H.r. Jashnani , M.r. Rahimi, A. Karimzadeh , M. Ettelaei ,
Volume 19, Issue 2 (2-2019)
Abstract
The properties such as weak wear resistance and low hardness of aluminum alloys have limited their use in various industries. In this research, it has been attempted to improve the mechanical and tribological properties of these materials by deposition of nickel-phosphorous-alumina functionally graded coating. Functionally graded coatings have been produced by a gradual change in the chemical composition and content of the nanoparticle, using continuous change in pulse parameters such as duty cycle and frequency during the coating process. So, the effect of the duty cycle and frequency has been investigated. Two types of coatings have been created with a gradual decrease in the duty cycle of 90% to 30% and a pulse frequency of 50 to 500 Hz. The result shows that the effect of frequency on the amount of phosphorus and nanoparticles is negligible, and it has mainly affected on grain size. However, in nanocomposite coats, the gradual decrease of duty cycle has led to an increase in the amount of phosphorus (5.3% to 15.5 wt. %) and alumina nanoparticles (0.7% to 2.6 wt. %) from the substrate to the top surface. With the gradual changes in chemical and microstructure, the adhesion of the coating to the substrate has improved. The results of micro-hardness have also shown that the creation of functionally graded coatings using duty cycle variation has a higher hardness than the one produced by frequency changing. Also, based on the results of the pin test on a disk against abrasive steel 52100, the wear resistance of functionally graded coatings has improved compared to single-layer coatings.
H. Mozafary , F. Akbaripanah , S.h. Nourbakhsh ,
Volume 19, Issue 4 (4-2019)
Abstract
In this study, 1.5vol.% of SiC nanoparticles was added to AZ31 magnesium alloy via a stir-casting method. Next, the as-cast ingots were extruded at 400°C with the ratio of 3.78. After extruding, the materials were subjected to multidirectional forging (MDF) at 320°C for 2, 4, 6, and 8 passes. In order to evaluate the mechanical properties of extruded and MDFed materials, shear punch (SPT) and Vickers microhardness tests were applied. The results of these tests showed that hard ceramic nanoparticles improved the shear strength and hardness of the matrix alloy. The shear yield strength, ultimate shear strength, and hardness of extruded alloy were 86.70 MPa, 119.43 MPa, and 52.55 HV, respectively, while in extruded AZ31/SiCp nanocomposite, these values increased by 9.91%, 5.48%, and 13.99%, respectively. It was also observed that nanocomposites processed with multi-directional forging offer better mechanical properties than non-MDFed materials. The results indicated that after the first two passes, there was a significant improvement in the mechanical properties of the nanocomposites, such that the shear yield strength, ultimate shear strength, and hardness were improved in contrast with the extruded state by 27.12%, 17.95%, and 16.03%, respectively. Mechanical properties during the next passes were periodically reduced and increased. Microstructural observations also showed that the average grain size variations were periodic during the increase of MDF passes. After the second pass, the grains were finer than the extruded state, and their size increased in the next two passes. From 4th to 6th pass, the grain size decreased and the smallest grains were obtained in this case, while in the last two passes, the grains grew slightly. Despite the smaller and homogeneous structure created by the 6th and 8th passes, the best mechanical properties were obtained in the second pass, which means, in addition to the microstructural changes, also modifications in the material texture during the MDF process had an impact on mechanical properties.
Mostafa Sayahbadkhor, Ali Mozafari, Alireza Naddaf Oskouei,
Volume 19, Issue 9 (9-2019)
Abstract
The ring inside the one-way valve has an important role in the reciprocating compressor. In this article, two different materials for rings were considered; stainless steel with the material number 1.5022 and sign 38si6, and carbon-peek composite. These two rings were prepared in valves with identical conditions in design and manufacturing and were used in reciprocating compressors with the same applications. The results of this experiment showed that the life of the valve with a steel ring was 145 days, while the valve with a carbon-peek ring was intact after 210 days. The most important reason for early failure in the steel ring is an inappropriate distribution of forces due to the springs below the ring. Another common cause of failure in these valves is the stresses on walls in the location of springs. Therefore, in this paper, the stresses in the chamber of springs, which are critical points in the design and construction of the valves, are also discussed. By using robust business codes like Abaqus software, the design and analysis stages of the valve are carried out in quasi-static conditions. The stresses and tensions on the chamber of spring and the ring are much stronger in the steel ring than the carbon-peek composite ring. The results obtained from numerical simulations are consistent with experimental observations. In addition, accurate thickness for the ring was determined by use of flow relations.
