Manufacturing Processes
R. Arokiadass*; K. Palaniradja; N. Alagumoorthi
Abstract
Metal matrix composites have been widely used in industries, especially aerospace industries, due to their excellent engineering properties. However, it is difficult to machine them because of the hardness and abrasive nature of reinforcement elements like silicon carbide particles (SiCp).In the present ...
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Metal matrix composites have been widely used in industries, especially aerospace industries, due to their excellent engineering properties. However, it is difficult to machine them because of the hardness and abrasive nature of reinforcement elements like silicon carbide particles (SiCp).In the present study, an attempt has been made to investigate the influence of spindle speed (N), feed rate (f), depth of cut (d) and various %wt. of silicon carbide (S) manufactured through stir cast route on tool flank wear and surface roughness during end milling of LM25 Al-SiCp metal matrix composites. Statistical models based on second order polynomial equations were developed for the different responses. Analysis of variance (ANOVA) was carried out to identify the significant factors affecting the tool flank wear and surface roughness. The contour plots were generated to study the effect of process parameters as well as their interactions. The process parameters are optimized using desirability-based approach response surface methodology.
Heat and Mass Transfer
M. Gnaneswara Reddy
Abstract
This paper was concerned with studying the magnetohydrodynamic steady laminar free convection flow of a micropolar fluid past a continuously moving surface in the presence of heat generation and thermal radiation. Similarity transformation was employed to transform the governing partial differential ...
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This paper was concerned with studying the magnetohydrodynamic steady laminar free convection flow of a micropolar fluid past a continuously moving surface in the presence of heat generation and thermal radiation. Similarity transformation was employed to transform the governing partial differential equations into ordinary ones, which were then solved numerically using the finite element method. Numerical results for the dimensionless velocity, microrotation and temperature profiles were obtained and displayed graphically for pertinent parameters to show interesting aspects of the solution. The skin friction and the rate of heat transfer were also computed and presented through tables. Favorable comparison with previously published work was performed.
Welding
Kondapalli Siva Prasad; Chalamalasetti Srinivasa Rao; Damera Nageswara Rao
Abstract
Austenitic stainless steel sheets have gained wide acceptance in the fabrication of components, which require high temperature resistance and corrosion resistance such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industries. In the case of single pass welding of thinner ...
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Austenitic stainless steel sheets have gained wide acceptance in the fabrication of components, which require high temperature resistance and corrosion resistance such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industries. In the case of single pass welding of thinner sections of this alloy, Pulsed Current Micro Plasma Arc Welding (PCMPAW) has been found beneficial due to its advantages over the conventional continuous current process. This paper highlighted development of empirical mathematical equations using multiple regression analysis, correlating various process parameters to pitting corrosion rates in PCMPAW of AISI 304L sheets in 1 Normal HCl. The experiments were conducted based on a five factor, five level central composite rotatable design matrix. The model adequacy was checked by Analysis of Variance (ANOVA). The main effects and interaction effects of the welding process parameters on pitting corrosion rates of the welded joints were studied using surface and contour plots. From the contour plots, it was understood that peak current was the most influencing factor on the pitting corrosion rate. The optimum pitting corrosion rate was achieved at peak current of 6 Amperes, base current of 4 Amperes, pulse rate of 40 pulses/second and pulse width of 50 % .
Fracture Mechanics
A. R. Shahani; H. Moayeri Kashani
Abstract
In this paper, three-dimensional modeling of the fatigue crack growth profiles was performed in a simple riveted lap joint. Simulation results showed that mode I was dominated on the one side of the plates and the crack straightly grew on this side, while the other side of the plates was in a mixed-mode ...
