F. Pashmforoush , M. Kazemi,
Volume 19, Issue 4 (4-2019)
Abstract
In sheet metal forming processes, one of the most important limitations relates to the elastic recovery after punch unloading, which usually leads to spring-back phenomenon. Production of precise parts without spring-back controlling is not possible. Hence, the main aim of the present research is to minimize the amount of spring-back as well as to prevent the crack initiation during bending process of Aluminum A1050-H14 sheet. For this purpose, firstly, the sheet metal bending process was numerically simulated in ABAQUS finite element package. Then, the effect of friction coefficient and punch velocity was investigated on elastic recovery and von Mises stress in order to minimize the spring-back as well as to prevent the crack initiation. In this regard, python programming language was utilized. Then, by linking multi-objective genetic algorithm and finite element method in modeFRONTIER software, the optimum values of the process parameters were determined. It should be mentioned that for validation purposes, the simulation results of the present study were compared with the experimental data available in literature, showing a 3.14% relative error between the numerical and experimental results.
M. Rajaee, S.j. Hosseinipour, H. Jamshidi Aval,
Volume 19, Issue 8 (8-2019)
Abstract
In this paper, the effect of geometric parameters of tube and die on the forming behavior of AA6061 step tube in hot metal gas forming process (HMGF) is investigated. For this purpose, empirical experiments and finite element simulations with ABAQUS software have been used. Investigations have been made at the different ratios of die to tube diameter (D/d) and the different ratios of tube thickness to diameter (t/d). A simple theoretical model for the relationship between these geometric parameters and the process parameters such as internal pressure and axial feeding is presented. The results show that under constant internal pressure and axial feeding conditions, the die filling percentage decreases with increasing the ratios of D/d and t/d. Also, in the constant D/d ratio, by increasing the t/d ratio to about 0.05, the die filling percentage reduces gradually, but with increasing t/d to 0.06, a sharp decrease occurs in the die filling percentage. Using different simulations, the internal pressure, and axial feeding are changed proportional to the t/d and D/d ratios. The results show that in accordance with the prediction of the theoretical model, the relative internal pressure and relative axial feeding should be increased linearly with increasing the t/d and expansion ratio
, respectively, to give specimens with approximately the same die filling percentage.
H. Faraji, Kh. Khalili , A. Ashrafi,
Volume 19, Issue 8 (8-2019)
Abstract
In this study, the use of internal mechanical insert to prevent wrinkling defects in the process of T-shape tube hydroforming and expanding the window of the hydroforming process is presented. The study was performed both experimentally and by finite element simulation. In wrinkling limit testing, the use of internal mechanical insert for different modes prevented 100% of wrinkling and the T-joint was formed flawless, so that the wrinkles with high lengths such as 69.5 and 67.1 mm were prevented. Also, in the case of an internal pressure of 13 MPa and displacement of 33 mm, despite the high amount of axial displacement and the low internal pressure, the internal mechanical insert caused a reduction of 85.06% of the wrinkling length and the wrinkling length reduced from 74.3 to 11.1 mm. To study the conditions of the hydroforming process for both cases of with and without internal mechanical insert, the simulation of finite element was used. Experimental tests were also carried out to verify the validity of simulation results. By comparing the results of the experimental study and the simulations, an appropriate match was found between them. The results showed that the use of internal mechanical insert prevents wrinkling in the piece. Therefore, it can be used to produce a piece without defects and develop the window of the hydroforming process.
A. Aminzadeh, A. Safari, A. Parvizi,
Volume 19, Issue 9 (9-2019)
Abstract
Due to higher demands for tailor welded blanks (TWBs) applications in the transportation industry, it is important to understand their forming characteristics in manufacturing processes, especially the deep drawing, in order to produce products with higher qualities. Due to differences between the base materials strength as well as the existence of the welding zone, the formability of TWBs is frequently less than the base metals. The aim of this study is the comparison of weld line displacement and drawing depth in TWBs designed and produced by laser welding and friction stir welding. Laser welding is more appropriate for TWBs production comparing to the other welding processes because of the creation of limited heat affected zone and suitable keyhole. The parameters of the friction stir welding process are very important due to having a high influence on complicated plastic zone variation, the material flow pattern and temperature distribution in TWBs sheets. In this paper, by design experiments, the effect of blank holder force and linear welding velocity on drawing depth and weld line displacement of TWBs have been investigated. Moreover, the harnesses of the weld zone in both processes have been examined. Results show that by increasing the linear velocity of laser welding, the amount of weld line displacement and drawing depth will be increased. Furthermore, the higher linear velocity of friction stir welding will result in the higher weld line displacement and drawing depth. Likewise, the harnesses of the laser welding zone are higher than those ones for friction stir welding zone.
