Showing 92 results for Ali
A. Salimi, A. Özdemir, A. Erdem,
Volume 12, Issue 3 (September 2015)
Abstract
On time replacement of a cutting tool with a new one is an important task in Flexible Manufacturing Systems
(FMS). A fuzzy logic-based approach was used in the present study to predict and simulate the tool wear progress in
turning operation. Cutting parameters and cutting forces were considered as the input and the wear rate was regarded
as the output data in the fuzzy logic for constructing the system. Flank wear was used as the tool life criterion and the
wear ranges were selected between 0 and 0, 3 based on ISO 3685 standard for new and worn tool respectively. For
conducting the tests, Taghuchi method was used to design an experimental table. The results of the measurements and
estimates confirmed the reliability of the fuzzy logic method for estimating tool wear. One significant feature of the
proposed system is that it can predict the wear rate on-line by transferring the cutting force signals from the sensor to
the fuzzy logic simulation box.
M. Alipour, M. Emami, R. Eslami Farsania, M. H. Siadati, H. Khorsand,
Volume 12, Issue 4 (December 2015)
Abstract
A modified strain-induced melt activation (SIMA) process was applied and its effect on the structural characteristics and hardness of the aluminum alloy Al–12Zn–3Mg–2.5Cu was investigated. Specimens subjected to a deformation of 40% at 300 °C were heat treated at various times (10-40 min) and temperatures (550-600 °C). Microstructural studies were carried out using optical and scanning electron microscopies (SEM). Results showed that the best microstructure was obtained at the temperature and time of 575 °C and 20 min, respectively. The hardness test results revealed superior hardness in comparison with the samples prepared without the application of the modified SIMA process.
T6 heat treatment including quenching to 25 °C and aging at 120 °C for 24 h was employed to reach to the maximum strength. After the T6 heat treatment, the average tensile strength increased from 231 MPa to 487 and 215 MPa to 462 for samples before and after strain-induced melt activation process, respectively. Ultimate strength of globular microstructure specimens after SIMA process has a lower value than as-cast specimens without SIMA process
H. Torkamani, H. Rashvand, Sh. Raygan, J. Rassizadehghani, Y. Palizdar, C. Garcia Mateo, D. San Martin,
Volume 14, Issue 3 (September 2017)
Abstract
In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature) was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J) in comparison with the base steel (23J). Moreover, Mo-added steel possessed higher hardness (291HV), yield (524MPa) and tensile (1108MPa) strengths compared to the base one.
M. Nouri, P. Alizadeh, M. Tavoosi,
Volume 14, Issue 3 (September 2017)
Abstract
In this study, the crystallization behavior of a 65GeO2-15PbO-10MgF2-10MgO glass (prepared by the conventional melt quenching technique) has been investigated. The microstructure and crystallization behaviors of this glass were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), non-isothermal differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that a fully glassy phase can successfully be prepared by the conventional melt quenching technique exhibiting one-stage crystallization on heating, i.e., the glassy phase transforms into crystalline MgGeO3 and Pb5GeO7 phases. The activation energy for the crystallization, evaluated from the Kissinger equation, was approximately 202±5 kJ/mole using the peak temperature of the exothermic reaction. The Avrami exponent or reaction order, n, indicates the nucleation rate in this glass to increase with time and the crystallization to be governed by a three-dimensional interface-controlled growth.
F. Sousani, R. Mozafarinia, A. Eshaghi, H. Jamali,
Volume 15, Issue 1 (March 2018)
Abstract
In this research, Germanium-carbon coatings were deposited on ZnS substrates by plasma enhanced chemical vapor deposition (PECVD) using GeH4 and CH4 precursors. Optical parameters of the Ge1-xCx coating such as refractive index, Absorption coefficient, extinction coefficient and band gap were measured by the Swanepoel method based on the transmittance spectrum. The results showed that the refractive index of the Ge1−xCx coatings at the band of 2 to 2.2 µm decreased from 3.767 to 3.715 and the optical gap increased from 0.66 to 0.72 eV as CH4:GeH4 increases from 10:1 to 20:1.