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In this paper, three-dimensional modeling of the fatigue crack growth profiles was performed in a simple riveted lap joint. Simulation results showed that mode I was dominated on the one side of the plates and the crack straightly grew on this side, while the other side of the plates was in a mixed-mode condition and the crack propagation path was not straight on this side. Afterward, the fracture mechanics-based life prediction of the riveted lap joint was considered using EIFS concept. Back extrapolation method was used for estimating EIFS. Results demonstrated that EIFS would depend on loading amplitude if ΔK had been implemented in EIFS estimation using Paris equation. In contrast EIFS dependency on loading amplitude significantly reduced when using ΔJ in EIFS estimation. Finally, fatigue life of the riveted lap joint was predicted based on safe life method using Brown-Miller critical plane criterion. Results represented that the predicted life using fracture mechanics concept was much closer to the experimental results.
Vibration
B. Asmar; M. Karimi; F. Nazari; A. Bolandgerami
Abstract
Crack identification is a very important issue in mechanical systems, because it is a damage that if develops may cause catastrophic failure. In the first part of this research, modal analysis of a multi-cracked variable cross-section beam is done using finite element method. Then, the obtained results ...
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Crack identification is a very important issue in mechanical systems, because it is a damage that if develops may cause catastrophic failure. In the first part of this research, modal analysis of a multi-cracked variable cross-section beam is done using finite element method. Then, the obtained results are validated usingthe results of experimental modal analysis tests. In the next part, a novel procedure is considered to identify the locations and depths of cracks in the multi-cracked variable cross-section beam using natural frequency variations of the beam based on artificial neural network and particle swarm optimization algorithm. In the proposed crack identification algorithm, four distinct neural networks are employed for the identification of locations and depths of both cracks. Back error propagation and particle swarm optimization algorithms are used to train the networks. Finally, the results of these two methods are evaluated.
Optimization
G. Kanagaraj; N. Jawahar
Abstract
This paper addresses the mixed integer reliability redundancy allocation problems to determine simultaneous allocation of optimal reliability and redundancy level of components based on three objective goals. System engineering principles suggest that the best design is the design that maximizes the ...
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This paper addresses the mixed integer reliability redundancy allocation problems to determine simultaneous allocation of optimal reliability and redundancy level of components based on three objective goals. System engineering principles suggest that the best design is the design that maximizes the system operational effectiveness and at the same time minimizes the total cost of ownership (TCO). To evaluate the performance of the TCO allocation numerical experiments were conducted and compared with previous for the series system, the series-parallel system, the complex (bridge) system and the over speed protection system. From the results of the numerical investigation, reliability redundancy allocation based on minimum TCO will lead to a more reliable, economical design for the manufacturer as well as user compared with the initial cost optimum design and conventional reliability optimum design.
Aerodynamics
ava shahrokhi; sahar noori
Abstract
The influence of the plug shape on the performance of an aerospike nozzle thrust force is studied in different back pressure conditions. To generate smooth plug contours, Cubic B-Spline technique is employed. In the current research, basis functions are obtained using Deboor’s relation. The flow ...
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The influence of the plug shape on the performance of an aerospike nozzle thrust force is studied in different back pressure conditions. To generate smooth plug contours, Cubic B-Spline technique is employed. In the current research, basis functions are obtained using Deboor’s relation. The flow field around the aerospike nozzle is investigated implementing various shapes and the best of the generated configurations is determined. The flow field is simulated using Navier-Stokes equations and k-ε turbulence model. A triangle unstructured grid is applied for discretization of the governing equations. The computational methodology utilizes steady state density-based formulation and a finite volume cell centered scheme is used to discretize the flow field equations. To accelerate the solution convergence, the flow field is divided into several zones and appropriate initial condition is assigned to each zone. Six different shapes of the plug are generated and the effect of the spike shape on the formation of the shock wave and expansion waves is investigated in each case. The thrust force is calculated for each case and the best configuration is determined in terms of the maximum thrust generation. Eventually, the temperature distribution is calculated along the nozzle for further investigations and it is concluded that the best configurations show a lower temperature rise compared to other designs.
