• Transactions of Materials Processing
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• v.29 no.2
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• pp.89-96
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• 2020

The finite element method has been widely applied in the sheet metal forming process. However, the finite element method is computationally expensive and time consuming. In order to tackle this problem, surrogate modeling methods have been proposed. An artificial neural network (ANN) is one such surrogate model and has been well studied over the past decades. However, when it comes to ANN with two or more layers, so called deep neural networks (DNN), there is distinct a lack of research. We chose to use DNNs our surrogate model to predict the behavior of sheet metal in the deep drawing process. Thickness variation is selected as an output of the DNN in order to evaluate workpiece feasibility. Input variables of the DNN are radius of die, die corner and blank holder force. Finite element analysis was conducted to obtain data for surrogate model construction and testing. Sampling points were determined by full factorial, latin hyper cube and monte carlo methods. We investigated the performance of the DNN according to its structure, number of nodes and number of layers, then it was compared with a radial basis function surrogate model using various sampling methods and numbers. The results show that our DNN could be used as an efficient surrogate model for the deep drawing process.

• Transactions of Materials Processing
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• v.15 no.6 s.87
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• pp.453-458
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• 2006

While the die casting has been mainly used to manufacture the magnesium alloy parts, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. Because the magnesium alloy has low formability at room temperature, forming at elevated temperatures is a necessary condition to obtain the required material flow for press forming. However, the elevated temperature forming does not always guarantee the sufficient formability under the dry friction condition because the surface damage such as scratch or wear may accelerate the material failure. In the present study, the solid-type lubricants such as PTFE, graphite and $MoS_2$ were tested for the square cup warm deep drawing using the magnesium alloy AZ31 sheet. The formability improvement by using the lubricant was examined by comparing the maximum deep drawing depth using the PTFE against no lubricant. The formability difference for the different lubricant was also examined based on the maximum deep drawing depth.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.291-297
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• 2011

This work investigated the microstructure and mechanical properties of 6063 Al alloy fabricated by shear-drawing (SD) technique where shear and drawing strains were combined together within a predetermined die. To find the optimum condition for sound deformation, three different dies having different inner angle and diameter of the exit channel were prepared. After single deformation of the present sample, the sound deformation took place without an abrupt failure of the sample if the inner angle would be greater than $135^{\circ}$ in this study, when the channel diameter of the SD die was reduced from 10 to 9 mm. Microstructural observation showed that the inner angle of $135^{\circ}$ was found to be more effective than that of $150^{\circ}$ in terms of the alignment of each grain to the shear direction imposed by SD method. In addition, the yield strength of the SD-deformed sample was twice higher than that of the initial counterpart while loosing ductility in tension.

• Design & Manufacturing
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• v.17 no.4
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• pp.8-13
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• 2023

In this study, it was studied whether a new measurement factor "frictional vibration" that occurs due to the material flow of the die and sheet metal in the flange area during deep drawing process, could be measured using an vibration sensor. The blank holder force acting on the flange area during drawing processing acts as a friction force in the opposite direction into which the sheet material flows and causes friction vibration. As the blank holder force increases, the friction force increases, and as the blank holder force decreases, the friction force also decreases. Because of this, friction vibration also increases and decreases in proportion to the size of the blank holder force. According to this theory, whether frictional vibration occurs was measured using a flange simulator and a vibration sensor. The initial pressure was created using a torque wrench, and it was confirmed that the amplitude increased by about 4 times when torque 6 Nm was increased. When the forming velocity was rapidly changed to 300 mm/min, the amplitude increased approximately 4 times. It was confirmed that the amplitude of frictional vibration according to the measurement location was greater the further away from the specimen. It was verified that a new measurement factor "friction vibration" in the flange area can be measured and used for online monitoring.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.27-30
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• 2004

Clad wire , which has the advantages of the high strength of a steel core and the electro-conductivity, corrosion resistance of a copper layer, is widely being used the telecommunications, electric-electronic and military technology industries, among others. It is important to obtain uniform coated rate when producing clad wires. Clad wire drawing process can be influenced on damage and coated rate of core and sleeve by process variables as semi-die angle and reduction in area. Therefore, in this study, the finite-element results established in previous study is used to analyze the effect of the various forming parameters, which included the semi-die angle, reduction in area etc. The coated rate will be predicted with observation copper coated rate variation according to total reduction in area and the optimal pass schedule will be set up through proper reduction in area and semi-die angle variation.

