M. Sedighi - Academia.edu (original) (raw)

Papers by M. Sedighi

In the article, the wire winding process for the reinforcement of a pressure vessel frame has bee... more In the article, the wire winding process for the reinforcement of a pressure vessel frame has been studied. Firstly, the importance of the wire winding method has been explained and literature was reviewed. The main step in the design process is the methodology axial force control. The frame consists of two columns and two semi-cylinders with circumstantial wires. A computational algorithm has been presented based on the governing equations and relations on stress-strain behavior of the whole system of the frame. Then a case study was studied to calculate the frame dimensions and wire winding procedure.

Aircraft Engineering and Aerospace Technology, 2009

PurposeStudying manufacturing process of compressor blade can reduce the production cost and time... more PurposeStudying manufacturing process of compressor blade can reduce the production cost and time in aircraft turbo‐engine industries. In the cold roll‐forging of thin compressor blades, the elastic behavior of machine structure and rolls is considerable due to the higher volume of roll separating force. Owing to this kind of elastic deformation during rolling, the adjusted gap between the rolling dies is increased and this causes unexpected flow of material, shape and thickness. The purpose of this paper is to present a new approach for simulation of cold rolling of thin blades and studying the effect of elastic behavior of the machine structure as well as rolls deflection on the material flow and roll separating force.Design/methodology/approachIn this paper, the process has been investigated using experimental test and simulation by introducing a new approach in a decision‐making flowchart. Instead of simulating of the entire system structure, a couple of virtual deformable rolls...

Mechanics & Industry, 2015

One of the best methods for applying severe plastic deformation (SPD) to the sheets is equal chan... more One of the best methods for applying severe plastic deformation (SPD) to the sheets is equal channel angular rolling (ECAR) process. In this paper, the effect of ECAR process on the AZ31 alloy has been evaluated. Firstly, the process has been accomplished on the magnesium specimens. Then, the effect of ECAR process on mechanical properties of AZ31 alloy such as: microhardness, strength and microstructure have been assessed. For evaluation of the ECAR parameters on the samples, numerical method also has been utilized. Finally, the results indicate that the microhardness after 8th pass ECAR has been increased about 45%. Also, the average grain size has been decreased about 94% after 8th pass ECAR. The yielding stress (Y.S) and ultimate tensile strength (UTS) of AZ31 sheet were decreased by increasing the pass number while, elongation has been improved.

Journal of Intelligent Manufacturing, 2009

The present work is aimed to optimize creep feed grinding (CFG) process by an approach using inte... more The present work is aimed to optimize creep feed grinding (CFG) process by an approach using integrated Genetic Algorithm-Neural Network (GA-NN) system. The aim of this creep feed grinding optimization is obtain the maximal metal removal rate (MRR) and the minimum of the surface roughness (R a). For optimization, metal removal rate is calculated with a mathematic formula and a Back Propagation (BP) artificial neural-network have been used to prediction of R a. The parameters used in the optimization process were reduced to three grinding conditions which consist of wheel speed, workpiece speed and depth of cut. All of other parameters such as workpiece length, workpiece material, wheel diameter, wheel material and width of grinding were taken as constant. The BP neural network was trained using the scaled conjugate gradient algorithm (SCGA). The results of the neural network were compared with experimental values. It shows that the BP model can predict the surface roughness satisfactorily. For optimization of creep feed grinding process, an M-file program has been written in 'Matlab' software to integrate GA and NN. After generation of each population by GA, firstly, the BP network predicts R a and then MRR has been calculated with mathematic formula. In this study, the importance of R a and MRR is equal in the optimization process. By using this integrated GA-NN system optimal parameters of creep feed grinding process have been achieved. The obtained results show that, the integrated GA-NN system was successful in determining the optimal process parameters.

