcome following open reduction and internal fixation of distal femur fractures with locking compression plate and to achieve restoration of the anatomical alignment of fracture fragments and stable internal fixation. Methodology: Patients with distal femur fracture treated by locking compression during Oct 2011 to April 2013 were assessed prospectively. Patients below 18 years and those with neuro-vascular deficits were excluded. Age, sex of the patient, type of fracture, mechanism of injury, type of implant used, operative time and postoperative complications were analysed. The Neer’s scale was used to assess the outcome of the patients. Results: The total number of patients was 30; 28 males and 2 females; mean age was 41.53 years. Road traffic accidents were the major causes of injury followed by falls. The average duration of hospital stay was 21.3 days. The overall complication rate note was 23.33%. The mean range of movement around the knee joint after 6 months of follow-up was 114.330. The average time for the radiological union was 14 weeks. Excellent to good results were noted in 26 patients (86.6%) and average to poor results were observed in 4 (13.33%) patients. Conclusions: The locking compression plate gives a rigid fixation for the fracture. It also provides a good purchase in osteoporotic bones. LCP is simple and a reliable implant appropriate for fixation of femoral fractures with promising results.

Keywords: distal femur fractures, locking compression plate, Neer’s criteria, neuro-vascular deficits

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Authors: Anuar Ishak

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The mixed convection stagnation point flow toward a vertical plate is investigated. The external flow impinges normal to the heated plate and the surface temperature is assumed to vary linearly with the distance from the stagnation point. The governing partial differential equations are transformed into a set of ordinary differential equations, which are then solved numerically using MATLAB routine boundary value problem solver bvp4c. Numerical results show that dual solutions are possible for a certain range of the mixed convection parameter. A stability analysis is performed to determine which solution is linearly stable and physically realizable.

Keywords: dual solutions, heat transfer, mixed convection, stability analysis

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Authors: Pooja Sharma

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In the present paper the effects of radiation is studied on unsteady flow of viscous incompressible electrically conducting fluid past a vertical porous plate embedded in the porous medium in the presence of constant heat flux. A uniform Transverse Magnetic field is considered and induced magnetic field is supposed as negligible. The non-linear governing equations are solved numerically. Numerical results of the velocity and temperature fields are shown through graphs. The results illustrates that the appropriator combination of regulated values of thermo-physical parameters is expedient for controlling the flow system.

Keywords: heat transfer, radiation, MHD flow, porous medium

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Authors: Andrey Boyko

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Nowadays, there is no consensus about the influence of urethral plate (UP) width on the surgical outcomes after distal hypospadias repair. The purpose of the research was to study the association between UP width and surgical outcomes after distal hypospadias repair in children. Materials and methods: The study included 138 patients with distal hypospadias. The mean age at the time of surgery was 4.6 years (6 months – 16 years). We measured UP width at the “midpoint within the glans” and used the HOSE scale to assess postoperative outcomes. The patients were divided into 2 groups: group 1 – the patients (107) with UP < 8mm, group 2 – patients (31) with UP > 8mm. All boys underwent TIP repair. Preincision means UP width after incision means UP width, and the UP ratio was analyzed. Statistical data were obtained using Statistica 10. Results: The findings were preincision mean UP width - 5.4 mm and 9.4 mm; after incision mean UP width - 13mm and 17.5 mm; UP ratio - 0.41 and 0.53 in group 1 and group 2, respectively. Most postoperative complications (fistula, meatal stenosis, and stricture) happened in patients with UP width < 8 mm versus ≥ 8 mm (7/107 versus 2/31, respectively). HOSE results were 15.77 (group 1), 15.65 (group 2). The follow up lasted up to 12 months. Statistical analysis proved the absence of correlation between UP width and postoperative complications. Conclusions: In conclusion, it should be noted that the success of surgical repair mostly depended on the surgical technique.

