Showing papers in "Journal of The Brazilian Society of Mechanical Sciences and Engineering in 2015"
TL;DR: In this article, the effect of Brownian motion on the effective thermal conductivity and viscosity of the nanofluid is calculated by KKL (Koo-Kleinstreuer-Li) correlation, which is then solved numerically by the fourth-order Runge-Kutta integration scheme featuring a shooting technique.
Abstract: The aim of the present paper is to study the nanofluid flow and heat transfer over a stretching porous cylinder. The effective thermal conductivity and viscosity of the nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In KKL model, the effect of Brownian motion on the effective thermal conductivity is considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved numerically by the fourth-order Runge–Kutta integration scheme featuring a shooting technique. Numerical results for flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction parameter, Reynolds number and different kinds of nanofluids. Results show that inclusion of a nanoparticle into the base fluid of this problem is capable to change the flow pattern. It is found that Nusselt number is an increasing function of nanoparticle volume fraction, suction parameter and Reynolds number.
199 citations
TL;DR: In this paper, a free vibration analysis of rotating functionally graded Timoshenko beam made of porous material using the semi-analytical differential transform method was presented, where the material properties are supposed to vary along the thickness direction of the beam according to the rule of mixture.
Abstract: This study presents free vibration analysis of rotating functionally graded Timoshenko beam made of porous material using the semi-analytical differential transform method.The material properties are supposed to vary along the thickness direction of the beam according to the rule of mixture, which is modified to approximate the material properties with the porosity phases. The frequency equation is obtained using Hamilton’s principle. It is demonstrated that the DTM has high precision and computational efficiency in the vibration analysis of porous FG rotating beams. The good agreement between the results of this article and those available in literature validated the presented approach. Detailed mathematical derivations are presented and numerical investigations are performed, while emphasis is placed on investigating the effect of the several parameters such as porosity, functionally graded microstructure, thickness ratio, rotational speed and hub radius on the normalized natural frequencies of porous FG rotating beams in detail.
104 citations
TL;DR: In this article, the effects of the squeeze number, radiation parameter, Schmidt number, Brownian motion parameter, thermophoretic parameter and Eckert number on flow, heat and mass transfer are considered.
Abstract: In this study, heat and mass transfer characteristic of unsteady nanofluid flow between two parallel plates is investigated considering thermal radiation. Two phase model is considered in order to simulate nanofluid. The basic partial differential equations are reduced to ordinary differential equations which are solved numerically using the fourth-order Runge–Kutta method. The effects of the squeeze number, radiation parameter, Schmidt number, Brownian motion parameter, thermophoretic parameter and Eckert number on flow, heat and mass transfer are considered. Results indicate that concentration boundary-layer thickness increases with increase of Radiation parameter. Also it can be found that Nusselt number has direct relationship with Eckert number, Schmidt number, squeeze parameter and Radiation parameter.
72 citations
TL;DR: In this article, the effects of convective heat and concentration conditions in magnetohydrodynamic flow of non-Newtonian fluid with nanoparticles were investigated, where the nonlinear partial differential equations were reduced into nonlinear ordinary differential equations by suitable similarity variables.
Abstract: This article investigates the effects of convective heat and concentration conditions in magnetohydrodynamic flow of non-Newtonian fluid with nanoparticles. Convective type boundary conditions are utilized for heat and nanoparticles concentration. The nonlinear partial differential equations are reduced into the nonlinear ordinary differential equations by suitable similarity variables. Homotopy analysis method is employed to obtain the dimensionless velocity, temperature and nanoparticles concentration expressions. Graphical results for temperature and nanoparticles concentration are plotted and examined. Numerical values of skin friction coefficient are computed and discussed. Heat transfer and nanoparticles concentration transfer rates at the wall are examined by plotting the graphs of different governing physical parameters. We noticed that the temperature and nanoparticles concentration profiles are enhanced when the values of Biot numbers are increased. An increase in thermophoresis parameter leads to an enhancement in the temperature and nanoparticles concentration. On the other hand the increasing values of Brownian motion parameter has reverse effects on the temperature and nanoparticles concentration fields.