M. Aghaei, F. Nazari, M. Honarpisheh,
Volume 19, Issue 12 (12-2019)
Abstract
Quenching heat treatment is one of the most used processes in the industry, which has a great influence on the properties of materials. Accurate understanding of the effects of this process on the behavior of materials can be effective in better use of this process. In this research, the effect of quenching media on the mechanical behavior of wide used steel of AISI 1045 has been investigated and the residual stress created in the structure has been studied using the contour method. In this regard, three cooling environments of water, oil, and molten salt have been utilized, and after examining the strength and contour of hardness resulted by each cooling environment, the residual stresses have been investigated by the contour method. Also, the uncertainty of residual stresses in the environment with the most influencing factor has been evaluated. Investigation of the results shows that quenching in water can create higher hardness and strength, and more excessive compressive residual stress with greater penetration depth than the other environments. But cooling media of water creates more heterogeneous of the structure between the surface and the center of the piece, while quenching in a molten salt environment, with maintaining a structural homogeneity close to the annealing state, can increase the hardness and strength, and generate compressive residual stresses with a penetration depth of about 1.3 mm. Investigation of uncertainty for quenching in the water environment showed that the greatest error in the residual stresses was about 9%, and the error resulting from data smoothing had the most effect on the measurement of residual stresses by the cantor method.
A. Rostamnejad Charati, H. Abdoos, E. Borhani, M. Naseri,
Volume 20, Issue 5 (5-2020)
Abstract
In the present study, multilayer nanocomposites fabricated by accumulative roll bonding (ARB) process. Aluminum sheets, copper sheets (with 0.1 and 0.3mm thickness) and multiwall carbon nanotubes (MWCNTs) were used as experimental materials. The rolling process continued to five cycles. Then, microstructure, hardness, tensile strength and electrical conductivity of nanocomposites were investigated. Necking and fracturing recognized as mechanisms of copper layers distribution in the aluminum matrix. The bonding strength between layers increased with the number of cycles due to the improvement of MWCNTs distribution. The results show that the hardness of aluminum increased with increasing copper layer thickness and these increases were about 30 and 32% for composites without nano reinforcements and nanocomposites contain MWCNTs, respectively. The highest hardness (147HV), is related to the sample containing carbon nanotubes and 0.3mm copper sheet, after five rolling cycles (446% increase compared to aluminum sheets). The results confirm the positive effect of copper and the MWCNTs on the improvement of strength. The highest strength and elongation is observed in the aluminum-copper-MWCNTs nanocomposite after four cycles. The results also indicated that the addition of copper and MWCNTs can simultaneously increase the strength and electrical conductivity of the resulted composites.
A. Najafi, A. Khoddami, S. Akbarzadeh,
Volume 20, Issue 10 (10-2020)
Abstract
Nowadays, many attempts have been made to replace conventional materials with polymers which have the advantage of having less weight and higher formability. Polymers besides these advantages have some shortcomings. One method to overcome these shortcomings is to strengthen them by adding other materials to polymers. As an example, polymer nanocomposites are made by adding nanoparticles to polymers to enhance their tribological performance. In this paper, an experimental and numerical study on the correlation between temperature rise and the wear rate in the polyethylene (PE) with 10% ZnO nanoparticles has been investigated. A comparison between pure PE and polymer nanocomposite has been made. A 3D finite element model has been developed in Abaqus to study the wear in the contact of pin and the disk. The results predicted by the FE model are compared to the experimental data obtained in this research using the pin on disk test rig. According to the results, a non-linear relation between temperature changes and wear rate has been developed.