R. Panahi Liavoli, M. Bakhshi Jooybari, H. Gorji, Mohammad Javad Mirnia,
Volume 19, Issue 10 (10-2019)
Abstract
Incremental forming is considered as one of the rapid prototyping methods and has a high degree of flexibility and cost-effectiveness at low production volume. Meanwhile, the lack of technical knowledge has challenged the use of this method in the industry. One of the things that can help the actual usage of this process is the suitable process window; a window used to determine maximum tearing depth of the sheet with respect to the material, thickness and wall angle. In this study, firstly, the formability of low-carbon steel sheet, St12, with the thicknesses of 1.25 and 1.50 mm in single point incremental forming of a truncated pyramid with different constant wall angles has been investigated experimentally. Then, it is compared with the formability of the truncated pyramid with variable wall angles under two different wall geometries. Based on the experimental results, the process windows are presented in terms of the maximum depth and wall angle and compared to each other under different circumstances. The results showed that the critical wall angle for St12 sheet in incremental forming of a truncated pyramid with a fixed wall angle differs from the pyramid with variable wall angle, but doesn't depend on the size of the pyramid base. The critical wall angle for the fixed and variable wall angle pyramids was obtained 67⁰ and 75⁰, respectively. For a pyramid with a fixed wall angle, the thickness distribution of the wall is almost constant, while for a pyramid with a variable wall, it varies along the path.
S. Haji Ahmadi, M. Elyasi, M. Shakeri,
Volume 19, Issue 10 (10-2019)
Abstract
In this research, a dimensionless model was developed based on the geometric parameters for the deep drawing process to reduce the manufacturing cost of square cup deep drawing in the large scales. In the following, a series of groups were found for dimensionless ratios based on the geometric parameters of the square cup by Π-Buckingham dimensional analysis method in the two states of circular and square sheets. In order to find the best group of dimensionless geometric parameters, three scales of cups were numerically evaluated by commercial finite elements software. The results were validated by an experimental test. After analyzing all the effective geometric parameters, a fittest dimensionless equation was obtained. The st12 metal sheet was used for experimental validation in the room temperature. Moreover, the results and tearing force as target parameter were compared in simulation states, experimental tests and the proposed dimensionless model based on Π-Buckingham theory. By comparing the results in the two states of the circular and square sheets, it can be concluded that the geometric characteristics of the main scale sample can be predicted by a sample in a small size through the proposed dimensionless model. Comparison of the results of the dimensionless model and experiments show that the proposed model has high accuracy in predicting the tearing force and geometric parameters in the square cup deep drawing process.
S.a. Hosseini-Moradi , B. Binesh, M.r. Yazdanpanah ,
Volume 19, Issue 11 (11-2019)
Abstract
In this research, semi-constrained groove pressing (SCGP) as one of the severe plastic deformation techniques was investigated to achieve an ultrafine-grained structure in interstitial free steel sheets. The maximum of four semi-constrained groove pressing passes was successfully applied on the samples and the effects of the number of SCGP passes on the microstructure and mechanical properties of the samples were investigated. The microstructural investigations of the deformed specimens indicate that the semi-constrained groove pressing can effectively reduce the grain/crystallite size so that it ranges from about 41 μm in annealed condition to 232 nm after four passes. The results also showed that the strength and hardness of the samples are increased significantly by applying the pressing process. The highest tensile and yield strengths were observed in the two-pass SCGP processed sample, which showed an increase of about 90% and 75%, respectively, compared to the initial sample. The maximum hardness value of 165 Vickers was obtained for a three-pass SCGP processed sample, which is about 68% higher than the annealed sample. Regarding the hardness tests results, the uniformity of deformation increased with increasing the number of SCGP passes. Finite element method was used to simulate the semi-constrained groove pressing, and the strain distribution was obtained for the deformed samples. The finite element simulation results correlated fairly well with the analytical results.
