Multi-stage Deep Drawing Process Research Articles

A Method for Benchmarking of FEM Packages for Multi-Stage Sheet Metal Forming Simulations

Computer simulation plays a crucial role in the designing of sheet metal stamping processes for the prediction of process output, before try-out die sets are manufactured. Different commercial software packages are available on the market for sheet forming simulation, but their accuracy can vary, depending on the selection of the pre-processing parameters and on their formulation. Software benchmarking can be used to select the most appropriate package for a given application. Calibration, i.e. the inverse determination of the correct set of pre-processing parameters, can be used for improving the prediction accuracy. The scientific literature on numerical simulations of sheet metal forming processes presents some examples of software calibration and very few examples of benchmarking. The literature generally neglects a critical and important issue: the inherent variability of real forming processes. In this work, the experimental results of two similar multi-stage deep drawing processes are presented and compared to the simulation output of two popular software packages used in the industry. Statistical methods for benchmarking and calibration are proposed. The paper demonstrates how benchmarking can be misleading if process variability is not considered.

다단 딥 드로잉 공정 두께 및 변형률 예측을 위한 심층 신경망 개발

다단 딥 드로잉 공정 두께 및 변형률 예측을 위한 심층 신경망 개발

Multi-stage deep drawing process of axis-symmetric extra deep drawing steel cylindrical cup

The paper investigates the design and optimization of the multi-stage deep drawing process for the axis-symmetric extra deep drawing (EDD) Steel cup. The geometrical and process parameters are focused on eliminating defects like thinning, thickening, and wrinkling. The explicit analysis is carried out by using a 3-dimensional finite element model to optimize the total number of deep drawing stages. The proposed multi-stage deep drawing process sequences are numerically simulated and the obtained strain distribution is utilized for the generation of forming limit diagram (FLD) for predicting the defects such as thinning and wrinkling. The numerically generated FLD is further validated by using analytical models such as Keeler Brazier and North American deep drawing research group (NADDRG). The obtained results point out that the proposed design process sequences can be implemented successfully without failure. Among both, the optimized design process sequence has better accuracy with less thickness variation compared to the design sequence with a bulge at the bottom.

Influence of forming parameters on the crash performance of capped cylindrical tubes using LS-DYNA follow-on simulations

In the automobile industry, accurate prediction of crashworthiness indicators is important in designing energy absorbing tubes for the protection of occupants. However, the deformation behavior of these tubes was found to be affected by the prior manufacturing (forming) process. Hence, it is necessary to incorporate these forming effects in the crash simulation model to improve the accuracy of the simulation results. Therefore the interactive computational approach was used in this research article to account for the forming and crash response of the proposed capped cylindrical tubes. In this procedure, the design of forming tools based on the computer-aided automated computing system is performed first and the results are considered in the multi-stage deep drawing process. Then, the influences of forming parameters of a multi-stage deep drawing process on the axial crushing response of thin-walled capped cylindrical tubes were numerically examined using LS-DYNA follow-on simulations. The residual forming history such as effective plastic strain, thickness variation, and residual stress was mapped to crash simulation models in order to understand the interaction between the forming process and subsequent crash performance of the proposed tubular structures. The capped cylindrical tubes of shell element with a constant thickness of 1.63 mm were also simulated for comparison purpose. The finite element crash model included with forming simulation results caused an increase in the initial peak crushing force by 15–30% over constant thickness tubes. In order to validate the numerical simulation results, experiments were performed. The application of a constitutive crash simulation model considering these forming parameters when studying the axial crushing characteristics of the tubular structures that have experienced earlier forming processes is strongly recommended.

An Analytical Solution of the Subsequent Drawing Force on Multistage Deep Drawing of Cylindrical Cup

In multistage deep drawing process, the subsequent drawing force (SDF) is a key reference value, which plays a significant role on the practical die structure design. In the present study, an analytical calculation of the radial stress at the die exit as well as the SDF in cylindrical cup drawing process are proposed, considering the previous strain hardening in the first drawing, normal anisotropy, frictional coefficient and die arc radius. As a result, the calculated maximum subsequent drawing force (MSDF) is in good agreement with experimental result. Besides, the MSDF decreases as normal anisotropy value increases, while increases as frictional coefficient and strain hardening exponent increases respectively.