Computational Fluid Dynamics (CFD)
Seyed Masoud Vahedi; Mohammad Sadegh Valipour; Filippo de Monte
Abstract
Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension ...
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Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension as an important and controversial risk factor among researchers on the efficacy of Heparin-Eluting Stents (HES). For this purpose, the effect of blood pressure is systematically investigated in certain cardiac cycle modes. A comprehensive study is conducted on two classes, pulsatile (time-dependent), to have a more realistic simulation, and non-pulsatile (time-independent) blood flow, each one in four modes. The governing equations applied to drug release dynamics are obtained based on porous media theory. The equations are solved numerically using Finite Volume Method (FVM). Results reveal that there is a significant difference when the plasma flow considered and when it is neglected (regardless of time dependency). Moreover, the concentration level is more decreased in pulsatile blood flow rather than the non-pulsatile blood flow, although the penetration depth for pressure and concentration are nearly 20% and 5% of the wall thickness, respectively. In other words, the mass experienced by the arterial wall is lower in pulsatile blood flow in comparison to non-pulsatile blood flow. As a consequence, the risk of toxicity is declined as the blood pressure increases. Also, it can be seen that the polymer is diffusion-dominated so that no significant changes in the release characteristics are observed in the presence of the plasma filtration.
Heat and Mass Transfer
Sidharth Sudhansu Chakrabarti; Akash Pandey; Pratik Dhage
Abstract
Solar energy is the highly recognized energy source, capable of fulfilling the world’s future energy demands. The solar photovoltaic technology involves the unmediated transformation of sunlight into electricity. A little fraction is converted into electricity and the remaining gets exhausted as ...
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Solar energy is the highly recognized energy source, capable of fulfilling the world’s future energy demands. The solar photovoltaic technology involves the unmediated transformation of sunlight into electricity. A little fraction is converted into electricity and the remaining gets exhausted as unused heat. This results in an increase in the operating temperature of the PV Panel. The conversion efficiency and the life span of the photovoltaic panel are affected by an increase in working temperature. Hence, an appropriate cooling technique is essentially required for maintaining the operating temperature of the module within the limits prescribed so as to obtain higher electrical yield and increased lifespan. The objective of this paper is to present a summary of the various cooling techniques used to enhance the performance of PV panels, namely air cooling - free and forced, water spray cooling, cooling by phase change materials, heat pipe cooling, liquid immersion cooling and forced water circulation. Several research articles are reviewed and classified on the basis of technology used for the thermal management of PV modules. The paper also investigates one of the passive evaporative cooling technique to control the temperature rise of the PV module and enhancement in efficiency. Around 12oC reduction in PV panel temperature under maximum insolation and 7.7 % increase in average electric power generation efficiency was observed under this technique.
Biomechanics
Diana Martins; Rui Couto; Elza M M Fonseca; Ana Rita Carreiras
Abstract
This work presents a numerical approach to predict the influence of material stiffness in a dental implant using different thread profile shapes, always with a constant number of threads, thread width and thread pitch. Dental implant affects bone tissue, in response to various mechanical stimuli where ...
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This work presents a numerical approach to predict the influence of material stiffness in a dental implant using different thread profile shapes, always with a constant number of threads, thread width and thread pitch. Dental implant affects bone tissue, in response to various mechanical stimuli where the biomechanical behavior plays a significant role in the study of stress and strain calculation. In this work, four different thread profile shapes were considered (Model1 - Plateau typeA, Model2 - Plateau typeB, Model3 - Triangular, Model4 - Rectangular) with two different inner diameters equal to 4 and 6 mm, using three different implant materials (titanium, an iso-elastic titanium and zirconium alloys). Two dimensional computational axisymmetric models of a bone-implant were constructed using the finite element method. This study presents the numerical results about the mechanical stimuli on dental implant according to the chosen material and profile shape. The main contribution of this work is giving additional information about the stability and implant loosening with the application on surgical techniques in dental science.