A. Sanatiean, A. Saghafi, H. Rastegari Koupaei,
Volume 20, Issue 6 (6-2020)
Abstract
Deep drawing process is one of the most important processes of sheet forming, which is widely used in the deformation of metal sheets in order to produce parts with complex geometry. Several studies have been carried out on some steels with good formability such as low-carbon and austenitic stainless steels. Among different types of plain carbon steels, high carbon eutectiod steels are capable to withstand cold and warm working without formation of any defect, due to their fully pearlitic microstructure without the presence of proeutectoid phases and nano-sized cementite lamella. However, no comprehensive research has been conducted on the deep drawing process of eutectoid steel. In the present research, the formability of CK75 steel sheets was experimentally evaluated using warm deep drawing process. Warm deep drawing process of the CK75 steel was studied in the temperature range near and below the eutectoid transformation temperature. The results show that deformation at 700°C (near to the eutectoid temperature) lead to the uniform distribution of thickness and less instability. On the other hand, maximum instability (e.g. thinning) was obtained by warm deformation at 550°C. At the temperature above the eutectoid transformation temperature, due to the formation of multi-phase structure and non-uniform distribution of cementite particle, the workability was reduced and led to the occurrence of rupture during deep drawing.
A. Abdollahi Taheri, S. Golabi,
Volume 20, Issue 6 (6-2020)
Abstract
In recent years, industrial applications of composite sheets have been increasingly expanded due to their extremely different properties such as high strength, low density, and good corrosion resistance compared to single layer sheets. For this reason, in the current study, it is investigated the flanging of composite metal sheets. Also, the behavior of an aluminum-copper sheet, cladded using explosive welding, during incremental forming of a circular collar have been experimentally and numerically studied. In addition, the experimental results are used to validate the numerical simulation of the forming process. At first, in order to understand collar forming of the perforated sheet, the effect of hole diameter, forming direction or layer arrangement on dimensional accuracy, thickness distribution and forming force were investigated and then, the effect of hole flanging and collar forming were compared using two strategies. The results show that by decreasing the initial hole diameter of sheet, the average vertical maximum force increases by 9%, the minimum thickness decreases and its location shifts toward the center of sheet. Aluminum-copper arrangement also experiences a 7% reduction in average force and a 4% increase in minimum thickness due to the protective property of copper layer in tensile state compares to copper-aluminum. Besides, the multi-step method leads to a 6% minimum thickness increase due to better material flow compared to single-step method.
M. Shabanpour, A. Fallahi Arezoodar ,
Volume 20, Issue 8 (8-2020)
Abstract
The use of two-layer sheets to improve mechanical properties such as ductility and strength and to improve chemical properties such as corrosion resistance has led to an increasing number of such materials in the industry. In this study, the formability of aluminum-copper two-layer sheets at a high strain rates is investigated by electromagnetic forming method. The simulation of electromagnetic forming of the two-layer sheet was performed at high strain rate using Maxwell and Abaqus software. By making coil and die and using sheets with different geometries and grids on the sheets, the forming limit diagrams (FLD) was also extracted experimentally. The simulation results showed that the electromagnetic pressure applied on the sheet in CA lay-up was 19% higher than in AC lay-up. Using the second derivative of strain criterion, the FLD of aluminum-copper two-layer sheet was derived. The FLD of aluminum-copper two-layer sheet with an initial thickness of 0.5mm is 30% higher in the AC lay-up than in CA lay-up. The reason for this improvement is that in the AC lay-up the sheet with more ductility (copper) is in the outer layer and has greater resistance to tensile stress and necking. The outer layer with better ductility can improve the ductility of the two-layer sheet. The FLD of aluminum-copper two-layer sheets has improved 120% in right-hand side and 55% in left-hand side at high strain rates compared to static conditions. There is about a 6% differences between the simulation and experimental results for forming limit diagram.
