• International Journal of Precision Engineering and Manufacturing
• /
• 제7권3호
• /
• pp.39-46
• /
• 2006

This paper presents an elastic deformation model of a spindle unit (S/U), which takes into account the non-linear properties of high-speed ball bearings (particularly the effect of high rotational speed). For this, a software for the estimation of the S/U elastic deformation properties was developed and intended for use by S/U designers. A computer aided analysis of the model using the developed software was carried out and experiments showed the significant effect of rotational speed, cutting load and bearing axial preload, and showed some new phenomena, from which the criteria for the choice of bearing axial preload is given.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2002년도 춘계학술대회 논문집
• /
• pp.163-168
• /
• 2002

Hot forging is widely used in the manufacturing of industry machine component. The mechanical, thermal load and thermal softening which are happened by the high temperature in hot forging process. Tool life decreases considerably due to the softening of the surface layer of a tool caused by a high thermal load and long contact time between the tool and billet. Also, tool life is to a large extent limited by wear, heat crack and plastic deformation in hot forging process. These are one of the main factors affecting die accuracy and tool life. That is because hot forging process has many factors influencing tool life, and there was not accurate in-process data. In this research, life prediction of hot forging tool by wear and plastic deformation analysis considering tempering parameter has been carried out for automobile component. The new developed technique in this study for predicting tool life can give more feasible means to improve the tool life in hot forging process.

• 한국생산제조학회지
• /
• 제25권3호
• /
• pp.211-216
• /
• 2016

Al alloys are useful materials having high specific strength and are used in machining of parts having thin-walled structures for weight reduction in aircraft, automobiles, and portable devices. In machining of thin-walled structures, it is difficult to maintain dimensional accuracy because machining deformation occurs because of cutting forces and heat in the cutting zone. Thus, cutting conditions and methods need to be investigated and cutting signals need to be analyzed to diagnose and minimize machining deformation and thereby enhance machining quality. In this study, an investigation on cutting conditions to minimize machining deformation and an analysis on characteristics of cutting signals when machining deformation occurs are conducted. Cutting signals for the process are acquired by using an accelerometer and acoustic emission (AE) sensor. Signal characteristics according to the cutting conditions and the relation between machining deformation and cutting signals are analyzed.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2002년도 춘계학술대회 논문집
• /
• pp.181-183
• /
• 2002

A new deformation process termed "continuouis confined sup shearing" (CCSS) has been developed for shear deformation of metallic sheets. The tools of CCSS were designed to provide a constant shear deformation of the order of 0.5 per pass while preserving the original sheet shape. In order to clarify the evolution of texture and microstructure during CCSS, strips of the aluminum alloy AA3004 were deformed by CCSS in up to three passes. FEM results indicated that CCSS provides a quite uniform shear deformation at thickness layers close to the strip center, although the deformation is not homogeneous in the die channel, in particular at the surface layers. The rolling texture of the initial sheet decreased during CCSS, and preferred orientations along two fibers developed. However, with an increasing number of CCSS passes the deformation texture did not develop futher. The evolution of annealing textures depended on the number of CCSS passes. A strong {112}<110> component in the deformation texture led to the formation of a strong {111}<112) orientation in the annealing texture. Observations by TEM and EBSD revealed the formation of very fine grains of ∼1.0$\mu\textrm{m}$ after CCSS.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2001년도 제4회 압출 및 인발가공 심포지엄
• /
• pp.99-106
• /
• 2001

The design for cold extrusion dies is very important, because the die insert is subjected to very high radial and hoop stresses. The design of cold extrusion dies has many constrained conditions. In this paper, the used assumptions are such that the yield strength of each ring is selected according to the allowable tensile or compressive hoop stress in each ring and the maximum allowable inner pressure, when yielding occurs in one ring of the dies, is obtained by the proposed equation. In order to obtain design variables, such as diameter ratios and interferences, using the maximum inner pressure, the flexible tolerance method was used for shrink-fitted thick-walled cylinders. ANSYS APDL was used to perform the repeated analysis of deformation of the dies due to the variation of the design variables. The response surface methodology is utilized to analyze the relationship between the design variables and the maximum radial displacement of the die insert during extrusion. From the results, it is found that outer diameter of the die Insert has the largest effect on the minimization of maximum radial displacement at the inner surface of the dies.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
• /
• pp.26-30
• /
• 2003

