Sh. Heidari, Y. Bakhshan, J. Khorshidi Mal Ahmadi, A. Afsari,
Volume 19, Issue 5 (5-2019)
Abstract
One of the new approaches to produce nanoscale metals with ultera fine grains is applying severe plastic deformation on initial sample with coarse grains. In this method, by applying intense strain to the sample in several steps, the size of the grain decreases to a nanoscale, which results in the improvement of the mechanical and physical properties of the metals. One of the most important methods for this purpose is the constrained groove pressing (CGP) method. Due to the need for a small weight of space structures, sheets of aluminum alloys, aluminum7075-T6, and steel 4130 were selected. The mechanical behavior of the sheets was studied experimentally. The simulation of the interaction between the fluid and the structure was performed for a curved fin model with three different alloys and the deformation of the flying rocket was compared. The results show that the size of the aluminum7075-T6 block decreases from 60 microns to 270 nm with increasing the stages of the process, while the yield strength in the fourth pass increases compared to the annealed sample by 38%. The tensile strength increased by 34%, and the length elongation in the fourth passes reduced by 40%. The total deformation in the fin of the aluminum 7075-T6 improved to 99.9% with the CGP process. However, the amount of deformation in the steel 4130 fin compared to the CGPed aluminum7075-T6 is less than 0.1% of the total deformation.
H. Abyar Firouzabadi, A. Abdullah,
Volume 19, Issue 6 (6-2019)
Abstract
Wire Electrical Discharge Machining (WEDM) is known as an advanced manufacturing process, especially for producing delicate and intricate shapes and cutting difficult-to-cut materials. Machining error on is an important problem associated with this process. The current paper investigates experimentally the machining errors of three-stage WEDM on the small straight and arced paths. To reveal the reason behind these errors and to compensate them, residual materials of each cutting stage on the straight and arced corner paths were separately measured and analyzed. Machining errors of each WEDM stage in both paths were accurately considered and the causes of these errors in the straight and small arced paths were experimentally and theoretically determined and discussed. Experiments showed that the roughing stage has such a serious deteriorating influence the machining errors on the arced paths that it cannot be compensated in the following finishing stages. The spark angle domains of the roughing stage on the arced paths were calculated and the effects of these domains on the machining errors due to wire diversion from the programmed path were analyzed. In addition, this research proposes a novel guide in multi-stage WEDM by defining some machining concepts and developing equations for error calculation of WEDM finishing stages on these paths. The machining errors estimated by equations have consistency with the related experimental ones. of this study can be employed in the accurate WEDM cuttings.
R. Khonsarian , M. Farrokhi,
Volume 19, Issue 7 (7-2019)
Abstract
In this article, a novel control of wheeled mobile robot based on machine vision is considered. One of the common methods for controlling such systems is the use of Model Predictive Control (MPC) algorithms. In these systems, the response speed of the control algorithm and the optimality of these are two basic factors for achieving the optimal performance. Also, the impossibility of achieving precise values of the robot parameters and their variation during the operation of the robot is an important challenge in the implementation of the controller, therefore, this paper focuses on real-time and robust MPC, so that it can ensure the system against uncertainties and environmental disturbances in addition to the optimal and real-time response. Hence, the optimization based on projection recurrent neural network (PRNN) has been used as an optimizer to reduce the calculation time cost. The combination of PRNN optimization with MPC leads to new formulation and constraints that are considered to be the article innovations. Finally, in order to verify the validity of the proposed algorithm, the robot passes through the corridor with the presence of obstacles, which is simulated in the V-REP software. The results show that the optimum control input speed has been increased in comparison with similar methods, and the optimal path selection by the fuzzy system in the presence of obstacles has been well suited.
H. Danandeh Oskuei, D. Jalali Vahid,
Volume 19, Issue 9 (9-2019)
Abstract
This paper examines the design, manufacture, and analysis a Gamma-type Stirling engine using the solar parabolic collector. The calculation base for designing is so that the size of the solar parabolic collector needed to start the engine is not too large. After finishing the design and manufacturing of the parts, the assembled Stirling engine was initially initiated by a 550W electric heater tested in two non-insulated and insulated conditions for different input power. In the non-insulated state, the Stirling engine has a maximum power of about 68.69W with an output of 12.66%; and insulated mode of Stirling engine maximum watts with an output of 15.72% was obtained. Then we constructed a solar parabolic collector based on the power of the heater used. Designing the collector is such that it has the ability to reflect around 550W. Thus, the diameter of the collector is 1m and its depth is 12cm. This solar parabolic collector provides the power needed by the engine to work during the day. The maximum output power of the solar Stirling engine is about 30W.
