• 소성∙가공
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• 제14권9호통권81호
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• pp.772-778
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• 2005

This paper is concerned with the analysis of material flow characteristics of combined tube extrusion using pipe. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The combined tube extrusion is analyzed by using a commercial finite element code. This simulation makes use of pipe material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. Deformation patterns and its characteristics in combined forward and backward tube extrusion process were analyzed for forming loads with primary parameters, which are various punch nose radius relative to backward tube thickness. The results from the simulation show the flow modes of pipe workpiece and the die pressure at the contact surface between pipe workpiece and punch. The specific backward tube thickness and punch nose radius have an effect on extruded length in combined extrusion. The combined one step forward and backward extrusion is compared with the two step extrusion fer forming load and die pressure.

• 한국정밀공학회지
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• 제34권2호
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• pp.83-87
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• 2017

A multi-step warm forging process for subminiature screws is investigated. Due to the low formability of Titanium alloys, bit forming of Titanium screws is difficult by cold forging. In order to overcome this low formability of Titanium alloys, two candidate processes, i.e., multi-step forging and warm forging are introduced. First, a multi-step (two-step) forging process is investigated. The punch shape and stroke of forging during the first step is designed via various analyses. Finally, the bit formability is investigated at different forging temperatures. Analyses are carried out for two-step forging at various temperatures and the formability under these thermal conditions is compared.

• 한국정밀공학회지
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• 제33권8호
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• pp.635-640
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• 2016

The shell body is the main exterior part of a compressor, and production of shell bodies has increased along with a growing demand for air conditioners, refrigerators, air compressors, and so on. Cracks frequently occur in the process of welding a shell body. In this study, a deep drawing process for creating a shell body from a blank is developed. The technique consists of a four-step deep drawing and a two-step trimming process. Analysis is performed by DEFORM software to examine the safety of the deep drawing and trimming processes. The deep drawing process for the shell body developed in this study would have wide application in many industrial fields.

• 한국정밀공학회지
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• 제21권11호
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• pp.155-162
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• 2004

The volume of the metal is not changed for the plastic deformation. For metal forming simulation, rigid-plastic FEM codes are widely used. Updating geometry using Euler method in the simulation, the volume loss is occurred. In this paper, hybrid method is introduced to perform a more accurate simulation reducing computation time. In the proposed hybrid method, RK2 method is used for geometry updating at first time step and after the boundary condition of the node is changed. At the others, Adams-Bashforth or theta method is applied to update geometry. The results show that the simulations of upsetting and side-pressing can be performed within 0.02％.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제3회 금형가공 심포지엄
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• pp.71-78
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• 2004

Most of member parts have experienced severe springback problems because of their open shape Now it becomes imperative to develop an effective method, which can resolve these problems. However, there remain several obstacles to get accurate estimation of shape error. In analysis, we have to analyze the total process including forming, trimming and flanging. Furthermore, it is another challenge to compare the computed result with the real shape. In this study we developed an analysis program for the springback analysis. We could achive a big enhancement in computation time in springback analysis by using latest equation solving technique and could get a more robust solution conversence by contination method. We have approached this problem in two steps. In the first step, we analyzed forming stage to solve tearing and wrinkling problems. In the second step, we have analyzed full process and have done springback analysis with the same boundary condition as field measuring conditions. We have investigated the accuracy of springback analysis in terms of gap and flush used for insfection of real autobody panels. We found good and effective agreement with the observed results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1376-1380
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• 2005

In recent automotive industry, vehicle weight can be reduced by one-step forming of tailored blanks welded with two or more sheets of metal blanks. Tailored blank(TB) welding is a production method for blanks involving welding together materials of different quality, thickness, and coating, and has proved popular in fabrication automotive parts. This paper deals with the forming characteristics of mash seam welded tailored blanks. Using these forming characteristics, the bumper beam was developed using the mash seam welded tailored blank with the different thickness. We performed the forming simulation with respect to strain distribution on blank during the stamping of the bumper rail part. Based on these results, we made some stamping tryouts with selected types of blank designs to investigate the formability of tailored blank with different thickness. During the tryouts, we knew that it was important the BHF(Blank Holding Force). We obtained to reducing 10.5% weight and cost with adapting the bumper beam of automotive component using the tailored blank of mash seam welding.