M. Khalili, M. Bakhshi Jooybari, H. Gorji,
Volume 20, Issue 10 (10-2020)
Abstract
Research results performed by researchers have illustrated that applying electric current to a deforming metal can lead to a reduction in the required deformation force and an improvement in the formability. This technique is known as electrically assisted forming and is used in various forming processes. In this paper, the forming of square cups through electrically assisted deep drawing process was investigated experimentally and the effects of process parameters, including current magnitude, pulse frequency, and waveform (sinusoidal and square) on the forming force, thickness distribution, and drawing depth are examined. In this regard, after designing and preparing the test setup and forming square cups, the experimental results obtained were compared to those of the conventional deep drawing tests. The results showed that increasing the current magnitude leads to reducing the maximum thinning and the forming force in the deep drawing process of the formed parts. Furthermore, it was found that at a higher frequency, the deformation force decreases significantly and thickness distribution becomes more uniform. The comparison of the two waveforms of pulses demonstrated that the sinusoidal waveform has a relatively more significant effect on the reduction of the force and thickness distribution and a considerable effect on the drawing depth.
Abolfazl Rajabloo, Mohammad Bakhshi Jooybari, Hamid Gorji,
Volume 21, Issue 5 (4-2021)
Abstract
In forming conical parts by traditional deep drawing techniques, due to the stress concentration at the contact area between the punch and the workpiece, thinning and rupture occurs on the sheet. There is also a high possibility of wrinkling in the free area of the sheet; where there is no contact between the punch and the sheet. Therefore, new methods have been examined in forming this group of parts. Electromagnetic forming is one of the relatively old methods of high-speed forming that has attracted more attention in recent years. In the present study, the process of pre-forming of aluminum conical parts using electromagnetic force has been discussed numerically and experimentally. First, experiments were carried out by a simple spiral coil and after confirming the validity of the numerical simulations, the effect of electromagnetic force density in radial and axial directions was investigated in different areas of the sheet. Using the obtained results, a new coil was designed and built that has the ability to provide suitable distribution of the force in the radial and axial directions. Reduction in power consumption by up to a quarter, an increase in the amount of radial inward force and the height of the preform formed cone up to 2 times, minimizing the friction force, reduction of the workpiece center thinning by 3% (while increasing the height by 2 times) and elimination of wrinkles in the flange area of the sheet are the advantages of using the new coil compared to the primary coil.
Seyyed Amir Ahmadian, Moein Taheri, Mehdi Modabberifar, Ali Jabbari,
Volume 21, Issue 7 (7-2021)
Abstract
Deep drawing is one of the sheet forming processes, in which a metal sheet with mechanical operation, reaches the desired shape. One of the most important issues in deep drawing is the optimal design of the initial blank. In this paper, the main purpose is to design the optimal initial blank (with minimum circumference and minimum defects), for deep drawing of parts with a rectangular cross section. To this end, in this study, a program in Visual Basic has been written in SolidWorks software, in which a rectangular piece and press velocity variables take the tensile depth as input and design the optimal blank. Also in this program, blanks with rectangular, circular, octagonal and rhombus contours have been obtained; So that they are tangent to the initial contour. A separate program has also been written to display contour blanks at different times. The blank design program obtained in this study has this unique feature that for any type of rectangular piece and with any desired dimensions, according to the dimensions of the piece and the depth of tension, it will be possible to design the optimal blank. To ensure the accuracy of the program written in Visual Basic language, the results of the program have been compared and validated by performing experimental work. Experimental results prove that the blanks obtained by the program are of acceptable accuracy. In experimental parts, defects such as earring and shrinkage have also been observed in parts produced with optimal blanks.