F. Yousefi, R. Taghiabadi, S. Baghshahi,
Volume 19, Issue 9 (9-2019)
Abstract
Hypoeutectic Al-Ni alloys are extensively used in automotive and aerospace industries due to their excellent castability and appropriate high-temperature specific strength. The addition of Mn to the composition of these alloys promotes the formation of Mn-rich precipitates and improves their strength and hardness, especially at high temperatures. However, if the Mn content exceeds 2 wt. %, increasing the size and volume fraction of Mn-rich compounds adversely affects the mechanical properties, especially the ductility and toughness of the alloys. On this basis, the current study was aimed to control the negative impact of high Mn content on tensile properties of hypoeutectic Al-Ni alloys by increasing the solidification rate and friction stir processing. For this purpose, the Al-4Ni-4Mn samples, prepared under different solidification rates of 3.5 and 10.4 °C/s, were subjected to friction stir processing (12 mm/min, 1600 rpm). Microstructural characterization and image analysis results show the substantial refinement of Mn-rich particles and their distribution in the matrix, refinement of grains, and elimination of casting defects such as gas/shrinkage porosities and entrained oxide bifilms. According to the results, increasing the solidification rate and applying of friction stir processing improved the tensile strength, yield strength, fracture strain, toughness, and microhardness of alloy by 63, 55, 123, 188 and 58%, respectively.
A.m. Rashidi, H. Ramazani,
Volume 19, Issue 11 (11-2019)
Abstract
In this research, the effects of partially austenitising time on the machinability of spheroidal graphite (SG) cast iron with ferrite-martensite dual matrix structure (DMS) were investigated to optimize its machinability. Specimens with non-alloy ferrite matrix structure were prepared by the casting process. Then the specimens were austenitized at temperatures of 900 oC at various times (5 to 25 min) and subsequently quenched into the water to produce DMS with martensite volume fractions. The Brinell hardness test method was used to determine the hardness of specimens. The machinability of the workpieces with ferrite and dual structures were investigated by measuring the surface roughness and primary cutting force. According to the results, the Johnson-Avram kinetic model was valid for correlation between the martensite volume fraction and autenitising time. The surface roughness was increased and the cutting force was decreased with increasing austentising time to 12 min, and consequently, with increase the hardness to 168 BHN. The heating at 900 oC for 12 min resulted in 16-20% and 15-23% improvement on the cutting force and specific cutting power, respectively, when compared to as-cast specimen, while the surface quality remained at the same level. The cutting force was correlated with feed rate as a power model with exponents of 0.77 and 0.73 for DMS (with 30% martensite) and ferritic as-cast samples, respectively.
A.h. Torabi, S. Elhami, M.r. Razfar,
Volume 20, Issue 1 (1-2020)
Abstract
Glass as a non-conductive material has special properties such as transparency, chemical resistance, and hardness. Traditional machining methods have noticeable limitations in their capability for shaping the glass parts. Electrochemical discharge machining (ECDM), as an advanced machining method, gives a chance to implement special processes on the glass. There are many effective parameters in the ECDM process and each of them has its special effect, but the influence of electrolyte type has been rarely evaluated in the literature. In this research, the effects of two types of NaOH and H2SO4 electrolytes on the glass have been studied. Electrolyte temperature, as another effective parameter on the chemical reactions, is also considered in these experiments. Surface quality, machining depth and overcut are considered as the machining outputs. The experimental results obtained in this research indicated that the application of H2SO4 acidic electrolyte after machining in NaOH electrolyte rather than machining solely in NaOH electrolyte has a significant effect on the walls of the holes. It is also observed that with a higher electrolyte temperature, the walls of the holes become smoother. It is also shown that, by applying two steps implementation of drilling and application of acidic electrolyte (NaOH/H2SO4), holes have a lower overcut, and the machining depth is improved up to 20.5% in the hydrodynamic regime.