M. Naseri, M. Alipour, A. Ghasemi, E. Davari,
Volume 15, Issue 1 (March 2018)
Abstract
One of the interesting state-of-the-art approaches to welding is the process of friction stir welding (FSW). In comparison with the fusion processes, FSW is an advantageous method as it is suitable for the non-fusion weldable alloys and polymeric materials joining. Regarding the materials pure solid state joining, it also provides joints with less distortion and enhanced mechanical properties. In the present work, a three-dimensional (3D) model based on finite element analysis was applied to study the thermal history and thermomechanical procedure in friction stir welding of high density polyethylene plate. The technique includes the tool mechanical reaction and the weld material thermomechanical procedure. The considered heat source in the model, includes the friction among three items: the material, the probe and the shoulder. Finally, the model was validated by measuring actual temperatures near the weld nugget using thermocouples, and good agreement was obtained for studied materials and conditions.
S. Gholami Shiri, Y. Palizdar, . A. Jenabali Jahromi, Eduardo F. de Monlevade,
Volume 15, Issue 3 (September 2018)
Abstract
The relation between microstructure and the fracture mechanisms of δ-TRIP steel with different Nb-content has been investigated using complementary methods of light microscopy, SEM, EDS, EBSD, X-ray phase analysis and tensile test. The results revealed a close dependency between the presences of constitutive phases i.e. ferrite, bainite, retained austenite and martensite and the mode and characteristics of fracture. All samples revealed almost different fractography pattern which could be associated to the effect of Nb microalloying element. The different fractography patterns were consisted of dimple rupture, riverside and Wallner lines pattern. The proportion of the cleavage fracture in comparison of dimple rapture increased by increasing the Nb-content due to the increase of primary martensite in the microstructure.
M. Abbasalizadeh, R. Hasanzadeh, Z. Mohamadian, T. Azdast, M. Rostami,
Volume 15, Issue 4 (December 2018)
Abstract
Shrinkage is one of the most important defects of injection molded plastic parts. Injection molding processing parameters have a significant effect on shrinkage of the produced parts. In the present study, the effect of different injection parameters on volumetric shrinkage of two polymers (high-density polyethylene (HDPE) semi-crystalline thermoplastics and polycarbonate (PC) as a representative of amorphous thermoplastics) was studied. Samples under different processing conditions according to a L27 orthogonal array of Taguchi experimental design approach were injected. Effect of material crystallinity on the shrinkage of injected samples was investigated. Obtained results revealed that semi-crystalline thermoplastics have larger shrinkage values in comparison with amorphous thermoplastics. Shrinkages of injected samples were also studied along and across the flow directions. Results showed that the flow path can dramatically affect the shrinkage of semi-crystalline thermoplastics. However for amorphous thermoplastics, results showed an independency of obtained shrinkage to flow direction. Analysis of variance (ANOVA) results illustrated that cooling time was the most effective parameter on shrinkage for both PE and PC injected samples; followed by injection temperature as the second important parameter. The optimum conditions to minimize shrinkage of injection molded samples are also achieved using signal to noise ratio (S/N) analysis.
S. Kord, M. H. Siadati, M. Alipour, H. Amiri, P.g. Koppad, A. C. Gowda,
Volume 15, Issue 4 (December 2018)
Abstract
The effects of rare earth element, erbium (Er) additions on the microstructure and mechanical properties of Al-15Zn-2.5Mg-2.5Cu alloy have been investigated. This new high strength alloy with erbium additions (0.5, 1.0, 1.5 and 2.0 wt%) was synthesized by liquid metallurgy route followed by hot extrusion. Microstructural characterization was performed using scanning electron microscope and electron probe microanalysis. Significant amount of grain refinement was observed with erbium addition in the hot extruded and heat treated alloy. Tensile test was performed to investigate the effect rare earth on mechanical behavior of alloy in as cast and hot extruded condition before and after T6 heat treatment. The combined effect of erbium addition, hot extrusion and heat treatment significantly enhanced the tensile strength of alloy (602 MPa) when compared to the as cast alloy without erbium addition (225 MPa). The strengthening of the alloy was attributed to grain refinement caused by erbium along with hot extrusion and formation of precipitates after T6 heat treatment. Fractograhic investigations revealed that the hot extruded alloy with erbium addition after heat treatment showed uniformly distributed deep dimples exhibiting ductile behavior.
