Conical Die Research Articles

Square-Cup Deep Drawing of Relatively Thick Sheet Metals through a Conical Die without Blankholder

The present study introduces a finite element analysis and experimental verification of the square cup drawing. Experimental results are presented for deep drawing using two different sheet metal; an annealed aluminum (AL99.5w) and brass alloy (CuZn37) having nominal thickness to of 2, 2.5 and 3 mm. The experiments were conducted using a conical die of 18o half cone angle with square aperture at the die exit of 44×44mm and different relative punch/die clearances 1.5, 1.0, 0.9, and 0.8to. The last three values for relative punch/die clearance give nominal simultaneous corrective ironing ratios 0, 10, and 20% respectively. Flat-bottomed square punches with nose radius of 4mm and different sizes of side wall lengths were used. The corner radii for the punch and die aperture were 8 and 10 mm respectively. The experimental and finite element results showed a very good agreement between results of the deep drawing loads, limiting drawing ratios and modes of failures.

Computer Aided Design and Analysis of Conical Forming Dies Subjected to Blast Load

In this paper design and analysis a die meant to cone explosive forming have been investigated. Since the explosive forming dies are subjected to blast loading, failure is too likely to pass. Likewise, the special geometry such as existing the several holes, sealing grooves, vacuum channel and fillets of this type of dies under explosion wave makes their analysis complicated. In the present work, the die was designed according to the final product dimension assisting a design software. In the next step the die under blast loading was analyzed using finite element method utilizing FEM software. The outcomes exhibit that the die is capable to withstand the explosion load. Besides, the trend of this paper is recommended as a routine for the designers who are going to design these types of dies.

Analysis of Failure in Dual Phase Steel Sheets Subject to Electrohydraulic Forming

In previous work, the formability of dual phase steel sheets formed under quasi-static and high strain rate conditions was investigated in macroscale (Golovashchenko et al., 2013, “Formability of Dual Phase Steels in Electrohydraulic Forming,” J. Mater. Process. Technol., 213, pp. 1191–1212) and microscale (Samei et al., 2013, “Quantitative Microstructural Analysis of Formability Enhancement in Dual Phase Steels Subject to Electrohydraulic Forming,” J. Mater. Eng. Perform., 22(7), pp. 2080–2088). The Nakazima test and electrohydraulic forming (EHF) were used for quasi-static and high strain rate forming, respectively. It was shown that dual phase steel sheets exhibit hyperplastic behavior when subject to EHF into a conical die and the micromechanisms of formability improvement were discussed (Samei et al., 2014, “Metallurgical Investigations on Hyperplasticity in Dual Phase Steel Sheets,” ASME J. Manuf. Sci. Eng. (in press)). In this paper, mechanisms of failure in dual phase steels formed under quasi-static and EHF conditions are discussed. For this purpose, the nucleation, growth, and volume fraction of voids were studied. Also, fractography was carried out to understand the different types of fractures in the three grades of dual phase steels. The main objective of this work was to determine how failure was suppressed in the EHF specimens formed in the conical die compared to the Nakazima specimens. The impact of the sheet against the die was found to be the major reason for the delay in failure in the EHF specimens.

Effect of shear factor on bubble nucleation of polystyrene using supercritical fluid as a foaming agent

Abstract The effect of shear factor on bubble nucleation during the foaming extrusion process with polystyrene (PS) using the supercritical fluid (SCF) carbon dioxide (CO2) as a foaming agent was studied based on the energy transformation in this article. The influence of shear factor (which is caused by the velocity gradient in a conical die) on the dynamics of bubble nucleation was investigated and determined. The critical radius for bubble nucleation is presented through the Taylor deformation theory by using a nuclear embryo to represent the state in the bud of the appearance of the nuclear bubble. Theoretical analysis shows that a spherical nuclear bubble can split into two new nuclear bubbles after the deformation in the shear flow field; the radius of the new nuclear bubble is greater than the critical radius, so it can finally grow into a larger nuclear bubble. The shear factor increased the number of the nuclear bubbles in the polymer melt and so increased the density of the bubbles and decreased the diameters of the bubbles. This article proposes a qualitative judgment which indicates that the shear factor in a conical die has a beneficial effect on bubble nucleation, and helps to produce foamed plastics with fine bubbles.