The International Journal of Advanced Manufacturing Technology, 2007

Mass production of CNG pressure vessels requires an accurate understanding of process effective p... more Mass production of CNG pressure vessels requires an accurate understanding of process effective parameters. In this paper, the finite-element method has been used to study the vessel manufacturing parameters. The FE model has been verified by experimental results. The entire manufacturing process, including deep drawing, redrawing and ironing, of an aluminum liner sample of CNG pressure vessels (without spinning) have been simulated. The deep drawing process has been modeled by using three types of dies: flat, conical and tractrix; then drawing force and wall thickness variations have been compared. In order to achieve the final diameter of the liner, the redrawing process has been implemented in a conical die. To obtain a uniform wall thickness, the ironing process has been simulated in two stages, and the required force and die angle for each process have been extracted. The result of this work presents an integrated perspective for decision-making on the manufacturing of CNG liners.

The International Journal of Advanced Manufacturing Technology, 2017

Recently, dieless forming processes have been introduced to prevent the high costs of dies and to... more Recently, dieless forming processes have been introduced to prevent the high costs of dies and tools. Local heating and axial compression process is an innovative method for producing metal bellows. In this research, producing metal bellows using simultaneous local electric arc heating and axial compression has been explained and investigated. SUS304 tubes with an outer diameter of 19 mm and a thickness of 1 mm have been employed to implement the tests. Various parameters could affect the process. Among these parameters, effects of applied displacement and device current, influencing convolution shape, thickness, and required forming force, are studied experimentally. It is found that the height, radius, and angle of the convolution and also the forming force could be controlled by alteration of these parameters. Furthermore, the result of buckling test showed that energy absorption capacity of the manufactured metal bellow has been increased in comparison to a typical tube. This method could be a suitable alternative for induction local heating and can reduce the high equipment costs.

$Research paper thumbnail of Investigation of through thickness residual stress distribution in equal channel angular rolled Al 5083 alloy by layer removal technique and X-ray diffraction$

Materials & Design, 2012

The layer removal technique and the x-ray diffraction method have been employed to evaluate the r... more The layer removal technique and the x-ray diffraction method have been employed to evaluate the residual stresses through the thickness of aluminium alloy 5083 processed by equal channel angular rolling (ECAR). ECAR is a severe plastic deformation process that introduces shear deformation to sheet metals. The process has been completed on 2 mm thick strips passed three times through die channels in a continuous manner. In this work, the profile of residual stresses was quantitatively determined. It was observed that after ECAR process, the residual stress magnitudes were changed from approximately zero in annealed condition up to half of the yield strength value of ECARed samples. The distribution of the residual stresses was found to be non-uniform through the thickness and the ECARed sample was compressive at the top surface while it was tensile at the bottom surface.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2010

In this article, preform optimization in closed-die forging has been studied. The main objective ... more In this article, preform optimization in closed-die forging has been studied. The main objective of the optimization process is to reduce forging force by changing the preform shape as a variable parameter. In this respect, a combination of neural network and genetic algorithms has been employed. The finite volume method (FVM) is used as a simulation tool for the forging process. Simulation results have been used in a neural network analysis and a genetic algorithm to optimize the forging force. The neural network was used in several stages for modelling the system. The optimization process contains three stages. In stage 1 the preform shape is obtained by open die forging. Stage 2 is used for closed-die forging process to obtain the forging force. Stage 3 is for the filling of the die cavity. The geometrical parametric design process was used to accelerate the operation. An aeronautical forging component has been selected as a case study. The final results showed a negligible discr...

In the present paper, the parameters of Johnson-Cook (JC) constitutive model for two steels have ... more In the present paper, the parameters of Johnson-Cook (JC) constitutive model for two steels have been identified, based on the Hopkinson pressure bar data found in the literature. Using the measured strain pulses, the experimental stress-strain and deformation-time curves can be extracted. The experimental data have been processed using two different methods. In the first method strain rate assume to be constant during deformation and in the other one the deformation has been applied to a modeled specimen. In each method, an optimal set of material constants for JC constitutive model have been computed by minimizing the standard deviation of the numerically obtained stressstrain curve from the experimental data. Also a sensitivity analysis has been performed on JC constitutive model parameters and temperature changes during test have been investigated. The obtained results show that using constant strain rate method, leads to considerable error in results; for example in this study the minimum error is about 14%.

