H. Roohi , H. Deilami Azodi, M. Safari ,
Volume 19, Issue 2 (2-2019)
Abstract
Incremental sheet forming is one of the novel processes which is used for rapid prototyping and manufacturing of parts with complex geometries. Forming limit of sheet metal in this process is high compared to other conventional forming processes. In this paper, warm single-point incremental forming process through uniform heating to sheet along with tool heating is studied experimentally and numerically. Formability of sheet is investigated in various process condition based on the straight groove test in experimental approach and numerical simulation using finite element method. Tool heating along with uniform heating to sheet makes tool and sheet isothermal, reduces the heat loss in deformation zone and improves the deformation process. So, attainment of high forming limit is made possible. Comparison of forming limit diagrams obtained from experimental and numerical approaches shows a good agreement between the results. Effects of temperature and feed rate on the forming limit of aluminum 1050 sheet are investigated. Results show that increasing the temperature improves the formability of sheet significantly; but, the temperature is more influential on forming limit in low feed rates. Increasing the feed rate reduces the forming limit slightly; this effect is more evident in higher temperatures.
V. Momeni, M.h. Alaei,
Volume 19, Issue 5 (5-2019)
Abstract
Metal injection molding (MIM) is a novel process classified in powder metallurgy. This process can produce complex metallic parts with high rate of production and consists of four stages, including mixing, injection,
debinding, and sintering, where the properties of the final part
highly depends on the parameters of each of these stages. In this study, the parameters of injection pressure, injection and mold temperature, holding pressure, holding time, injection speed, and cooling time on the density, strength, and hardness of the final MIM compact have been investigated. By the design of experiments and response surface methodology (RSM) method, 50 samples have been injected using different parameters. In order to measure the density, tensile strength,
ad hardness of the samples, the debinding and sintering procedures have been done on the injected samples. The results show that the injection pressure, injection temperature, and mold temperature have the highest effect on the strength and density of the final part, respectively, and on the other hand, holding pressure, holding time, and cooling time have a negligible effect. Within the measured properties, density and strength are more affected by the injection parameters compared to hardness. Finally, the optimum injection parameters for samples made of 4605 low alloy steel include injection pressure of 133 bar, injection temperature of 158
, mold temperature of 60
, the holding pressure of 70
bar, holding time of 8 second, injection speed of 112 mm/min, and cooling cycle of 17 second.
S. Mortezaei, H. Arabi, S.h. Seyedein, A. Momeni, M. Soltanalinezhad,
Volume 19, Issue 6 (6-2019)
Abstract
In this study, a constitutive equation based on the hyperbolic sine Arrhenius-type model has been developed to describe the hot deformation behavior of a Fe-17Cr-7Ni (17-7PH), semi-austenitic precipitation hardening stainless steel. The experimental data obtained from hot compression tests at 950-1100°C and strain rates of 0.001-1 s-1 establish the constitutive equation. The material constants of α, A, n, and Q were calculated, using the developed model related to the applied strain by 6 The average error (AARE) and correlation coefficient (R) were used to evaluate the accuracy of the constitutive equation. The average values obtained for AARE and R were 5.17% and 0.9904, respectively. The results indicated that the developed constitutive equation can predict the flow stress behavior of the studied alloy with good accuracy over a wide range of experimental conditions. The model can be, therefore, recommended for analysis of hot deformation mechanism and microstructure evolution.