Deep Drawing Characteristics of Square Cups through Conical Dies

This paper studies the deformation characteristics of a newly developed process for increasing the drawability of square cups. The process has a simple tooling set in which a circular blank can be easily deformed by a flat headed square punch through a conical die with a square aperture. Finite element analysis (FEA) was used to study the influences of the geometric parameters on the formability of square cup in order to find out the optimum setup dimensions of the present process. The effects of die fillet radius, die corner radius, die throat length, punch profile radius; punch corner radius, punch shape factor, relative die clearance and blank thickness on the drawability of square cup were mainly investigated. Cup drawability was also studied with the change of material strain hardening exponent, n, strength coefficient, K, average anisotropy, R, and friction coefficients between die-sheet-punch to find the best operating conditions. The limiting drawing ratio (LDR) was used to evaluate the effects of all these parameters on the square cup drawability. The LDR's, maximum drawing loads, cup thickness, cup height and modes of failure were predicted. The analysis reveals that the determination of the optimum setup dimensions of our developed process has increased the drawing ratio up to 3.1 for brass alloy (67/33 Cu-Zn) and 3.15 for aluminum (Al99.5w) in a single-drawing stroke. Experiments have been also done in order to compare and verify the FE-predictions. Successful square cups with drawing ratio of 3.07 for brass and 2.93 for aluminum were produced. These LDR's are significantly higher than that of the improved conventional methods with blank holder.

Efficient Oxyhydrogen Mixture Determination in Gas Detonation Forming

Oxyhydrogen is a mixture of Hydrogen (H2) and Oxygen (O2) gases. Detonative mixtures of oxyhydrogens with various combinations of these two gases were used in Gas Detonation Forming (GDF) to form sheets of mild steel. In die forming experiments, three types of conical dies with apex angles of 60, 90 and 120 degrees were used. Pressure of mixtures inside the chamber before detonation was varied from 3 Bar to 5 Bar to investigate the effect of pre-detonation pressure in the forming process. On each conical die, several experiments with different percentages of Hydrogen were carried out to determine the optimum gaseous mixture. According to our results the best forming process occurred when approximately 50-70%. Hydrogen was employed in the mixture. Furthermore, the experimental results were compared to the ones from FEM analysis. The FEM simulation results of thickness strain, hoop strain, thickness variation and deformed geometry are promising. method is used to investigate the deformation mechanisms and examine the effect of detonation pressure on the work piece (7). The FE computations are based on three-dimensional explicit dynamics formulations (8). The strain rate effects are incorporated using Johnson-Cook material model (9). In this paper results of experimental tests obtained from GDF apparatus are presented. The experimental tests reported in this paper are divided into two groups: Die forming of clamped circular mild steel sheets; and efficient combination determination by varying the percentage of Hydrogen in the mixture. Also, the effect of the primary variables including pre-detonation pressure of oxyhydrogen mixture inside the chamber, the effect of die angles, and percentage of Hydrogen in mixture, on the amount of deformation and strain distribution are discussed. Furthermore, a FEM model is used to simulate this process and obtained numerical results are compared with the experimental data.

End Formation of a Round Tube into a Square Section with Reduced Forming Loads

Low formation loads are desirable in metal stamping industries as it reduces the press capacity of the machine and the tooling cost. In the previous study, the author had successfully developed a 2-stage end formation process of a round tube into a square section having small corner radii. However, the formation load in this process increased linearly with the punch stroke in the 1st stage due to the continuous expansion of the tube end by the conical die. Hence, buckling and cracks occurred at the circular section and the bottom end of the square section respectively when the punch stroke was excessive. In this study, the author proposes a circular die having a conical bottom replacing the conical die for the expansion of the tube end. Although the formation load increases when the tube end is expanded at the conical bottom, the amount of increase becomes small when the tube end reaches the circular section of the die due to its constant diameter. At the circular section, the tube end curls and wraps over the die when the punch stroke is increased. In the 2nd stage, the squaring process is performed with a conical bottom square punch and a taper square die for the two different expanded tubes i.e. the one formed with the conical die and the one formed with the conical bottom circular die. Both Finite Element Method (FEM) simulation and experiment were performed to evaluate these two processes. The distribution of plastic strains, forming loads and product appearances are investigated. With the circular die, the maximum forming loads are successfully reduced by 20% and 33% in the 1st and the 2nd stages respectively in the experiment when compared to the ones formed with the conical die. No buckling and cracks are observed for the tube formed with the circular die.

