Showing papers in "Journal of The Brazilian Society of Mechanical Sciences and Engineering in 2009"
TL;DR: In this paper, a study on Taguchi's optimization methodology, which is applied to optimize cutting parameters in turning of age hardened Al6061-15% vol. SiC 25 µm particle size metal matrix composites with Cubic boron nitride inserts (CBN KB-90 grade using steam as cutting fluid, is presented.
Abstract: This paper presents the study on Taguchi's optimization methodology, which is applied to optimize cutting parameters in turning of age hardened Al6061-15% vol. SiC 25 µm particle size metal matrix composites with Cubic boron nitride inserts (CBN) KB-90 grade using steam as cutting fluid. Analysis of variance (ANOVA) is used to study the effect of process parameters on the machining process. This procedure eliminates the need for repeated experiments, time and conserves the material by the conventional procedure. The turning parameters evaluated are speed, feed, depth of cut, nozzle diameter and steam pressure. A series of experiments are conducted using PSG A141 lathe (2.2 KW) to relate the cutting parameters on surface roughness, tool wear, cutting force, feed force, and thrust force. The measured results were collected and analyzed with the help of the commercial software package MINITAB15. As well, an orthogonal array, signal-to-noise ratio is employed to analyze the influence of these parameters. The method could be useful in predicting surface roughness, tool wear, cutting force, feed force and thrust force as a function of cutting parameters. From the analysis using Taguchi's method, results indicate that among the all-significant parameters, steam pressure is the most significant parameter.
68 citations
TL;DR: The problem of flow inside a square cavity whose lid has constant velocity is solved by the Navier-Stokes equations using the finite volume method with numerical approximations of second-order accuracy and multiple Richardson extrapolations.
Abstract: The problem of flow inside a square cavity whose lid has constant velocity is solved This problem is modeled by the Navier-Stokes equations The numerical model is based on the finite volume method with numerical approximations of second-order accuracy and multiple Richardson extrapolations (MRE) The iterative process was repeated until the machine round-off error achievement This work presents results for 42 variables of interest, and their discretization errors estimates, on the 1024 x 1024 nodes grid and the following Reynolds numbers: 001, 10, 100, 400 and 1000 These results are compared with sixteen sources in literature The numerical solutions of this work are the most accurate obtained for this problem to date The use of multiple Richardson extrapolations reduces the discretization error significantly
64 citations
TL;DR: In this paper, the performance and emissions characteristics of a turbocharged and aftercooled diesel engine operated with natural gas as primary fuel, and diesel fuel as ignition source were investigated, and the results showed that, over a wide range of operating conditions (engine speed, load, and load), the dual fuel engine clearly showed the benefits of reduced NOX emissions.
Abstract: The aim of this paper is to investigate the performance and emissions characteristics of a turbocharged and aftercooled diesel engine operated with natural gas as primary fuel, and diesel fuel as ignition source. In such dual fuel operation, much of the energy released comes from the combustion of the gaseous fuel, while only a small amount of diesel fuel provides ignition through timed cylinder injection. The effects of diesel-natural gas substitution ratios, engine speed, and load on the equivalent brake specific fuel consumption and gaseous emissions of hydrocarbons, carbon monoxide and nitrogen oxides are examined for natural gas-diesel fuel operation and, afterward, compared with the original diesel operation. The results show that, over a wide range of operating conditions (engine speed, load), the dual fuel engine clearly shows the benefits of reduced NOX emissions. However, under low loads, the results indicate high CO and HC emissions and a higher BSFC when compared to those of the corresponding diesel engine.
55 citations
TL;DR: In this paper, the performance of single cylinder water-cooled diesel engine using methyl-ester of Jatropha oil as fuel was evaluated for its performance and exhaust emissions, and the fuel properties of biodiesel such as kinematic viscosity, calorific value, flash point, carbon residue and specific gravity were found.