44 citations
TL;DR: In this paper, a multilayer perceptron neural network was used with the Levenberg-Marquardt learning algorithm, whose inputs were the raw acoustic emission (AE) signal and statistics derived from this signal.
Abstract: The grinding operation gives workpieces their final finish, minimizing surface roughness through the interaction between the abrasive grains of a tool (grinding wheel) and the workpiece. However, excessive grinding wheel wear due to friction renders the tool unsuitable for further use, thus requiring the dressing operation to remove and/or sharpen the cutting edges of the worn grains to render them reusable. The purpose of this study was to monitor the dressing operation using the acoustic emission (AE) signal and statistics derived from this signal, classifying the grinding wheel as sharp or dull by means of artificial neural networks. An aluminum oxide wheel installed on a surface grinding machine, a signal acquisition system, and a single-point dresser were used in the experiments. Tests were performed varying overlap ratios and dressing depths. The root mean square values and two additional statistics were calculated based on the raw AE data. A multilayer perceptron neural network was used with the Levenberg–Marquardt learning algorithm, whose inputs were the aforementioned statistics. The results indicate that this method was successful in classifying the conditions of the grinding wheel in the dressing process, identifying the tool as “sharp” (with cutting capacity) or “dull” (with loss of cutting capacity), thus reducing the time and cost of the operation and minimizing excessive removal of abrasive material from the grinding wheel.
42 citations
TL;DR: In this paper, the effects of the taper angle, wall deformation, and severity of the stenosis within its fixed length on velocity profiles, volumetric flow rate, and resistive impedance are studied considering their dependencies with time.
Abstract: A nonlinear two-dimensional pulsatile blood flow through a stenosed artery is investigated by treating the deformable vascular wall as an elastic cylindrical tube containing the Newtonian fluid. In order to establish a resemblance to the in vivo conditions, the mathematical model of an improved shape of the time-variant overlapping stenosis is considered in the tapered arterial lumen. By applying a suitable coordinate transformation, the tapered cosine-shaped artery becames a non-tapered rectangular and rigid artery. The continuity and the nonlinear momentum equations are numerically solved under the appropriate physically realistic prescribed boundary conditions. In order to solve the resulting simultaneous equation system, the finite difference approximation code is developed and utilized. The effects of the taper angle, wall deformation, and severity of the stenosis within its fixed length on velocity profiles, volumetric flow rate, and resistive impedance are studied considering their dependencies with time. The present results are found in agreement with similar data from the literature.
36 citations
TL;DR: In this article, an attempt has been made to optimize the process parameters of friction stir welding (FSW) for tensile strength and percentage elongation using Taguchi-based gray relation analysis (GRA).
Abstract: In this experimental study, an attempt has been made to optimize the process parameters of friction stir welding (FSW) for tensile strength and percentage elongation using Taguchi-based gray relation analysis (GRA). An orthogonal array of L9 has been implemented to fabrication of joints. The experiments have conducted according to the combination of rotational speed, tool tilt (TLT) and types of tool pin profile (TPP). The results revealed that the rotational speed is most significant process parameter with percentage contribution of 96.24 %. On optimization, tool rotation speed of 1,550 rpm, TLT angle of 4° and octagonal-type TPP have been found to be the best parameter setting for FSW process of aluminum 6061 and 6082 alloy welds. To ensure the robustness of GRA, a confirmation test was performed at selected optimal process parameter setting.
35 citations
TL;DR: In this paper, the effect of WEDM parameters, such as pulse on time, pulse off time, peak current, spark gap voltage, wire feed rate and wire tension has been varied to investigate their effect on material removal rate and overcut for pure titanium.