An investigation of enhanced formability in AA5182-O Al during high-rate free-forming at room-temperature: Quantification of deformation history

The goal of this work is to improve our understanding of formability enhancement in aluminum (Al) sheet alloys that has generally been observed during high-strain-rate forming. In the work presented here, experiments and numerical modeling were used to investigate the room-temperature formability of AA5182-O Al alloy sheet (1mm thick) at high strain-rates using the electro-hydraulic forming (EHF) technique. A finite element model, using Johnson–Cook constitutive equation, was developed to simulate the high-rate forming behavior of Al under EHF and test samples were designed to obtain different strain paths at the apex of the EHF domes. The deformation history of Al sheets, under free-forming conditions and inside a conical die, was experimentally determined and compared to the model predictions. Experimental data shows that the high-rate formability of AA5182-O Al at minor strains of ∼−0.1 and ∼0.05, relative to its corresponding quasi-static formability, was enhanced locally by ∼2.5× and ∼6.5× under free-forming and when forming inside the conical die, respectively. The in-plane peak engineering strain-rate associated with the enhanced formability during free-forming was measured to be ∼3900/s while the pre-impact strain-rate during conical-die forming was estimated to be ∼4230/s. The strain-path associated with enhanced formability was experimentally determined under a free-forming case and was found to be in good agreement with that predicted by the numerical model. To the authors’ knowledge, these results are the first to experimentally quantify the deformation history associated with enhanced formability that has often been reported in the literature.

Formability of dual phase steels in electrohydraulic forming

Electrohydraulic forming (EHF) is based upon the electro-hydraulic effect: a complex phenomenon related to the discharge of high voltage electrical current through a liquid. In EHF, electrical energy is stored in a bank of capacitors and is converted into the kinetic energy needed to form sheet metal by rapidly discharging that energy across a pair of electrodes submerged in a fluid. The objective of this paper is to report the results of formability testing of dual phase steels in EHF conditions and to provide an explanation of the observed formability improvement based on analysis of the experimental results and through the use of a modeling technique developed as part of this work for simulating the EHF process. Comparison of the maximum strains resulting from EHF into a conical die and a v-shape die to the maximum strains resulting from quasistatic LDH testing (limiting dome height) indicated that substantially higher strains can be accomplished in the EHF process. In order to obtain the maximum benefits of increased formability with EHF technology, it is necessary to get to the high strain rate regime and the accompanying high hydrostatic stresses in the sheet, which occurs mostly in the contact area between the blank and the die. If the blank decelerates and gets to quasistatic forming conditions before filling the die cavity completely, very limited improvement in formability can be anticipated. A numerical model of the EHF process has been developed, incorporating four distinct models that are integrated into one: (1) an electrical model of the discharge channel, (2) a model of the plasma channel, (3) a model for the liquid as a pressure-transmitting medium, and (4) a deformable sheet metal blank in contact with a rigid die. The relative improvement in plane strain formability in EHF conditions was between 63% and 190%, depending on the grade of dual phase steel. Numerical modeling showed that the peak strain rates occurring in EHF are approximately 20,000 units per second.

Research on the Wear Behaviors of WC-8Co and Al<SUB>2</SUB>O<SUB>3</SUB>-TiC Conical Dies

采用冷、热压烧结技术分别制备了WC-8Co和Al 2 O 3 -TiC两种拉拔模具. 研究了该两种不同拉拔模具用于实际拉拔加工45#钢线时的摩擦磨损行为, 并对其磨损机理进行了分析. 结果表明: 两种拉拔模具均具有较好的强度和硬度, 能较好地进行拉拔加工, 其内孔磨损在工作区及定径区最为严重, 磨损面有金属脱落元素、模具颗粒脱落元素及润滑脂残留物. WC-8Co和Al 2 O 3 -TiC两种拉拔模具的磨损机理不尽相同, WC-8Co模具主要为粘着磨损和磨粒磨损, 而Al 2 O 3 -TiC模具则以磨粒磨损和表面疲劳磨损为主. Al 2 O 3 -TiC拉拔模具更适合于45#钢线材的拉拨.

