Comparison between Results Obtained from Experimental Tests and Numerical Model Simulation of the Effects of Punch and the die Noses Radii on the Deep Drawing of 304 Stanless Steel
محمد کاظم بشارتی
گیوی
author
آرش
مشایخی
author
text
article
2008
per
In the present work, the effects of changing punch and the die radius on several process parameters involved in deep drawing of AISI 304 steel have been studied. Deep drawing process of a cylindrical cup was simulated and analysed by numerical modeling. The results were compared with those of obtained from a serie of experimental cupping tests. The comparison shows that: maximum drawing force decreases with increasing the die nose radius. Changing in the thickness of cup wall decreases as the punch nose radius increases and thinning of the material occurs in cup wall region in which work hardening is enhanced. Finally, the comparison shows the best verification of experimental and computer simulation results.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19172_da653d7246d4786f6a6c651296948851.pdf
The Effect of Thickness on Spring Back of Double Curved Sheet Metals by a New Method
محمد حبیبی
پارسا
author
محمد
کاظمی
author
محمد حسن پیش
بین
author
text
article
2008
per
Spring back is responsible for inaccuracy of press formed sheet product. Therefore, prediction of spring back is important for precise forming of stampings. To predict the amount of spring back many successful attempts have been made for simple cases such as single curved and U or V shape sheet metals. However, for more complex shapes containing double curves or double variable curved surfaces there are few research works. In order to propose a method to solve such problem, theoretical researches followed by experimental examinations have been carried out. A new formulation for prediction of spring back in a double curved sheet metal has been proposed by authors. In this formulation an improved yield criterion that have been proposed by Yoshida, has been incorporated. This yield criterion is capable to reveal the influence of transient Baushinger effect and work hardening stagnation on spring back analysis. Using proposed formulation, the effect of thickness on spring back has been calculated and compared with experimental results. Results show that by increasing of sheet thickness, spring back increases. Reveal behaviors have been explained based on the variation of neutral axis position.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19173_9c32beabc7086cab92ecba081c440cd7.pdf
Hypo-Elasticity Models and its Integrability Properties
بیژن عباسی
خزایی
author
محمد حبیبی
پارسا
author
text
article
2008
per
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19174_8bafcf2d8074fdd40e33ee95addb539c.pdf
Study of Morphology of Oxide Film Formed on Magnesium Alloys in Casting Conditions (AZ91)
علی رضا
میرک
author
مهدی
دیواندری
author
سید محمد علی
بوترابی
author
text
article
2008
per
Morphology of surface oxide film formed during pouring of molten magnesium alloy has been investigated. Due to surface turbulence during casting, the oxide film necessarily makes folded cause in a dry surface to dry surface mode creating a double oxide film with the volume of air that can be encapsulated between folds of the film and this led to make gas bubbles or shrinkage cavities form. These kinds of oxides called new oxide films that form in a very short time during pouring. It seems to be one of the main reasons for dross-like defects. However, study of characterization and features of oxide film affected on prediction of final mechanical properties. The inner, unwetted surfaces of the doubled film representing an unbounded interface in the liquid and therefore, effectively constitute a crack. Samples for the study were prepared based on a technique in which an oxide metal sandwich was made by the bubble impingement technique, after impingement the contact areas of two adjacent and entrapped bubbles oxide-metal-oxide layer (OMO) were selected for the study. Features such as thickness, size, morphology and chemical composition of the oxide film were studied using a scanning electron microscope (SEM). Energy dispersive X-ray (EDX) microanalysis was performed for detection of the composition of the oxide layers. Results showed that the morphology of the oxide film in molten of magnesium alloys is folded and quite rough included globally phases of magnesium oxide. Recently, researches showed that the morphology of the oxide film in aluminum alloys is different due to composition of base alloy. Magnesium alloys in liquid state due to high oxidation rate is sensitive to formation of oxide film. Thickness of the oxide film folds in magnesium alloys is 2-4 µm that in comparison to aluminum alloys are ten times higher. However, potential of casting defects is higher in Mg alloys. The contacting interface between impinged bubbles (OMO) represents an elegant and powerful means for studying surface films of liquid metals and study for solidification structure
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19175_62a7a82b715ce6ae9f67fadd1d9670c3.pdf
Study of High Temperature Oxidation of duplex and Functionally Graded Materials of Thermal Barrier Coating (FGM TBC)
بهناز
سعیدی
author
علیرضا صبور روح
اقدم
author
علی محمد
خدامی
author
text
article
2008
per
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19176_1c37ed2713e30fd7b233dcf9270cad32.pdf
Effect of Austempering Heat treatment on Strength Properties and Hardness of Aluminum Grey Cast Iron
احسان
شجاعی
author
مهدی
دیواندری
author
سید محمد علی
بوترابی
author
text
article
2008
per