Strength of Materials, 2012

Èðàíñêèé óíèâåðñèòåò íàóêè è òåõíîëîãèè, Òåãåðàí, Èðàí Èññëåäóåòñÿ âëèÿíèå õîëîäíîé ïðîêàòêè íà ð... more Èðàíñêèé óíèâåðñèòåò íàóêè è òåõíîëîãèè, Òåãåðàí, Èðàí Èññëåäóåòñÿ âëèÿíèå õîëîäíîé ïðîêàòêè íà ðàñïðåäåëåíèå îñòàòî÷íûõ íàïðÿaeåíèé â òðåõñëîéíûõ ëàìèíàòàõ èç àëþìèíèåâîãî è ìåäíîãî ñïëàâîâ, ïîëó÷åííûõ ñâàðêîé âçðûâîì. Ïîñëå ïîëó÷åíèÿ ìíîãîñëîéíûõ îáðàçöîâ Al-Cu-Al ñ ïîìîùüþ ñâàðêè âçðûâîì èõ ïîäâåðãàëè õîëîäíîé ïðîêàòêå äî óìåíüøåíèÿ òîëùèíû íà 11, 30, 40 è 56%. Ïðîôèëè ðàñïðåäåëåíèÿ îñòà-òî÷íûõ íàïðÿaeåíèé ïî ãëóáèíå ñâàðåííûõ âçðûâîì è õîëîäíîêàòàíûõ ìíîãîñëîéíûõ îáðàçöîâ èçìåðÿëè ïðè ïîñëåäîâàòåëüíîì âûñâåðëèâàíèè â íèõ îòâåðñòèÿ. Ïîëó÷åííûå ðåçóëüòàòû ïîêàçûâàþò, ÷òî íà ïîâåðõíîñòè ñâàðåííîãî âçðûâîì ìíîãîñëîéíîãî ìàòåðèàëà îòìå÷àþòñÿ âûñîêèå ðàñòÿãèâàþùèå îñòàòî÷íûå íàïðÿaeåíèÿ, óðîâåíü êîòîðûõ ñíèaeàåòñÿ â ðåçóëüòàòå õîëîäíîé ïðîêàòêè. Óñòàíîâëåíî, ÷òî óðîâåíü ðàñòÿãèâàþùèõ îñòàòî÷íûõ íàïðÿaeåíèé íà ïîâåðõíîñòè õîëîäíîêàòàíûõ ìíîãîñëîéíûõ îáðàçöîâ îêàçûâàåòñÿ âûøå ïðè õîëîäíîé ïðîêàòêå, îáåñïå÷èâàþùåé áîëüøåå óìåíüøåíèå òîëùèíû îáðàçöîâ. Êëþ÷åâûå ñëîâà: îñòàòî÷íûå íàïðÿaeåíèÿ, ñâàðêà âçðûâîì, ñíèaeåíèå òîëùèíû, êîýôôèöèåíò êàëèáðîâêè. Introduction. New explosive-welded multilayer materials superior corrosion/ wear resistance and mechanical properties and are used in aerospace and nuclear industries [1]. The explosive welding is known as an unconventional technique [2]. Similar and dissimilar materials such as aluminum and copper are bonded together using this process [3-6]. Because of high energy density of explosive material, the process can join high surface area of plates [7]. Residual stresses are produced in explosive-welded multilayer due to different linear expansion coefficients of dissimilar materials [8-10]. The created residual stresses in the explosive-welded multilayers affect the mechanical properties of multilayers. Therefore, it is necessary to evaluate residual stresses in explosivewelded multilayers. Residual stresses in engineering structures are created by a variety of different mechanisms and influence crack initiation, crack growth and fracture [11]. Incremental hole-drilling (IHD) method can be used to evaluate non-uniform residual stress in thickness direction of explosive-welded multilayers