Z. Zarei, M. Talafi Noghni, M.h. Shaeri, I. Ansarian,
Volume 19, Issue 8 (8-2019)
Abstract
In this research, Cu-30Zn alloy was subjected to severe plastic deformation (SPD) by Multi-Directional Forging (MDF) process up to 6 passes at room temperature. After the samples fabrication, microstructure, mechanical, and electrical properties were investigated. Mechanical properties of the samples were measured by shear punch, tensile, and hardness tests at room temperature after each pass of MDF process. In addition, electrical properties of the samples were evaluated by Eddy Current method. The results of microstructure characterization by scanning electron microscopy equipped with EBSD attachment showed that the grain size of the initial annealed specimen reduced from about 230 µm to less than 1 µm, after 6 passes of MDF process. Furthermore, grain size reduction was accompanied by slip process, formation of twinning, and shear bonds in a specific direction. According to the results, mechanical properties were significantly improved after 6 passes of MDF. MDF process led to a 212% increase in hardness, enhancement of 105% and 73% in shear yield and ultimate shear strengths, and also improvement of 298% and 190% in tensile yield and ultimate tensile strengths, respectively. The results of the electrical conductivity showed that the electrical conductivity of the Cu-30Z alloy reduced slightly during the MDF process. Comparison of mechanical and electrical properties results demonstrated that high-strength alloys can be obtained in the MDF process without significantly reduction in the electrical conductivity.
H. Salari, M. Mahmoodi, E. Borhani,
Volume 19, Issue 9 (9-2019)
Abstract
The cold roll bonding (CRB) is a type of bonding process between similar and/or dissimilar metals that is bonded through plastic deformation via rolling process at room temperature. In addition, the accumulative roll bonding (ARB) process is considered as one of the methods for applying severe plastic deformation (SPD) with the ability to achieve ultra-fine grains (UFG) structure and improved mechanical properties. In this research, a combined method was suggested consisting of ARB and CRB processes in order to fabricate UFG copper strip with simultaneous increase of strength and electrical conductivity. Microstructure, mechanical properties, and electrical conductivity of copper specimen fabricated via combined method and ARB processes were investigated. Field emission scanning electron microscope (FESEM) micrographs showed in the crystalline structure of the specimen fabricated via combined method, a large amount of the UFG with uniform distribution are observable. Also tensile strength and hardness of strips increased with increasing the number of rolling passes. Finally, investigation the electrical conductivity of the specimens by four-point probes test showed electrical conductivity decreases with increasing the number of ARB cycles, while the specimen fabricated via combined method increased simultaneously strength, hardness, and high electrical conductivity.
J. Mirahmadi, S.h. Hosseini, M. Sedighi,
Volume 19, Issue 9 (9-2019)
Abstract
This paper presents a novel severe plastic deformation method entitles modified friction assisted tube straining for producing ultrafine-grained cylindrical tubes. Using friction power generates heat to locally increase temperature of the deformation area and creates severe combined strains and lower pressing force. Experimental tests were executed on Cu/30Zn alloy to investigate applicability of the presented method. The optimum process parameters, 710Rev/min rotary speed and 0.08mm/Rev feed rate were found, applying experimental test to process tubs fault free. Microstructure study of processed specimens showed a significant grain refinement from the initial value of 76μm to 9μm and 7μm in longitudinal and peripheral directions, respectively. Yield stress and ultimate tensile strength of processed specimens increased to 325 and 202MPa from the initial values of 160MPa in peripheral and longitudinal directions, respectively. Also, hardness significantly increased to 72Hv from the initial value of 48Hv.
S.j. Zakavi, H. Mohammadi Asl, D. Babaee,
Volume 19, Issue 9 (9-2019)
Abstract
In this paper, finite element analysis with combined (nonlinear isotropic/AF kinematic hardening model) and chaboche hardening models are employed to investigate ratcheting behavior in stainless steel branch pipes under dynamic moments and internal pressure. Obtained results show that the maximum value of ratcheting strain takes place in the junction of branch pipes in the hoop stress direction. In this case, the rate of progressive strains increases with the increase of the bending moment levels in constant internal pressure. Furthermore, this study reveals that the geometry and dimensions of branch pipes have a significant impact on the rate of progressive strains. The bending moment levels to initiate strain accumulation phenomena will be increased with the increase of the dimensions of branch pipes. In the BSS1 sample, comparison between results obtained using progressive strains with combined and chaboche hardening models are much better than those of Armstrong-Fredrick hardening model and are near to the experimental data. Of course, in BSS2 sample, the behavior of ratcheting with combined hardening model is near the experimental results. For the BSS3 sample, the prediction of ratcheting with the chaboche hardening model is better than using the other strain hardening models and are near to the experimental data. Like the carbon steel samples studied in the recent paper, compared to the Armstrong-Frederick hardening model, the chaboche and combined hardening models exhibit an appropriate prediction and similar to experimental results in stainless steel samples.