A. Pak, M. Mahmoodi, M. Safari,
Volume 20, Issue 1 (1-2020)
Abstract
In the process of manufacturing, the operation of improving the quality of the surfaces is important due to the different working conditions, the resistance to corrosion and fatigue life, friction, the type of contact between the surfaces and appearance. The purpose of this research is the experimental investigation of burnishing process on the flat surface by ultrasonic vibration in order to investigate the initial surface roughness as an input variable as well as its interaction effect on the final surface roughness of aluminum Al6061-T6 alloy. Response surface methodology (RSM) was utilized to correlate the empirical relationship between input and output variables and their interaction effects. Experimental tests with a constant frequency of 20 kHz were done to find the effect of the initial maximum surface roughness, ultrasonic vibration amplitude and static load on the surface roughness. The results show that the initial surface roughness has no direct effect on the output surface roughness, but the effect of vibration amplitude and static load on the final surface roughness depends on the initial surface roughness. The higher static load is needed for the high surface roughness, and the increase of static load has decreased the effect of initial surface roughness on the surface roughness. Also, in high vibration amplitude by increasing the initial surface roughness, the surface roughness is increased and at low vibration amplitude by increasing the initial surface roughness, the surface roughness is decreased. By increasing the vibration amplitude and the static load, the surface roughness is increased. Furthermore, the amplitude of vibration, the interaction effect of static load and the initial maximum surface roughness and static load have the highest effect on the final surface roughness, respectively.
A. Ahmadlou, M.h. Sadeghi, R. Ghaffari Torab Torki ,
Volume 20, Issue 2 (1-2020)
Abstract
Micro milling is widely used for producing industrial micro parts. In micromachining, approaching the depth of cut to tool cutting tip radius causes some problems in achieving desired surface quality and burr formation. It is impossible to use conventional deburring methods in micro parts due to the reduction of machining scale and the importance of high dimensional accuracy and surface quality. Therefore, it is important to comprehend micro end milling and the effect of process parameters on reducing these problems. In this study, the effect of spindle speed, feed rate and depth of cut on surface roughness and burr size during micro end milling of AISI1045 steel have been investigated using the response surface method. Two flute endmills with 0.8 mm diameters have been used in this study. Results show that feed rate with 55.26, 37.53 and 44.55 percent contribution on burr size in up milling side, down milling side and surface roughness is the most effective parameter in the micro end milling process. Selecting the maximum amount of spindle speed, feed rate, and the minimum amount of depth of cut causes minimum burr size in both up milling and down milling side. 36000RPM spindle speed, 5.7mm/s feed rate and 0.086 mm depth of cut causes the best surface quality in micro-milling of mentioned steel.
D. Dindar, B. Jabbaripour,
Volume 20, Issue 4 (4-2020)
Abstract
Increasing workpiece surface quality and reducing tool wear are always the most important ones in machining purposes. There are basic challenges to achieve optimum conditions for workpiece surface and tool life in different machining operations of austenitic stainless steel 304L due to low thermal conductivity and creating high temperatures at the cutting zone. Applying conventional cooling methods such as flood techniques does not usually provide desirable control of machining temperature. Also, their use often creates environmental problems. Recently, the cryogenic cooling process has been considered by researchers to reduce these problems in various machining methods. In this research, turning of 304L stainless steel using cryogenic cooling of CO2 have been studied to investigate the effect of flow rate and fluid spraying method on workpiece surface roughness and tool wear. For this purpose, the tool-workpiece contact zone has been cooled in five different methods of CO2 fluid spraying according to the number and position of the spraying nozzles (Up1, Up2, Down, Up1-Down, Up2-Down) and three different flow rates (12, 18 and 24 l/min). The minimum main flank wear of the tool was achieved in the Up1 cooling method and 18 l/min flow rate and the minimum workpiece surface roughness was achieved in the Up1 cooling method and 12 l/min flow rate. Regarding economic considerations to reduce the consumption of spraying flow of CO2 fluid and achieving the minimum main flank wear of the tool, built-up edge and workpiece surface roughness, the optimum spraying method and flow rate were obtained as Up1 and 12 l/min, respectively.ش
F. Pashmforoush, A. Hassanpour Babajan, R. Beyraghi Baranlou,
Volume 20, Issue 4 (4-2020)
Abstract
In this study, an abrasive water jet machining process was used to evaluate the machinability of Hardox 400 steel, as one of the most widely used materials in the sheet metal industry. In this regard, surface roughness and geometrical tolerances (flatness, parallelism, and perpendicularity) were considered as the machining outputs, and water jet pressure, the weight percentage of abrasive particles, nozzle gap and feed rate were considered as the process input parameters. Followed by machining tests, the measurement of geometrical tolerances and surface roughness was performed through coordinate measuring machine (CMM) and surface roughness tester, respectively. The obtained results indicate that by the increase of jet pressure, decrease of feed rate, decrease of nozzle gap and increase of abrasives particles weight fraction, the surface quality improves and the geometrical errors reduce. Also, it was observed that the best surface roughness and geometrical tolerances have been obtained in the case of water jet pressure of 300 MPa, the feed rate of 10 mm/min, the abrasive weight percentage of 30% and nozzle gap of 1 mm. By repeating the experimental tests, it was shown that the relative error of the obtained results is less than 10%, which indicates the high repeatability of the results.