Composite Materials
Manoj Kumar Shukla; Kamal Sharma
Abstract
The synergetic effect of amine functionalized multiple graphene layers (AMGL) and multi-walled carbon nanotube (AMWCNT) nano-fillers mixed with epoxy resin is investigated on the particle size distribution (PSD) and tensile properties of hybrid composites. The hybrid composites with an equal ratio of ...
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The synergetic effect of amine functionalized multiple graphene layers (AMGL) and multi-walled carbon nanotube (AMWCNT) nano-fillers mixed with epoxy resin is investigated on the particle size distribution (PSD) and tensile properties of hybrid composites. The hybrid composites with an equal ratio of nano-fillers at a weight percent of 0.25, 0.50, 1, and 2 wt % are fabricated. The particle size analysis (PSA) is performed by the dynamic light scattering (DLS) technique and image analysis (IA) method; both verify PSD for composites. This is further verified by the analyses of scanning electron microscopy (SEM) images using Image J software. The optimum composite particle size of 6.8 µm and homogeneous mixture with a poly-dispersity index (PI) of 0.74 is investigated for a sample having filler content of 0.5 wt %. Tensile stress and elastic modulus is also found to be maximum at 0.5 wt %, which is 49.91 MPa of 2302 Mpa, respectively. The chemical composition of composite affecting its PSD is characterized by energy dispersive X-ray (EDX) process. Dimensional analysis of particle size in the domain of epoxy matrix provides deep insights to the researchers and may also provide them a direction for selecting an appropriate material for a particular application.
Control
R. Mestiri*; F. Aloui; S. Ben Nasrallah
Abstract
The technique used to control the airflow is based on the electro-hydrodynamic actuator which is also called plasma actuator. This actuator ensures the airflow control thanks to the electric wind created by the electrical corona discharge. This ionic wind is developed at the profile surface tangential ...
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The technique used to control the airflow is based on the electro-hydrodynamic actuator which is also called plasma actuator. This actuator ensures the airflow control thanks to the electric wind created by the electrical corona discharge. This ionic wind is developed at the profile surface tangential to the initial free airflow so that it has a significant effect on the boundary layer flow. The studied profile was a NACA4412 airfoil. The electro-hydrodynamic actuator was placed at the surface of the NACA profile. The PIV visualizations made at angle of attack of 18° show an earlier flow reattachment to the profile surface when the plasma actuator is active. PIV measurements confirm that downstream of the actuator, when the discharge is ON, the wall velocity gradient is increased as illustrated by the velocity profiles taken at several positions on the NACA4412 wall. Then the plasma actuator can decrease the boundary layer thickness.
Heat and Mass Transfer
S. Mohammed Ibrahim; K. Suneetha
Abstract
An analytical investigation is conducted to study the unsteady free convection heat and mass transfer flow through a non-homogeneous porous medium with variable permeability bounded by an infinite porous vertical plate in slip flow regime while taking into account the thermal radiation, chemical reaction, ...
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An analytical investigation is conducted to study the unsteady free convection heat and mass transfer flow through a non-homogeneous porous medium with variable permeability bounded by an infinite porous vertical plate in slip flow regime while taking into account the thermal radiation, chemical reaction, the Soret number, and temperature gradient dependent heat source. The flow is considered under the influence of magnetic field applied normal to the flow. Approximate solutions for velocity, temperature, and concentration fields are obtained using perturbation technique. The expressions for skin-friction, rate of heat transfer, and rate of mass transfer are also derived. The effects of various physical parameters, encountered in the problem, on the velocity field, temperature field, and concentration field are numerically shown through graphs, while the effects on skin-friction, rate of heat, and mass transfer are numerically discussed by tables.