Abstract: Titanium and its alloys have been experiencing extensive development over the past few decades stimulated by a series of their unique properties, i.e. high strength to weight ratio maintained at elevated temperature, high hot hardness, high fracture resistance, and exceptional resistance to corrosion at temperature below 500 °C. Machining of titanium, however, is considered as cumbersome with the conventional manufacturing practices, and there is a critical need for developing and establishing cost-effective methods of machining. This research work is mainly focused on the effect of WEDM parameters, such as pulse on time, pulse off time, peak current, spark gap voltage, wire feed rate and wire tension has been varied to investigate their effect on material removal rate and overcut for pure titanium. The experiments are planned, conducted, and analyzed through response surface methodology. An attempt has also been made to construct a micro-model for prediction of material removal rate using dimensional analysis. The predictions from this model have been validated by conducting experiments.
33 citations
TL;DR: In this paper, an investigation has been made into the electrical discharge machining process (EDM) when both graphite powder and surfactant-mixed dielectric fluid were used during EDM of precipitation hardening stainless steel PH17-4.
Abstract: In the present work, an investigation has been made into the electrical discharge machining process (EDM) when both graphite powder and surfactant-mixed dielectric fluid were used during EDM of precipitation hardening stainless steel PH17-4 The addition of graphite powder in the dielectric fluid results in uniform distribution of discharge, which improves surface finish However, agglomeration of graphite particles is found in the dielectric due to the electrostatic forces among the graphite powder particles The addition of surfactant in the dielectric increases dielectric conductivity and in turn reduces relay time of discharge This increases actual discharge time, which results in more material removal At the same time, uniform distribution of graphite powder particles in the dielectric fluid is achieved This leads to increase in discharge frequency, which results in increase in material removal rate and surface finish Taguchi parameter design approach was used to get an optimal parametric setting of EDM process parameters namely: peak current, surfactant concentration and graphite powder concentration that yields to optimal process performance characteristics such as material removal rate, surface roughness, white layer thickness and surface crack density Individual effect of process parameters on performance characteristics was also studied To identify the significance of parameters on measured response, the analysis of variance has been carried out Further, mathematical models were developed by performing nonlinear regression analysis to predict process performance characteristics Confirmation tests were conducted at their respective optimal parametric settings to verify the predicted optimal values of performance characteristics
33 citations
TL;DR: In this article, a study of fluid-solid interaction in a free surface flow by smoothed particles hydrodynamics method is presented, where different cases of symmetry and asymmetry wedge water entries are presented.
Abstract: This article presents a study of fluid–solid interaction in a free surface flow by smoothed particles hydrodynamics method. Different cases of symmetry and asymmetry wedge water entries are presented. All cases are performed at constant speed, considering the effect of gravity. First-order density filter, turbulence modeling and a pressure filter have been utilized. Through these compiling options, low-pass pressure filter has been able to eliminate the undesirable fluctuation of pressure, and good results have been achieved. Pressure distribution and free surface profiles have been produced in all cases. In the cases of symmetry wedge water entries, the obtained results were compared against the results of BEM, similarity and asymptotic solutions, but in the cases of asymmetry wedge water entry, the obtained results were compared against those of analytical work. Through these comparisons, it was found that although the general trend of the computed pressure distributions follows the results of the previous studies, there still exist some differences among them. Main difference between the obtained results and other studies is related to the position of the pressure peak. It was concluded that this may indeed be attributed to the nature of the applied methods and due to the methodology of cutting the edges in schemes like BEM to overcome the abrupt flow at the edge. Vertical force in particular symmetry and asymmetry cases was also computed and presented. It was found that the global behavior of the vertical force in both the symmetry and asymmetry wedge water entry is the same and that there are some differences among them in terms of decreasing rate as well as the maximum value of the force.
31 citations
TL;DR: In this paper, an integrated system was developed for image acquisition, modeling and control of the welding process, allowing a real-time response, through artificial neural networks, to predict parameters such as welding speed, wire feed velocity and arc voltage.