Keywords: children, distal hypospadias, tip repair, urethral plate width

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Authors: Piotr Wadolowski, Grzegorz Krzesinski, Piotr Gutowski

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The aim of the presented work is to recognize the impact of mini-plate application approach on the stress and displacement within the stabilization devices and surrounding bones. The mini-plate osteosynthesis technique is widely used by craniofacial surgeons as an improved replacement of wire connection approach. Many different types of metal plates and screws are used to the physical connection of fractured bones. Below investigation is based on a clinical observation of patient hospitalized with mini-plate stabilization system. Analysis was conducted on a solid mandible geometry, which was modeled basis on the computed tomography scan of the hospitalized patient. In order to achieve most realistic connected system behavior, the cortical and cancellous bone layers were assumed. The temporomandibular joint was simplified to the elastic element to allow physiological movement of loaded bone. The muscles of mastication system were reduced to three pairs, modeled as shell structures. Finite element grid was created by the ANSYS software, where hexahedral and tetrahedral variants of SOLID185 element were used. A set of nonlinear contact conditions were applied on connecting devices and bone common surfaces. Properties of particular contact pair depend on screw - mini-plate connection type and possible gaps between fractured bone around osteosynthesis region. Some of the investigated cases contain prestress introduced to the mini-plate during the application, what responds the initial bending of the connecting device to fit the retromolar fossa region. Assumed bone fracture occurs within the mandible angle zone. Due to the significant deformation of the connecting plate in some of the assembly cases the elastic-plastic model of titanium alloy was assumed. The bone tissues were covered by the orthotropic material. As a loading were used the gauge force of magnitude of 100N applied in three different locations. Conducted analysis shows significant impact of mini-plate application methodology on the stress distribution within the miniplate. Prestress effect introduces additional loading, which leads to locally exceed the titanium alloy yield limit. Stress in surrounding bone increases rapidly around the screws application region, exceeding assumed bone yield limit, what indicate the local bone destruction. Approach with the doubled mini-plate shows increased stress within the connector due to the too rigid connection, where the main path of loading leads through the mini-plates instead of plates and connected bones. Clinical observations confirm more frequent plate destruction of stiffer connections. Some of them could be an effect of decreased low cyclic fatigue capability caused by the overloading. The executed analysis prove that the mini-plate system provides sufficient support to mandible fracture treatment, however, many applicable solutions shifts the entire system to the allowable material limits. The results show that connector application with the initial loading needs to be carefully established due to the small material capability tolerances. Comparison to the clinical observations allows optimizing entire connection to prevent future incidents.

Keywords: mandible fracture, mini-plate connection, numerical analysis, osteosynthesis

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Authors: Manjit Singha, Sandeep Singh Sandhu, A. S. Shahi

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Stellite 6 is cobalt based superalloy used for protective coatings. It is used to improve the wear performance of stainless steel engineering components subjected to harsh environmental conditions. This paper reports the high temperature wear analysis of satellite 6 cladded on AISI 304 L substrate using SMAW process. Bead on plate experiment was carried out by varying current and electrode manipulation techniques to optimize the dilution and hardness. 80 Amp current and weaving technique was found to be the optimum set of parameters for overlaying which were further used for multipass multilayer cladding on two plates of AISI 304 L substrate. On the first plate, seven layers seven passes of stellite 6 was overlaid which was used in as cladded form and the second plate was overlaid with five layers five passes of satellite 6 with further TIG remelting. The wear performance was examined for normal temperature environmental condition and harsh temperature environmental condition. The satellite 6 coating with TIG remelting was found to be better in both the conditions even with lesser metal deposition due to its finer grain structure.

Keywords: surfacing, stellite 6, dilution, overlay, SMAW, high-temperature frictional wear, micro-structure, micro-hardness

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Authors: Mokhtar Bouazza

Abstract:

In this paper, the simplified theory will be used to predict the thermoelastic buckling behavior of rectangular functionally graded plates. The material properties of the functionally graded plates are assumed to vary continuously through the thickness, according to a simple power law distribution of the volume fraction of the constituents. The simplified theory is used to obtain the buckling of the plate under different types of thermal loads. The thermal loads are assumed to be uniform, linear, and non-linear distribution through the thickness. Additional numerical results are presented for FGM plates that show the effects of various parameters on thermal buckling response.

Keywords: buckling, functionally graded, plate, simplified higher-order deformation theory, thermal loading

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Authors: Amir R. Askari, Masoud Tahani

Abstract:

The objective of the present paper is to investigate the effect of size on the vibrational behavior of fully clamped rectangular micro-plates based on the modified couple stress theory (MCST). To this end, a size-dependent Kirchhoff plate model is considered and the equation of motion which accounts for the effect of residual and couple stress components is derived using the Hamilton's principle. The eigenvalue problem associated with the free vibrations of fully clamped micro-plates is extracted and solved analytically using the extended Kantorovich method (EKM). The present findings are compared and validated by available results in the literature and an excellent agreement between them is observed. A parametric study is also conducted to show the significant effects of couple stress components on natural frequencies of fully clamped micro-plates. It is found that the ratio of MCST natural frequencies to those obtained by the classical theory (CT) only depends on the Poisson's ratio of the plate and is totally independent of plate's aspect ratio for cases with no residual stresses.