Vibration
Rouhollah Hosseini; Keikhosrow Firoozbakhsh; Hossein Naseri
Abstract
Because the underlying physiology of pathological tremor in a Parkinson's patient is not well understood, the existing physical and drug therapies have not been successful in tremor treatment. Different mathematical modeling of such vibration has been introduced to investigate the problem and reduce ...
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Because the underlying physiology of pathological tremor in a Parkinson's patient is not well understood, the existing physical and drug therapies have not been successful in tremor treatment. Different mathematical modeling of such vibration has been introduced to investigate the problem and reduce the existing vibration. Most of the models have represented the induced vibration as a sinusoidal wave for mathematical simplification. In this study, a more realistic model based on random vibration was used to attack the problem of tremor suppression. A simple approach for suppressing the tremor associated with Parkinson's disease was presented. This paper was concerned with a multi-objective approach for optimum design of linear vibration absorber subject to random vibrations. Analytical expressions, for the case of non-stationary white-noise accelerations, were also derived. The present approach was different from conventional optimum design criteria since it was based on minimizing displacement as well as accelerating variance of the main structure responses without considering performances required against discrepancy in response. In this study, in order to control the tremor induced on biomechanical arm model excited by non-stationary based acceleration random process, multi-objective optimization (MOO) design of a vibration absorber was developed and performed using modern imperialist competitive optimization algorithm for multi-objective optimization. The results demonstrated importance of this method and showed that multi-objective design methodology provided significant improvement in performance stability and giving better control of the design solution choice.
Thermodynamics and Cumbustion
M. V. S. Murali Krishna; R. P. Chowdary; T. Kishen Kumar Reddy; P. V. K. Murthy
Abstract
Investigations were carried out to evaluate the performance of direct injection diesel engine with medium grade low heat rejection (LHR) combustion chamber and 3 mm air gap insulated piston, 3 mm air gap insulated liner, and ceramic coated cylinder head [ceramic coating with the thickness of 500 µ ...
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Investigations were carried out to evaluate the performance of direct injection diesel engine with medium grade low heat rejection (LHR) combustion chamber and 3 mm air gap insulated piston, 3 mm air gap insulated liner, and ceramic coated cylinder head [ceramic coating with the thickness of 500 µ was made on the inside portion of the cylinder head].The engine had different operating conditions [normal temperature and pre–heated temperature] of crude waste fried vegetable oil (WFVO) which was collected from restaurants, hotels, etc. with varied injector opening pressure and injection timing. Performance parameters and exhaust emissions were evaluated at various values of brake mean effective pressure of the engine, while combustion parameters were determined at full load operation of the engine using special pressure–crank angle software package. Comparative studies were performed between vegetable oil operation and diesel operation in the engine with both versions of the combustion chamber with varied injection timing and injector opening pressure. Conventional engine (CE) showed deteriorated performance, while the engine with medium grade LHR combustion chamber had improved performance with waste fried vegetable oil operation at the recommended injection timing and pressure. Performance of both versions of the combustion chamber improved with advanced injection timing and at higher injector opening pressure compared with CE with pure diesel operation. The optimum injection timing was 32o bTDC (before top dead centre) with conventional engine, while it was 30o bTDC for the engine with LHR combustion chamber and vegetable oil operation. Compared with pure diesel operation in the conventional engine, at manufacturer's recommended injection timing of 27o bTDC, peak brake thermal efficiency increased by 9% at full load operation, brake specific energy consumption decreased by 2%, volumetric efficiency decreased by 13%, smoke levels decreased by 10%, and nitrogen oxide (NOx) levels increased by 44% with waste fried vegetable oil operation in the engine with LHR combustion chamber.
Perturbation Technique
shaik Mohammed ibrahim; Kanna Suneetha; G.V Ramana Reddy
Abstract
The paper addresses the effects of Soret on unsteady free convection flow of a viscous incompressible fluid through a porous medium with high porosity bounded by a vertical infinite moving plate under the influence of thermal radiation, chemical reaction, and heat source. The fluid is considered to be ...