T. Ebadzadeh, S. Ghaffari, M. Alizadeh, K. Asadian, Y. Ganjkhanlou,
Volume 16, Issue 1 (March 2019)
Abstract
The densification behavior, structural and microstructural evolution and microwave dielectric properties of Li2TiO3 + xZnO (x = 0, 0.5, 1, 1.5, 2, 3, and 5 mol%) ceramics have been investigated using X-ray diffraction, Field Emission Scanning Electron Microscopy, Raman spectroscopy and microwave resonant measurement. The Maximum density of 3.33 g/cm3 was obtained in Li2TiO3 + 2ZnO ceramic at low sintering temperature of 1100˚C. SEM investigations revealed good close packing of grains when x = 2 and preferential grain growth when x ≥ 3. The maximum values of Q × f = 31800 GHz and εr = 22.5 were obtained in Li2TiO3 + 3ZnO and Li2TiO3 + 2ZnO compositions, respectively. The observed properties are attributed to the microstructural evolution and grain growth (first case) or high density of the obtained ceramic (second case).
I. Hajiannia, M. Shamanian, M. Atapour, R. Ashiri, E. Ghassemali,
Volume 16, Issue 2 (June 2019)
Abstract
In this study, the effects of the second pulse resistance spot welding on the microstructure and mechanical properties of TRIP1100 steel were evaluated. The thermal process after welding was designed to improve metallurgical properties with pulse currents of 6kA, 9kA and 12kA after initial welding with 10kA current. The effect of the second pulse on mechanical and microstructural properties was investigated. The fracture of the welds was for pulsed samples of 6kA and 9kA PO with CTS test. Due to existence of the microstructure including the equaxial dendritic and finer in FZ in the pulsed current 9kA, the maximum fracture energy and maximum force were observed. A significant decrease in the FZ hardness in 6kA current was observed in the nanohardness results, which was attributed to existence martensitic and ferrite temper. The highest ratio of CTS / TSS was obtained for 6kA and 9kA, respectively, and force displacement rate was maximum in 9kA. The fracture surfaces included dendrites and dimples. The results of partial fracture revealed separation in the coherent boundaries of the coarse grain of the annealed region.
A. Khalili, M. Mojtahedi, M. Goodarzi, M. J. Torkamani,
Volume 16, Issue 3 (September 2019)
Abstract
The aim of this work was to synthesize TiC reinforced coating on carbon steel via reduction of ilmenite powder. A mixture of ilmenite and graphite was pre-placed on AISI 1020 steel surface. The effect of the addition of excess graphite amounts on the progress of synthesis of carbide particles was studied. The evolution of phases in different coatings was analysed via X-ray diffraction and scanning electron microscopy. Then again, the initial powder mixtures were mechanically activated for various durations, to accelerate the reactions in transient melt pool. Finally, the Fe-TiC hard coating was successfully synthesized by carbothermic reduction of ilmenite through laser surface treatment. Moreover, it is proved that combination of mechanical activation with additive laser melting effectively improves the level of ilmenite reduction, besides enhancing the distribution of hard particles and the hardness of the coatings to more than 1300 HV.