Morteza Mohebbi, Valiollah Panahizadeh, Mohammad Hoseinpour,
Volume 21, Issue 7 (7-2021)
Abstract
Cold work hardening and nonlinear strain path, cause the failure strain change. Therefore, it is necessary to consider the created cold-work hardening and its distribution for predicting and simulating the behavior of products. The composite rupture disc cold-work hardened during manufacturing and burst and release pressure in a pressure commensurate with this hardening. In this case, the sheet metal undergoes a nonlinear strain path during forming and after slotting during the burst test. In this paper, the burst pressure of a composite Rupture disc estimated by using finite element simulation in Abaqus-implicit and explicit and by considering the strain hardening during bulge forming before the slotting process. The burst pressure is estimated according to the maximum plastic failure strain that changed due to nonlinear strain path and work hardening. The burst pressure predictions were compared and validated by experimental tests. In this paper, the effect slotting pattern, investigated by using FEM simulations and experiments. In the prepared samples for this paper, by slotting after bulge forming, the burst pressure reduces more than 80%. The simulation with this method predicts this pressure reduction with an error of about 3%.
Hassan Badparva, Dr. Hassan Moslemi Naeini, Dr. Mohammmad Mehdi Kasaei, Yaghob Dadgar Asl, Behnam Abbaszadeh,
Volume 22, Issue 1 (12-2021)
Abstract
In this paper, using finite element simulations and experimental results, the changes in deformation length and longitudinal strain in flexible roll forming are investigated and the relationship between them is determined. Flexible roll forming is a novel manufacturing process for producing profiles with variable cross-section. One of the important parameters of this process is the distance from the starting point of the deformation before the forming station to the central cross-section of the rolls at that station, which is called the deformation length. This parameter plays a key role in determining the distance between the forming stations and the deformation behavior of the sheet. The effect of roll diameter and mechanical properties of the sheet on the deformation length is also determined. The results showed that the maximum deformation length occurs when forming the stretching zone of the channel profile with variable cross-section, which is due to the additional tension applied to the edge due to the concave geometry of the flange in this zone. The results also showed that with increasing roll diameter and yield stress, the deformation length in all four of the stretching and compression zones and the slim and wide areas of the channel profile with variable cross-section increases, while with increasing sheet thickness, the deformation length in these zones decreases.
Ermia Gholamzadeh, Valiollah Panahizadeh, Mohammad Hoseinpour, Morteza Alizad-Kaman,
Volume 22, Issue 1 (12-2021)
Abstract
Forming limit diagrams (FLDs) are very important in predicting the behavior of the sheet. Therefore, predicting and drawing these diagrams by theoretical and experimental methods has been one of the main objectives of this paper. In this paper, the formability behavior of 5083 aluminum sheet was investigated by considering the strain hardening behavior. Tensile tests has performed in seven directions 0°, 15°, 30°, 45°, 60°, 75° and 90° from the rolling direction due to identify and calibrate coefficients of BBC2008 advanced yield criteria. The yield stresses was defined in the plane strain mode, also the anisotropy coefficients and the appropriate error function were extracted; Then the relationships of the plane strain yield stress were added to the error function. The error function was optimized using Genetic Algorithm and limit strains were calculated using yield coefficients. The results showed that if the strain hardening exponent increases by 0.1, the limit strains increase by 30 to 40%. Also the results showed that the initial imperfection factor (
) has a great effect on determining the FLD and with a very small change, it has a great effect on the FLD; So that by increasing this factor to about 0.016, the values of the limit strains are almost doubled. Using the results of this paper and having sheet properties such as yield strengths and anisotropy coefficients and proper selection of yield criteria, the FLD of different sheets to be theoretically determined with acceptable accuracy.
Hamed Deilami Azodi, Saeed Rezaei, Hassan Badparva, Ali Zeinolabedin Beygi,
Volume 22, Issue 2 (1-2022)
Abstract
Incremental sheet forming is a flexible forming technology in which the sheet metal is gradually formed by the movement of tools in specified path. Due to the progressively localized deformation of the sheet and concentration of the forces on contact area of tool and sheet metal, the formability of the sheet increases compared with other common forming methods. In this study, numerical simulation of the incremental forming of AA3105-St12 two-layer sheet has been performed to calculate forming force and final thicknesses of the layers. The validity of the simulation results is evaluated by comparing them with those obtained from experiments. Numerical models for estimating the vertical force applied on the tool and the final thicknesses of the layers in terms of the process variables have been obtained using artificial neural network. Multi-objective optimization has been conducted to achieve the minimum force and the minimum thickness reduction of layers using obtained numerical models based on genetic algorithm method. Optimum thickness of the two-layer sheet and the thickness ratio the layers in different states of contact of the aluminum or the steel layers with the forming tool have been determined.