Abstract: Biomass derived vegetable oils are quite promising alternative fuels for agricultural diesel engines. Use of vegetable oils in diesel engines leads to slightly inferior performance and higher smoke emissions due to their high viscosity. The performance of vegetable oils can be improved by modifying them through the transesterification process. In the present work, the performance of single cylinder water-cooled diesel engine using methyl-ester of Jatropha oil as fuel was evaluated for its performance and exhaust emissions. The fuel properties of biodiesel such as kinematic viscosity, calorific value, flash point, carbon residue and specific gravity were found. Results indicated that B25 has closer performance to diesel and B100 has lower brake thermal efficiency, mainly due to its high viscosity compared to diesel. The brake thermal efficiency for biodiesel and its blends was found to be slightly higher than that of diesel fuel at tested load conditions and there was no difference between the biodiesel and its blended fuels efficiencies. For Jatropha biodiesel and its blended fuels, the exhaust gas temperature increased with increase in power and amount of biodiesel. But, diesel blends showed reasonable efficiency, lower smoke, CO2, CO and HC.
43 citations
TL;DR: In this article, the authors showed the resulting height and shape of the burrs produced by drilling holes with ratio L/D = 3. The tool used in the tests was the solid twist HSS drill coated with TiAlN, with diameter of 10 mm, to drill the microalloyed steel DIN 38MnS6.
Abstract: This work shows the resulting height and shape of the burrs produced by drilling holes with ratio L/D = 3. The tool used in the tests was the solid twist HSS drill coated with TiAlN, with diameter of 10 mm, to drill the microalloyed steel DIN 38MnS6. The height of the burr was studied under different lubricant/coolant systems, namely: dry machining, use of Minimum Quantity Lubrication (MQL) at the flow rate of 30 ml/h, and fluid applied in the conventional way (flooding). The following cutting fluids were used: vegetable oil (MQL), mineral oil (MQL and flooding) and semi-synthetic oil (flooding). The trials were carried out at two cutting speeds (45 and 60 m/min) and the criterion adopted for the end of the test was the catastrophic failure of the drill. The results showed that the height of the burr increases primarily with the wear of the tool and that this increase is almost exponential after 64% and 84% of drills life, for the speeds of 45 and 60 m/min, respectively. Furthermore, the results generally showed that the smallest burr height was obtained for the dry machining and the largest for the MQL systems.
39 citations
TL;DR: In this paper, a thermal model of a tunnel kiln is developed allowing the numerical simulation of kilns and dryers aiming toward a more efficient and less energy consuming design, which is then systematically applied in the design of a new kiln to be used for firing clay tiles, bricks and similar products, with natural gas and sawdust as fuels.
Abstract: The available technology for tunnel kilns in Brazil is practically empirical and there is a lack of fundamental studies developed as an aid for the design of new kilns or for the retrofit of old ones. Here, a thermal model of a tunnel kiln is developed allowing the numerical simulation of kilns and dryers aiming toward a more efficient and less energy consuming design. The model is then systematically applied in the design of a new kiln to be used for firing clay tiles, bricks and similar products, with natural gas and sawdust as fuels. The results include the three-dimensional temperature distribution within the walls, gas and load along the kiln and a complete thermal energy balance including all energy fluxes related to the process. The strategies for kiln design are discussed and the advantages of combining the low cost of the wood sawdust and the ease of adjustment and quality of the natural gas combustion are evidenced.
38 citations
TL;DR: In this paper, a GA is used as an optimization tool to deal with nonconvex, multimodal and discrete optimization problems in hybrid laminated composites. And the GA converges faster than other obtained from the literature.
Abstract: This work aims at developing a genetic algorithm (GA) to pursue the optimization of hybrid laminated composite structures. Fiber orientation (predefined ply angles), material (glass-epoxy or carbon-epoxy layer) and total number of plies are considered as design variables. The GA is chosen as an optimization tool because of its ability to deal with non-convex, multimodal and discrete optimization problems, of which the design of laminated composites is an example. First, the developed algorithm is detailed explained and validated by comparing its results to other obtained from the literature. The results of this study show that the developed algorithm converges faster. Then, the maximum stress, Tsai-Wu and Puck (PFC) failure criteria are used as constraint in the optimization process and the results yielded by them are compared and discussed. It was found that each failure criterion yielded a different optimal design.
29 citations
TL;DR: In this paper, the physical and rheological properties mixtures of water and kaolinitic clay that form the interstitial fluid found in muds from inundations or torrential lava were described.