In the present work, the effect of aluminum content, austenitizing temperature and austempering time and temperature on the mechanical properties and hardness of Fe-C-Al grey cast iron was investigated. For this purpose, three alloys containing 1, 2 and 4 weight percent of aluminum were provided. The tensile samples were austenitized at 850?C and 900?C for 120 min, followed by austempering process at 275 ?C, 325 ?C and 375 ?C for 1-120 min. The ultimate strength and hardness of samples with tensile and hardness tests were investigated. The results showed that the samples without aluminum had the maximum strength. When amount of aluminum increased to 2 wt% ultimate strength decreased and while the amount of aluminum increased to 4 wt% the ultimate strength improved somewhat. The increase of austenitizing temperature from 850 ?C to 900?C in the samples not containing aluminum and containing 4 wt% aluminum increases ultimate tensile strength and hardness. In the alloys with 1 wt% and 2 wt% aluminum, the increase in the austenitizing temperature leads to decrease in the ultimate tensile strength and hardness. The results also indicate that in the samples not containing aluminum and/or containing 4 wt% aluminum, the first stage of transformation is completed after 30 minutes. Between 30 and 60 minutes, the second stage of transformation starts and the increase of austempering time to over 60 minutes leads to the beginning of the third stage of transformation. In the alloy with 1 wt% of aluminum maximum elongation was seen after 30 minutes but more austempering time caused the decrease of the elongation. In the alloy containing 2 wt% aluminum, using low austempering temperature (275 ?C, 325 ?C) and increasing the austempering time leads to the rising of elongation. In the high austempering temperature (375 ?C), the third stage of transformation begin after 30 minutes and the elongation decreases.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19177_b8bf2cf82db4796a1b05147b0fd80fe6.pdf
Development of MgAl2O4 Spinel Coating on Graphite Surface via Sol-Gel Citrate Route to Improve its Water-Wettability and Oxidation Resistance
علی
صابری
author
حسین
سرپولکی
author
فرهاد گلستانی
فرد
author
text
article
2008
per
Low water-wettability and oxidation resistance of graphite have limited its application in carbon containing refractory castables. The aims of this study were improvement of water-wettability and the oxidation resistance of natural flaky graphite by applying an oxide coating on its surface. To develop the coating, magnesium aluminate spinel sol was formulated via a citrate-nitrate route and graphite powder was then added to the sol. The mixture was heat treated in appropriate temperature and atmosphere to get the polycrystalline MgAl2O4 coating on graphite particles surface. The microstructure of coating was studied by X-ray diffractometer, SEM and TEM. The water-wettability was evaluated by measuring the water drop contact angle and plotting the zeta potential vs. pH. The results showed the development of a stable nanocrystalline MgAl2O4 spinel coating which improved the water-wettability and oxidation resistance of graphite significantly.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19178_4b209257322517c8a896ba5728cfbedc.pdf
The Investigation of Synthesis and Phase Transformation in Molybdenum Disilicide by Mechanical Alloying
بهروز
قاسمی
author
جلیل وحدتی
خاکی
author
مسعود
گودرزی
author
text
article
2008
per
The molybdenum dicilicide is an intermetallic compound with two allotropies tetragonal ?-MoSi2 and hexagonal ?-MoSi2.The ?-MoSi2 phase is established to 1900 ?C and ?-MoSi2 phase from 1900 to 2050 ?C. This material has considerable properties that provide different applications in different industries such as air-space industry and gas turbines. The molybdenum synthesis can be down in various ways such as melting and casting, SHS (Self propagating High temperature Synthesis). Recently, the mechanical alloying method because of its considerable advantages such as powder particle compound homogenizing, fragmentation and contact area increasing and also crystal defect increasing that affects ductility increasing of brittle compound such as intermetallic compounds, is used for progressive materials synthesizing. In this research, the synthesis and formation of molybdenum diciliside was investigated by mechanical alloying method from stoichiometric mixing molybdenum and silicon (Mo/2Si) and also its phase transformations. A mixture of elemental molybdenum and silicon powders at the stoichiometric composition of MoSi2 were ball milled to 100 hours using a planetary ball mill. The milling was performed at rotational speeds (vial speeds) of 300 and 400 rpm and stainless steel balls (5 and 10 mm in diameter). Other synthesis conditions such as ball to powder weight ratio and mass of the charged powder were chosen similarly. The results demonstrate that mechanical milling affects the formation of nanocrystalline MoSi2 from elemental powders through solid state reaction. In other words, formation of molybdenum disilicide from its primary elements during mechanical alloying depends on effective parameters in mechanical alloying (collision frequency of ball to powder particles, contact area creation and heat transferred to powder particles view point) according to XRD results. The results indicate that increasing in milling intensity and decreasing in ball diameter cause to fast formation of MoSi2, which is derived of increasing in milling energy. The thermal analysis investigation confirmed affection of mechanical activation on the acceleration of MoSi2 synthesis with reduction of formation temperature of molybdenum disilicide during mechanical alloying and electron microscopic investigation showed that MoSi2 forms on the surface of molybdenum grains during mechanical alloying. It was also demonstrated that formation of MoSi2 (? and/or ?) depends on mechanical activation conditions and selection of parameters during mechanical alloying. So that if intensity of mechanical activation be chosen high and/or selection of parameters contribute with high heat production in milling vials, ?- MoSi2 phase alone or with ?- MoSi2 phase (that has low activation energy with respect to ?- MoSi2) will be produced. In lower milling intensity, usually at first ?- MoSi2 is produced. Phase transformation of ? ? ? occurs during mechanical alloying when the crystallite size decreases to approximately 12 nm. The final product of mechanical alloying is ?- MoSi2.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19179_017cca7d1dfd774e4820bebdef13f22a.pdf