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The paper addresses the effects of Soret on unsteady free convection flow of a viscous incompressible fluid through a porous medium with high porosity bounded by a vertical infinite moving plate under the influence of thermal radiation, chemical reaction, and heat source. The fluid is considered to be gray, absorbing, and emitting but non-scattering medium, and Rosseland approximation is considered to describe the radiative heat flux in the energy equation. The dimensionless governing equations for this investigation are solved analytically by using perturbation technique. The effects of various governing parameters on the velocity distributions, temperature distributions, concentration distributions, local skin-friction coefficient, local Nusselt number and local Sherwood number are shown in figures and tables and analyzed in detail. It was noticed that the velocity distribution increased with increasing buoyancy parameters, temperature profiles decreased with increasing Prandtl number and concentration fields decreased with increasing the Schmidt number and chemical reaction parameter.
Computational Fluid Dynamics (CFD)
chakravarthula S K Raju; P DurgaPrasad; S.V.K. Varma
Abstract
In this study, the Brownian motion and thermophoresis effects on the MHD ferrofluid flow over a cone with thermal radiation were discussed. Kerosene with the magnetic nanoparticles (Fe3O4) was considered. A set of transformed governing nonlinear coupled ordinary differential equations were solved numerically ...
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In this study, the Brownian motion and thermophoresis effects on the MHD ferrofluid flow over a cone with thermal radiation were discussed. Kerosene with the magnetic nanoparticles (Fe3O4) was considered. A set of transformed governing nonlinear coupled ordinary differential equations were solved numerically using Runge-Kutta based shooting technique. A simulation was performed by mixing ferrous particles with base fluids. Also, dual solutions for Casson Ferrofluid flow over a cone with rotation and without rotation effects were presented. An agreement of the present solutions with those published in literature was found. The effect of dimensionless parameters on velocity, temperature and concentration profiles along with the friction factor coefficients, Nusselt number, and the Sherwood numbers were discussed with the help of graphs and tables. It was found that the volume fraction of Ferro nanoparticles, magnetic field parameter, and Brownian motion parameters are controlling the friction factor coefficients, Nusselt number and Sherwood numbers for both the rotation and without rotation effects cases.
Robotics
Eram Neha; Mohd. Suhaib; Shruti Asthana; Sudipto Mukherjee
Abstract
The structure of the human hand is a complex design comprising of various bones, joints, tendons, and muscles functioning together in order to produce the desired motion. It becomes a challenging task to develop a robotic hand replicating the capabilities of the human hand. In this paper, the analysis ...
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The structure of the human hand is a complex design comprising of various bones, joints, tendons, and muscles functioning together in order to produce the desired motion. It becomes a challenging task to develop a robotic hand replicating the capabilities of the human hand. In this paper, the analysis of the four-fingered robotic hand is carried out where the tendon wires and a spring return mechanism is used for the flexion and extension motion of the fingers, respectively. Stable grasping and fine manipulation of different objects are desired from any multi-finger robotic hand. In this regard, it becomes necessary to check the performance of the four-fingered robotic hand. Simulations are performed for the hand to grasp objects of different size and shapes, and the hand model is controlled in a MATLAB environment using the SimMechanics toolbox. Here the Kinematics and Dynamics study of the hand system is carried out by importing the Solidworks model into the SimMechanics. Simulation results demonstrate that the developed hand model is able to grasp objects of varying size and shapes securely.
Hydraulic and Pneumatic Systems
Amir Saidani; Ali Fourar; Fawaz Massouh
Abstract
The paper investigates the temperature effect on water hammers in an isothermal pressurized copper pipe rig, for single and two-phase flows. The study concerns pressure wave’s intensity, celerity, and attenuation. Also, the volume of cavities created during low-pressure periods is inspected. The ...