Zahra Sangarimotlagh, Amir Momeni, Omid Bayat, Zahra Dinmohamadi, Mahnaz Asadbeigi,
Volume 20, Issue 12 (11-2020)
Abstract
In this study, the hot-working behavior of Mn-25Ni-5Cr alloy was studied using hot compression tests at the temperatures of 850 ˚C, 900 ˚C, 950 ˚C and 1000 ˚C and the strain rates of 0.001 s-1, 0.01 s-1, 0.1 s-1 and 1 s-1 to a true strain level of 0.7. The results of flow curves showed that the flow stress decreases with increasing temperature and decreasing strain rate. Regarding the shape of flow curves, peak appearance represents the dynamic recrystallization. The peak stress and strain of flow curves appeared in fewer strains at high temperatures and strain rates. The microstructural evolution is mainly controlled by dynamic recrystallization. The presence of evolving boundaries around the recrystallized grains also indicates the occurrence of continuous dynamic recrystallization during hot working. In closer scrutiny of microstructure and fasciology, using by SEM microscope equipped with EDS detector, in addition to the background phase, second phase consisting of manganese, nickel and chromium was identified. The constants of n, α and β were determined using constitutive, power and exponential equations at 0.3 strain. According to the constitutive equation of the hyperbolic sinus, the amount of activation energy in the strain of 0.3 is 394.6258 kJ/mol.
Mehdi Lak, Seyed Ali Sadough Vanini, Ali Ghasemi,
Volume 21, Issue 2 (1-2021)
Abstract
Abstract
Ultrasonic needle penning is a modern technique that enhances the surface properties of metallic components by imposing static and dynamic loadings. The efficiency of this technique dramatically is dependent on the process parameters. In this study an experimental and numerical investigation on ultrasonic needle penning was carried out. The numerically predicted residual stress profile was verified using X-ray diffraction measurement of residual stress. A 3D finite element model of ultrasonic needle penning was simulated by ABAQUS software. Moreover, a parametric study was performed to investigate the effects of needle diameter, amplitude, device moving speed and static force on residual stress distribution. In order to design of experiments and determine the optimized process parameters of ultrasonic needle penning, Taguchi’s method was implemented. Based on the results, needle diameter had the lowest impact on maximum compressive residual stress and residual stress increases by increasing amplitude and reducing device moving speed. The maximum residual stress was achieved for the needle diameter of 4mm, the amplitude of 16µm, the device moving speed of 1.5cm/s and the static force of 10N. For the optimum case, compressive residual stress was improved 24%.
Ali Sonboli, Reza Beygi, Mohammad Hossein Alirezaie Majdabad Kohneh,
Volume 21, Issue 2 (1-2021)
Abstract
In this study, aluminum-to-copper welding was performed by friction stir welding (FSW) process and then the mechanical properties of the joints were evaluated and compared with the ones rolled to reductions of 30 and 60 percent. Tensile strengths (UTS) of the joints were 99 MPa, 143 MPa, and 132 MPa, for the initial weld, 30% rolling reduction, and 60% rolling reduction, respectively and in the non-rolled weld specimen, fracture occurred from the aluminum base material but in rolled welds, the fracture occurred precisely from the weld interface. Microstructural studies of the weld region and fracture surface of the specimens showed that the Al4Cu9 and Al3Cu intermetallic compounds, which are the most common intermetallic compounds in this type of dissimilar joining, formed in these areas. The presence of these compounds at the weld interface and propagation cracking during rolling has been one of the important factors in the failure of the weld interface in the rolled specimens. Results of the hardness test also confirmed the existence of these intermetallic compounds. By increasing the percentage of rolling reduction from 30% to 60%, the welding strength decreased due to the increase in the number of micro-cracks of the intermetallic compounds. Finally, it can be said that by choosing the optimal percentage reduction in the rolling process (30%), can be significantly increased (about 43%). the ultimate tensile strength of dissimilar Al/Cu joints produced by friction stir welding (FSW).
Saeed Rahmanian,
Volume 21, Issue 3 (2-2021)
Abstract
In the present study, the usability of high-density polyethylene (HDPE) based composites in medical applications under impact loads was investigated. Due to the importance of biocompatibility of composites in the medical applications and body environment, zinc oxide nanoparticles (ZnO) were selected as reinforcements. ZnO nanoparticles are generally safe and have superior antibacterial properties. A finite element simulation process with a new approach were used to study the impact properties of the composites in the standard Charpy impact test; moreover, in the experimental procedure, a new method was introduced for the production of HDPE/ZnO composites without use of the compatibilizers. Fourier-transform infrared spectroscopy (FTIR) test was used to check the diffusion of particles in composites. Field emission scanning electron microscopy (FESEM) was utilized to examine the presence of particles in composites. The results of the simulation showed that the HDPE/1%ZnO composites have the best impact resistance in comparison to other composites. Experimental results also showed that HDPE/1%ZnO composites have the best performance in terms of impact strength with an error of about 11% compared to simulation results and are economical. Moreover, the results of antibacterial test of HDPE/1%ZnO composites confirm the excellent performance of this composites against gram-positive and negative strains.