Prediction of shear fracture in multi-stage deep drawing process including ironing process for Al3003 sheet

To predict fracture caused by both tensile and shearing stresses, we applied the GISSMO (generalized incremental stress state-dependent model) in conjunction with the TFD (triaxiality failure diagram) in the finite element (FE) software LS-DYNA. Required damage parameters were determined by fitting to the load-displacement curves from tensile tests necessary to set up the TFD those obtained by corresponding FE analyses. Curve fitting was performed using the optimum design tool LS-OPT. For validation, the obtained GISSMO damage parameters were applied to the problem of rectangular cup forming for Al3003 material. Good agreement between the numerically obtained fracture locus and that observed in real forming shows that accurate shear fracture prediction is possible with the presented GISSMO-based approach.

Scratch Modeling of Paint Coated Sheet Metal for Multi-Stage Deep Drawing Process

The scratch phenomenon of paint coated sheet metal in multi-stage deep drawing has been investigated. The tensile tests at a quasi-static strain rate of sheet metals coated with two different types of paint were conducted along the rolling, diagonal, and transverse directions of the sheet metal in order to consider strain hardening and anisotropy. It has been found that the types of paint are negligible for plasticity behavior. Finite element simulations of the multi-stage deep drawing process was performed using the obtained material properties and the simulation results were compared with the actual testing. Through the simulation results, three approaches, which include the contact pressure, the accumulated slip distance, and the accumulated friction work were implemented to investigate the scratch phenomenon and they were compared for the scratched and non-scratched regions. It was found that the accumulated slip distance at the scratched region was larger than that of the non-scratched region with a good correlation from experimental observation, whereas either the contact pressure or accumulated friction work approach did not predict the experiments. Therefore, it is concluded that the accumulated slip distance is a good method to identify the scratch on the paint coated sheet metal during deep drawing process.

Deep Drawability of Ti/Steel/Ti Laminated Sheets

Cladding is the bonding together of dissimilar metals. One of clad products is the titanium clad steel sheet. It is effective to cover with pure titanium sheet to improve the corrosion resistance of the steel sheet. Titanium clad steel sheets are often achieved by rolling sheets together under high pressure. In the current study, the blank comprising three laminar non-bonded sheets, such as the titanium/steel/titanium sheet, is arranged in the die. The formability of pure titanium clad sheet by multistage deep drawing was investigated to enhance corrosion resistance of steel cup. In the experiment, the blanks were pure titanium sheets JIS1-TP270, JIS2-TP340, ultralow-carbon steel SPCC, and stainless steel SUS316L. The initial thickness of the sheet was 0.2 to 0.5 mm in thickness. The blank diameter was 70 mm. The blanks are merely adjacent sheet; however, not joined with each other. In the deep drawing process, a hydraulic press was used in the experiment and the forming speed for the press was about 10 mm/min. The lubricant used was the solid powders of molybdenum disulfide. For the prevention, pure titanium blank was treated by oxide coating. The conditions of heat treatment were annealed at 973 K for 3.6 ks to 7.2 ks. By oxide coating, the titanium sheet has sufficient ability in preventing the seizure in multistage deep drawing. The drawn cups of the three-layer laminated sheet were formed. The seizure did not cause. The oxidatively-treated titanium sheets have sufficient ability in preventing the seizure. In addition, the clad cups until 6th stage were formed by multistage deep drawing. Long clad cups were successfully formed in multistage deep drawing process.