Abstract: The need to improve productivity and quality has led to the development and improvement of techniques and systems for monitoring and controlling welding processes. This work presents a methodology to perform the modeling, optimization and control of the weld bead width, enabling the adjustment of process parameters in real time. An integrated system was developed for image acquisition, modeling and control of the welding process, allowing a real-time response, through artificial neural networks. Parameters such as welding speed, wire feed velocity and arc voltage are predicted in the function of a desired weld bead width. To get the closed-loop control system, it was designed with a “fuzzy” controller, in which the difference between the width to be achieved and the actual width of the bead is taken as reference. This weld bead is measured through an acquisition system and images processed using a low-price webcam. The control action is carried out preferably at welding speed, a parameter that has the greatest influence on the weld bead width and has no influence on the metal transfer behavior. Weld beads with pre-defined width, good appearance and quality were obtained.
TL;DR: This research has presented an analytical approach to compute the reliability measures of a system, which contains a mixed configuration, which consists of three subsystems connected in mixed configurations (i.e. combination of series and parallel configuration).
Abstract: In safety critical applications, it becomes common to improve the reliability through k-out-of-n redundancy. In this research, the authors have presented an analytical approach to compute the reliability measures of a system, which contains a mixed configuration. The system consists of three subsystems, namely A, B and C, connected in mixed configurations (i.e. combination of series and parallel configuration). Subsystem A is of the type 1-out of-2:G. Subsystem A is connected to subsystem B in a parallel configuration and these two subsystems are connected in series configuration with subsystem C. The considered system has three states, namely, good, degraded and failed. Markov process, supplementary variable technique and Laplace transformation have been used for solution and reliability measures like availability, reliability, mean time to failure, sensitivity analysis and cost-effectiveness have been evaluated of the considered system.
TL;DR: In this article, an integrated approach of GT-PCA which combines the methodology of grey theory and principal component analysis (PCA) was used to predict the optimal level of friction welding parameters.
Abstract: Solid-state welding processes have widened the scope of joining metal matrix composites. The aim of this work was to study the possibility of producing good quality joints with Al/SiC/Al2O3 composites using continuous drive friction welding. Taguchi’s L9 orthogonal array was used to study the effect of welding parameters like frictional pressure, upset pressure, burn off length and rotational speed on the quality characteristics of joints. The quality of joints was evaluated by observing the tensile strength, elongation and micro hardness. An integrated approach of GT-PCA which combines the methodology of grey theory and principal component analysis (PCA) was used to predict the optimal level of friction welding parameters. Frictional pressure was identified as the prime parameter affecting the observed responses. Microstructure of the weld zone was examined using optical microscopy and the fractured surface was also investigated using the field emission scanning electron microscopy images.
TL;DR: In this paper, the boundary layer flow of viscoelastic fluid over a stretching cylinder is examined and the governing boundary layer partial differential equations are reduced into ordinary differential equations through suitable transformations.
Abstract: Boundary layer flow of viscoelastic fluid over a stretching cylinder is examined in this paper. Brownian motion and thermophoresis effects are studied in the presence of mixed convection. The governing boundary layer partial differential equations are reduced into ordinary differential equations through suitable transformations. The homotopic series solutions have been developed. Influence of physical parameters on the velocity, temperature and concentration fields are analyzed graphically. Local Nusselt and Sherwood numbers are computed numerically for different values of parameters. Physical interpretation is discussed.
TL;DR: In this article, the free vibration of simply supported rectangular nanoplates based on two-variable refined plate theory using strain gradient elasticity theory is presented, and the results of the present work can be used as a bench mark for future works.
Abstract: In this paper, the free vibration of simply supported rectangular nanoplates based on two-variable refined plate theory using strain gradient elasticity theory is presented. Various formats of gradient elasticity theory are available in the literature. In this work, strain gradient elasticity theory with two gradient constants is used. An analytical method is adopted to find the natural frequencies of rectangular nanoplates. Present results are compared with the results of other works done previously. It is mentioned that it is the first time that two-variable refined theory and strain gradient elasticity theory with two gradient constants are used together for free vibration of nanostructures, so the results of the present work can be used as bench mark for future works.
TL;DR: In this paper, extended Isogeometric analysis (XIGA) is successfully extended to evaluate the fatigue life of a homogenous finite plate in the presence of multiple defects (cracks, holes and inclusions) under cyclic loading condition.
