Showing papers in "Journal of The Brazilian Society of Mechanical Sciences and Engineering in 2018"
TL;DR: In this paper, the phase distribution of the pressure fluctuation wave in the impeller and diffuser can be divided into four regions, namely, flow channel region, impeller transition region, diffuser transition region and diffusion channel region.
Abstract: Multistage pump can provide high-pressure liquid, which is widely used in various areas of national economy. In order to improve the stability and reduce the noise of multistage pump, the relationships among the pressure fluctuation, vibration, and noise were studied deeply by using computational fluid dynamics and experimental measurement. Based on the unsteady numerical calculation, the phase of the pressure fluctuation wave in the middle section of the impeller and the diffuser was obtained, and the unsteady velocity distribution was acquired in the rotor–stator interaction (RSI) region between the rotational impeller and the stationary diffuser. Moreover, the vibration and noise tests of a five-stage pump with radial diffuser were performed. The results show that the phase distribution of the pressure fluctuation wave in the impeller and diffuser can be divided into four regions: the impeller flow channel region, the impeller transition region, the diffuser transition region, and the diffuser flow channel region. In addition, the pressure fluctuation, vibration and noise of the multistage pump are strongly related to each other, that is, RSI induces strong unsteady flow and pressure fluctuation in the pump, which makes the pump produce serious vibration and cause the corresponding noise. The key to controlling the vibration and noise is to reduce the effect of RSI between the impeller and the diffuser.
66 citations
TL;DR: The modification is focused on an additional intensive exploitation phase which provides more chance to solutions to improve itself and indicates that the MBOA provides very competitive results in comparison with other existing optimization algorithms.
Abstract: This paper presents a modified butterfly optimization algorithm (MBOA) for solving mechanical design optimization problems. The modification is focused on an additional intensive exploitation phase which provides more chance to solutions to improve itself. The performance of the proposed algorithm is validated on fifteen benchmark test functions and three engineering design problems which have different natures of objective functions, constraints and decision variables. The experimental results are analyzed in comparison with those reported in the literature. The results indicate that the MBOA provides very competitive results in comparison with other existing optimization algorithms.
62 citations
TL;DR: A comparative study of electrical energy consumption during melting of known quantity of metallic material in microwave oven and in conventional muffle electric furnace is carried out in this paper, where non-ferrous bulk metallic materials such as tin, zinc, aluminum and brass are used as candidate materials.
Abstract: Foundry industries aim at reducing energy consumption in processing of materials. Continuous efforts are ongoing to exploit unconventional energy sources such as microwave energy to overcome drawbacks of conventional sources. In the present work, a comparative study of electrical energy consumption during melting of known quantity of metallic material in microwave oven and in conventional muffle electric furnace is carried out. The non-ferrous bulk metallic materials such as tin, zinc, aluminum and brass are used as candidate materials. A 900-W modified domestic microwave oven, operating at 2.45 GHz and a conventional muffle furnace are used for the study. The electrical energy consumed for melting of known quantity of metallic materials is presented along with the observed material wastage during melting process. The study shows that microwave oven consumes significantly lesser time than the conventional muffle electric furnace for the melting of known quantity of candidate materials. It is found that melting bulk metallic materials by microwave irradiation reduces electrical energy consumption than that of conventional melting process. In addition, material wastage is around twofold lesser by microwave melting process than the conventional melting process for the known quantity of candidate materials.
59 citations
TL;DR: An approach for analyzing the behavior of an industrial system under the cost free warranty policy is presented and various parameters such as reliability, mean time to system failure, availability and expected profit are derived for a system.
Abstract: The objective of the manuscript is to present an approach for analyzing the behavior of an industrial system under the cost free warranty policy. Under this policy, the various parameters of the system behavior under the working as well as the rest conditions are taken into the account. To increase the working efficiency and reduce the failure rate during and beyond warranty, the system goes under rest period after working a random amount of time. After taking complete rest, the system restarts again. Further, during the formulation, the failure and repair rates of the components of the systems are taken as a negative exponential distribution. A mathematical model of the system is developed based on the Markov process and hence the various parameters such as reliability, mean time to system failure, availability and expected profit are derived for a system. The effect of various parameters on to the system performance is analyzed. Finally, an illustrative example is taken for demonstrating the approach.
59 citations
TL;DR: In this article, the impact of Cattaneo-Christov heat flux on radiative Oldroyd-B two-phase flow across a cone/wedge is addressed.
Abstract: Impact of Cattaneo–Christov heat flux on radiative Oldroyd-B two-phase flow across a cone/wedge is addressed. RKF-45 method with shooting technique is used to obtain solution of the problem. The obtained results are presented through graphs and tables. We examined the results under non-linear variation of thermal radiation. Our simulations established that influence of physical parameter highly effective for cone when compare to wedge.