M. Palizdar, Z. Aslam, R. Aghababazadeh, A. Mirhabibi, P. Sangpour, Z. Abadi, Y. Palizdar, R. Brydson,
Volume 16, Issue 4 (December 2019)
Abstract
In this paper the chemical interaction between catalyst and support has been studied to understand the observed different growth rate of CNTs in our previous paper. Both pure MgO and Mg(NO3)2 . 6H2O as sources of the MgO catalyst support and Fe2(SO4)3 · xH2O as the source of the Fe catalyst, were employed. A Fe catalyst supported on MgO has been synthesized using the wet impregnation method followed by calcination. To compare the catalyst grain size and its distribution, the sample were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and BET specific surface area (SSA) measurement and X-ray photoelectron spectroscopy (XPS). XPS technique have utilized complementary to demonstrate the existence of chemical interaction between MgO support and Fe catalyst. Results revealed that the type of precursor used to prepare the support has a significant influence on the morphology of the support and the associated distribution of the Fe catalysts. The highest yield of MgFe2O4 phase was obtained using a pure MgO precursor which after calcination results in a homogenous distribution of nano-sized Fe particles over the support surface
M. Mahdi, A. Abdul-Hameed, B. Ali, H.f Al-Taay,
Volume 17, Issue 1 (March 2020)
Abstract
Silicon nanowires (SiNWs) are synthesized through a metal-assisted chemical etching (MACE) method using Si(100) substrates and silver (Ag) as a catalyst. Scanning electron microscope (SEM) images confirmed that length of prepared SiNWs was increased when etching time increased. The prepared SiNWs demonstrated considerably low light reflectance at a wavelength range of 200–1100 nm. The photoluminescence (PL) spectra of the grown SiNWs showed a broad emission band peaked at a wavelength of about 750 nm. A solar cell and photodetector based on heterojunction SiNWs/PEDOT:PSS were fabricated using SiNWs that prepared with different etching time and its J–V, sensitivity, and time response were investigated. The conversion efficiency of fabricated solar cell was increased from 0.39% to 0.68% when wire length decreased from 24 µm to 21 µm, respectively. However, the sensitivity of the heterojunction SiNWs/PEDOT:PSS photodetector was decreased from 53774% to 36826% when wire length decreased from 24 µm to 21 µm, respectively.
O. Kaliuzhnyi, V. Platkov,
Volume 17, Issue 2 (June 2020)
Abstract
A method has been advanced to form porous poly(tetrafluoroethylene) (PTFE) using a partially gasified porogen. Sodium hydrogen carbonate (NaHCO3) was selected as a porogen. The standard technology of porous materials production including mixing, pressing, thermal treatment, porogen leaching and drying was employed.The formation of porous PTFE structures was investigated in a wide range of NaHCO3 concentrations. The mechanism for formation of such structures has been proposed. It is shown that the NaHCO3 porogen affords permeable porous structures with porosities down to 50% (cf. the lowest bound porosity of 70% attainable with the standard NaCl porogen).The flow rate characteristics of the pressure difference as a function of the air flow rate have been measured on porous PTFE samples formed using the partially gasified NaHCO3 porogen and the NaCl porogen. The obtained flow rate characteristics were linear, which suggests a laminar air flow in the pores. The permeability of the porous PTFE structures formed using the above porogens has been estimated.The use of the NaHCO3 porogen has allowed a five-fold cut of the leaching time, a more than three times enhancement of the permeability of the porous structures and an increase in the hydraulic pore diameter by a factor of 1.8 as compared to the corresponding data obtained with the NaCl porogen.
S. Mortezaei, H. Arabi, H. Seyedein, A. Momeny, M. Soltanalinezhad,
Volume 17, Issue 3 (September 2020)
Abstract
Dynamic Recrystallization (DRX) is one of the likely mechanisms for fine-graining in metals and alloys. The dynamic recrystallization (DRX) phenomena occurs in different thermo-mechanical processing (TMP) conditions for various metallic materials. DRX depends on various materials and thermo-mechanical parameters such as temperature, strain rate, strain, stress and initial microstructure. in the present study, the restoration mechanism of the 17-7PH stainless steel has been investigated using a hot compression test under different conditions of thermo-mechanical treatment. The microstructural characteristics and the behavior of the hot deformation of the under study steel are investigated using flow curves and microstructure images obtained from optical microscopy. The results show that the maximum and steady state stresses are significantly affected by the strain rate and the deformation temperature. So that, the flow stress increases with decrease in the deformation temperature and increase in the strain rate. Microstructural studies confirm the occurrence of DRX as a restoration mechanism in the microstructure for the two phases of austenite and ferrite.