Hamid Reza Ghahreman, Mohammad Honarpisheh, Mohammad Bagher Sarafrazi,
Volume 22, Issue 5 (4-2022)
Abstract
One of the forming pipes methods is the rotary draw bending process. Today, bending of thin-walled pipes with low radius of curvature is widely used in the automotive, military and aerospace industries, which is used to bend high-strength pipes. In this paper, at first the necessary models were created to simulate the bending process of the rotary pipe, and then the necessary mechanical and physical properties for stainless steel 304 and elastomers were determined. Then, experimental and numerical study of the forming force and changes in pipe wall thickness were performed. The process simulation was analytically performed using polyurethane elastomeric mandrels and nitrile rubber based on ABAQUS finite element software on 304 steel. The results show a good agreement between simulation and experimental results. Finally, the effects of process parameters including mandrel type, pipe diameter and bending radius were analyzed on the maximum forming force by factorial analysis. The results showed that the maximum forming force for both types of mandrel materials is obtained for pipes with small diameter and high curvature radius. Also, the bending forces increase 5 times by 30%increasing the bending radius, for pipes with smaller diameters. In addition, in equal diameter and radius of bending, the bending forces in the case of using polyurethane mandrel are 25% more than nitrile mandrel.
Morteza Shakibaseresht, Mahmood Zabihpoor,
Volume 22, Issue 6 (5-2022)
Abstract
ABSTRACT
Equal Channel Angular Pressing (ECAP) is one of the methods of refining and fine-graining metal materials. In this research, ECAP operation was performed on samples of 5182 alloy in 1 to 4 passes at ambient temperature. After implementation of the specimens through ECAP, prepared to obtain mechanical properties such as hardness, tensile and metallography. The results of these experiments showed that the mechanical properties of the packed materials through ECAP have improved compared to the normal state. Using a scanning microscope, it was observed that the average grain size decreased from 131 μm in the initial state to 745 nm after the ECAP process after the fourth pass. The results of hardness test also showed a 213% increase compared to normal. The increase in yield stress after 4 passes is about 3 times. Finally, the crack growth of these materials under fatigue loading was compared with the non-ECAP mode by creating a suitable pre-crack. It was observed that crack growth is faster in ECAP materials and the failure surface is smoother compared to normal. Also, the deviation of the crack from its path in microstructure materials is less than normal. Finally, by comparing the Experimental results of crack growth with the results of numerical analysis, the accuracy of the numerical results is validated and confirmed.
Fatemeh Taghizadeh Rami, Majid Elyasi,
Volume 22, Issue 6 (5-2022)
Abstract
In this study, bending of titanium tubes using steel balls in 0.5 and 0.85 mm sizes and resistance heating with experimental and simulation methods have been investigated. In order to apply temperature in rotatory draw bending of tubes, electric current cables were connected to both sides of the tube, and experiments were performed at room temperatures, 100℃, 200℃, 300℃ and 400 ℃ with a bending ratio of 1.8 and a bending angle of 90 ° was done. After the experiments, cross-sectional distortion, wrinkles, cracking and thickness distribution of bent tubes were investigated. The results of this study showed that in the case of bending at room temperature with and without metal balls, the tubes could not be bent. In the bending process with a constant speed of 0.8 Rad/s, by placing metal balls inside the tube and increasing the temperature 100℃, 200℃ and 300℃, the thickening in the intrados of the bent tube decreased by 9.8% and the thinning at the extrados of the bent tube increased by 8.4%. Also, by changing the bending speed from 0.8 to 0.4 Rad/s the cracking defect was eliminated at 400℃. Due to increased pressure due to steel balls in bending area, cross section distortion in tubes decreased by 10.4%. The best bending conditions and the least amount of defects were obtained at 300℃ with steel balls.