57 citations
TL;DR: In this paper, a modified porosity model that represents porosity and Young's modulus in an implicit form is presented, where the density is assumed as a function of the porosity parameter, while Young's ratio of the mass density with porosity to that without porosity is assumed.
Abstract: This work studies the mechanical bending and vibration of functionally graded nanobeams using finite elements according to Euler beam theory. We implement a modified porosity model that represents porosity and Young’s modulus in an implicit form, where the density is assumed as a function of the porosity parameter, while Young’s modulus is assumed as a ratio of the mass density with porosity to that without porosity. The effect of nano-scale is described by the nonlocal continuum theory by adding the length scale into the constitutive equations as a material parameter comprising information about nanoscopic forces and its interactions. The material gradation of constituents is described by a power function through the thickness of nanobeam. The beam is simply supported and is assumed to be thin, and hence, the kinematic assumptions of Euler–Bernoulli beam theory are held. The mathematical model is solved numerically using the finite-element method. Numerical results show that the increase of porosity, material graduation, and nano-scale parameters tend to decrease the bending resistance as well as the fundamental frequencies of the nanobeam.
53 citations
TL;DR: In this paper, a grey relational grade analysis was used to optimize the spindle speed, feed rate, and drill diameter of hybrid glass fiber reinforced polymeric nanocomposites.
Abstract: Among many machining operations, drilling has become one of the important machining operations performed in polymer composites. The quality of the drilled hole is closely associated with the drilling parameters and conditions. The current work focuses on the optimization of multiple response characteristics during drilling of hybrid glass fiber reinforced polymeric nanocomposites. Taguchi’s L25, orthogonal array is used to conduct the experiments and for optimization of the process parameters. The machining parameters such as spindle speed, feed rate, and drill diameter are optimized for the response which includes delamination, thrust force and torque via grey relational analysis technique. From the grey relational grade analysis, it is clear that the drill diameter is the most influencing factor followed by the feed rate and the spindle speed. The optimized process parameter settings were found as spindle speed of 2700 rpm, the feed rate of 30 mm/min and drill diameter of 4 mm, respectively, for lower delamination, torque and thrust force. Among the various modeling techniques used, ANN is found to be suitable for the process with minimum error percentage of 0.526.
52 citations
TL;DR: In this paper, the effect of AWJM parameters on the cutting of mild steel and to optimize the process parameters were investigated and the results showed that traverse speed is the prime factor influencing surface roughness and kerf taper angle followed by stand-off distance and abrasive flow rate.
Abstract: Abrasive water jet machining (AWJM) is a popular method used for cutting purposes. It uses a thin jet of ultra-high pressure water and abrasive slurry to cut the material and the cutting is mainly by erosion. The purpose of this paper is to investigate the effect of AWJM parameters on the cutting of mild steel and to optimize the process parameters. The process parameters considered for investigation are traverse speed, abrasive flow rate and standoff distance. The subsequent response parameters that have been determined are surface roughness and kerf taper angle. Taguchi L9 orthogonal array has been used to design the experiments. ANOVA is used to decide the influencing process parameters. 3D surface plots are presented for interaction effects of input process parameters. The study revealed that traverse speed is the prime factor influencing surface roughness and kerf taper angle followed by stand-off distance and abrasive flow rate. Response models are verified on the basis of estimation capability. Later on, multi-objective optimization using response surface methodology has been used for minimizing surface roughness and kerf taper angle which further resulted in composite desirability of 0.9497. The optimum values of abrasive flow rate, standoff distance and traverse speed are found to be 420 g/min, 3 mm and 85 mm/min, respectively. To validate the results, confirmation test is performed using optimum cutting parameters. It showed 9.17 and 8.57% error for surface roughness and kerf taper angle.
51 citations
TL;DR: In this article, a mathematical model is constructed to examine the impact of magnetic field and thermal radiation on flow and heat transfer analysis of carbon nanotubes-based nanofluids by taking base fluid as the water between two rotating stretchable disks with convective boundary conditions.
Abstract: A mathematical model is constructed to examine the impact of magnetic field and thermal radiation on flow and heat transfer analysis of carbon nanotubes-based nanofluids by taking base fluid as the water between two revolving stretchable disks with convective boundary conditions in the present investigation. The most extensively validated finite element technique is employed to solve the reduced nonlinear ordinary differential equations together with boundary conditions. Velocity and temperature distributions are calculated and are displayed through graphs for various values of pertinent parameters entered into the problem. Furthermore, the values of rates of change of velocity and temperature are examined in detail and are portrayed in tabular form. The values of skin friction coefficient at both upper and lower disks elevates in the boundary layer regime with rising values of Deborah number in both nanofluids, and this augmentation is higher in MWCNTs–water- than SWCNTs–water-based Maxwell nanofluid. Temperature of the fluid in both nanofluids deteriorates as the values of nanoparticle volume fraction parameter upsurge, and this deterioration in temperature distributions is higher in SWCNTs–water- than the MWCNTs–water-based Maxwell nanofluid.