M. Mirabdolahi, M.m. Abootorabi,
Volume 19, Issue 10 (10-2019)
Abstract
In plasma cutting, a noble gas at high speed is blown from the nozzle and ionized with the help of a frequency spark at high voltage and an electric arc is created which cause the gas changes to the plasma state. Plasma cutting is an ideal process for cutting of the hard metals. In this research, the effect of the input parameters and their optimization in plasma cutting of AISI 309 stainless steel were studied. By conducting the different experimental tests, the effect of input parameters including amperage, gas pressure and the cutting speed of torch on the three output parameters of the width of cut (Kerf), heat-affected zone (HAZ) and surface roughness (Ra) were investigated. Analysis of the results showed that the amperage, cutting speed and gas pressure have the highest impact on the output parameters, respectively. The artificial neural network (ANN)-genetic algorithm was used to predict and optimize the output parameters. The results indicate that the artificial neural networks model trained by the genetic algorithm are able to predict the output parameters accurately. Finally, the optimization of output parameters to achieve the best cutting conditions was carried out using the genetic algorithm. The artificial neural network models were considered as the objective function and also, the parameters of the heat-affected zone, surface roughness, and the width of cut were introduced as inputs of the algorithm. According to results, a combination of the neural network and genetic algorithm is an efficient method for optimization of the plasma cutting process. This method can be easily modified and utilized for other advanced cutting methods.
S. Mirzakhani, M. Javanbakht,
Volume 19, Issue 11 (11-2019)
Abstract
In the present work, the nonlinear finite element method is used to solve the phase field equations for phase transformations at the nanoscale. In the phase field theory, the evolution of a martensitic nanostructure is described in terms of several order parameters and the Ginzburg-Landau equation is a linear relationship between the of the change rate of an order parameter and the thermodynamic forces which are the variational derivative of the free energy of the system with respect to the order parameter. Since the free energy includes nonlinear terms of the order parameter, the thermodynamic forces are nonlinear functions of the order parameter. Therefore, the phase field equations are solved using the nonlinear finite element method and the self-developed code. The studied transformation is the conversation of cubic to tetragonal phase in NiAl by temperature changes and neglecting the mechanical effects. Therefore, the transformation is the induction temperature type and is defined using only one order parameter. To validate the numerical work, the profile, width, energy, and velocity of the austenite- martensite interface were calculated and compared to the previous works and a very good agreement is found between them. Also, various physical problems such as plane interface propagation, martensitic nucleation, and propagation undercooling, and reverse phase transformation under heating are simulated. The obtained results present a proper tool to solve more advanced phase field problems for phase transformations at the nanoscale including mechanics effects and complex initial and boundary conditions.
A. Nikueimanesh, S. Akbarzadeh,
Volume 20, Issue 1 (1-2020)
Abstract
Wear is one of the most detrimental mechanisms which can affect the performance of many industrial systems. TiN coating due to its unique properties such as resistance to wear, oxidation, and heat is widely used in mechanical elements. In this research, TiN coating has been coated on steel substrate using a physical vapor deposition method. The coating’s properties have been obtained using nano-indentation test. Pin on disk wear test has been conducted while the disks are coated. The tests are conducted under three different loads and different speeds. It was shown that the samples with thicker coating show a better tribological performance. In this study, the relationship between wear and entropy has been investigated in order to predict the wear rate for different materials by predicting temperature. Also, temperature changes over time were predicted in two states of with and without coating. It was also shown that the samples with thicker coating have better wear resistance. One of the innovations of this research is the ability to establishing a correlation between the wear rate and produced temperature.