Abstract: In this work, extended Isogeometric analysis (XIGA) is successfully extended to evaluate the fatigue life of a homogenous finite plate in the presence of multiple defects (cracks, holes and inclusions) under cyclic loading condition. In isogeometric analysis, same basis functions, i.e. non uniform rational B-splines are used for defining the geometry and solution. In XIGA, the crack faces are modeled by discontinuous Heaviside jump functions, whereas the singularity in stress field at the crack tip is modeled by crack tip enrichment functions. The modeling of holes and inclusions is performed by jump function and distance function, respectively. These simulations show that the defects/discontinuities, distributed near to the main crack, have significant effect on the SIF values, whereas the defects/discontinuities away from the main crack have got very small effect on the SIFs.
TL;DR: In this paper, a numerical method is used to investigate the influence of a step on the pressure distribution, hydrodynamics characteristics, and wake profile of a modern high-speed chine planing hull.
Abstract: Drag increases rapidly with speed in high-speed planing hull. During the last decades, many researchers have tried to reduce hull drag in order to achieve the highest speed. Based on these researches, several methods have been applied to reduce drag such as hull form optimization, marine coating, and planing equipments. One of the most efficient strategies is to use a step on the hull bottom that leads to significant wetted surface reduction, resulting in a considerable reduction in total drag. In the current study, the numerical method is used to investigate the influence of a step on the pressure distribution, hydrodynamics characteristics, and wake profile of a modern high-speed chine planing hull. The numerical results obtained show a good agreement in comparison with the experimental results.
TL;DR: In this article, the second law of thermodynamics over a stretching permeable surface in the presence of the uniform vertical magnetic field in the slip nano-fluid regime was studied.
Abstract: The main purpose of the present article is to study the second law of thermodynamics over a stretching permeable surface in the presence of the uniform vertical magnetic field in the slip nano-fluid regime. In this study, four types of nanoparticles; i.e., Copper Cu, Copper oxide CuO, Aluminum oxide Al2O3, and Titanium dioxide TiO2 and also water as the base fluid are considered. Entropy generation equations, for the first time in this problem, are derived as a function of velocity and temperature gradients. Velocity profile as well as temperature distribution and averaged entropy generation are obtained using optimal homotopy analysis method (OHAM). An excellent agreement exists between the present result and the other researchers’ result. The obtained result of present study presents that by decreasing magnetic parameter, nanoparticle volume fraction parameter, suction parameter, Reynolds number, Brinkman number, and Hartmann number as well as increasing the slip velocity parameter, the generated entropy reduces.
TL;DR: In this paper, a mobile robot that moves suspended on electric power lines which can surmount different types of obstacles, placed at any position on cable is presented, and the kinematics model of the mobile robot and a methodology for spherical obstacle surmounting are presented.
Abstract: Many theoretical and experimental studies have been carried out in order to develop autonomous robots to travel along telecommunication lines and power transmission lines to perform inspection and/or repair work. These robots can improve the efficiency, reduce labor and are expected to reduce the risks of accident of maintenance personnel. In spite of theoretical researches and technological developments of robotic systems, problems related to stability, controllability, ability to transpose/surmounting obstacles and autonomy still exist. Thus, this paper presents a mobile robot that moves suspended on electric power lines which can surmount different types of obstacles, placed at any position on cable. Firstly is presented a review of some existing robots. After, the kinematics model of the mobile robot and a methodology for spherical obstacle surmounting are presented. Finally, numerical and experimental results are presented to validate the proposed model.
TL;DR: In this paper, the machining force and its Cartesian components were investigated according to the process variables, such as: (1) tool path direction, (2) cutting way, (3) cutting speed, and (4) tool-surface contact (lead angle); when milling free form geometries with a ball-end cutting tool.