Abstract: This paper describes the physical and rheological property mixtures of water and kaolinitic clay that form the interstitial fluid found in muds from inundations or torrential lava. Several compositions with varying volume concentrations (Cv) were tested in a high-precision R/S rheometer (shear rate x shear stress). The rheometric parameters such as critical stress, apparent viscosity and outflow curves were established. A detailed analysis of the possible thixotropic fluid (shear thinning) and preparation of the mixtures were carried out. Such mud-type mixtures were well adjusted to the Herschel-Bulkley rheologic model at 03 parameters namely τ =τ=τc + Kγn , where τ is the shear stress; τc the yield stress (or initial rigidity); k is the consistency term; n the flow index; and γ= du dy the deformation rate or shear rates. Considering that this is a thorough research that seeks to infer laws of friction on a canal taking into account the non-Newtonian rheology of the flowing material, it is observed that the tested mixturesspecifically keep away from the Newton model, though less for the Bingham model, and adjusted well to the Herschel-Bulkley model, especially for lower deformation rates. Finally, from a refined literature review on the subject, it was appropriate to describe in detail a wider range of deformation rates and overall behavior laws of the various parameters of the Herschel Bulkley as a function of the concentration by volume (Cv).
26 citations
TL;DR: In this paper, a comparative study between distance measures or metrics for use in nonlinear model updating using vibration test data is performed. And the relative performances of the different metrics are investigated based on numerical simulations.
Abstract: The aim of this paper is to perform a comparative study between different distance measures or metrics for use in nonlinear model updating using vibration test data. Four metrics derived from both frequency and time domain updating approaches are studied, including the harmonic balance method, the constitutive equation error, the restoring force surface and the Karhunen-Loeve decomposition. In the first section, a benchmark model with local nonlinear stiffness is defined in order to illustrate each method. Secondly, each nonlinear updating metric is succinctly reviewed. Finally, the relative performances of the different metrics are investigated based on numerical simulations. These results allow us to characterize the applicability and limitations of the different approaches.
24 citations
TL;DR: In this article, an immersed boundary formulation for three-dimensional incompressible flows is presented that uses the momentum equation to calculate the Lagrangian force field indirectly imposing the no-slip condition on solid interfaces.
Abstract: This paper presents an immersed boundary formulation for three-dimensional incompressible flows that uses the momentum equation to calculate the Lagrangian force field indirectly imposing the no-slip condition on solid interfaces. In order to test the performance of this methodology the flow past a sphere for Reynolds numbers up to 1,000 have been calculated. Results are compared with numerical data from other authors and empirical correlations available in the literature. The agreement is found to be very good.
21 citations
TL;DR: In this paper, a theoretical analysis of the effects of couple stresses on the squeeze film lubrication between circular stepped plates is presented, where a modified Reynolds type equation is derived for the couplestress fluids.
Abstract: In this paper, a theoretical analysis of the effects of couple stresses on the squeeze film lubrication between circular stepped plates is presented. Modified Reynolds type equation is derived for the couplestress fluids. Closed form solution is obtained. According to the results obtained, the influence of couple stresses enhances the squeeze film pressure, load carrying capacity, and decreases the response time as compared to classical Newtonian-lubricant case. The load carrying capacity decreases as step height increases.
TL;DR: In this paper, the authors used pulsed ultrasonic Doppler velocimetry to measure simultaneously the local velocity and the local concentration in a flow of solid-liquid suspension in a horizontal pipe.
Abstract: In this experimental study, the pulsed ultrasonic Doppler velocimetry was used to measure simultaneously the local velocity and the local concentration in a flow of solid-liquid suspension in a horizontal pipe. In order to distinguish between the Doppler signals coming from the continuous phase, water and those of the glass bead particles larger than the Kolmogorov length scale and the wavelength of the ultrasonic wave, a threshold is imposed on the integral of the power spectral density of the Doppler signal. The new approach measurement of the local concentration was used. It consists of counting a number NP of the Doppler signals of the solid particles crossing the measurement volume and a number NPt of the Doppler signals of the solid particles crossing the control volume. The concentration profile is then represented by the ration NP / NPt. The results obtained show that the suspension of fine particles, which represents a tracer, behaves as a homogenous fluid. For large particles, we confirmed the existence of the slip velocity and the effects of both concentration and size particle on the turbulence. The use of two distinct measurement volumes allows the direct determination of the turbulent length scales. The results show that the turbulence characteristics of the carried fluid are modified by the presence of the solid particles.