H. Mehman Navaz, G.h. Liaghat, M.a. Nabakhteh, Hamid Fazeli, M. Rouhbakhsh, A. Heidari,
Volume 20, Issue 1 (1-2020)
Abstract
Recently the use of reactive shaped charges with bimetallic liners are taken into consideration to increase destruction quality in water environments. In this research, according to the results of a series of valid experimental results, the analysis of a reactive shaped charge with a bimetallic liner made of copper-aluminum liner has been numerically verified. In this verification, a suggested theory for the cutoff velocity of bimetallic liners has been used to calculate the cutoff velocity. The amount of penetration depth using a numerical solution is in good agreement with the experimental value. These results have been compared with the values obtained from the analytical solution. Finally, the behavior of the shaped charge with bimetallic liner has been compared with a single metallic liner using the same target geometry in both and it has been shown that the overall penetration quality such as depth, diameter and the profile of reactive shaped charge with a bimetallic liner was found to be better than the single metal liner.
S.m. Ghalehbandi , A. Fallahi, H. Hosseini Tudeshki ,
Volume 20, Issue 2 (1-2020)
Abstract
The focus of this paper is to investigate the possibility of consideration of grains and grain boundaries and their elastic-plastic behavior to predict the stress-strain behavior of ECAPed 7075 Al alloy using a finite element micromechanical approach. For this purpose equal channel angular pressing is performed on the alloy and hardness and tensile tests were performed in the macro mode as well as the micro-indentation test on distinct areas of microstructure. Mathematical relations were obtained for the correlate the hardness and static strength properties of the alloy using the obtained data from hardness and tensile tests. In addition to the mathematical relations, backward simulation of the micro-indentation process has been used in the Abaqus finite element software to convert the hardness in the grain and its boundary to stress-strain curves. The elastic-plastic behavior of the phases has been used in microstructural modeling. Modeling of the strain test has been performed in the finite element software for the microstructures using the microstructural image. The predicted stress-strain behavior from microstructural modeling has been compared with experimental results.
A. Bagheri-Bami, S. Amini , R. Teymouri ,
Volume 20, Issue 2 (1-2020)
Abstract
The ball deep rolling process is used to improve the surface properties of the workpiece. In this research, the optimum state was determined using the design of the experiment to improve the properties including optimum hardness and roughness. It was determined 3 passes and the type of traditionally and ultrasonic process and proposed regression model at the speed of 1000mm/min. In this case, it showed the hardness of 131 micro vickers and also determined minimum roughness in the mean roughness of 0.179 microns and the maximum roughness of 1.01 microns. The microstructure and tensile tests have been investigated in the optimal sample, compared to the surface topographic reference sample. The microstructure has been shown the decreases from about 30-50 microns to about 300 nanometers in thickness at about 50 microns below the surface by scanning electron microscopy. The tensile stress and percentage increase in length were determined by 10% and 29% increase, respectively by the tensile strength test. Topography has also shown the reduction of roughness by 40%. The hardness of the subsurface was studied in the thickness of the workpiece and it was compared to the same traditional and modern optimum specimen. The result showed the effect of increasing the hardness due to the of the structure fracture and strain rate.
I. Ansarian, M.h. Shaeri,
Volume 20, Issue 3 (2-2020)
Abstract
Commercial pure (CP) titanium has many applications in biomaterials especially in implants due to its excellent biocompatibility. Despite the importance of surface properties in bio-applications, limited research has been conducted to improve surface properties of CP titanium by improving the structure. Therefore, the purpose of this research is to improve the corrosion and wear properties of CP titanium by reducing grain size by multi-directional forging (MDF) process. For this purpose, annealed CP titanium samples were forged by MDF up to six passes at ambient temperature and 220°C. To investigate the corrosion properties of specimens, the tafel polarization test was performed in a simulated body fluid (SBF) solution. The tribological properties were also investigated by pins-on-disk test at sliding speed and applied stress of 0.2 (m/s) and 1MPa, respectively. The results of microstructure analysis of the samples using a scanning electron microscope (SEM) equipped with EBSD showed that the ultrafine grain structure was formed in titanium CP, after 6 passes of the MDF. The results of the investigation of the tafel polarization test showed that the corrosion resistance of the samples increased with applying MDF and increasing the pass number, regardless of the processing temperature. Also, the corrosion resistance of MDFed samples at 220°C temperature was higher than the MDFed samples at ambient temperature. Wear resistance of CP titanium was also increased, by decreasing the grain size. The results of the investigation of surface morphology of samples using a field-emission scanning electron microscope showed mainly the abrasive and delamination wear mechanisms.