Axial crash performance of press-formed open and end-capped cylindrical tubes – A comparative analysis

Thin-walled cylindrical tubes are usually employed as impact energy absorbing members in automotive vehicles due to their high energy absorption capacity through progressive plastic deformation. Despite their superior impact performance, high initial peak force is the crucial problem which has potential to cause serious injury to the occupants. Hence in this study, end-capped cylindrical tubes with reduced initial peak force are proposed as energy absorbing members when subjected to axial static and impact loading conditions. The proposed tubes were fabricated by a multi-stage deep drawing process, that induces forming effects such as thickness variation, and residual stress/strain. Subsequently, numerical simulations were carried out using HyperForm 14.0® and LS-DYNA R-971® with particular attention for the transfer of forming history from deep-drawing simulations to the subsequent crash models. The axial crash performance of the end-capped tubes was also compared with open cylindrical tubes and it was found that the initial peak force of the end-capped tube is significantly reduced by 15–30% than the open cylindrical tube without compromising the energy absorption capacity. The results revealed that end-capped tubes can stabilize the deformation behavior and could be used as a good alternative to the conventional energy absorbing structures in aerospace and automotive applications respectively.

An Expert System of Die Design for Multi Stage Deep Drawing Process

Deep drawing process is mainly used to produce automotive & aerospace components, house hold utensils, casings of electronic devices and many more. It is a plastic deformation process consists of tools viz. punch, die and blank holder. The workpiece is set on the die and hold with blank holder. Then, punch travel to deform the workpiece. The tooling of the process varies with different material and geometrical aspects. The die of the deep drawing process plays a vital role because the precision and accuracy of final product is depending upon the accuracy, surface quality and tolerance of the die. The die designing for any component is a combination of art, science and expertise. Of course, it is also tedious job and that requires highly skilled man power. Hence, an expert system has been developed to design die for multi stage deep drawing operations using VB.NET and AUTOCAD. Multi stage deep drawing process (MSDDP) is normally used for the components having high length to diameter ratio (LDR). This system is indigenous of its kind which requires few data i.e. work material type, physical properties & shape and size of final product. The system will predict and estimate number of draws, clearance and force required by punch & blank holder during each pass. The knowledge of die design experts (industries, academics and professionals) are fed in terms of rules. The system is quite capable to generate manufacturing drawing of die sets for all sequence of operations. Moreover, it is most suitable to make templates of products which are normally used during inspection and testing. This will reduce indirect costs and lead time. It also improves quality and productivity.

Applying a punch with microridges in multistage deep drawing processes.

The developers of high aspect ratio components aim to minimize the processing stages in deep drawing processes. This study elucidates the application of microridge punches in multistage deep drawing processes. A microridge punch improves drawing performance, thereby reducing the number of stages required in deep forming processes. As an example, the original eight-stage deep forming process for a copper cylindrical cup with a high aspect ratio was analyzed by finite element simulation. Microridge punch designs were introduced in Stages 4 and 7 to replace the original punches. In addition, Stages 3 and 6 were eliminated. Finally, these changes were verified through experiments. The results showed that the microridge punches reduced the number of deep drawing stages yielding similar thickness difference percentages. Further, the numerical and experimental results demonstrated good consistency in the thickness distribution.

12 mm Thick Circular Blanks of Al-killed AISI 1020 Steel -Applied for Cylindrical Cup Manufacturing by Multistage Deep Drawing with Simultaneous Ironing

In this paper a new modified processing route has been proposed for producing long cylindrical cups from 12 mm thick circular blanks of AISI 1020 steel (Aluminium (Al) -killed). In this route, flat blanks were made to preformed shape by stamping operation, followed by multistage deep drawing processes(without blank-holder and with inter-stage stress relief annealing) to increase cup depth. Wall ironing was also purposefully included in each draw step to reduce wall thickness and earing tendency on cup edges. Thus, evolution of wall thickness distribution, Drawability and Ironability, punch force history, and strain distribution profiles on outer cup surfaces were obtained as the effects of interaction between processes, tools and material. The overall draw stages showed: LDR 2.06; overall draw reduction >50% with a drawing efficiency ~72%; LIR 3.55; overall ironing reduction >70% with an ironing efficiency ~68%, which were achieved in the experimental works.