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The paper investigates the temperature effect on water hammers in an isothermal pressurized copper pipe rig, for single and two-phase flows. The study concerns pressure wave’s intensity, celerity, and attenuation. Also, the volume of cavities created during low-pressure periods is inspected. The mathematical model of hyperbolic equations is described by the dynamic and continuity equations, which have been transformed by the characteristics method into ordinary differential equations. Water hammer solver was built considering two different models of cavitation and column separation, the discrete vapor cavity model and the discrete gas cavity model. In addition to the quasi-steady friction model, two unsteady friction models were incorporated into the code, the convolution-based model proposed by Vardy and Brown and the instantaneous acceleration model proposed by Brunone. The simulations concern temperature range within 4°C to 95°C. Although the single and the two-phase water hammers don’t behave in the same manner, the results obtained with the different models, show a significant influence of the temperature.
Manufacturing Processes
Sachin G Ghalme; Yogesh Bhalerao; Kamlesh Phapale
Abstract
Composite materials have proven their applicability for various structural components. Excellent properties of glass fiber reinforced plastic (GFRP) composite materials have presented GFRP composites for potential applications in aerospace and automobile-related industries. Drilling is an important operation ...
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Composite materials have proven their applicability for various structural components. Excellent properties of glass fiber reinforced plastic (GFRP) composite materials have presented GFRP composites for potential applications in aerospace and automobile-related industries. Drilling is an important operation for composite structures during final assembly. This paper investigates the factors affecting delamination in GFRP composite during the drilling process. Drill speed and feed rate are selected two parameters affecting delamination during the drilling process. The response surface methodology approach has been used for experimental design and analysis of variance. Delamination was evaluated at the entry, middle, and exit positions of the hole. An attempt has been made to optimize the speed and feed rate for minimization of delamination at the three positions using grey relational analysis. The results of this work will help in selecting an optimum level of speed and feed rate to minimize delamination at the entry, middle, and exit positions of the hole to improve quality of the drilled hole.
Nonlinear Solution
Wah Yen Tey; Yu Maan Kong
Abstract
The theory of superposition of waves has been widely deployed in many engineering applications such as medical imaging, engineering measurements, and wave propagation in structures. However, these applications are prone to the interference of unwanted waves. The root cause of the weakness could be ascribable ...
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The theory of superposition of waves has been widely deployed in many engineering applications such as medical imaging, engineering measurements, and wave propagation in structures. However, these applications are prone to the interference of unwanted waves. The root cause of the weakness could be ascribable to the wave propagation pattern, which is not actively controlled. A new concept of imposing a time-lagging effect on the source of the wave as an active wave emission strategy is introduced and discussed in this paper. A numerical solver has been developed based on the finite volume Euler explicit method to investigate the wave propagation pattern when there is a time-lagged effect and frequency difference at the source of the wave. Our results reveal that time-lagged wave propagation will be more immune to the disturbance of other waves. The larger the time lag, the more resilient the wave is to resist the interference of other waves, even at a higher frequency. Time-lagged waves can be regarded as a promising active wave emission method that has many potential and robust engineering applications to be explored in the future.
Damage Mechanics
E. Homaei; K. Farhangdoost; M. Akbari
Abstract
The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes ...
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The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes such as radial cracks and plastic deformation in dental prostheses, which consist of a brittle outerlayer (porcelain)/ metal (Au, Pd, Co)-core/ substrate (dentin) trilayer system. XFEM not only has the ability to model crack initiation process, but also could solve crack propagation problems. Generally speaking, porcelain layer shouldn't be thinner than 0.5 mm, as the stresses due to bending become tensile critically in porcelain undersurfaces and radial cracks would occur in low loads. Also, it could be concluded that XFEM in axisymmetric model could properly estimate crack initiation and propagation path. Yielding of metal core makes additional flexural stress at overlaying brittle surface and consequently, facilitates radial cracks. In dental applications, the optimum porcelain thickness would be between 0.75 and 1.25 mm. Furthermore, yield strength and stiffness of metal is better to be high sufficiently to prevent it from plastic deformation and ensuing radial cracks.