Faezeh Delfariban, Morteza Alizadeh, Moslem Tayyebi, E. Salahinejad,
Volume 21, Issue 5 (4-2021)
Abstract
In this research, vinyl ester matrix composite coatings reinforced by E-glass fibers, Nano TiO2, and Carbon Nanofiber were prepared by hand lay-up method and their mechanical properties were investigated. The mechanical properties of fiber-reinforced composites were investigated by the tensile, impact, hardness, shear test, and wear tests. Scanning electron microscopy was employed in order to study the fracture surface of the prepared samples. The results of the tensile test showed that the presence of the E-glass fibers in the vinyl ester matrix increases the strength about 4 times and the elongation about 8 times. There was no change in the fiber-reinforced composite strength by reinforcing the composite with nanoparticles of TiO2 and carbon Nanofiber, but the elongation of the fiber-reinforced composite increased by 1.6 times. Impact resistance of fiber-reinforced composite and fiber-reinforced nanocomposite relative to vinyl ester resin increased about 20 and 29 times. The presence of glass fiber and Nanoparticles in the vinyl ester matrix increases the hardness of the samples about 1.5 to 2 times. The results of the adhesion test demonstrated that the presence of nanoparticles in fiber-reinforced nanocomposite improves adhesion to concrete surfaces. Also, the results of the wear test showed that the presence of glass fiber in the matrix of vinyl ester reduces wear resistance and the presence of Nanoparticles in fiber-reinforced nanocomposite improves wear resistance of the fiber-reinforced composite.
Javad Khosravan, Hamid Reza Rezaei Ashtiani, Hamed Deilami Azodi,
Volume 21, Issue 7 (7-2021)
Abstract
The flow forming process is widely used in the production of axisymmetric industrial parts. The advantage of the flow forming process over other manufacturing methods is the use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical properties and surface quality of finished parts. In this research, the warm flow forming process of AA6061-O aluminum alloy has been investigated for the first time. For this purpose, laboratory equipment and samples were designed and fabricated. In this study, the effect of temperature, thickness reduction, and number of passes (number of forming steps) on dimensional accuracy (thickness variation) and mechanical properties of warm flow formed AA6061-O alloys pipes have been experimentally investigated. The experimental results show that flow forming increases the strength and decreases the ductility of the formed pipe at all process levels compared to the initial non-flow forming pipe. However, the ductility of the pipe increases and its strength and microhardness decrease by increasing the forming temperature from 20 to 300 ° C. While with increasing the percentage of thickness reduction from 20% to 60% at a constant forming temperature, the strength and micro-hardness of the warm flow-formed pipe increases and its ductility decreases.
Mohammad Sadegh Aghareb Parast, Hanieh Aroo, Mohammad Azadi, Mahboobeh Azadi,
Volume 21, Issue 8 (8-2021)
Abstract
In internal combustion engines, due to cyclic loading and wear between the upper surface of the piston ring and the upper groove of the piston, the fretting fatigue phenomenon could occur. In this research, the effect of lubrication and the heat treatment on the fretting fatigue behavior of aluminum-matrix nano-composite have been investigated. The fretting fatigue test was performed in fully-reversed loading condition and at the room temperature. In addition, the S-N curve and fretting fatigue properties of piston alloys were obtained. The microstructure and the fracture surface were examined by the optical and microscopy and the field emission scanning electron microscopy. The results showed that the failure behavior was brittle. In addition, the lubrication and the heat treatment improved the fretting fatigue lifetime of the piston alloy.