Keywords: vibrational analysis, modified couple stress theory, fully clamped rectangular micro-plates, extended Kantorovich method.

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Authors: Irnie Zakaria, W. A. N. W. Mohamed, W. H. Azmi

Abstract:

Thermal enhancement of a single mini channel in Proton Exchange Membrane Fuel Cell (PEMFC) cooling plate is numerically investigated. In this study, low concentration of Al2O3 in Water - Ethylene Glycol mixtures is used as coolant in mini channel of carbon graphite plate to mimic the PEMFC cooling plate. A steady and incompressible flow with constant heat flux is assumed in the channel of 1mm x 5mm x 100mm. Nano particle of Al2O3 used ranges from 0.1, 0.3 and 0.5 vol % concentration and then dispersed in 60:40 (water: Ethylene Glycol) mixture. The effect of different flow rates to fluid flow and heat transfer enhancement in Re number range of 20 to 140 was observed. The result showed that heat transfer coefficient was improved by 18.11%, 9.86% and 5.37% for 0.5, 0.3 and 0.1 vol % Al2O3 in 60:40 (water: EG) as compared to base fluid of 60:40 (water: EG). It is also showed that the higher vol % concentration of Al2O3 performed better in term of thermal enhancement but at the expense of higher pumping power required due to increase in pressure drop experienced. Maximum additional pumping power of 0.0012W was required for 0.5 vol % Al2O3 in 60:40 (water: EG) at Re number 140.

Keywords: heat transfer, mini channel, nanofluid, PEMFC

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Authors: S. J. Shahidzadeh Tabatabaei, A. M. Fattahi

Abstract:

Modal analysis of a FGM plate containing the ceramic phase of Al₂O₃ and metal phase of stainless steel 304 was performed using ABAQUS, with the assumptions that the material has an elastic mechanical behavior and its Young modulus and density are varying in thickness direction. For this purpose, a subroutine was written in FOTRAN and linked with ABAQUS. First, a simulation was performed in accordance to other researcher’s model, and then after comparing the obtained results, the accuracy of the present study was verified. The obtained results for natural frequency and mode shapes indicate good performance of user-written subroutine as well as FEM model used in present study. After verification of obtained results, the effect of clamping condition and the material type (i.e. the parameter n) was investigated. In this respect, finite element analysis was carried out in fully clamped condition for different values of n. The results indicate that the natural frequency decreases with increase of n, since with increase of n, the amount of ceramic phase in FGM plate decreases, while the amount of metal phase increases, leading to decrease of the plate stiffness and hence, natural frequency, as the Young modulus of Al₂O₃ is equal to 380 GPa and the Young modulus of stainless steel 304 is equal to 207 GPa.

Keywords: FGM plates, modal analysis, natural frequency, finite element method

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Authors: JinWoog Lee, SeongHyeok Lee, ChanYong Choi, Yujin Lim, Hojin Cho

Abstract:

Primary function of the trackbed in a conventional railway track system is to decrease the stresses in the subgrade to be in an acceptable level. A properly designed trackbed layer performs this task adequately. Many design procedures have used assumed and/or are based on critical stiffness values of the layers obtained mostly in the field to calculate an appropriate thickness of the sublayers of the trackbed foundation. However, those stiffness values do not consider strain levels clearly and precisely in the layers. This study proposes a method of computation of stiffness that can handle with strain level in the layers of the trackbed foundation in order to provide properly selected design values of the stiffness of the layers. The shear modulus values are dependent on shear strain level so that the strain levels generated in the subgrade in the trackbed under wheel loading and below plate of Repeated Plate Bearing Test (RPBT) are investigated by finite element analysis program ABAQUS and PLAXIS programs. The strain levels generated in the subgrade from RPBT are compared to those values from RC (Resonant Column) test after some consideration of strain levels and stress consideration. For comparison of shear modulus G obtained from RC test and stiffness moduli Ev2 obtained from RPBT in the field, many numbers of mid-size RC tests in laboratory and RPBT in field were performed extensively. It was found in this study that there is a big difference in stiffness modulus when the converted Ev2 values were compared to those values of RC test. It is verified in this study that it is necessary to use precise and increased loading steps to construct nonlinear curves from RPBT in order to get correct Ev2 values in proper strain levels.

Keywords: modulus, plate load test, resonant column test, trackbed foundation

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