Abstract: Milling of free form geometries is an usual machining operation in dies and moulds industry. A ball-end cutting tool is frequently used because its geometry allows the finishing and semi-finishing milling operations of any complex shape. However, unlike the ordinary milling machining, the tool-surface contact alternates constantly what makes the process unstable. Due to the geometrical characteristics of this process, the value of the effective tool diameter depends on the depth of cut and the surface curvature, which alters the lead angle (angle formed between tool axis and surface normal direction). The effective tool diameter alternates constantly along the machining. Moreover, it can be zero when the tool is using its centre to remove material, what makes the cutting speed null. A preview work has shown the severe alteration on the Cartesian components of the machining force when milling free form geometries. Such force oscillation is still not predictable by the up methods, and its cutting phenomenon is still not clear. The current work aims to quantify the influences of the lead angle and the engagement of the tool tip centre into the cutting region, which may lead to improvements on the choice of milling strategy in machining research and application. To do so, the machining force and its Cartesian components were investigated according to the process variables, such as: (1) tool path direction, (2) cutting way, (3) cutting speed, and (4) tool-surface contact (lead angle); when milling free form geometries with a ball-end cutting tool. Geometrical analyses together with milling experiments were carried out. The results show that the tool-surface contact had the greatest impact on the forces, because it can either be related to the effective tool diameter or with the tool tip on the cutting zone. In this area, the material is removed part by shearing and part by ploughing (plastic deformation), which increases the forces. The ascendant feed direction propitiates more stable process than its counterpart, and the cutting speed had also an influence on the forces, regardless the contact between the tools with the machined surface.
TL;DR: A new driller system has a closed-circuit cooling system to reduce the undesired temperature rise during the bone drilling process to prevent the overheating in orthopedic surgical applications.
Abstract: In bone drilling process during the surgical operations, heating increases extremely due to undesired temperature rise that sometimes seriously damages the bones and soft tissues The overheating is usually recog- nized as the temperature exceeds 47 C known as a critical limit above which the drilling causes osteonecrosis In this study, a new driller system is developed to prevent the overheating in orthopedic surgical applications The driller system has a closed-circuit cooling system to reduce the undesired temperature rise during the bone drilling process The driller system is designed and manufactured as a prototype and tested experimentally in vitro by drilling fresh bovine bones using different processing parameters A drill bit with a diameter of 10 mm is designed with a closed-circuit cooling channel internally and used in the bone drilling tests In the drilling tests, the temperatures levels of the bones are measured using both non-contact and thermocouple sensors Based on the results measured in the experiments, the developed driller system provides a valuable temperature reduction during the bone drilling process Therefore, the bone temperature reduction was measured range of 20-25 % for lower spindle speeds (rpm) that is usually preferred by surgeons The temperature levels measured from the drilling tests of the developed driller system having a cooling system are compared with the use of regular bone drilling process without cooling A valuable temperature reduction is obtained using the driller system during the bone drilling tests
TL;DR: The peristaltic flow of power law fluid in an asymmetric channel is discussed in this paper, where the effects of the Biot numbers and the power-law nature of the fluid on the longitudinal velocity, temperature and pumping characteristics are studied in detail.
Abstract: The peristaltic flow of power law fluid in an asymmetric channel is discussed. The flow is generated because of peristaltic waves propagating along the channel walls. Heat transfer is examined through convective conditions of channel walls. Mathematical model is presented using the long wavelength and low Reynolds number approximations. The differential equations governing the flow are nonlinear and can admit non-unique solutions. There exist two different physically meaningful solutions one of which satisfies the boundary conditions at the upper wall and the other at the lower wall. The effects of the Biot numbers and the power-law nature of the fluid on the longitudinal velocity, temperature and pumping characteristics are studied in detail. Important conclusions have been pointed out. The streamlines pattern and trapping are given due attention.
TL;DR: In this article, the effects of Grashof number Gr and slip parameter λ on nanoparticle volume fraction, velocity, temperature, average Nusselt number Nuavg, and pressure coefficient σ have been investigated in details.