M. Jalili, B. Soltani, A. Nayebi,
Volume 20, Issue 3 (2-2020)
Abstract
In the present research, a multiscale method based on crystal plasticity finite element method and computational homogenization is proposed to simulate monotonic and cyclic plastic deformation of a highly textured rolled magnesium alloy AZ31. All active deformation mechanisms including slip, twinning as well as detwinning have been simulated in the model through user material subroutine in ABAQUS (UMAT). All representative volume elements have been constructed, synthetically. Polycrystal laminate has been reproductive by representative volume element (RVE) and periodic boundary conditions have been applied on the RVE faces. For cyclic validations, uniaxial compression-tension along extrusion direction has been applied for 2 loading cycles and the problem at the macroscopic scale has been solved by the ABAQUS finite element solver. The results are in good accordance with the experimental curves and the proposed model can accurately predict all cyclic behavior characteristics like asymmetry in a stress-strain curve due to alternating twinning-detwinning, tensile and compressive peak stresses, twinning and detwinning.
M. Nazari, H. Eskandari, M.r. Golbaharhaghighi ,
Volume 20, Issue 3 (2-2020)
Abstract
In this research, friction stir processing was used to produce mono and hybrid surface composite layers of aluminum matrix containing TiB2 and graphene particles. Microstructural evaluation of the samples was performed by optical microscopy and field emission scanning electron microscopy of the composite samples cross-sections. The mechanical properties of the samples were investigated using microhardness and tension tests. Among the samples reinforced with TiB2 and graphene, the samples with 20wt% TiB2 and 1wt% graphene exhibited the highest hardness and strength compared to other samples. Aso, the highest mechanical properties are observed in the sample reinforced with hybrid powders include 20wt% TiB2 and 1wt% graphene. The yield and ultimate strength of the sample increased from 75 and 160MPa (corresponding to the initial 6061 AA) to 191 and 271MPa, respectively. Also, the average hardness of this sample in the stir zone is equal to VHN101 which was significantly higher than the initial alloy (VHN62) and the non-powdered friction-stir sample (VHN71).
M. Sayah-Badkhor , A. Naddaf-Oskouei , D. Kashani, M. Agha Mola Tehrani ,
Volume 20, Issue 3 (2-2020)
Abstract
There are many effective parameters in impact mechanics. In this article, the relation between the depth of penetration and the projectile nose shape has been investigated. Projectiles were made of AISI 4340 material with flat, ogive, and hemispherical nose shapes. Semi-infinite targets made of alumina ceramic 99.5 and aluminum 7000. The projectile impact velocity in this experimental test was about 400m/s and the thickness of ceramic and aluminum were 4 and 20mm, respectively. A numerical simulation has been conducted by Abaqus software. The results of the numerical simulation show a good agreement with the empirical observations. The depth of penetration for the flat projectile and ogive projectile was highest and lowest, respectively. The ballistic limit velocity for the flat projectile and ogive projectile was lowest and highest, respectively. Projectile erosion is affected by the ceramic thickness and the shape of the projectile. The amount of this erosion for the flat projectile and ogive projectile was lowest and highest, respectively. Increasing ceramic thickness leads to more erosion in the projectile. Also, the changes of ballistic limit velocity have been determined with the changes of ceramic and backing metal thickness.