Heat and Mass Transfer
M. Gnaneswara Reddy; Sandeep N
Abstract
This article explores the heat and mass transfer behaviour of magnetohydrodynamic free convective flow past a permeable vertical rotating cone and a plate filled with gyrotactic microorganisms in the presence of nonlinear thermal radiation, thermo diffusion and diffusion thermo effects. We presented ...
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This article explores the heat and mass transfer behaviour of magnetohydrodynamic free convective flow past a permeable vertical rotating cone and a plate filled with gyrotactic microorganisms in the presence of nonlinear thermal radiation, thermo diffusion and diffusion thermo effects. We presented dual solutions for the flow over a rotating cone and a rotating flat plate cases. Similarity variables are employed to convert the nonlinear partial differential equations into ordinary differential equations. Comparisons with previously published work are performed and results are found to be in excellent agreement. The resultant non-dimensional governing equations along with associated boundary conditions are solved numerically using Runge–Kutta and Newton’s methods. The impact of pertinent parameters on velocity, temperature, concentration and density of the motile microorganisms along with the friction factor, local Nusselt, Sherwood numbers and the local density of the motile microorganisms was determined and analyzed with the help of graphs and tables. Results proved that there is a significant variation of heat and mass transfer in the flow over a rotating cone and a plate. It is also found that the heat and mass transfer performance of the flow over a rotating cone is significantly high when compared with the flow over a rotating plate.
Vibration
M. Shariati; H. Hatami; M. Damghani Nouri
Abstract
In this research, softening and ratcheting behaviors of Ck20 alloy steel cylindrical shells were studied under displacement-control and force-control cyclic axial loading and the behavior of hysteresis curves of specimens was also investigated. Experimental tests were performed by a servo-hydraulic INSTRON ...
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In this research, softening and ratcheting behaviors of Ck20 alloy steel cylindrical shells were studied under displacement-control and force-control cyclic axial loading and the behavior of hysteresis curves of specimens was also investigated. Experimental tests were performed by a servo-hydraulic INSTRON 8802 machine. The mechanical properties of specimens were determined according to ASTM E8 standard. Under force-control loading with non-zero mean force, ratcheting behavior occurred on cylindrical shell and plastic strain accumulation continued up to the collapse point of cylindrical shell. The rate of ratcheting strain became higher using the higher force amplitude. Softening behavior was observed under displacement control loading and, due to the occurred buckling in compression zone, this behavior became more extreme. The behavior of hysteresis curves of this alloy was not symmetrical under tensile and compressive loads. Moreover, the influence of loading history was studied on the behavior of hysteresis curves of the specimens under various types of loadings.
Plates and Shells
Abdolhossein Fereidoon; Kamal Kolasangiani; Amin Akbarpour; Mahmoud Shariati
Abstract
In this paper, simulation and analysis of thin steel cylindrical shells with elliptical cutouts under oblique loading were studied using finite element method. First, the numerical results were validated by the results of experimental test performed by an INSTRON 8802 servo hydraulic machine. Also, the ...
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In this paper, simulation and analysis of thin steel cylindrical shells with elliptical cutouts under oblique loading were studied using finite element method. First, the numerical results were validated by the results of experimental test performed by an INSTRON 8802 servo hydraulic machine. Also, the effect of cutout angle (θ), cutout size, cutout position (L0/L) and cutout aspect ratios (b/a) were investigated, where parameter (a) shows size of the cutout along longitudinal axis of the cylinder, parameter (b) is size of the cutout in circumferential direction of the cylinder on the buckling and post-buckling behavior of cylindrical shells with finite element method. It can be concluded that increasing width of the cutout extremely decreased the buckling load while the cutout height was constant. Moreover, changing position of the cutout from the mid-height of the shell toward the edges increased the buckling load.
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