Abstract: Thermally fully developed mixed convection flow of nanofluids in a vertical annular pipe was investigated. Because of the non-adherence of the fluid–solid interface in the presence of nanoparticles, known as slip condition, the Navier’s slip condition was considered at the pipe walls. The Buongiorno’s model was employed for nanofluids that incorporate the effects of Brownian motion Nb and thermophoresis Nt numbers. Using the similarity variables, the governing partial differential equations were transformed into a system of ordinary ones with a constraint parameter and a solution was prepared via a reciprocal numerical algorithm. The effects of Grashof number Gr and slip parameter λ on nanoparticle volume fraction, velocity, temperature, average Nusselt number Nuavg, and pressure coefficient σ have been investigated in details. Results indicate that an increase in Gr and λ reduces the peak value of the dimensionless velocity profile in the core region of the annulus, away from the pipe walls, however, the velocity closer to the pipe walls increases. Furthermore, it was shown that nanofluids can transfer heat more efficiently in a slip condition than in a no-slip condition.
TL;DR: In this paper, the performance, emission and combustion characteristics of a single-cylinder, four-stroke variable compression ratio engine with waste cooking oil methyl ester and its blends with the aid of artificial neural network (ANN) were predicted.
Abstract: The intention of this study is to predict the performance, emission and combustion characteristics of a single-cylinder, four-stroke variable compression ratio engine fuelled with waste cooking oil methyl ester and its blends—standard diesel with the aid of artificial neural network (ANN) The tests were performed with fuel blends of 20, 40, 60 and 80 % biodiesel with standard diesel, with an engine speed of 1,500 rpm and at compression ratios of 18:1, 19:1, 20:1, 21:1 and 22:1 under different loading conditions Three different ANN models based on standard feed-forward back-propagation algorithm have been developed to predict the performance, emission and combustion characteristics of VCR engine To train the network, compression ratio, blend percentage and percentage load were used as input parameters whereas engine parameters such as brake thermal efficiency, specific fuel consumption, brake power, indicated mean effective pressure, mechanical efficiency and exhaust gas temperature were used as output parameters for the performance model and exhaust emissions such as carbon dioxide, carbon monoxide, hydrocarbon and NOx were used as output parameters for emission model Separate model is developed for combustion characteristics in which compression ratio, blend percentage, load percentage and crank angle were used as the input parameters whereas combustion pressure, heat release rate, ignition delay, combustion duration and mass fraction burnt were used as the output parameters This study shows that there is a good correlation between the ANN-predicted values and the experimental data for different engine performance, emission parameters and combustion characteristics
TL;DR: In this article, the influence of gear tooth geometrical variations in the performance of a double wave harmonic drive through statistical analysis is determined through state-of-the-art analytical and numerical models to evaluate kinematic error, load capacity, bending fatigue strength, and pitting.
Abstract: The objective of this research is to determine the influence of gear tooth geometrical variations in the performance of a double wave harmonic drive through statistical analysis This work incorporates state of the art analytical and numerical models to evaluate kinematic error, load capacity, bending fatigue strength, and pitting The geometric variables considered in this study include gear modulus, pressure angle, and tooth correction factor The statistical analysis follows a three-level full-factorial design of experiments Nonlinear dynamic simulation is accompanied by finite element analysis to estimate contact and bending stresses Largest bending fatigue strength is also determined Results demonstrate that gear modulus is the geometric parameter with prevalent influence on the kinematic error, and pitting life is rather high for all geometric variables considered
TL;DR: In this paper, an efficient finite element scheme for solving the nonlinear Reynolds equation for compressible fluid coupled to compliant structures is presented, which can be used in the analysis of airfoil bearings with simplified or complex foil structure models.
Abstract: An efficient finite element scheme for solving the non-linear Reynolds equation for compressible fluid coupled to compliant structures is presented. The method is general and fast and can be used in the analysis of airfoil bearings with simplified or complex foil structure models. To illustrate the computational performance, it is applied to the analysis of a compliant foil bearing modelled using the simple elastic foundation model. The model is derived and perturbed using complex notation. Top foil sagging effect is added to the bump foil compliance in terms of a close-form periodic function. For a foil bearing utilized in an industrial turbo compressor, the influence of boundary conditions and sagging on the pressure profile, shaft equilibrium position and dynamic coefficients is numerically simulated. The proposed scheme is faster, leading to the conclusion that it is suitable, not only for steady-state analysis, but also for non-linear time domain analysis of rotors supported by airfoil bearings.