S. Das, R. Ghadai, A. Krishna, A. Trivedi, R. Bhujel, S. Rai, Sh. Ishwer, K. Kalita,
Volume 17, Issue 4 (December 2020)
Abstract
Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 o to 9.63 o and 26.4 o to 26.3 o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO..Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 o to 9.63 o and 26.4 o to 26.3 o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO.
Z. Abasali Karaj Abad, A. Nemati, A. Malek Khachatourian, M. Golmohammad,
Volume 17, Issue 4 (December 2020)
Abstract
The graphene oxide -TiO2 (GO-TiO2) and pre-reduced graphene oxide -TiO2 (rGO-TiO2) nanocomposites were fabricated successfully by hydrothermal method. The microstructure of synthesized nanocomposites was investigated using field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS) analysis. Moreover, galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods in three electrode system were applied to evaluate electrochemical properties. The results revealed that nanoparticles distributed more uniformly on graphene sheets, at lower concentrations of TiO2. The rGO-TiO2 and GO-TiO2 nanocomposites showed 224 and 32 F/g specific capacitance at 5 mV s-1 scan rate in 1 M KOH aqueous electrolyte, respectively. The pre-reduction of graphene oxide is the main reason for the better electrochemical performance of rGO-TiO2 nanocomposite compared to GO-TiO2 nanocomposite.
Jafar Shafaghat, Ali Allahverdi,
Volume 18, Issue 1 (March 2021)
Abstract
Microscopic studies has shown that adjacent to the interface between cement paste and aggregate, there exists an area with high porosity and low binding compounds that is referred to as interfacial transition zone (ITZ). ITZ in concrete and mortar imposes a number of negative effects, including flexural and compressive strengths reduction and permeability enhancement. That’s why many research attempts have been devoted to limit ITZ and its negative effects. The present study investigates the possibility of utilizing fine Portland cement (PC) clinker as a reactive aggregate in mortar for the same purpose. For this, natural quartz sand in normal mortar (NM) was totally replaced with PC clinker of the same particle size distribution and the most important engineering properties of the new mortar referred to as Reactive Aggregate Mortar (RAM) were measured and compared with NM as control. The results of compressive strengths measurements represented 65% and 21% increases at curing ages of 7 and 90 days, respectively, for RAM compared to NM. Chloride penetration depth in RAM displayed reductions by about 33% and 26% after 14 and 28 days of exposure, respectively. The effect of PC clinker reactivity on the microstructure and size of ITZ was studied by using scanning electron microscopy.
Amir Hosein Paryab, Sorosh Abdollahi, Rashid Khalilifard, Hamid Reza Madaah Hosseini,
Volume 18, Issue 1 (March 2021)
Abstract
As an alternative to conventional fertilizers, e.g. NPK (the Nitrogen-Phosphorous-Potassium containing chemical fertilizers) which release their nutrients in a short period of time, due to high solubility in irrigation water, glass fertilizers are ideal as they release macro- and micronutrients for crops and plant nourishment. Also, despite conventional ones, they have no ground-water pollution. In the present study, glass fertilizers were synthesized via Polymer-Derived Ceramics (PDC) method. Despite the melt-casting procedure, PDC needs lower temperatures in heat treatment. The precursors consist of poly-siloxane and active fillers. Thus, thanks to gaseous release during heat treatment of the present active fillers, i.e. Ca(OH)2, MgCO3, and Al(OH)3, a porous microstructure can be generated. In order to manipulate the pore size and specific surface area, fractions of active fillers were used as calcined. The experiments showed that upon increase of non-calcined active fillers, the specific surface area and the amount of porosity was increased due to more gaseous release during heat treatment. Thus, affected by microstructure, the release rate of macro and micro-elements was higher in the sample containing non-calcined active fillers, in comparison to other samples. Additionally, the porous samples were able to be loaded by extra nutrients containing Nitrogen, like KNO3.