A. Pak, H. Yaghooti, V. Tahmasbi,
Volume 20, Issue 5 (5-2020)
Abstract
The use of ultrasonic vibrations to reduce the temperature in bone drilling is one of the most important advanced processes that has attracted the attention of bone surgeons. Therefore, the study of temperature behavior in the ultrasonic-assisted drilling process and the prediction of temperature behavior have an important effect on improving the use of this method in orthopedic surgery. In this research, the influence of process parameters on change in the temperature was studied using response surface methodology and data analysis. Data analysis was carried out to find the effect of process factors such as rotational speed, feed speed, and ultrasonic vibrational amplitude and their interaction on the temperature. Moreover, using the statistical method of Sobol sensitivity, the effect, and sensitivity of each input factor on temperature were studied. The results show that the use of ultrasonic vibrations reduces the temperature, and rotational speed (%48), vibrational amplitude (%33) and feed speed (%19) had the greatest effect on temperature in ultrasonic-assisted bone drilling, respectively. As a result, the use of ultrasonic vibration can reduce the dependency of process temperature on the feed speed, and thus make it possible to perform surgery in a shorter time. The minimum temperature is 37°C at the rotational speed of 500rpm and the feed speed of 20mm/min and the vibration amplitude of 15μm.
S. Oskueyan , V. Abedini , A. Hajialimohammadi ,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, the effect of using of aluminum oxide and silicon oxide nanoparticles simultaneously into dielectric has been investigated in the process of electrical discharge machining of titanium alloy Ti-6Al-4V. After analyzing the parameters affecting the process of the electrical discharge machining using nanoparticles, intensity of the current, concentration, pulse on time, and particle composition were considered as input parameters. The effect of each parameters has been investigated on three levels; the material removal rate (MRR), the tool wear rate (TWR) and the surface roughness (SR) of the work piece. With respect to the development of the industry in the use of environmentally friendly dielectrics, deionized water was used as the dielectric fluid. Also, Design Expert software has been employed for the design of the experiments, analysis of the results and optimization of the parameters. The results showed that the best surface morphology is obtained by machining with the addition of nanoparticles in the relative composition of 50%. In this percentage of the composition, the surface roughness has the least value of the crack and the recast layer. In addition, the maximum value of the MRR and minimum value of TWR can be achieved in 12A of current intensity, 100µs of pulse on time and 75% of relative composition.