48 citations
TL;DR: A complete evaluation of the MEMS accelerometers was performed by measuring amplitudes and frequencies of oscillations and comparing their dynamic characteristics with other accelerometers with higher precision to propose these sensors for measuring mechanical vibrations.
Abstract: In this paper, the use of MEMS accelerometers for measuring mechanical vibrations is presented. Also a wide review of the literature is performed by presenting the uses of the MEMS accelerometers in a great number of applications. These sensors are known for their low prices, low power consumption and low sizes, which enhance their use in applications such as energy harvesters, monitoring processes and for educational purposes. In order to propose these sensors for measuring vibrations, a complete evaluation of the MEMS accelerometers was performed by measuring amplitudes and frequencies of oscillations and comparing their dynamic characteristics with other accelerometers with higher precision. Moreover, two experiments were conducted: In the first one, the measurements of the amplitude given by a MEMS and a standard accelerometer while being excited with sinusoidal waves with different frequencies using a vibration exciter were taken and compared. For the second experiment, three MEMS sensors and a piezoelectric accelerometer were used to measure the accelerations of a 3-DOF shear-building excited by an unbalanced DC motor. The signals obtained were compared in the time and frequency domains; for the last case, the wavelet transform, the wavelet coherence and the power spectrum density were used.
47 citations
TL;DR: In this article, a CNC assisted fused layer modeling process is proposed for the fabrication of flexible electrically conductive polymer composite objects by using the material in pellet form instead of a filament, which eliminates the issues of filament buckling and allows flexible object fabrication.
Abstract: The applications of electrically flexible conductive polymer composites are rapidly growing over the time due to their widespread use in fabrication of health monitoring devices, sensors, and flexible displays fabrication, etc. Various techniques have been explored to develop electrically conductive polymer composites. In the recent past, fused deposition modeling (FDM) process has been gained tremendous attention to fabricate electrically conductive parts considering rigid polymers along with conductive filler particles. This allows to avail all advantages and benefits of additive manufacturing in the fabrication of complex electrically conductive parts. However, FDM process faces challenges of filament buckling while fabricating flexible parts. Hence, there is need to develop an economically viable and simplified process to fabricate the flexible electrically conductive polymer composite objects. In the present study, fabrication of flexible electrically conductive polymer composite objects has been attempted by developing a novel CNC assisted fused layer modeling process. The developed process uses the material in pellet form instead of a filament, which eliminates the issues of filament buckling and allows flexible object fabrication. The ethylene vinyl acetate (EVA) and graphite (Gr) particles have been used as the polymer matrix and conductive filler material respectively. Solvent and melt blending techniques have been employed to develop EVA/Gr composites. Three-dimensional flexible electrically conductive objects have been fabricated successfully. The experimental result shows the remarkable improvements in electrical conductivity of EVA polymer by incorporation of graphite particles. The outcome of the presented approach may help to fabricate flexible electrically conductive complex structures for soft robotics and electronics applications.
TL;DR: In this article, the development of a pellet-based additive manufacturing (AM) system for processing EVA material has been presented, which is compatible with the three-axis CNC milling machine.
Abstract: The processing of elastomers through fused deposition modeling (FDM) is challenging task due to low column strength and high melt viscosity. Ethylene vinyl acetate (EVA) is an elastomer which is widely used for fabricating flexible objects. However, the potential of this material has not been explored in the FDM process. Pre-fabricated EVA filament cannot be processed in standard filament feed extrusion mechanism of commercial FDM machine due to buckling of the filament. However, development of pellet-based extrusion additive manufacturing (AM) may eliminate the issues caused by elastomer filament. The current study demonstrates the development of pellet-based AM system for processing EVA material. The developed system is compatible with the three-axis CNC milling machine, which provides high precision positioning to the deposition path and required power for screw rotation. Details about hardware and software related to the developed system have been presented. Flexible parts using EVA pellets have been fabricated successfully, which shows the capability of the developed extrusion AM system. Experiments have been performed for tuning process parameters. Further, mechanical characterization has been done to analyze the dimensional accuracy, flexibility, strength and hardness of printed parts. Obtained results show that EVA demonstrates approx. 300–550% higher elongation as compared to ABS and PLA materials, which indicates EVA can be used to make highly flexible parts. The outcome of this study will be helpful to the engineers for the development of low-cost flexible parts for those applications where customized flexible parts are needed in short span of time.