Yousef Mollapour, Esmaeil Poursaeidi,
Volume 21, Issue 9 (9-2021)
Abstract
The aim of this paper is to investigate the growth of pitting corrosion in CUSTOM 450 stainless steel and to obtain strain values in growing pits at the maximum bending region. In this regard, a two-point bending specimen was made and subjected to a potentiostatic test under the potential of 350 mVSCE in the 3.5 wt% sodium chloride solution. Then, the depth of the grown pits is calculated using Eddy Current device. By simulating a sample under the pitting corrosion in COMSOL Multiphysics software and matching its results with the results of the Eddy Current device, it was found that the simulation can largely replace the laboratory test. To calculate the tensile stress distribution in the cross section of the sample under pitting corrosion, the Laplace equation governing the sample was discretized. The same results were obtained by solving the discrete equations and comparing them with the results of COMSOL Multiphysics software. According to the results, the pit tends to grow superficially. This means that the surface growth of the pit is greater than its growth in the direction of depth. This is due to the fact that near the sample surface, tensile stress and electrical potential are high, as well as chemical reactions and corrosion in areas near to the pit surface.
Mohammad Ravandi, Soheil Dariushi, Ahmad Bateni,
Volume 21, Issue 12 (12-2021)
Abstract
The fibers of date palms, which are widely available in the south of Iran, are a variety of natural fibers that can be used as a reinforcement in polymer composites. This work investigates the effect of alkali treatment on the mechanical properties of date palm fibers and their adhesion to thermoset polymer. The sodium hydroxide (NaOH) solution at three different concentrations (1 wt%, 3 wt%, and 5 wt%) was used to treat the fibers. The single fiber tensile test and fiber pull-out tests were performed to measure the mechanical properties and fiber/matrix interfacial share strength, respectively. Comparing the SEM images of the untreated and treated fibers showed that the 3% NaOH treatment could effectively remove non-cellulosic materials, i.e. lignin and wax, with minimum damage to the fiber surface. The experimental results showed a clear improvement of the mechanical properties and fiber/matrix adhesion after treatment. It was found that the 3% NaOH solution is the optimal concentration to achieve the maximum improvement in the fiber and bonding properties.
Parisa Fekri Dolatabad, Vahid Pouyafar, Ramin Meshkabadi,
Volume 22, Issue 2 (1-2022)
Abstract
The defectless microstructure of metal matrix composites, the uniform distribution of particles and their good properties are determined by the production parameters and the base material and reinforcement. In this study, high-energy planetary ball mill was used to fabricate Al6063-SiC composite powder. Aluminum chips were milled with different time and ball to powder weight ratio (BPR) in high energy planetary ball mill. The resulting powder was mechanically alloyed by adding different weight percentages of silicon carbide (SiC) and BPRs at different times. During the milling process under argon atmosphere, stearic acid was used as a process control agent (PCA) to prevent excessive cold welding and agglomeration of the powder. After mechanical alloying, the effect of alloying time, BPRs and weight percentage of silicon carbide, on the obtained composite powder were examined morphologically by particle size analysis (PSA), field emission scanning electron microscope (FESEM), and the fuzzy compounds by X-ray diffraction (XRD) spectroscopy. According to the X-ray diffraction pattern of the samples, grain size was calculated using the Williamson-Hall model. The results of mechanical milling and alloying process have shown that in short milling times with high BPRs composite powder with finer particle size could be achieved. Also, the presence of silicon carbide reinforcing particles accelerates the process of mechanical alloying and further reduces the particle size.
Arash Lhiabani, Mahdi Nasri, Yazdan Shajari, Zahra-Sadat Seyedraoufi,
Volume 22, Issue 3 (3-2022)
Abstract
1.4923 stainless steel is one of the options for producing Iranian gas turbine (IGT25) compressor blades and upgrading IGT25 +., as well as the importance of wear resistance in turbine parts and the small number of studies in the field of wear as a destructive mechanism of turbine parts, in this research the effect of residual stress caused by shot peening on the wear resistance of steel 1.4923 was investigated. To create the compressive residual stress, shot peening operations were used at 5, 10, 15 and 20 minutes. Microstructural studies by optical microscopy (OM) and scanning electron microscopy (SEM) showed that with increasing shot peening time, the thickness of the plastic deformation area increases so that the plastic deformation area can be divided into three plastic deformation areas. Severe, ordinary plastic deformation and the area affected by plastic deformation. Calculations on the results of X-ray diffraction (XRD) showed that with increasing shot peening time, the amount of compressive residual stress increases to 694 MPa. With increasing compressive residual stress on the surface, the wear resistance of the samples increased up to 90% due to the increase in the density of dislocations and grain refining. Also, the investigation of worn surfaces by SEM showed that the wear mechanism in the samples is oxide adhesive wear and increasing the residual stress of the samples causes the transfer of the wear regime to mild wear abrasion with the appearance of crater areas.