Since the dimension of cold forged part is larger than the cavity size of forging die, the difference results from the various features, such as, the elastic characteristics of die and workpiece, thermal influences, and machine-elasticity. All of these factors should be considered to get more accurate prediction of the dimension of forged part. In this paper, severe FE techniques are proposed to improve the prediction accuracy of dimension for cold forged part. To validate the importance of the above mentioned factors, and the estimated results are compared with the experimental results. The used model is a closed die upsetting of cylindrical billet. The calculated dimensions are well coincided with .the measured values based on the proposed techniques. The proposed techniques have put two simple but important points into Fe simulation. One is the separation of forging stages into 3 steps, from a loading through punch retraction to ejecting stage. The other is the dimensional change, according to the temperature changes due to the deformation. The FE analysis could predict the dimension of cold forged part within the $10{\mu}m$, based on the more realistic consideration.

• 한국정밀공학회지
• /
• 제31권12호
• /
• pp.1093-1100
• /
• 2014

The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.

• 대한기계학회논문집A
• /
• 제29권8호
• /
• pp.1146-1152
• /
• 2005

Recently, multi cell tube which is used for a cooling system of automobiles is mainly manufactured by the conform extrusion but this method is inferior as compared with direct extrusion in productivity per the unit time and in the equipment investment. Therefore, it is essential for the conversion of direct extrusion with porthole die. The direct extrusion with porthole die can produce multi cell tube which has the competitive power in costs and qualities compared with the existing conform extrusion. This study is designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection that is affected by variation of porthole shape in porthole die. Estimation is carried out using finite element method under the non-steady state. Also this study was examined into the cause of mandrel fracture through investigating elastic deformation of mandrel during the extrusion.

• Design & Manufacturing
• /
• 제10권1호
• /
• pp.12-18
• /
• 2016

Although magnesium alloy has received much attention to date for its lightweight and high specific strength, their applications are impeded by the low formability which is caused by the hexagonal crystal structure at room temperature. In general, equal-channel angular extrusion(ECAE) is recognized as one of the attractive severe plastic deformation techniques where the processed bulk metals generally achieve ultrafine-grained microstructure leading to improved physical characteristics and mechanical properties. ECAE process has several parameters such as angle of die, process temperature, process route and speed. During ECAE process of Mg alloy, these parameters has great influence on the extrudability and the mechanical properties of alloy. The aim of this study is to estimate the influences of process conditions on the formability of AZ31 and AZ31-CaO alloys. Mg alloys are processed through ECAE at elevated temperatures using three types of die with channel angle of $90^{\circ}$, $110^{\circ}$, $135^{\circ}$ using route $B_c$, respectively. This study discusses the feasibility of using ECAE to improve both formability and strength on magnesium alloys by comparative analyzing the mechanical properties and microstructural evolution in each condition.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 춘계학술대회 논문집
• /
• pp.374-377
• /
• 2008

Magnesium alloy sheets are usually formed at temperatures between $150^{\circ}C$and $300^{\circ}C$ because of their poor formability at room temperature. In the present study, the formability of AZ31B magnesium alloy sheets was investigated by the analytical and experimental approaches. First, tensile tests and the limit dome height test were carried out at elevated temperatures to get the mechanical properties and forming limit diagram, respectively. And then deep drawing of cross shaped die was tried to get the minimum corner radius and forming limit at specific temperature. Blank shape, punch velocity, minimum corner radius, fillet size, etc, were determined by finite element analysis physical try-outs. Especially, optimum punch and die temperature were suggested through the temperature-deformation analysis using Pam-stamp.