TL;DR: In this article, a position and orientation automatic control of an underwater vehicle to perform inspection tasks of submerged structures without using the knowledge of a previous dynamic model in the control law and mainly by using a low-cost embedded minimal instrumentation.
Abstract: This work deals with the implementation of a position and orientation automatic control of an underwater vehicle to perform inspection tasks of submerged structures without using the knowledge of a previous dynamic model in the control law and, mainly, by using a low-cost embedded minimal instrumentation. This instrumentation does not employ expensive components to determine the position and orientation of the vehicle, like a central inertial. In this way, a computer vision system is used as a sensory source in order to assist the control. It was developed an algorithm to image processing and a system for integrating the different sensors. Experimental results using the proposed sensing show that the closed-loop control of the vehicle was suitable for the conduction of inspections.
TL;DR: The present paper applies the Bayesian approach to identify the parameters of the bit–rock interaction model considering a simplified drill-string dynamical model which takes into account only torsional vibrations.
Abstract: A drill string is a slender structure used to search for oil and gas. Many works have tackled the problem of modeling the drill-string dynamics in a vertical well. One important aspect in this dynamics is the bit–rock interaction, and, therefore, an identification of the parameters of the bit–rock interaction model becomes crucial. Few works related to this identification problem have been published. The present paper applies the Bayesian approach to identify the parameters of the bit–rock interaction model considering a simplified drill-string dynamical model which takes into account only torsional vibrations. It is assumed an additive Gaussian noise model, and the Metropolis–Hasting algorithm is used to approximate the posterior distribution of the variables analyzed.
TL;DR: In this article, a novel three-way diffuser/nozzle element of valveless piezoelectric micropump is presented, and an orthogonal design of the tube is done by computational fluid dynamics.
Abstract: A novel type of three-way diffuser/nozzle element of valveless piezoelectric micropump is presented, and an orthogonal design of the tube is done by computational fluid dynamics. Comparison of the simulation results between the traditional diffuser/nozzle element and the three-way diffuser/nozzle element shows that the latter has a better performance. The λ defined as the ratio of the total pressure loss coefficient for flow in the negative direction to that in the positive direction of the novel element is 1.2 and 16 % larger than that of the former traditional one as Δp = 10 kPa and Δp = 50 kPa, respectively. Then a three-way diffuser/nozzle element is fabricated, and the experiment is carried out. The results show that the simulation results are in good agreement with the experiment results. The maximum differences between the simulation and experiment are 6.23 % at Δp = 20 kPa in the negative direction and 3.53 % at Δp = 100 kPa in the positive direction when the pressure differences are given from 10 to 100 kPa. The micropump is fabricated, and the experiment results show that the maximum flow rate and back pressure are 0.451 ml/min and 3.11 kPa with the frequency of 225 Hz when the sinusoidal voltage is 100 VP-P.
TL;DR: In this article, a fiber laser with an average power of 1.5kW was used to weld two 1.6-mm-thick sheets in T-joint configuration.
Abstract: Laser beam welding may be used in the place of the traditional riveting process for the welding of the stringers to the skin in aircrafts. This work intends to investigate the mechanical behavior of laser-welded aluminum AA6013, subjected to post-welding heating treatments (PWHT). A fiber laser with an average power of 1.5 kW was used to weld two 1.6-mm-thick sheets in T-joint configuration. After welding, the samples were separated in three groups: the first just welded, the second subjected to a PWHT during 4 h at 190 °C and the third during 2 h at 205 °C. Hoop tensile tests showed that the thermal treatment at 190 °C for 4 h increased the tensile strength in 76 MPa, but the strain had decreased 4 %; the thermal treatment at 205 °C for 2 h increased maximum strength in 65 MPa, with a decrease in strain of 5 %. In T-pull tensile tests, the tensile properties of as-welded and PWHT samples remained the same. Standard S–N curve showed that the welding reduce the number of cycles to failure for the tested stairs. PWHT did not affect fatigue properties.