Keyvan Shiri, Seyyed Ehsan Eftekhari Shahri, Habibollah Rastegari Kupaii,
Volume 22, Issue 3 (3-2022)
Abstract
Crack nucleation and propagation in engineering segments and structures are unavoidable. Replacing a damaged part is the easiest way to prevent failure, but it is not always cost-effective. Therefore, in many cases, by repairing a component, the life of defective working parts can be increased. One of the effective strategies, is mending the cracked area using composite patches witch are glued in crack formation place. The purpose of this study was to investigate the effect of patch on crack growth behavior as well as the effects of patch geometry on the mechanical properties of repaired Al5251 aluminum alloy. For this purpose, a Kevlar-epoxy composite patch with rectangular and H-shaped geometry has been used. Tensile test was performed to evaluate the mechanical properties and the crack growth behavior in the samples. The influences of patch geometry and effective area on tensile force, specimen ductility, toughness and crack forming force have been investigated. The results showed that with the use of composite patch, ductility, force at the moment of cracking and the failure force increased compared to samples without repair. Also, comparison of patches with equal effective area showed that samples repaired with H-shaped patch have more load capacity than rectangular patch. In addition, the amount of toughness in the sample repaired with H-shaped patch has increased.
Masuod Bayat, Saeid Amini,
Volume 22, Issue 6 (5-2022)
Abstract
Machining of hard workpieces is one of the most important challenges of the manufacturing industry. Hence, new methods were added to traditional machining. Ultrasonic vibration machining is one of these methods. The advantages of using ultrasonic vibrations compared to traditional machining include reducing machining forces, reducing tool wear and friction, increasing tool life, creating intermittent cutting conditions, increasing surface quality, and so on. To vibrate the tool, a horn with a resonant frequency of 20,633 Hz was analyzed by Abacus software. In this study, the effects of cutting speed, feed rate, conventional machining conditions, and vibration machining conditions at three different hardness of 15, 30, and 45 Rockwell C for the workpiece on surface roughness and tool wear were evaluated. The experiments were designed at full factorial, and a total of 54 experiments were performed. The results showed that at higher workpiece hardness by applying vibration the surface roughness was reduced. The surface roughness (Ra) in machining by means of ultrasonic vibrations is up to about 36% less than conventional machining in various machining parameters. In addition, the temperature in vibration machining is lower about 15% at higher stiffness of the workpiece. Also, with the increase in the hardness of the workpiece, the tool wear was increased, which is less by applying ultrasonic vibrations. Also, by applying vibrations, tool wear was reduced in total, which can be minimized by selecting cermet tools and applying vibrations in 4140 AISI steel machining.
Maryam Morakabati, H. Saki, R. Mahdavi,
Volume 23, Issue 3 (3-2023)
Abstract
Metastable beta titanium alloys are suitable for use in the aerospace industry due to their high strength and good ductility, as well as their high strength-to-weight ratio. The aim of the current research is to investigate the microstructure and tensile properties of the alloy after single-step and two-step aging following thermal-mechanical cycles of single-phase β annealing and two-phase α+β annealing. For this purpose, on one strip of the alloy, solution annealing heat treatment in the single-phase β region, cold rolling and recrystallization and on the other strip, solution annealing heat treatment in the two-phase α+β region was performed. Afterwards, the specimens from the strips were subjected to single-step aging at 550⸰C. In addition, in order to perform two-step aging, specimens were subjected to heat treatment at 300 and 550⸰C for primary and secondary aging, respectively. Then the structural evolution of the alloy was investigated by SEM and X-ray diffraction pattern and the tensile properties of it by tensile test. It was found that the optimum heat treatment cycle of the Ti-3873 alloy was two-step aging after α+β solution treatment leading to 1190 MPa yield strength and 14.7% elongation. In this case, the obtained structure has no grain boundary alpha and the formed secondary alpha has a length of less than 0.5 µm and its average thickness is 0.15 µm.