• Corrosion Science and Technology
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• v.10 no.1
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• pp.1-5
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• 2011

The major purpose of the present study is to evaluate the performance of various galvanized (GI) or galvannealed (GA) mild steels and AHSS in stamping applications. Finite Element Analysis (FEA) of selected stamping operations was conducted to estimate the critical pressure boundary conditions that exist in practice. Using this information, laboratory tribotests, e.g. Twist Compression (TCT), Deep Drawing (DDT) and Strip Drawing (SDT) Tests, were developed to evaluate the performance of selected lubricants and die materials/coatings in forming galvanized steels of interest. The sheet materials investigated included mild steels and AHSS (e.g. DP600 GI/GA, DP780 GI/GA, TRIP780 GA and DP980 GI/GA). Experimental results showed that galvanized material resulted in more galling, while galvannealed material showed more powdering and flaking. The surface roughness and chemical composition of galvanized sheet materials affected the severity of galling under the same testing conditions, i.e. lubricants and die materials/coatings. The results of this study helped to determine the critical interface pressure that initiates lubricant failure and galling in stamping selected galvanized sheet materials. Thus, to prevent or postpone the critical interface conditions, the results of this study can be used to select the optimum combination of galvanized sheet, die material, die coating and lubricant for forming structural automotive components.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.93-98
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• 2005

The purpose of this study is to confirm the improvement of formability of AZ31 magnesium alloy sheet by using local heating and cooling technique. For this, the experiments of warm deep drawing were done under the temperatures of $100^{\circ}C\~400^{\circ}C$, and the punch velocity of 10, 100mm/min. Also FE analysis under the temperatures of blankholder and die of $150^{\circ}C,\;225^{\circ}C\;and\;300^{\circ}C$ for tools(holder and die) was executed with considering heat teansfer. From the results, the formability of AZ31 magnesium alloy, espicially the temperatures of $225^{\circ}C\~250^{\circ}C$ for tools(holder and die)improved remarkably. And the experiments and simulations showed that necking under room temperature for tools occured under the part of punch shoulder while at $300^{\circ}C$ for tools, at the part of die shoulder.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.199-207
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• 2023

The stainless steel basket-bowl, a critical component of washing machines, is characterized by its unique two-tiered circular shape. This study explores the potential of a draw-bead free die design to address tearing concerns in the prospective plastic layer during the drawing operation. In order to prevent wrinkles that may arise from the absence of a draw-bead, a two-stage punch configuration is proposed. The influence of the blank holder force on wrinkle reduction is also examined. Finite element analysis is employed to evaluate the proposed die design by analyzing the wrinkle shape and strain mode. The results confirm that the stainless steel basket-bowl can be successfully drawn without wrinkles utilizing the proposed two-stage punch without a draw-bead on the blank holder. These findings contribute to the development of more efficient and reliable manufacturing processes for the stainless steel basket-bowl production.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.46-50
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• 2000

The progressive die are multiple operations performed by means of a die having above two stages, on the each of stages performs a different operation as the sheet metal passes through the die hole. In the field of design and making tool for press working, the progressive die for sheet metal (STS 304, thickness : 0.5mm) is a specific division. In order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, I. e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die components, know-how and so on. In this study, we designed and constructed a progressive die of multi-stage and performed try out. Out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the part 1 of this study we treated die design mostly.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.213-217
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• 2000

The progressive die are multiple operations performed by means of a die having above two stages, on the each of stages performs a different operation as the sheet metal passes through the die hole. In the field of design and making tool for press working, the progressive die for sheet metal (STS 304, thickness : 0.5mm) is a specific division. in order to prevent the defects, the optimum design of the production part, strip layout, die design, die making and tryout etc. are necessary. They require analysis of many kinds of important factors, i.e. theory and practice of metal press working and its phenomena, die structure, machining condition for die making, die materials, heat treatment of die components, know-how and so on. In this study, we designed and constructed a progressive die of multi-stage and performed try out. Out of these processes the die development could be taken for advance. Especially the result of tryout and its analysis become the characteristics of this paper (part 1 and part 2) that nothing might be ever seen before such as this type of research method on all the processes. In the part 1 of this study we treated die design mostly.