TL;DR: In this paper, the authors analyzed the performance of the TiN/TiCN, TiAlN, TiN,TiAlN and TiN-AlN/WCC coatings on HSS M2 drills used in the drilling of the ISO 3522 AlSi8Cu3Fe, correlating the life of the tools to the coating adhesion characterization experiments.
Abstract: This work analyses the performance of the TiN/TiCN, TiAlN, TiN/TiAlN and TiN/TiAlN/WCC coatings on HSS M2 drills used in the drilling of the aluminium-silicon alloy ISO 3522 AlSi8Cu3Fe, correlating the life of the tools to the coating adhesion characterization experiments. Coating adhesion was characterized using Rockwell C indentation tests and scratch tests with progressive load. The performance of the coatings in the life experiments was the following, in decreasing order: TiN/TiCN, TiAlN, TiN/TiAlN/WCC and TiN/TiAlN. In the adhesion characterization experiments with TiN/TiCN there were no cracks or delamination of the coatings, which justifies its best performance in the life experiments.
TL;DR: In this paper, the minimum quantity lubrication (MQL) has been applied to the plunge cylindrical internal grinding operation and the conventional cooling method was used to evaluate the roughness and roundness.
Abstract: Precision cylindrical grinding is used extensively in the manufacture of precision components in the metal-mechanical industry in general. Modern CNC grinding machines have improved this process with respect to the positioning and rigidity of the machine-workpiece-tool system, allowing the production of high precision parts with low dimensional tolerances. Besides the difficulties inherent to the process, awareness has grown in recent years regarding the environmental issues of cutting fluids. As a response, the industry has begun to seek alternative lubrication and cooling methods. Among the various existing techniques, Minimum Quantity Lubrication (MQL) has been considered as an alternative. This technique can be understood as a combination of conventional lubrication and cooling methods and dry machining, in which a small quantity of lubricating oil mixed with compressed air flow is delivered in the wheel-workpiece interface. The MQL technique is already widely employed in machining processes with tools of defined geometry (e.g. turning), in which produces very satisfactory results. However, the MQL technique has been little explored in grinding processes (non-defined tool geometry), in which the really effective heat removal methods are required due to the frictional heat generation in the grinding zone. Consequently, the aim of this study was to evaluate the plunge cylindrical internal grinding operation when using the MQL technique and the conventional cooling method. Roughness and roundness were the outputparameters. As a result, it was found that the best values of roughness Ra were obtained with the conventional lubrication method. The MQL technique applied as proposed was not able to flush the chips away from the grinding zone, leading to the highest Ra values. No significant differences were detected among the cooling methods when analyzing the roundness results. The workpiece fixture method selected was responsible for the overall unsatisfactory results.
TL;DR: In this article, the authors evaluated the mechanical properties of steel sheet coated with zinc and 55%Al-Zn in terms of tensile strength, yield strength, total elongation and hardening coefficient.
Abstract: Steel sheet coated with zinc or 55%Al-Zn is widely used at the civil construction, mainly for roofing and cladding applications. The 55%Al-Zn coated steel shows mechanical properties slightly different from zinc coated steel, even under the same heat cycle processing, due to the higher molten metal temperature and also to the higher strength of the 55%Al-Zn coating. The knowledge of those differences can be used by the final users to evaluate if some of those products are not suitable for any specific application. Although those two coated products are widely used at the civil construction in Brazil, only a limited literature is available on the difference between the mechanical properties of those products. Through tensile tests of commercial grade samples - as coated and after removing the coating - the aim of this paper is to evaluate the mechanical properties (tensile strength, yield strength, total elongation and hardening coefficient) and also how much the coating influences the mechanical properties of the zinc and 55%Al-Zn coated steel. The 55%Al-Zn coated steel showed higher yield and tensile strength and lower total elongation and hardening coefficient compared to zinc coated steel and the coating showed a significant influence on the mechanical properties of both products.