TL;DR: In this paper, the authors mainly focused on parametric optimization of squeeze cast hybrid (LM24-SiCp-coconut shell ash) composite through Taguchi method and genetic algorithm.
Abstract: This paper mainly focuses on parametric optimization of squeeze cast hybrid (LM24–SiCp–coconut shell ash) composite through Taguchi method and genetic algorithm. The composite samples have been cast through squeeze casting for each experimental trial based on L9(3)4 orthogonal array. From analysis of variance, it has been found that reinforcement and squeeze pressure were the casting parameters making significant improvement in the impact strength. A mathematical model representing the process was developed using nonlinear regression analysis. The optimum casting conditions were obtained through Taguchi method and genetic algorithm and checked through the confirmation experiments. In this study, it was confirmed that the castings obtained for the optimum squeeze casting conditions exhibited nearly 20% improvement in impact strength compared to the gravity die casting condition.
TL;DR: In this paper, a study on dynamic response of a bimorph FGP cylindrical nanoshell based on nonlocal strain gradient theory is presented, where the material properties are assumed to be variable across thickness direction according to power law distribution.
Abstract: Functionally graded piezoelectric materials (FGPMs) have emerged as promising candidates for electronic nanodevices. In this paper, a study on dynamic response of a bimorph FGP cylindrical nanoshell based on nonlocal strain gradient theory is presented. The material properties are assumed to be variable across thickness direction according to power law distribution. The electric potential is considered to be quadratic through thickness direction. The governing equations and boundary conditions are obtained on the basis of first-order shear deformation theory using Hamilton’s principle. As case study, free vibration of simply supported bimorph FGP cylindrical nanoshell is studied and the influences of different parameters on natural frequency are illustrated. The results obtained provide detailed insights into dynamic response of bimorph FGP cylindrical nanoshell and provide evidence for its size dependency especially by increase in thickness and decrease in length, which is an important conclusion for obtaining appropriate functionality in sensors and actuators.
TL;DR: In this paper, the buckling and nonlinear vibration of functionally graded (FG) porous nanobeam for the first time were studied and the generalized differential quadrature method (GDQM) was used in conjunction with the iterative method to solve the equations.
Abstract: Although many researchers have studied the vibration and buckling behavior of porous materials, the behavior of porous nanobeams is still a needed issue to be studied. This paper is focused on the buckling and nonlinear vibration of functionally graded (FG) porous nanobeam for the first time. Nonlinear Von Karman strains are put into consideration to study the nonlinear behavior of nanobeam based on the Euler–Bernoulli beam theory. The nonlocal Eringen’s theory is used to study the size effects. The mechanical properties of ceramic and metal are used to model the functionally graded material through thickness, and the boundary conditions are considered as clamped–clamped (CC) and simply supported–simply supported (SS). The generalized differential quadrature method (GDQM) is used in conjunction with the iterative method to solve the equations. The parametric study is done to examine the effects of nonlinearity, porosity, sized effect, FG index, etc., on the vibration and buckling of porous nanobeam.
TL;DR: In this paper, the effect of slide burnishing on the obtained roughness, micro-hardness, residual stress, fatigue strength (life) and wear resistance of chromium-nickel steels is investigated.
Abstract: Chromium–nickel steels are widely used in various fields of the engineering practice because of their increased corrosion resistance. One of the most used chromium–nickel steel is AISI 316Ti. It is known from the engineering practice that processing this steel by cutting creates difficulties and problems. However, there is no information regarding the effectiveness of the slide burnishing (SB) method in terms of quality of the processed surface of this chromium–nickel steel. A comprehensive experimental and FEM study of the surface integrity of slide burnished specimens made of AISI 316Ti austenitic stainless steel has been carried out. The effect of the SB parameters on the obtained roughness, microhardness, residual stress, fatigue strength (life) and wear resistance has been studied. A fully coupled thermal-stress FEM analysis has been conducted to be appreciated the effect of the generated temperature in SB process on the residual stress formation. The SB of AISI 316Ti steel achieves: roughness of Ra = 0.055 μm; micro-hardness increased by more than 32%; significant wear resistance; introduced residual stress with a maximum absolute value, which significantly exceeds the yield limit of the bulk material; increased fatigue strength by 38.9%; fatigue life increasing more than 385 times. The obtained experimental outcomes for the main characteristics of the surface integrity prove that SB can be successfully applied as a mixed burnishing for finishing symmetrical rotational components made of chromium–nickel steels.