Polyamide‐6 structure modification by combined solid‐phase extrusion

AbstractMethods of wide‐angle X‐ray analysis and transmission electron microscopy were performed to investigate structural and phase transformation occurring in polyamide‐6 (PA‐6) by combined solid‐phase processing including extrusion through a conical die (ED) and the following equal‐channel multiple‐angular extrusion (ECMAE). It was shown that high level of plastic and strength characteristics of extruded PA‐6 is determined by the formation of a duplex structure consisting of elongated disoriented fiber‐like entities and fragmented globular formations. Conservation of high values of plasticity of deformed PA‐6 is also controlled by the transition of the crystals of α‐form to the crystals of γ‐form with higher plasticity reserve. We have established rational technology parameters of PA‐6 processing by ED‐ECMAE processes (the deformation degree εED at ED, deformation intensity ΔΓ and the value of accumulated deformation εECMAE at ECMAE). POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

A Study on Mathematical Model of Deformation Force for Tube Nosing with Conical Die

Based on analyzing the stress-strain characters of material in nosing deformation zone, and considering two influencing factors, i.e. material thickness variation and material work-hardening, according to ignoring and considering the influence of additional bending stress at the entrance of die, and the different forms of work-hardening of metal materials, a new set of mathematical models of deformation force calculated for tube nosing with conical die are set up by utilizing slab method that belongs to one of the theoretic methods solving the problems of metal plastic forming. Furthermore, the scope of the application of every mathematical model of deformation force calculated for tube nosing with conical die is classified from conical die semi-angle and work-hardening of metal material point of view in theory.

Finite Element Simulation of the Nosing Process of Metal Tubes with a Conical Die

In this paper, the nosing process of metal tube with a conical die is investigated using the finite element method, and a series of simulations on the tube nosing process by using the program ABAQUS is carried out. The concrete process of tube nosing deformation is described. Some simulation results on tube nosing deformation such as the distributions of the Von Mises stress and effective strain, the material thickness variation of deformation zone are obtained and analyzed.

縮径押通し曲げによるネック付きエルボ成形法の開発

Tube bending without the use of a roll die or a mandrel recently been developed. In this bending method, straight pipes are clamped and bent by the bending arm, while they are reduced in diameter by squeezing with a conical die. The stress induced by bending and squeezing prevents the flattening or wrinkling of pipes in small-radius bending. Moreover, the bending moment is controlled by adjusting two parameters, the length [LR] between the center of the rotating arm and the exit of the conical die, and the ratio [λ] of feeding velocity by the pusher to the circumferential velocity by the rotating arm. In this study, the deformation behaviors of the intrusion bending with squeezing are clarified by experimental tests and finite element analysis.

Effect of mechanical properties on wrinkling limit diagrams for Aluminum 5086 alloy annealed at different temperature

This article deals with the wrinkling limit diagrams for Aluminium 5086 alloy sheets having thickness of 2.00 mm annealed at three different temperatures namely 200, 250 and 300 °C. The study pertains to deep drawing into cylindrical cups through conical die using a flat bottom punch. When a conical die is employed, the need for a hold down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early stages of a drawing process in which thin sheet blanks are used. It is proved by these researchers and others that the onset of wrinkling takes place when the ratio of strain increments (der/deθ) or the ratio of strain (er/eθ) reaches a critical value during the drawing process. These values which could be determined experimentally over which the wrinkling takes place has been shown in the form of wrinkling limit diagrams for the above grade at different annealed temperatures. An attempt is also made to develop the wrinkling theory that predicts the wrinkling based on results obtained in the form of wrinkling limit diagrams established for the above grade at different annealed temperatures. Further it was observed that the annealed sheets having high n-value, high R-value and high UTS/σy ratio improve the resistance against wrinkling.

Stamping Formability of ZE10 Magnesium Alloy Sheets

Abstract ZE10 magnesium alloy sheets were prepared through ingot casting and the hot-rolling process. The mechanical properties, conical cup value ( CCV), bore expanding performance, and limit drawing ratio ( LDR) were investigated to examine the stamping formability of ZE10 alloy sheets, at temperatures ranging from 20 to 300 °C. The results showed that the tensile strength decreased, whereas, plasticity, drawing-bulging performance, bore expanding properties, and deep drawing performance increased markedly at elevated temperatures. The CCV specimens could be drawn into the conical die's underside cylindrical hole from the conical cliff, without cracking, and could have the minimum CCV at 200 and 250 °C. In the bore-expanding test, the bore (Φ10 mm) could be expanded to the dimension of the punch (Φ25 mm) and the maximum bore-expanding ratio could be achieved at above 150 °C. The limiting drawing ratio ( LDR) of 2.85 is acquired during the deep drawing test at 230 °C. with the punch temperature of 20 ∼ 50 °C, the punch velocity of 50 mm · min −1, and the mixture of graphite and cylinder grease as lubricant.