H. Esmaeili , H. Adibi , S.m. Rezaei ,
Volume 20, Issue 6 (6-2020)
Abstract
Ceramic Matrix Composites (CMCs) are designed to overcome the main drawbacks of monolithic ceramics, especially their brittleness, in high-performance and safety-critical applications. Owing to the inherent properties of CMCs, especially heterogeneous structure, anisotropic thermal and mechanical behavior, and the hard nature of fibers or matrix, the machining process becomes extremely challenging as the generated surface suffers from undesirable quality. Taking the high hardness of ceramic matrix into account, grinding with diamond abrasives is the only efficient way for machining of CMC materials. The aim of this paper was to study the influence of grinding parameters (cutting speed, feed speed, and depth of cut) and different cooling-lubrication conditions (i.e. dry, fluid, and minimum quantity lubrication) on surface roughness, process efficiency, and tool wear. The results indicated that MQL leads to the best results in terms of surface quality and process performance. Furthermore, increasing of cutting speed and feed speed decreased and increased surface roughness, respectively, while depth of cut had an insignificant effect on the roughness value. Regarding the experimental results, four machining strategies considering quality, productivity, and efficiency criteria were developed. Eventually, the material removal mechanism was evaluated using SEM photos, indicating that brittle fracture is the dominant removal behavior of CMC materials.
M. Bayat, M. Abootorabi,
Volume 20, Issue 6 (6-2020)
Abstract
Reducing energy consumption in production is an urgent need. In manufacturing processes, especially machining, more than 90% of the environmental impacts are due to energy consumption in machine tools. The purpose of the present study is to estimate and compare the energy consumption of AISI 316 steel milling process in conventional (wet) and minimum quantity lubrication (MQL) modes as well as the experimental measurement of energy consumption in each of these two modes. Studies have suggested different types of energy consumption modeling in machining but few studies have been conducted on the use of these modeling techniques and the minimum quantity lubrication method has been rarely compared with the wet state in terms of energy consumption. Empirical experiments were used to confirm the modeling performed to predict energy consumption in the milling process. The results show that the proposed method is efficient and practical for predicting energy consumption with 5% error. After confirming the modeling, using two levels for feed rate and spindle speed and applying full factorial design of experiments, energy and power consumption in MQL and wet cutting modes using the power meter connected to the input 3-phase power cable of the milling machine were experimentally measured. Energy consumption in the minimum quantity lubrication method was decreased by 16% compared to the wet state. The average power consumption in MQL milling is 33% lower than in wet milling.
A. Mehrvar, A. Mirak, M. Rezaei,
Volume 20, Issue 7 (6-2020)
Abstract
Electrochemical machining (ECM) has unique features and advantages which is a suitable method for machining when surface quality and residual stresses are of importance. Because of various parameters that influence this process, numerical and experimental studies play a key role in feasibility, practical utilization, and selection of optimal machining parameters in different materials and applications. On the other hand, with the high technology used in the casting of nickel-based single crystal superalloys, no grain boundaries are created in the material. Therefore, by improving the mechanical properties of this material, the traditional machining processes are not effective and economical. Also, they cause defects such as residual stresses, tool wear, and poor surface quality. The purpose of this research is to investigate numerically the electrochemical machining on this special superalloy. Comsol software is used for process modeling and numerical analysis. Firstly, the electrical current and voltage in the machining gap are determined, and finally, the workpiece displacement boundary is obtained. Then the numerical conditions of machining parameters are implemented for experimental investigation by electrochemical machining machine. About 8% error between the results of numerical simulation and experimental investigation shows the feasibility and capability of this modern machining for this particular superalloy.
H. Emami, E. Shakouri , P. Saraeian ,
Volume 20, Issue 7 (6-2020)
Abstract
Aluminum alloys, due to their high variety and favorable mechanical properties, are widely used in industries. Aluminum alloy 111H-5754 due to its properties such as high strength to weight ratio, ductility, toughness, and corrosion resistance, are applied in the manufacture of automotive body, offshore, and offshore oil equipment. The presence of 3% magnesium in the chemical structure of this alloy makes it susceptible to heat and therefore, it is not possible to perform most of the traditional machining processes on it. Water jet machining with abrasive particles (AWJM), because of the use of water and abrasive particles as cutting tools, can be a good method for machining these materials. In the present study, the effect of water jet and abrasive particle machining process parameters, including water jet pressure, traverse speed and loading coefficient on surface roughness, angle of striation, and burr formation in aluminum alloy 111H-5754 samples is discussed. The results showed that after traverse speed, water jet pressure and loading coefficient have the most effects on the surface quality characteristics, respectively. So, for a loading factor of 45% and a jet pressure of 300MPa, increasing the traverse speed from 200 to 300mm/min, the surface roughness value in the smooth area is about 50%, and the angle of striation of the lines in the rough area, increased by about 25%.