TL;DR: In this paper, powder-mixed electro-discharge machining on Inconel 718 was carried out by mixing SiC powder in the dielectric media in consideration with varied peak discharge current, and the morphology and topographical features of the machined surface including surface roughness, crack density, white layer thickness, metallurgical aspects (phase transformation, crystallite size, micro-strain and dislocation density), material migration, residual stress as well as micro-indentation hardness, etc., are studied.
Abstract: Inconel 718 is a nickel-based superalloy widely applied in aerospace, automotive and defense applications. Low thermal conductivity, extreme high temperature strength, high work-hardening characteristics make them ‘difficult-to-machine.’ In order to improve EDM performance on Inconel 718, powder-mixed electro-discharge machining is reported herein. PMEDM is carried out by mixing SiC powder in the dielectric media in consideration with varied peak discharge current. As compared to conventional EDM, the morphology and topographical features of the machined surface including surface roughness, crack density, white layer thickness, metallurgical aspects (phase transformation, crystallite size, micro-strain and dislocation density), material migration, residual stress as well as micro-indentation hardness, etc., are studied. Additionally, effects of peak discharge on PMEDM performance features, namely material removal rate, tool wear rate, surface roughness, surface crack density, white layer thickness, are discussed and compared with conventional EDM.
TL;DR: In this paper, the authors analyzed the characteristics of static moving wedge for unsteady 2D Falkner-Skan flow of cross fluid in the presence of nonlinear thermal radiation.
Abstract: The purpose of current communication is to analyze the characteristics of static–moving wedge for unsteady 2D Falkner–Skan flow of cross fluid in the presence of nonlinear thermal radiation. Furthermore, revised Buongiorno’s relation of nanomaterials is implemented for mathematical modeling of Falkner–Skan flow of cross fluid. Nanofluid characteristics for Brownian movement and thermophoresis are deliberated in this communication. In the considered model, we have utilized the aspects of constructive–destructive phenomenon to elaborate the mechanism of mass transfer. The transformed nonlinear system of ODEs are computed numerically by implementing bvp4c scheme. Physics related to the assumed flow model is described graphically. Furthermore, the graphical analysis revealed that the considered physical model has a significant impact on the physical parameter involved in this problem. It is anticipated from graphical data that declining conduct is observed with the impact of chemical reaction parameter temperature profile for n = 0.5, for static–moving wedge.
TL;DR: In this paper, a parametric study of dry sliding wear behavior of TiB2-reinforced aluminium matrix composites (AMCs) was conducted, and an accurate wear model has been developed, and it can be used as a predictive tool for wear applications.
Abstract: Present work deals with the parametric study of dry sliding wear behaviour of TiB2-reinforced aluminium matrix composites (AMCs). Aluminium 6082-T6 alloy specimens reinforced with 0, 3, 6, 9 and 12 wt% of TiB2 particles were fabricated by the in situ reaction of K2TiF6 and KBF4 in heated liquid aluminium. Experiments were conducted to study the wear behaviour of AA6082–T6/TiB2 composites using pin-on-disc apparatus at room temperature. Weight percentage of reinforcement, sliding speed, load and sliding distance were the process parameters studied in the present investigation, with five different levels of each parameter. The parametric optimization was done employing response surface methodology. The results confirmed that an increase in the amount of reinforcement and sliding speed decreased the wear loss, and an increase in load and sliding distance increased the wear in TiB2-reinforced AMCs. However, the relative significance of these parameters on the sliding wear resistance of the AMCs was very much different. Analysis of variance showed that the sliding distance was the most dominating factor with 65.28% to influence the wear loss in the fabricated composites; it was preceded by the sliding speed with 14.78%, load (9.39%) and reinforcement percentage (3.86%), respectively. The present model was validated by conducting confirmation tests. Thus in this work an accurate wear model has been developed, and it can be used as a predictive tool for wear applications.
TL;DR: In this paper, the principle concern of the present analysis is the inclined magnetohydrodynamic Casson nanofluid flow at a nonlinear stretching plate, considering variable viscosity with slip and convective boundary conditions.
Abstract: The principle concern of the present analysis is the inclined magnetohydrodynamic Casson nanofluid flow at a nonlinear stretching plate, considering variable viscosity with slip and convective boundary conditions. Mathematical formulation is developed by assuming boundary layer approach. The leading differential equations modeled by considering similarity transformations and improved numerical BVP4C (MATLAB package) are utilized to calculate the solution. Parametric behavior of several physical constraints, for instance, Casson fluid factor β, Prandtl number Pr, magnetic field factor M, Brownian motion factor NB,nonlinear constraint n, variable viscosity constant θr, inclined parameter γ, Lewis number Le, thermophoresis diffusion factor NT, velocity slip constant k and Biot number δ on velocity, concentration and temperature distributions, is deliberated. Expressions of friction factor, rate of heat and mass transfer are evaluated graphically also in tabular form for different values of parameters. Conclusions are made on the basis of entire investigation, and it is comprehended that fluid velocity is reducing function of all parameters, temperature profile falls down against Prandtl number Pr, while Brownian motion parameter NB, thermophoresis number NT and Biot number δ enhance the temperature of fluid. Concentration profile reduces against Brownian motion parameter NB and Lewis number Le, while it enhances for thermophoresis number NT.