Phase Transformations and Resulting Microstructures in Ti-47Al-2Cr Alloy
حسن قاسمی
ارمکی
author
سعید حشمتی
منش
author
حمیدرضا
جعفریان
author
محمود نیلی
احمدآبادی
author
text
article
2008
per
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19180_a7ee5b76f4691f5ae8a361b51d95d1a7.pdf
The Effects of Mechanical Vibration, Grain Refinement and Modification on the Structure and Mechanical Properties of A380 Aluminum Alloy
حسین
یداللهتبار
author
حسن
ثقفیان
author
محمود
شهبازی
author
سعید
شبستری
author
text
article
2008
per
This research concentrates on the effects of low frequency, vertical mechanical vibration during solidification on the microstructure and mechanical properties of A380 aluminum alloy. Two series of Sr-modified and Al-5Ti-B grain refined A380 alloy samples were solidified in both static and dynamic conditions in the frequency and amplitude of 60 Hz and 0.2 m, respectively. Their Physical, micro-structural and mechanical properties such as ?UTS, ?Y, elongation, hardness, density and SDAS were compared to those of sample solidified in the dynamic condition without any additives. The results indicated that the gas and shrinkage porosities were reduced by vibration through intensifying mass feeding. As a result, density and hardness increased with applying vibrational energy. Vibration decreased SDAS and refined eutectic silicon in unmodified condition and caused coarsening of eutectic silicon in Sr-modified samples. Mechanical parameters such as ?UTS, ?Y, elongation and quality indices were increased in dynamically solidified samples. Vibration influenced elongation more than tensile strength.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19181_65de6ca4370b7694820274ad25943444.pdf
The Effect of Annealing Temperature on the Bond Strength and Structure of Interface in Ag/Cu Strips
علی
حقیری
author
مصطفی
کتابچی
author
نادر
پروین
author
text
article
2008
per
Copper–silver bimetallic strips were produced by cold roll welding process and were treated by diffusion annealing in the temperature range 250–800 ?C. The interface bonding strength was determined by bending and peeling tests, Resistance, conductivity and micro hardness profiles were determined and microstructure in the interface region was observed by optical microscope.
Electrical resistance and bonding strength in the interface depend on the diffusion annealing temperature. Diffusion annealing above 600 ?C produces fine-grained eutectic phases in the interface region and silver matrix.
The eutectic phase formation and the movement of interface is a chemical–diffusion process. It is observed that the strength is greatly reduced by increasing the thickness of eutectic compounds. These compounds have detrimental influences on physical and mechanical properties of the interface. The results indicate that there is an optimum annealing temperature at which the sheet exhibits a satisfactory formability together with a high bonding strength.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19182_27307f940e192f005ef7c628d7a5a6db.pdf
Reagents in zinc recovery from Pb- flotation tailings of
امیرحسین نویدی
کاشانی
author
فرشته
رشچی
author
text
article
2008
per
Effect of concentration parameters on recovery of zinc oxidized minerals from lead flotation tailings of Dandy mineral processing plant in north-western Iran was studied. A sulfidization-flotation method has been used on a laboratory scale to investigate the effect of various reagents such as sodium sulfide as sulfidizing agent, primary amine as collector, dispersants and flocculants with different concentrations to reach an optimum zinc recovery. Among the dispersants tested, hexametaphosphate gave a higher zinc grade 40.4% and 70% recovery. Usually de-sliming is used to increase the recovery of zinc, however, analyses have shown that fine particles in the sample mostly contain zinc, thus de-sliming is not suggested.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19183_c515f7581795cab4c8b589be7ea1c650.pdf
Investigation on the Effect of Chemical Composition on the Texture and Bake Hardening IF Steels
مهدی
کریمان
author
text
article
2008
per
Interstial free steels have good formability and also excellent deep drawability. These features make them one of the applicable materials in automotive industry. Chemical composition and thermomechanical treatment used to process these steels have important role in final properties of them. In this study, the effect of chemical compositon on texture, anisotropical properties and bake hardenability of these steels were investigated. The results showed that contribution of vanadium as a weak carbonitride former element with titanium as strong carbonitride former could change the texture of steels. Replacing titanium with vanadium caused harmful effect on mechanical properties. In this research deep drawing properties of five steels were compared based on parameters. The results of bake hardenability test showed that there were critical limits for vanadium volume fractions above which bake harden properties was improved. It was shown that the bake harden properties of Nb-steels were better than that of Ti-steels. This was due to the better solution of Nb(C,N) compared to Ti(C,N). Addition of vanadium to Ti-steels may improve bake harden properties of IF-steels.
University College of Engineering
دانشکده فنی
0803-1026
41
v.
11
no.
2008
https://jfe.ut.ac.ir/article_19184_a24fd08b7393189a0795b67a00d562a8.pdf