Using a punch with micro-ridges to shorten the multistage deep drawing process for stainless steels

The manufacture of deep drawn parts involves many stages, which results in high costs. Therefore, the design goal for these processes is to reduce the number of stages. This study used punches with micro-ridges to simplify the multistage deep drawing process for stainless steel. To achieve this objective with minimal changes, the characteristics (i.e., the high drawing ratio) of punches with micro-ridges are leveraged to replace two stages of a deep drawing process that uses a punch without micro-ridges with one stage that uses a punch with micro-ridges. Using DEFORM 2D software, the multistage deep drawing process for a stainless steel vibration motor casing that is manufactured using a six-stage deep drawing process is simulated. The punch that does not have micro-ridges (used in the first and fifth stages) is replaced with a punch that has micro-ridges, which eliminates the second and sixth stages of the initial process, so the six-stage deep drawing process is reduced to four stages. The simulation results show that the punch that has micro-ridges allows fabrication and this is subsequently verified through experimental testing. The analysis and test results show that using the punch with micro-ridges enables two stages of the initial deep drawing process to be eliminated, which reduces the overall thinning rate and forming load for the process. The test results are also consistent with those from the simulation analysis.

Numerical Analysis of The Multi-Stage Reverse Deep Drawing Process

The paper presents an analysis of the multistage deep drawing process considering the three deformation stages namely drawing reverse and reverse redrawingrespectively. This work aim to study the mechanism of deformation during the redrawing process where the second and the third stages were done in reverse redrawing and study the effect of this mechanism on produced cup wall thickness, strain distribution across the wall of the drawn part. 2-D model of cylindrical cup (46.75mm) diameter has been developed in the first stage from sheet with thickness (0.5mm) of the low carbon steel (AISI 1008) and (85mm) diameter, while for second and third stages of drawing a punch diameter (32.725mm, 27.489mm) respectively, and inside diameter of dies equal to (33.825mm, 28.589mm) respectively, the clearance is chosen for three stage equal to 0.55mm. A commercial available finite element program code (ANSYS 11), is used to perform the numerical simulation of the multistage deep drawing. The results show that, when considering multi-stage drawing, the task is even more difficult because the strain and thickness distribution resulting from the first stage will influence the subsequent results,increase in thinning in the wall cup will appear in the second and third stages. Finally this work introduces new method (multi reverse redrawing) to produce circular cup throw three stages of drawing reduction in one stroke without the need to the loading and unloading the tools among the stages as in direct redrawing which means reducing the cost, time, efforts and enhancing cup production.

多段深絞り加工による純チタン角筒容器の成形性

In press forming, pure titanium sheet has sufficient ductility. However, the seizure tends to occur during the deep drawing due to high reactivity with die materials. The authors reported that the heat oxided sheets were treated by oxide coating so as to get oxide surface layer effective for preventing the seizing. In the current study, the square titanium cups were formed by multistage deep drawing using oxided titanium sheets for preventing seizing. The sheets were employed and a flat sheet blank is formed into a square by a punch. Various cups were drawn by exchanging the punch and die. The die was a funnel shape without a blankholder in the subsequent stages. The effects of the oxide layer and die shape on the occurrence of seizure in multistage deep drawing were examined. The square cups were successfully drawn by oxide coating. As the number of drawn cups increases, the thickness strain increases at the corner of cups. However, the seizure did not cause even for cups of the 12th stage. It was found that the oxide titanium sheets have sufficient ability in preventing the seizure in multistage deep drawing processes.

AA1070 알루미늄 합금의 사각형상 충격압출 성형에 미치는 공정 조건의 영향

Impact extrusion is an economical and productive process that can replace the multistage deep drawing process for producing deep rectangular cases. In the current work, a three-dimensional finite element analysis of the impact extrusion process of a commercial purity aluminum alloy (AA1070) was performed to predict loads, material flow, and deformed shapes using the Hansel-Spittel rheology law, which describes the flow stress at various temperatures and strain rates. The role of various process parameters such as friction, clearance between punch and die, aspect ratio and thickness of billet on the process and the shapes was analyzed.