TL;DR: In this paper, an infinite wavy sheet (as an organism surface) swimming through a non-Newtonian cervical mucus, i.e., Johnson-Segalman fluid, is considered.
Abstract: The dynamics of microorganism is described by the frictional interactions between the microbodies and the mechanical properties of surrounding fluid. Here, we mathematically study such rheological interactions by considering an infinite wavy sheet (as an organism surface) swimming through a non-Newtonian cervical mucus, i.e., Johnson–Segalman fluid. Since, the flow is generated due to the organism movement in narrowly spaced boundaries, therefore flow equations are setup under long wavelength approximation. Moreover, because of the small mass of many such microorganisms like spermatozoa, the inertial forces could be neglected in the description. A perturbation technique is used to attain the analytic expressions for cervical fluid velocity and pressure gradient in both regions above and below the swimmer. These expressions are further utilized to obtain the swimming speed, flow rate of cervical liquid and energy expanded, which are valid for small rheological parameters. To estimate swimming speed for large rheological parameters, a hybrid numerical procedure based on implicit finite difference method along with modified Newton–Raphson method is employed. Our analysis reveals that microorganism could attain maximum speed by suitably adjusting the rheology of the surrounding liquid. By keeping the organism fixed, a special case (pumping problem) is also discussed at the end of the article. The analysis presented here further finds applications in more realistic bio-rheological simulations for non-invasive hemodynamics for intraocular surgery, fluid dynamic characterization of stress-engineered microrobots for pharmacological drug-targeting and microsensing/mapping for lymphatics and intestinal diagnosis.
TL;DR: In this article, the influence of the laser power of the selective laser melting (SLM) process on the morphological properties of the manufactured surfaces has been investigated, and the results are shown in graphic form of 2D and 3D morphology profiles and charts.
Abstract: Additive technologies are increasingly widespread in the aviation industry, medicine and implantology. It is essential that the parts manufactured for these applications meet the highest requirements not only as far as their strength, but also surface quality. Thus, high importance should be attached to performing analysis of the manufactured part’s surface morphology to ensure optimised functionality, and to selecting appropriate post-processes so as to arrive at the required external surface structure. The paper aims to establish the influence of technological parameters (chiefly of the laser power) of the selective laser melting (SLM) process on the morphological properties of the manufactured surfaces. The changes of characteristics of the Sa and Sq parameters in the laser power P function are non-linear. However, for some values of laser power P (150, 175 W), the Sa and Sq parameters are considerably higher than that in case of the remaining laser power values. The change of the laser power has a strong influence on the structure of individual surfaces, as evidenced by the fact that the highest values of the Sa and Sq parameters were achieved at different laser powers (175 W for the top surface and 150 W for the side surface). The results are shown in graphic form of 2D and 3D morphology profiles and charts. Based on the analysis of parameters describing surface structure properties, optimum values of laser power during SLM process are established. The study also revealed that surface structure analysis should not be focused solely on basic parameters such as average height (Sa) or root-mean-square height (Sq), but also on parameters such as kurtosis (Sku) and skewness (Ssk), which yield important information on surface stereometry. Precisely established surface stereometry allows assessing properties such as wear resistance, corrosion, tribological properties, and the ability to integrate medical implants with live organism tissue.
TL;DR: In this article, a multi-objective grey analysis was used to establish hole characteristics in abrasive water jet drilling using multiobjective gray analysis. And the results from analysis of variance and analysis of means were compared and good correlation was obtained.