TL;DR: In this paper, a tracking control model for a flexible link robotic manipulator using simultaneously motor torque and piezoelectric actuators is proposed, and the stability of this control is guaranteed by the Lyapunov stability theory.
Abstract: This work proposes a tracking control model for a flexible link robotic manipulator using simultaneously motor torques and piezoelectric actuators. The dynamic model of manipulator is obtained in a closed form through the Lagrangian approach. The control uses the motor torques for the tracking control of the joints and also to reduce the low frequency vibration induced in the manipulator links. The stability of this control is guaranteed by the Lyapunov stability theory. Piezoelectric actuators and sensors are added for controlling the high frequency vibrations beyond range of motor torque control. Additionally, this work introduces a formulation for simultaneous control and piezoelectric inserts geometry optimization through the maximization of the control action dissipated energy. Simulations on Matlab/Simulink are used to verify the efficiency of the control model.
TL;DR: In this article, the authors describe the steps involved for the modelling of a reciprocating linear compressor, where the dynamics of the mechanical components are described with the help of multibody dynamics (rigid components) and finite elements method (flexible components).
Abstract: In this work, the steps involved for the modelling of a reciprocating linear compressor are described in detail. The dynamics of the mechanical components are described with the help of multibody dynamics (rigid components) and finite elements method (flexible components). Some of the mechanical elements are supported by fluid film bearings, where the hydrodynamic interaction forces are described by the Reynolds equation. The system of nonlinear equations is numerically solved for three different restrictive conditions of the motion of the crank, where the third case takes into account lateral and tilting oscillations of the extremity of the crankshaft. The numerical results of the behaviour of the journal bearings for each case are presented giving some insights into design parameters such as, maximum oil film pressure, minimum oil film thickness, maximum vibration levels and dynamic reaction forces among machine components, looking for the optimization and application of active lubrication towards vibration reduction.
TL;DR: An obstacle motion tracking module based only on 2D laser scan data was developed and proved the usefulness of considering obstacle paths and velocities while navigating at reasonable computational costs, which will allow future controllers to obtain a better performance in highly dynamic environments.
Abstract: All over the world traffic injuries and fatality rates are increasing every year. The combination of negligent and imprudent drivers, adverse road and weather conditions produces tragic results with dramatic loss of life. In this scenario, the use of mobile robotics technology onboard vehicles could reduce casualties. Obstacle motion tracking is an essential ability for car-like mobile robots. However, this task is not trivial in urban environments where a great quantity and variety of obstacles may induce the vehicle to take erroneous decisions. Unfortunately, obstacles close to its sensors frequently cause blind zones behind them where other obstacles could be hidden. In this situation, the robot may lose vital information about these obstructed obstacles that can provoke collisions. In order to overcome this problem, an obstacle motion tracking module based only on 2D laser scan data was developed. Its main parts consist of obstacle detection, obstacle classification, and obstacle tracking algorithms. A motion detection module using scan matching was developed aiming to improve the data quality for navigation purposes; a probabilistic grid representation of the environment was also implemented. The research was initially conducted using a MatLab simulator that reproduces a simple 2D urban-like environment. Then the algorithms were validated using data samplings in real urban environments. On average, the results proved the usefulness of considering obstacle paths and velocities while navigating at reasonable computational costs. This, undoubtedly, will allow future controllers to obtain a better performance in highly dynamic environments.
TL;DR: In this paper, a phase-field model is proposed for the simulation of microstructure and solute concentration during the solidification process of Fe-C-P ternary alloys.
Abstract: A phase-field model is proposed for the simulation of microstructure and solute concentration during the solidification process of Fe-C-P ternary alloys. A relation between material properties and model parameters is presented. Two-dimensional computation results exhibit dendrites in Fe-C-P alloys for different phosphorus concentrations. Alterations in the phosphorus concentration appear to affect the advance speed of the solid-liquid interface. Such an alteration is due to the small diffusivity of phosphorus during the solidification process.
TL;DR: The outcome of the study reveals that adaptive implicit methodologies can be a good choice when unstructured grids are present, allowing the use of time steps with the same order of magnitude as the ones used in FI procedures, but with reduction in the computational effort.