Effects of notch geometry on bursting fracture of a V-notched rectangular cup for Li-Ion secondary batteries

A V-notched rectangular cup produced by a multi-stage deep drawing process is presented as a primary safety structure of the lithium-ion (Li-Ion) secondary batteries. The V-notched rectangular cup is required to sustain an inner pressure resulting from the elevated temperature induced by the chemical reaction of the electrolyte during normal operation, and it has to fail when the inner pressure reaches a critical pressure. The inner pressure below approximately 0.500 MPa is considered to be safe, and the battery that reaches the pressure above the critical limit must leak the excess inner pressure, without any explosion. In this study, a V-notched structure on the outer surface of a rectangular cup is proposed as the primary safety device. Predictions with respect to the bursting fracture pressure are presented, where geometric parameters such as the notch angle and depth are considered. The bursting behavior is predicted by adopting an implicit elasto-plastic finite element scheme combined with Cockcroft and Latham’s ductile fracture criterion. The predicted bursting fracture pressure is compared to the results from experimental investigations. It is confirmed that the bursting pressure of the V-notched rectangular cup is well matched with the variation of 5.88% between the predicted and experimentally measured results.

Improvement of Formability for Multistage Deep Drawing of Ti-15V-3Cr-3Sn-3Al Alloy Sheet

The improvement of formability has been investigated in the multistage deep drawing of beta titanium alloy sheet. The beta titanium alloys have good cold workability in the metal forming. However, a seizure tends to occur during metal forming due to high reactivity with other metals. The occurrence of the seizure becomes remarkable in sever forming operations such as deep drawing and ironing. Especially, it is hard to prevent the occurrence of seizure in multistage deep drawing process. In this study, to improve the formability of titanium alloy sheet, the formability in multistage deep drawing process of beta titanium alloy was investigated. The blank used was the commercial beta titanium alloy Ti-15V-3Cr-3Sn-3Al. To prevent the occurrence of seizure, the blank treated by oxide coating was used. The coated sheet was not in direct contact with the tools of die and punch during deep drawing due to the existence of the oxide layer. The effects of the surface roughness and hardness on the formability in the multistage deep drawing processes were examined. The improvement of surface roughness of drawn cup was also attempted by using heat treatment. A long titanium alloy cup was successfully formed by intermediate annealing at the 3rd stage. The drawn cup by multistage deep drawing could be formed to the 6th stage. It was found that the beta titanium alloy sheet covered with oxide layer has sufficient ability in preventing the seizure in multistage deep drawing processes.

Influence of cavity pressure on hydrodynamic deep drawing of aluminum alloy rectangular box with wide flange

Abstract The multi-stage deep drawing process had been traditionally adopted for the box part with super wide flange using multiple annealing procedures with problems of poor surface quality, long manufacturing cycle, high cost and low yield. The hydrodynamic deep drawing (HDD) method was suggested to solve these issues during the multi-stage drawing process, in which the loading path of cavity pressure was one of the key parameters immediately related to the product's quality. The effects of cavity pressure on forming quality and precision were explored according to theoretical analysis, numerical simulations and experiments, and the process window of cavity pressure was established through stress analysis of the corner and straight regions. Meanwhile, wall thickness distributions were investigated with different parameters, including pre-bulging pressure, piecewise stroke and maximum pressure. Furthermore, the reasonable loading path was validated by process experiments. The results indicate that the proper control of cavity pressure will be beneficial in improving the drawability of aluminum alloys effectively, and the conventional drawing process consisting of three drawing operations and two intermediate anneals can be replaced by the one-step HDD process.

Multi-Stage Deep Drawing Process of Thin Sheets for the Sleeve Housing Component of a Spindle Motor in HDD

High-precision micro-fluid dynamic bearing is the key part in a hard disk drive, as it offers low noise levels, high speeds and high rates of accuracy with low amount of vibration. To enhance the performance, a thin sheet component called sleeve housing are newly adopted in FDB. In this paper, multi-stage sheet metal forming process is utilized to fabricate the sleeve housing component. Multi-stage drawing simulations are conducted to investigate the adequate process parameters preventing wrinkling and tearing. From the simulation result, multi-stage drawing processes are conducted with progressive die sets in order to evaluate the forming accuracy. The results reveal that it is successful to fabricate the sleeve housing component with multi-stage drawing process.