Progress in Natural Science: Materials International, 2012

Equal Channel Angular Pressing (ECAP) is currently one of the most popular methods for fabricatin... more Equal Channel Angular Pressing (ECAP) is currently one of the most popular methods for fabricating Ultra-Fine Grained (UFG) materials. In this work, ECAP process has been performed on commercial pure aluminum up to 8 passes by route A. After verification of FEM work, the influences of four die channel angles, three outer corner angles and pass number up to 8 have been analyzed to investigate strain distribution behavior of ECAPed material. Two methods for quantifying the strain homogeneity namely inhomogeneity index (C i) and standard deviation (S.D.) are compared. It is shown that C i is not a good candidate for examining the strain distribution uniformity. Moreover, it is suggested that designing of ECAP die geometry to achieve optimum strain distribution homogeneity is more suitable than the optimum effective strain magnitude. The best strain distribution uniformity in the transverse plane is obtained with F¼ 601 and C ¼ 151 and for the bulk of the sample, F¼ 1201 and C ¼151 or 601, gives the highest strain dispersal uniformity.

Acta Astronautica, 2003

The static and dynamic structural behavior of a micro-satellite has been studied using Finite Ele... more The static and dynamic structural behavior of a micro-satellite has been studied using Finite Element Method. At first, the micro-satellite has been modeled parametrically using ANSYS code and after several computations and initial satisfaction for static loads with an acceptable safety factor, the geometry parameters initially freezed for dynamic analysis. Then, based on the data provided by ARIANE-5 launcher, the criteria for safe vibration range are extracted. The natural frequencies of the satellite have been derived by changing the most effective geometry parameters like tray thickness and stringer height. By using these results, the optimum shape of the satellite has been designed.

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2016

The objective of this research is to study the strain forming limits of Al–Mg alloy (5083) sheet,... more The objective of this research is to study the strain forming limits of Al–Mg alloy (5083) sheet, fabricated by equal channel angular rolling process at room temperature. For this purpose, the equal channel angular rolling process was executed at room temperature in three passes. Mechanical properties, microhardness, and microstructure were investigated after the equal channel angular rolling process. Uniaxial tensile tests of the equal channel angular rolling process produced samples and showed that yield and ultimate stresses increase, while the uniform elongation to fracture decreases in comparison with the annealed state. There was a continuous hardness enhancement by increasing the number of the equal channel angular rolling passes. After the third pass, the amount of hardness raised by 73% in comparison with the annealed sample. In the fourth pass, the hardness reduced slightly, that was attributed to the strain saturation in room temperature and was followed by high surface c...

Journal of Materials Research and Technology, 2022

The hydroxyapatite particles as reinforcement materials have been widely considered to produce ma... more The hydroxyapatite particles as reinforcement materials have been widely considered to produce magnesium biocomposites used in biodegradable implants. However, Mg/HA biocomposites, which show poor ductility at room temperature due to their intrinsic properties, must be deformed at elevated temperatures. Thus, optimum hot deformation conditions of Mg/HA biocomposites can improve the corrosion behavior of these materials in addition to their mechanical and microstructural properties. In the present study, the high-temperature deformation behavior of Mg/1wt.% HA and Mg/2.5 wt.% HA biocomposites have been scrutinized using compression tests in the temperature ranges of 523e673 K and strain rates between 0.005 and 0.1 s À1. The true stress-true strain diagrams, constitutive analysis, 3D processing map for power dissipation efficiency and instability in the strains from 0.1 to 0.6, and microstructural observations were assessed for both biocomposites. The results indicated that the proposed constitutive model could predict the Mg/HA biocomposites' high-temperature deformation behavior with adequate accuracy. The activation energy which obtained from constitutive equations for both Mg/1wt.% HA and Mg/2.5wt.% HA biocomposites were identified to be 256.302 Kj/mol and 224.798 Kj/mol, respectively. According to 3D processing maps, the highest value of power dissipation efficiency for Mg/1wt.% HA has occurred in the strain of 0.2, strain rate of 0.005 s À1 , and temperature of 573 K; however, for Mg/2.5wt.% HA, it has located at the strain, temperature, and strain rate of 0.3, 530 K, and 0.09 s À1 , respectively. The microstructural characterizations showed more dynamic recrystallization occurrence in Mg/2.5wt.% HA than the Mg/1wt.% HA biocomposite.