• 소성∙가공
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• 제17권7호
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• pp.511-516
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• 2008

A drawbead die for the experimental determination of drawbead forces was newly introduced in this paper. While the conventional Nine's drawbead die inevitably includes effects of a blank holding force on the measured drawbead forces, the new drawbead die excludes it by removing the blank holder contact in the dieface. Therefore, the new drawbead die can provide more realistic drawbead forces without considering somewhat arbitrary effect of blank holder with the computational procedure of forming process. The drawbead opening force and restraining force obtained by adopting the two experimental dies were compared for the validation of accuracy in the FEM simulation of automotive fender forming process. The compared section strains and draw-ins confirmed that the present drawbead die provides better drawbead forces for an accurate FEM simulation of sheet metal forming process.

• 소성∙가공
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• 제14권9호통권81호
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• pp.791-797
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• 2005

Extensive width reduction of slabs is an important technology for achieving continuous production between the steelmaking and hot rolling processes. However, the vertical horizontal rolling process has many disadvantages, e.g., large width deviations and less efficient width reduction. This study was carried out to investigate the deformation of slab by sizing press with two steps die. To do it, dog-bone and camber are discussed in width sizing process considering the deformation behavior according to the deviation of anvil velocity and the deviation of initial slab temperature. In this paper, the various causes of the sizing press phenomena are mentioned for the purpose of understanding of rolling conditions. As a result, the optimal anvil shape having a minimum-forming load is obtained by FE-simulation and ANN.

• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.418-426
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• 2006

In the artificial heart application, productivity and hemodynamic properties of artificial heart valves are crucial in successiful application to long term in vivo trials. This paper is about manufacture and assessment of trileaflet polymer heart valves using vacuum forming process(VFP). The VFP has many advantages such as reduced fabrication time, reproducibility due to relatively easy and simple process for manufacturing. Prior to VFP of trileaflet polymer heart valves, polyurethane(Pellethane 2363 80AE, Dow Chemical) sheet was prepared by extrusion. The sheets were heated and formed to mold shape by vacuum pressure. The vacuum formed trileaflet polymer heart valves fabrication is composed of two step method, first, leaflet forming and second, conduit forming. This two-step forming process made the leaflet-conduit bonding stable with any organic solvents. Hydrodynamic properties and hemocompatibility of the vacuum formed trileaflet polymer heart valves was compared with sorin bicarbon bileaflet heart valve. The percent effective orifice area of vacuum formed trileaflet polymer heart valves was inferior to bileaflet heart valve, but the increase of plasma free hemoglobin level which reflect blood damage was superior in vacuum formed trileaflet polymer heart valves Vacuum formed trileaflet polymer heart valves has high productivity, and superior hemodynamic property than bileaflet heart valves. Low manufacturing cost and blood compatible trileaflet polymer heart valves shows the advantages of vacuum forming process, and these results give feasibility in in vivo animal trials in near future, and the clinical artificial heart development program.

• Geomechanics and Engineering
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• 제19권2호
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• pp.105-114
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• 2019

In this paper, simulation tests were conducted with similar materials to study the distribution of residual voids in longwall goaf. Short-time step loading was used to simulate the obvious deformation period in the later stage of arch breeding. Long-time constant loading was used to simulate the rheological stage of the arch forming. The results show that the irregular caving zone is the key area of old goaf for the subsidence control. The evolution process of the stress arch and fracture arch in stope can be divided into two stages: arch breeding stage and arch forming stage. In the arch breeding stage, broken rocks are initially caved and accumulated in the goaf, followed by the step deformation. Arch forming stage is the rheological deformation period of broken rocks. In addition, under the certain loads, the broken rock mass undergoes single sliding deformation and composite crushing deformation. The void of broken rock mass decreases gradually in short-time step loading stage. Under the water lubrication, a secondary sliding deformation occurs, leading to the acceleration of the broken rock mass deformation. Based on above research, the concept of equivalent height of residual voids was proposed, and whose calculation equations were developed. Finally, the conceptual model was verified by the field measurement data.