Abstract: Inconel 617, a group D category of Superalloys, is the prime material for ultra-supercritical power plant components. Nontraditional machining methods are explored for machining Inconel 617 as the traditional processes are limited. Abrasive water jet machining is very promising in processing hard-to-machine materials and machining of superalloys using abrasive water jet machining needs attention. This paper focuses on establishing hole characteristics in abrasive water jet drilling using multi-objective grey analysis. The form and orientation characteristics of the hole are defined using entry and exit hole overcut, entry and exit hole circularity, taper angle of hole and depth averaged radial overcut apart from drill rate and surface roughness. The process parameters are water jet pressure, standoff distance, and abrasive mass flow rate. Analysis of variance of the individual responses is used to identify the pattern in which each parameter affects the performance of the process. Interaction effects of the various factors have been elaborated using plots. Analysis of means was conducted to obtain the mean effects plot. The results from analysis of variance and analysis of means were compared and good correlation was obtained. The parameter levels for obtaining optimal individual responses were identified and reported. Grey relational analysis combines the attributes of each of the responses into a single grey grade. The grey grade represents the overall hole characteristic of the drilled hole. Analysis of means of the grey grade gives the optimal parameter setting. The adjudged optimal parameters are tested experimentally and reported.
TL;DR: In this article, the authors investigated machining performance of Inconel 825 using physical vapor deposition-titanium nitrate inserts, with a focus on sustainable machining.
Abstract: Sustainability is a vital issue for present and future generation, and it aims to obtain overall efficiency in terms of economic, environmental and social aspects. Inconel 825 belongs to the family of nickel-based super alloy and is widely used in the chemical and marine industries. This work attempts to investigate machining performance of Inconel 825 using physical vapor deposition-titanium nitrate inserts, with a focus on sustainable machining. The effect of cutting parameters, viz. cutting speed (v), feed (f) and depth of cut (d) on three aspects of sustainability has been explored in two different machining environments, viz. dry and minimum quantity lubrication (MQL). The experimental results show a significant improvement in MQL machining and tool wear, and cutting power is reduced by 16.57 and 8.47%, respectively, and surface roughness is improved by 10.41%. The interacting effects of parameters on responses are studied using 3-D surface plots; it shows cutting speed and feed are found as dominating parameters on all the three responses. The novelty of this work is to optimize the process for the sustainable production of components by optimizing the process parameters with multiple and conflicting objectives. The sustainable optimization using genetic algorithm provides surface roughness (Ra) as 0.49 µm, tool flank wear (VB) as 110.68 µm and cutting power (P) as 5.44 kW with better convergent capability having 4% deviation. For the application of manufacturing industry, an optimization table is generated for selection of optimum process parameters for achieving desired surface roughness with minimum VB or minimum P.
TL;DR: In this paper, clearance-induced dynamic responses of a spatial mechanism are investigated, where different clearance sizes and driving speeds are performed to evaluate the impact force and energy dissipation during the contact process.
Abstract: A suitable value of clearance in a joint connection is essential for the relative motion necessity of adjacent links. Even if the size of clearance is small, it should be considered at the governing equation of the system. During the mechanism motion, joint clearance is the basis of contact–impact forces between joint parts. In this study, clearance-induced dynamic responses of a spatial mechanism are investigated. Different clearance sizes and driving speeds are performed. For the computational approach, mechanism model is built using the simulation software ADAMS. The actual features of the system such as contact and friction are also considered at the model mechanism. A contact–impact model that comprises the impact function and the energy dissipation during the contact process is also utilized for the computational evaluations. At the experimental stage, clearance-induced vibrations are obtained from the system bearing as a reflection of impulsive forces. Two accelerometer sensors are used for necessary measurements. The results show that the clearance-based impulsive forces have crucial effects on the vibration responses. Clearance is a reason for the non-periodic vibration behaviors. Both the peak frequency and the vibration amplitude are affected from the clearance sizes and driving speeds.
TL;DR: In this article, the effects of hot ultrasonic assisted turning (HUAT) on titanium and Hastelloy-X alloys in terms of cutting forces, cutting tool temperatures and effective stresses were investigated.
Abstract: Aviation alloys exhibit superior properties such as high-strength-to-weight ratio and corrosion resistance but these alloys possess poor machinability. To overcome this disadvantage, new machining methods (Ultrasonic assisted machining, hot machining, etc.) are developed. Hot ultrasonic assisted turning (HUAT) is a new hybrid machining method which changes the cutting system between tool and workpiece, therefore, reduced cutting forces and better surface finish for workpiece are obtained. In this study, 2D finite element (FE) analysis is carried out to investigate the effects of these machining methods on titanium and Hastelloy-X alloys in terms of cutting forces, cutting tool temperatures and effective stresses. DEFORM-2D software is used during analyses. In addition, an experimental study is conducted to verify numerical results. During verification, cutting tool temperature is taken into consideration. It is confirmed that HUAT technique reduces cutting forces and effective stress significantly but cutting temperature increases compared to conventional and ultrasonic assisted turning.
TL;DR: In this paper, the effect of different ratios of Cr particle reinforcement on the hardness and wear resistance of Cu matrix composites produced by using (P/M) method was evaluated by examining the intensity and SEM images.