A. Khoddami, B. Mohammadi,
Volume 20, Issue 4 (4-2020)
Abstract
In the present study, solid particle erosion of Ti-6Al-4V alloy under multiple particles impact was investigated using finite element modeling. The erosive behavior of this ductile alloy has been simulated as a micro-scale impact model based on Johnson-Cook plasticity and failure equations. Erosive behavior is usually described by the volumetric erosion rate, which is introduced as the eroded volume ratio of alloy surfaces to the mass of the eroding particles. In this paper, the results of the finite element model were validated by comparing with results of typical erosion models. Then, effective factors on erosive behavior of alloy, such as impacting particles velocity, particles size, particles impact angle, temperature effects, and particles shape will be investigated. Results show that there is an exponential relation between particle velocity and erosion rate. Also, as particle size increases, the erosion rate increases at first and after a specific particle size, erosion rate presents a constant trend. The maximum erosion rate has been recorded at an impact angle of 40 degrees and a temperature of 473 Kelvin (average temperature of the middle stages of the compressor). It is shown that when spherical particles shape changes to the angular shape, the erosion rate increases more than four times.
M. Sayah Badkhor, T. Mirzababaie Mostofi, H. Babaei,
Volume 20, Issue 4 (4-2020)
Abstract
In this paper, an experimental and numerical study on the inelastic deformation of fully clamped circular, rectangular and triangular plates under the low-velocity hydrodynamic loads has been conducted using the drop-hammer machine. In the experimental section, steel and aluminum plates with three different geometries of circular, rectangular and triangular in different thicknesses of 1 to 3 mm were examined. Experiments were carried out under different levels of energy by changing the height and mass of the hammer and the maximum permanent transverse deflection was recorded as the test output. For better understanding the effect of effective parameters in these experiments, the Design-Expert software was used. In this software, the simultaneous effect of these parameters was investigated using the response surface method. The plate thickness, the standoff distance of the hammer and the mass of hammer were considered as independent quantitative parameters, and the geometry of the plates along with the material of plates was considered as independent qualitative parameters. The obtained regression model has a confidence level of 95% for output prediction. Accordingly, the p-value for the model is less than 0.05, which means that the regression model is significant. The values of R2 and R2adj was 0.9803 and 0.97131, respectively. The results of the regression model have a good agreement with experimental results. In all experiments, the standoff distance of the hammer was the most effective parameter while the mass of the hammer had the least effect on the response. The optimum conditions for each plate were also determined.
A. Siahsarani , Gh. Faraji, F. Samadpour,
Volume 20, Issue 4 (4-2020)
Abstract
Magnesium and its alloys have received much attention not only in the aerospace and electronics industry, but also in medical applications due to its low density, excellent physical properties, and biocompatibility. However, magnesium and its alloys have low ductility and poor strain hardening ability because of the hexagonal crystal structure with the limited number of slip systems at room temperature. Therefore, it seems necessary to improve their ductility and other mechanical properties via novel technologies. In this research, hydrostatic cyclic expansion extrusion has been used to produce ultrafine-grained magnesium rod. Properties of produced rods have been investigated morphologically and mechanically. The numerical investigation has also been performed to show the effects of hydrostatic pressure on strain distribution. Due to the brittleness of magnesium, the process has been conducted at elevated temperatures. Also, due to the fluid limitation at high temperatures, melted polyethylene has been used as the fluid in the process. The results showed that the yield and ultimate strength increased by 54% and 43% after only one pass of the hydrostatic cyclic expansion extrusion process, respectively. Also, elongation increased by 46%. Furthermore, microhardness has also increased with an average of 57 Hv to 70 Hv. The microstructure result showed that the grains become ultrafine-grained after only one pass of the process. Finite element investigation revealed that high hydrostatic pressure has a good effect on improving the strain distribution and the microstructure. This process seems very appropriate for industrial applications due to its ability to produce long ultrafine-grained rods.