Study of tube flaring forming limit in the tube flaring process

The aim of the current paper is to develop analytical theories for industry to predict the relations between the punch stroke, flaring ratio, tube thickness, and flaring forming limit in the tube flaring process. The volume incompressible condition, Levy-Mises equation, and explicit die profile description are combined to derive the analytical expressions relating the flaring ratio to the punch stroke and velocity in the tube flaring process. Then, according to the stress equilibrium state of a small tube element, the relation of the tube-end thickness ratio to the flaring ratio is developed on the basis of Tresca's criterion. Combining these two analytical theories and the fractured thickness at the tube end, the flaring forming limit can be determined. An elastoplastic finite element method based on the updated Lagrangian formulation is also developed to verify the analytical theories. A flaring experiment, using a 30° semi-cone angle to describe the conical die, is conducted to validate the analytical theories and simulated results. It is found that relations such as tube thickness ratio to flaring ratio, and punch stroke ratio to flaring ratio, show good agreement between analytical theories, finite element prediction, and experiment.

Material Formability and Coil Design in Electromagnetic Forming

Pulsed electromagnetic forming is based on high-voltage discharge of capacitors through a coil. An intense transient magnetic field is generated in the coil and through interaction with the metal work-piece; pressure in the form of a magnetic pulse is built up to do the work. Data on formability of two aluminum alloys employed for exterior (6111-T4) and interior (5754) automotive body panels will be shown. Comparison of traditional Forming Limit Diagrams obtained by stretching of aluminum sheet with hemispherical punch to the results on formability, where hemispherical punch is replaced by a coil will be provided. It will be shown that material formability in high-rate forming conditions can significantly depend upon interaction with the forming die: electromagnetic forming into an open round window provides only slight improvement in formability, while forming in a V-shape die or into a conical die indicates a significant improvement. An important part of the electromagnetic forming technology is the design of the coil. The coil failure modes and measures preventing them are discussed.

Design of brass alloy drawing process using Taguchi method

In wire drawing processes, many factors must be controlled to obtain the required plastic strain and desired tolerance values. The major factors include the area reduction, the lubricant, the drawing speed, and the die angle. This paper employs the rigid-plastic finite element (FE) DEFORM™ 2D software to investigate the plastic deformation behavior of brass alloy (CuZn37) wire as it is drawn through a conical die. Under various drawing conditions, the FE analysis investigates the damage factor distribution, the effective stress–strain distribution, the die load and the maximum principal stress in the wire. The relative influences of the semi-angle of the conical die, the friction factors, the length of the bearing part of the die and the brass alloy temperature are systematically examined. Additionally, the Taguchi method is employed to optimize the wire drawing process parameters. The simulation results confirm the effectiveness of this robust design methodology in optimizing the drawing process of the current CuZn37 brass alloy.

The influence of friction on the prediction of wrinkling of prestrained blanks when drawing through a conical die

This work deals with the deep drawing of prestrained circular blanks into cylindrical cups when drawing through a conical die using flat-bottomed punch. It is well established that the use of a conical die can enhance the limiting drawing ratio compared with that obtainable in a conventional drawing operation. When a conical die is employed, the need for a hold-down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early staged of a drawing process in which thin sheet blanks are used. There has been no wrinkling when thick sheet blanks are used for drawing. For the resent work, annealed prestrain sheet blanks or commercially pure zinc, SS301, SS304 and SS316, having thickness 1.6 mm and different diameters are drawn though a conical die under two different frictional conditions (smooth and rough surfaces of blanks), until the appearance of a first stage wrinkle. It is shown that the onset of wrinkling takes place when the ratio of the plastic strain increment (d ε r /d ε θ ) reaches a critical value. This critical value is plotted against the ratio of initial blank diameter to initial thickness of the sheet blank for the above said metals. This shows a straight line relationship with different slope values for different frictional conditions and metals.