S. Dinarvand, B. Jabbaripour,
Volume 20, Issue 7 (6-2020)
Abstract
Modern intermetallic compound of gamma titanium aluminide (γ-TiAl) due to its low density, high elastic modulus, high resistance to oxidation, corrosion, and ignition has recently been considered in the aerospace and automotive industries. Traditional machining of this alloy is so difficult. In the current study, electrical discharge machining of γ-TiAl samples is investigated using different tool electrodes of graphite, copper, and aluminum. The results show that when using aluminum electrodes, tool wear rate is averagely 3.2 times more than copper and 5.8 times more than graphite tools. In addition, when using graphite electrodes, the average material removal rate is 4.2 times more than copper and 7.7 times more than aluminum. Machining by aluminum tool leads to formation of Al2O3 and TiO2 oxide compounds on the work surface but in machining by graphite electrode, TiC and Ti8C5 carbide phases are created on the work surface. In machining by graphite due to formation of hard carbide compounds in the recast layer, the microhardness is higher than the machined sample by the aluminum tool, where oxide compounds exist on the surface and the hardness of recast layer in the machined sample by copper electrode is less than the other two electrodes, because of existing phases such as copper oxide with less hardness. The highest electrochemical corrosion resistance belongs to the machined specimen using graphite tool and the lowest corrosion resistance is related to the machined sample by aluminum electrode. Reducing oxide and aluminum compounds and increasing carbide phases enhance the corrosion resistance of γ-TiAl machined samples.
Arsalan Torabi, Mohammad Reza Razfar,
Volume 20, Issue 11 (11-2020)
Abstract
In recent years, forming a 3D microfluidic channels on the electrical non-conductive material such as Polydimethylsiloxane (PDMS) in the micro-electromechanical system (MEMS) and medical applications is of great interest. Lithography is the most know process to create patterns on the PDMS however there are a few drawbacks to this process such as high operational cost and time, and sidewall angle. In all applications, the quality of the microchannel surface determines the performance of it. In this research as innovatively the electrochemical discharge milling (ECDM) which is known for lower operational cost and proper material removal rate (MRR) (i.e. process time), and is capable of creating patterns on electrical non-conductive material, was used to form a microchannel on the PDMS. To that end, the effect of process parameters such as electrolyte concentration, feed rate and cutting speed and voltage on the surface roughness and surface integrity deeply investigated. It was observed that ECDM is capable of creating patterns on the PDMS with surface integrity which is comparable with the lithography microchannel. It is also observed that decreasing the rotational speed from 10000 to 0 rpm results in increasing the surface roughness 2 to 4 times, this happens due to the increasing the thickness of the gas film around the tool, and subsequently increasing the flying sparks which results in higher surface roughness. Increasing the Voltage from 38 to 42 V results in 38% enhancement of surface roughness. The 25% electrolyte concentration results in lower surface roughness.
Mahdi Barghamadi, Payam Saraeian, Sadegh Rahmati, Ehsan Shakouri,
Volume 21, Issue 3 (2-2021)
Abstract
Today, a variety of implants with different applications are used to replace or support a damaged biological structure, the most common of which are dental and orthopedic implants. Due to the widespread use of stainless steel 316 L in the manufacture of implants and the occurrence of cracks and residual stresses during the process of electrical discharge machining for the production of these products, the use of effective and economical polishing methods such as burnishing in It is effective in increasing the surface properties and compatibility of these products with living tissue. In this study, after performing the electrical discharge machining process on the surface of the sample and making the ball burnishing, the burnishing operations were performed by changing the input parameters and in accordance with the experiments designed using the mini tab software. Thus, the effect of variable burnishing force, feed speed and number of tool passes on surface roughness properties, micro-hardness and corrosion resistance of the final surface of the work piece were investigated. During the optimization of the response surface methodology, the optimal value for surface roughness, micro-hardness and surface corrosion rate of the samples were obtained, respectively, 0.108 μm, 435.34 Vickers and 2.18*105 respectively. Compared to the control sample, the surface roughness of the samples decreased by about 97% and the micro-hardness and corrosion resistance of the samples increased by about 2 and 11 times, respectively.
