• Journal of Welding and Joining
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• v.20 no.6
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• pp.99-99
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• 2002

In order to evaluate the proper fracture strength of microstructures in a steel weldment, smaller size loading ball than used for a conventional small punch(CSP) testing is required due to regional limitation on constitutive structures. In this study, the minimized loading ball(φ 1.5mm) and bore diameter of lower die(φ 3mm) were designed for an advanced small punch(ASP) test. The results obtained from the ASP test were compared with those from a CSP testing for a X20CrMoV121 steel weldment. It was found that the ASP test clearly showed the microstructural dependance on fracture strength and ductile-brittle transition behavior of the weldment. In the ASP test, especially, the cracks tend to initiate for various directions within hemispherical indentation region of an objective structure in SP test. This indicates that the evaluation of more proper fracture strength for F.L+CGHAZ, FGHAZ and ICHAZ can be performed by means of the ASP test in a steel weldment.

• Design & Manufacturing
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• v.16 no.3
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• pp.39-43
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• 2022

In this study, we designed an vibration cutting tool that can achieve improvements such as low cutting force, interrupted chip evacuation and better surface quality of cutting performance to obtain high-quality surface roughness and improvement of tool wear, which is an issue in the machining of high-hardness mold steel. Among the resonance frequency modes of the vibration cutting tool, the bending mode was used to maximize the driving amplitude of the vibration tool tip, and the resonance frequency was confirmed through the finite element method. After measuring the actual resonant frequency of the designed tool using an optical fiber sensor, the cutting force and machining surface of vibration cutting and conventional cutting were compared and analyzed in the turning process of high hardness mold steel (STAVAX). As a result of the experiment, the cutting force was reduced by about 20 % compared to the conventional cutting process, and the surface roughness was also improved by about 60 %. This study suggested that the tool wear and surface quality of high-hardness steel can be improved through the vibration cutting method in the machining of high hardness mold steel.

• Design & Manufacturing
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• v.18 no.2
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• pp.23-28
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• 2024

The automobile industry is a wide range of related industries, including parts manufacturing and vehicle assembly, press processing is an essential element in making automobiles. Press processing is a processing method for metal sheets that has relatively high dimensional and shape precision and is suitable for mass production. It refers to processing by attaching a special tool, a mold, to a press machine. Recently, the automobile industry is attempting to reduce the weight of automobiles in order to reduce carbon emissions due to global warming, and the use of high-strength steel sheets, which are lighter than general structural steel sheets, is a natural trend. Shear processing is required to use high-strength steel, and the shape of the shear surface created by shear processing has a significant impact on the quality of the automobile. Therefore, various methods are being attempted to improve the share surface during shear processing. Among them, shaving processing is a method of shearing the primary shearing area again, and it is difficult to obtain an accurate answer because complex deformation occurs in the microscopic shear area. Therefore, in this study, the effect of machining allowance on shaving processing was analyzed using the finite element method using high-strength steel plate (SPFH590), and the differences were compared and examined through actual experiments under the same conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.42-47
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. Therefore, a tool life is one of the important issues on cold forging industry. However, since variables related with tool life are many complicated, the studies for solution should be investigated by the systematic research approach. The shape and process changes of die, the hardness changes of material and the tolerance of dies to decrease the die stress are analyzed by the FEM software. The heat-treatment of tool material is investigated to improve the tool life. Deep cryogenic treatment of tool steel is very efficient to improve the wear resistance due to the fine carbide. And, it is investigated that the shape and dimension of tool give effect into both tool life and quality of forged product..

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.518-523
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• 2006

Wet wire drawing of brass coated steel wire, used for tire reinforcement, is realized with Tungsten Carbide(WC) dies sintered with a cobalt(Co) binder. Dies wear represents an important limitation to the production process and cost savings. Several parameters, such as Co content, WC grain size of tungsten carbide, sintering conditions, and so on, affect on the wear of the drawing die. In this study, the effect of the diamond abrasive particle size on the life of the WC centered dies of the wet wire drawing was investigated. Wet wire drawing experiments were carried out on a wet wire drawing machine. From the experiments, the dies life, dies fracture, wire surface roughness, and wire breaks were investigated. From the results, it was found that the wear of the WC dies increased with the increase in the diamond abrasive particle size.

• Journal of Power System Engineering
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• v.6 no.3
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• pp.31-35
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• 2002

Brake tube is considered one of the most important parts in automobile. The shape of brake tube end has a great influence on the function of brake, and the quality and productivity of brake tube have relation to die design. The forming process of brake tube end is performed by hydraulic press forming machine. In this paper, the forming processes of tube end for automobile is analyzed and designed to make the optimal form of brake tube end. Also, finite element analysis has been carried out using $DEFORM^{TM}% 3D to predict the optimal shape of brake tube end and the results obtained showed the optimal length between punch and chuck is $1.0{\sim}1.2mm$. The shape of tube end is in good agreement with the finite element simulations and the experimental results.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.3
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• pp.127-132
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• 2014

The semi-solid metal forming process has been applied to realize a near-net shape fabrication of a high speed tool steel. A complicatedly shaped part out of SKH51 was successfully manufactured by introducing pertinent materials, tooling and processing conditions. A SKH51 billet with globular grains was heated at temperatures between 1300 and $1350^{\circ}C$ using high frequency induction heater to get semi-solid microstructure before high rate injection of mushy metal into a die cavity for the forming process. It was necessary to control the preheating of dies between 300 and $400^{\circ}C$ to maintain the homogeneous microstructure during the semi-solid metal forming process. Significant defects such as pores, high fraction of liquid fraction and segregation could be removed from the part by using air vents.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.839-846
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• 2001

Some deep drawing characteristics at elevated temperatures were investigated for the SCPI steel sheets by using a Cr-coated die. For this investigation, six different temperatures between room temperature and 250$\^{C}$, and six different drawing ratios ranging from 2.4 to 2.9 were considered. As a result, the limiting drawing ratio, the maximum drawing force and the maximum drawing depth were found to be affected sensitively by temperature, and more stable through-thickness strain distribution was observed at elevated temperatures. Some experimental results compared favorably with theoretical results obtained by using the finite element method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1267-1273
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• 2009

Hot press forming can produce high-strength components by rapidly cooling between closed punch and die after hot forming using quenchable boron steel austenized in a furnace. In the hot press forming process, the cooling rate is influenced by the size, position and arrangement of the cooling channel and the file condition of cooling water in the die. Also, mechanical properties of the final components and operation time are related to cooling rate. Therefore, the design of optimized cooling channel is one of the most important works. In this paper, the effect of position and size of the cooling channel on the cooling rate was investigated by using design of experiment and FE analysis in hot press bending process. Therefore the optimum cooling channel ratio was presented in the HPB.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1990.04a
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• pp.83-88
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• 1990

The study is concerned with the theoretical and experimental investigation of axisymmetric fluid pressure-drive hydronforming of sheet metal by forming over the die cavity. The rigid-plastic finite element method is employed to calculate the stress and strain distribution The effect of blank size and die radius is also studied in the finite element analysis. Experiments are carried out for hydroforming of cold rolled steel sheets under various process conditions. The computational results are compared with the experimental results for the forming pressure vs. pole displacement relations and strain distributions. Comparison has shown that theoretical predictions by the finite element method are in good agreement with the experimental observations. Thus, it is shown that the rigid-plastic finite element method is effectively used in the analysis of axisymmetric fluid pressure-driven hydroforming process.