Abstract: This work presents a comparative study among three linearization schemes widely used in petroleum reservoir simulation, namely the Implicit Pressure Explicit Saturation (IMPES), Fully Implicit (FI) and Adaptive Implicit Method (AIM). Attention is given to the criterion used for switching from IMPES to FI and vice-versa. The black-oil model considering the oil-water flow is employed. The equations are discretized using an unstructured Voronoi mesh in a finite-volume framework. The numerical results are analyzed based on the number of iterations in the Newton and solver procedures, number of implicit volumes, and mass balance error of components. The effect of the stopping criterion on Newton's iterations is also investigated. The outcome of the study reveals that adaptive implicit methodologies can be a good choice when unstructured grids are present, allowing the use of time steps with the same order of magnitude as the ones used in FI procedures, but with reduction in the computational effort.
TL;DR: In this paper, the instability of two-and three-dimensional perturbations in the compressible mixing layer was investigated by numerical simulations, and the results demonstrated the applicability of the theory developed by Pierrehumbet and Widnall.
Abstract: Mixing layers are present in very different types of physical situations such as atmospheric flows, aerodynamics and combustion. It is, therefore, a well researched subject, but there are aspects that require further studies. Here the instability of two-and three-dimensional perturbations in the compressible mixing layer was investigated by numerical simulations. In the numerical code, the derivatives were discretized using high-order compact finite-difference schemes. A stretching in the normal direction was implemented with both the objective of reducing the sound waves generated by the shear region and improving the resolution near the center. The compact schemes were modified to work with non-uniform grids. Numerical tests started with an analysis of the growth rate in the linear regime to verify the code implementation. Tests were also performed in the non-linear regime and it was possible to reproduce the vortex roll-up and pairing, both in two-and three-dimensional situations. Amplification rate analysis was also performed for the secondary instability of this flow. It was found that, for essentially incompressible flow, maximum growth rates occurred for a spanwise wavelength of approximately 2/3 of the streamwise spacing of the vortices. The result demonstrated the applicability of the theory developed by Pierrehumbet and Widnall. Compressibility effects were then considered and the maximum growth rates obtained for relatively high Mach numbers (typically under 0.8) were also presented.
TL;DR: In this paper, the authors describe how to design a best possible system of viscoelastic vibration absorbers for an available visco-elastic material, known by its four fractional parameter model, by using a novel objective function, defined through a Frobenius norm.
Abstract: Vibration absorbers, also called vibration neutralizers, are mechanical systems to be attached to another mechanical system, or structure, called the primary system, with the purpose of reducing vibration and sound radiation. The simplest form of a vibration absorber is that of a single degree of freedom system, where the “spring” is made of a viscoelastic material, perhaps with some metallic inserts. This paper sets out to describe how to design a best possible system of viscoelastic vibration absorbers for an available viscoelastic material, known by its four fractional parameter model, by using a novel objective function, defined through a Frobenius norm. A real example is presented and discussed. Keywords : vibration absorber, vibration neutralizer, viscoelastic material, vibration abatement, vibration control
TL;DR: In this article, the robustness of each controller when different disturbances are considered is compared with an actual underactuated manipulator robot with 3 degrees of freedom, of which joints can be configured as active or passive ones.
Abstract: and µ-synthesis, plus computed torque method. These controllers are applied in an actual underactuated manipulator robot with 3 degrees of freedom, of which joints can be configured as active or passive ones. The study performed in this paper compares the robustness of each controller when different disturbances are considered.
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TL;DR: In this paper, the primary control system of a hydropower plant in isolated mode is studied and four controllers are evaluated: traditional, PI, PID, and PI-PD.
Abstract: The aim of this work is to study the primary control system of a hydropower plant in isolated mode. The power plant is modeled by differential equations and results are compared to field data from an actual hydropower plant, presenting deviations lower than 1.0%. The study of primary control system is conducted in order to define useful sets of parameters for controllers. Four controllers are studied: traditional, PI, PID and PI-PD. The performances are evaluated by stability criteria and a performance index. For the hydropower plant studied, the PI controller has the best performance.
TL;DR: In this article, the vortex shedding from a circular cylinder near a moving ground is studied using the Vortex Method, and the results of the numerical simulations show that the critical drag behavior is directly related to a global change in the wake structure of the cylinder in the ground effect.