Abstract: The aim of this study was to determine the effect of different ratios Cr particle reinforcement on the hardness and wear resistance of Cu matrix composites produced by using (P/M) method. Cr particles were added at different weight ratios of 5, 10 and 15%, in pure Cu dust. The prepared mixtures were shaped under a pressure of 400 MPa. The shaped pieces were sintered at 900 °C for 30 min. The success of the sintering process was evaluated by examining the intensity and SEM images. Microscope studies were performed using scanning electron microscopy (SEM). Hardness measurement method was used for determining hardness. In the SEM analysis, it was observed that the Cr phase was uniformly distributed in the Cu matrix composed of coaxial grains. In addition, an increase in the hardness was observed depending on the increase in the Cr ratio. The wear behaviors of the composite materials produced were investigated by pin-on-disk wear test. As the disk, a surface-hardened AISI 1050 steel was used. As a result of this examination, composite materials; depth of wear, losses in the weight, variation of friction coefficient, variation of wear diameters at 0.4 m/s shear rate and 1500 m shear distance were investigated by applying 50 N and 75 N loads. As a result of these investigations, it has been found that as the Cr particle reinforcement ratio in the Cu matrix composites increases, hardness and the wear resistance were increased positively.
TL;DR: In this article, the problem of Williamson nanoliquid flow over an oscillatory stretching sheet is addressed and the results indicate that heat transfer enhancement is possible with insertion of nanoparticles.
Abstract: The paper addresses the problem of Williamson nanoliquid flow over an oscillatory stretching sheet. The effects of heat source/sink are initiated in the energy equation. The convective conditions at boundary are introduced to examine the mass and heat transport phenomenon. A set of appropriate variables are introduced to reduce number of independent variables in the governing equations. Analytic solutions by homotopic procedure are derived for coupled non-linear differential equations corresponding to non-Newtonian liquid. The interesting results of the problem are interpreted both from theoretical and practical aspects. The results indicate that heat transfer enhancement is possible with insertion of nanoparticles.
TL;DR: In this paper, a hybrid approach based on grey relational analysis-based genetic algorithm has been proposed and implemented for the multi-objective optimization of different quality characteristics, such as hole circularity, hole taper and hole dilation.
Abstract: Nickel-based superalloys are being increasingly used in aerospace, automotive industries due to their excellent thermo-mechanical properties. These applications require complex shapes and profiles which may not be obtained by conventional machining processes. These materials are also known as difficult-to-machine due to their excellent thermo-mechanical properties. The electrical discharge drilling proves its suitability in the precision drilling of superalloys. During, the electrical discharge drilling of these materials, hole taper, hole circularity and hole dilation are key attributes which influence the drilled hole quality. In this research paper, the experiments have been conducted by L27 orthogonal array and this experimental data have been utilized for developing the models of different geometrical quality characteristics such as hole circularity, hole taper and hole dilation. Further, a new hybrid approach grey relational analysis-based genetic algorithm has been proposed and implemented for the multi-objective optimization of different quality characteristics. The effects of different process parameters on various geometrical quality characteristics have also been discussed. Finally, the confirmation tests have been performed to validate the predicted results obtained by the proposed hybrid methodology to the experimental results. It has been observed by the comparison results that the machining performance in the electrical discharge drilling process has been remarkably improved through proposed approach.
TL;DR: In this article, the effect of cryogenic treatment of tool and minimum quantity lubrication in terms of indicators such as surface quality of workpiece, tool wear and material removal rate was examined.
Abstract: Inconel 718 is a popular, but difficult to machine, nickel-based supper alloy. Machining performance of this material can be improved by appropriate modelling and optimization. In the present study, response surface modelling and optimization for turning of Inconel 718 under four machining conditions: dry with untreated inserts, dry with cryogenically treated inserts, minimum quantity lubrication with untreated inserts and minimum quantity lubrication with cryogenically treated inserts is carried out. With the aim of improving the machinability of Inconel 718, an attempt has been made to examine the effect of cryogenic treatment of tool and minimum quantity lubrication in terms of indicators such as surface quality of workpiece, tool wear and material removal rate. Cutting speed, feed rate and depth of cut are used as the control parameters. Whereas, cutting force, tool vibration, cutting temperature, surface roughness and tool wear are the measured responses. Prediction models are developed for each response. Later, all the responses are optimized together by desirability approach and are validated using confirmation experiments. A spider plot is drawn to display the relationships among control and response parameters. The plot shows that application of minimum quantity lubrication with cryogenically treated inserts resulted in least cutting force, tool vibration, cutting temperature, minimum surface roughness of workpiece along with least tool wear and best material removal rate compared to other three conditions used. This clearly shows machinability improvement of Inconel 718.