Abstract: The objective of this paper is to study the vortex shedding from a circular cylinder near a moving ground; this is done using the Vortex Method. A moving ground has been widely used in the field of experimental vehicle aerodynamics, especially of high-performance racing cars, to properly consider the ground effect on the vehicles aerodynamic. In experimental work as well as in numerical simulations, the ground plane develops a boundary layer that interferes with the body viscous wake, leading to not so precise results. A ground moving with the incoming flow velocity, however, does not allow the development of a boundary layer. The results of our numerical simulations show that the critical drag behavior is directly related to a global change in the wake structure of the cylinder in the ground effect. Comparisons with experimental data are encouraging.
TL;DR: In this paper, the authors show experimental results about soot suppression on a laboratorial scale jet free diffusion flame of liquefied petroleum gas submitted to acoustic oscillations, and quantify the soot presence using laser induced incandescence.
Abstract: The present paper shows experimental results about soot suppression on a laboratorial scale jet free diffusion flame of liquefied petroleum gas submitted to acoustic oscillations. The experiments were conducted to verify the influence of amplitude and frequency of oscillations in the regions of soot formation and suppression through the flame. To quantify the soot presence the laser induced incandescence was utilized. The results show combinations of frequency and amplitude of oscillation which the presence of soot is close to zero. Keywords : pulsating combustion, soot presence, diffusive flame
TL;DR: In this paper, the authors investigated the SCC susceptibility of pipeline steels in contact with soil and found that the hydrogen embrittlement has an important contribution to cracking initiation and propagation.
Abstract: Environmentally induced cracking of pipeline steels in contact with soil have been investigated. Different soils were prepared in order to determine their physical, chemical and bacteriological characteristics. Slow strain rate testing was carried out by using electrolytes obtained from soil samples and NS4 standard solution. Stress vs. strain curves of API 5L grade X46, X60 and X80 steels were obtained at different electrode potentials (Ecorr, 100 mV below Ecorr and 300 mV below Ecorr) with 9 x 10-6 s-1 strain rate. The results obtained with API 5L X46 in soil solution were compared with slow strain rate test (SSRT) results obtained using a strain rate of 9 x 10-7s-1 to the same steel. All results showed the incidence of cracking and their dependence on the potential imposed, revealing the SCC (Stress corrosion cracking) susceptibility of the steels. It was also observed that the hydrogen embrittlement - HE - has an important contribution to cracking initiation and propagation. Cracking morphology was similar to the SCC reported on field condition where transgranular cracking were detected in a pipeline collapsed by land creeping. It was important to point out that even under cathodic potentials the material showed the incidence of secondary cracking and a significant reduction of ductility.
TL;DR: In this article, the authors investigated the burr formation mechanisms at the edges (lateral and exit) during face milling of mold steel using carbide tools, and proposed minimization was achieved by optimizing the cutting conditions: cutting speed (Vc), feed per tooth (fz), and depth of cut (doc).
Abstract: The aim of the present work is to investigate the burr formation mechanisms at the edges (lateral and exit) during face milling of mould steel using carbide tools. The effects of the cutting parameters were studied and strategies of burr minimization were discussed. The proposed minimization was achieved by optimizing the cutting conditions: cutting speed (Vc), feed per tooth (fz) and depth of cut (doc), with the aid of surface response technique.
TL;DR: In this article, the authors compared the resonant characteristics and the surface vibration modes between a homogeneous piezoelectric ring and a 1-3 piezocomposite ring, both used in power ultrasonic transducers.
Abstract: Some power ultrasonic transducers, such as Tonpilz transducers, require high-power transmitting capability as well as broadband performance. Optimized vibrational modes can achieve these requirements. This work compares the resonant characteristics and the surface vibration modes between a homogeneous piezoelectric ring and a 1-3 piezocomposite ring, both used in power ultrasonic transducers. This is the first step in the design of power transducers. Analytical models and finite element results are validated by electrical impedance measurements and the surface acoustic spectroscopy method. Excellent agreement between theoretical and experimental results was obtained. Results show that using piezocomposite ceramics minimize superposition of undesirable modes and increase the bandwidth, as shown in sonograms.