• 소성∙가공
• /
• 제27권6호
• /
• pp.356-362
• /
• 2018

A liner is a crucial component that directly affects the penetration performance of the shaped charge warhead. If the material of the liner has fine grain size and high strength, then the penetration performance can be further improved. There have been attempts to use a preform obtained by a severe plastic deformation (SPD) process. In this study, the process of minimizing the strain deviation to maintain the characteristics of material obtained by the severe plastic deformation process was investigated. The FE analysis of liner forging process was performed using the design of experiments (DOE), to optimize various shape parameters of the forming process such as shape of preform and forging die. As a result, the combination of design variables with the minimum effective strain deviation in the liner forging process were obtained.

• 소성∙가공
• /
• 제4권1호
• /
• pp.9-16
• /
• 1995

Model material technique, which requires only the small space of experimental set-up and low cost for experiment, is used to estimate the deformed profile and the forging load in rotary forging. The materials and working conditions are determined to satisfy the similitude conditions between the model test and the prototype test. The model material of the so-called plasticine and the mild steel are chosen as specimens, and they represent almost the same value of strain gardening exponent in the stress-strain relationship. Lubricant in the model test is also carefully selected so that it gives the same frictional conditions at the tool-specimen interface. Experiments for two kinds of specimens are carried out in each testing equipment at room temperatue. From the experiments the deformed dimensions and the forging loads are measured and compared with each other by using the simulation coefficients. It is shown that there are good agreements between the model test and the prototype test. Finally, for verifying the availability of the model material technique this mathod is applied to forging of bevel gear product. the good result is obained which can demonstrate that the model material technique is very efficent for estimating or developing a new process.

• 제어로봇시스템학회논문지
• /
• 제21권5호
• /
• pp.427-433
• /
• 2015

Hot forging industry workers are prone to encounter several health risks due to lack of automation and poor working environment conditions. These workers particularly suffer from muscle fatigue owing to the constant handling of heavy products during the forging process. Thus we developed an assistant robot for workers who carry out hot forging tasks. The purpose of a robot is to compensate gravity-loads for heavy products. To verify the functionality of a robot, we performed a muscle fatigue analysis using Electromyography (EMG) signals. Four muscles of the upper extremity were chosen to measure muscle activity. And experiment conditions were setup to imitate the hot forging process. Post experimental analysis of the captured muscle activity revealed a reduction in the median frequency of the EMG signals, which means clear fatigue reduction due to a robot's assistance. The developed assist robot with compact and economical components can be efficiently utilized at forging work sites to create better working conditions for operators.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 춘계학술대회 논문집
• /
• pp.135-138
• /
• 2007

A semi-solid forming processing has been developed for manufacturing near net-shape components. The semi-solid forming has two methods. One is thixo-forming with reheating prepared billet, the other is rheo- forming with cooled melt until semi-solid state. In indirect forging processing, this experiment used aluminum rheology materials by electromagnetic stirring system. Rheology material is made by A16061. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. Forged samples are found microstructures and mechanical properties. Forged samples are accomplished heat treatment T6 for high mechanical properties.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 추계학술대회 논문집
• /
• pp.219-222
• /
• 1995

The objective of this study is to demonstrate the ability of a computer simulation of microstructural evolution in hot forging of C-Mn steels. The finite element method is applied to the prediction of the microstructural evolution, and it should be coupled with heat transfer analysis to consider the change of thermomechanical properties during the deformation. In this study, Yada's recrystallization model and rigid-thermoviscoplastic finite element method were employed in order to analyze microstructural evolution during hot forging process. To show the validity and effectveness of the proposed method, the experiment of hot compression process was accomplished and the results of experiment were compared with those of simulation. Consequently, this approach shows a good agreement with experimental results.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.586-591
• /
• 2001

In the cold forging, elastic deformation of the die has been investigated to improve the accuracy of cold forged parts with F.E.M analysis using DEFORM, and with experiments using strain gauges. In the experiments, initial billet was selected to easily find the effect of elastic deformation according to the forging modes, extrusion and upsetting type, and only extrusion type. Elastic deformation of the die can be obtained by the signal from the strain gauges and this signal can be amplified by data acquisition system during the process. In the F.E.M analysis, two types of analysis are used to predict elastic strain of the die. To improve an accuracy of forged product and die dimension, this study compared with strain distribution between experiment and F.E.M analysis. As a result, the history of the deformation of the die and elastic recovery of forged product can be obtained by the elastic strain analysis of forged product and die according to the forging modes.

• 한국생산제조학회지
• /
• 제22권1호
• /
• pp.173-177
• /
• 2013

The purpose of this paper is to investigate the influences on mechanical properties of two-stroke cycle motor pistons manufactured by casting, conventional forging and powder forging, through the comparison of characteristics, merits and disadvantages of each forming technology. For each forming technology, the optimal process parameters were determined through the experiments for several conditions, and microstructure, hardness, tensile strength and elongation of pistons are compared and analyzed. In conventional forging process, material temperature was $460^{\circ}C$ and the die temperature was $210^{\circ}C$ for the Al 4032. The optimal condition was found as solution treatment under $520^{\circ}C$ for 5 hours, quenching with $23^{\circ}C$ water, and aging under $190^{\circ}C$ for 5 hours. In powder forging process, the proper composition of material was determined and optimal sintering conditions were examined. From the experiment, 1.5% of Si contents on the total weight, $580^{\circ}C$ of sintering temperature, and 25 minutes of sintering time were determined as the optimal process condition. For the optimal condition, the pistons had 76.4~78.3 [HRB] of hardness, and 500 [MPa] of tensile strength after T6 heat treatment.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.1051-1055
• /
• 1997

Hot forging is widely used in the manufacturing of automotive component. The mechanical, thermal load and thermal softening which is happened by the high temperature die in hot forging. Tool life of hot forging 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 workpieces. The service life of tools in hot forging process is to a large extent limited by wear, heat crack, plastic deformation. These are one of the main factors affecting die accuracy and tool life. It is desired to predict tool life by developing life prediction method by FE-simulation. Lots of researches have been done into the life prediction of cold forming die, and the results of those researches were trustworthy, but there have been little applications of hot forming die. That is because hot forming process has many factors influencing tool life, and there was not accurate in-process data. In this research, life prediction of hot forming die by wear analysis and plastic deformation has been carried out. To predict tool life, by experiment of tempering of die, tempering curve was obtained and hardness express a function of main tempering curve.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.193-197
• /
• 2002

In this study, the casting/forging process was applied to the Shift-Fork, a manual transmission part of automobiles. In the casting experiments, the effects of additives, Sr, Ti＋B and Mg, on the mechanical properties and the microstructure of a cast preform were investigated. When 0.03% Sr were added into the molten aluminum alloy, the finest silicon-structure was observed in the cast preform and the highest tensile strength and elongation accomplished. And when 0.2% Ti＋B were added into the molten Al-Si alloy, the highest values of tensile strength were obtained. The maximum hardness was in case of 0.2% Mg. In the forging experiment, it was confirmed that the optimal configuration of the cast preform could be predicted by FE analysis. To minimize the cost as the press size, the compact shape of preform was proposed to reduce the volume of flash. The modification of shape in designing preform was performed to attain a satisfactory performance in the areas where the mechanical strength were more required. By using FVM(Finite Volume Method) software, it was verified that a proposed casting design was available. To identify the relationship between effective strain and mechanical properties of the final forged product, the compression test was performed. As the result, the tensile strength and elongation of a cast preform were much higher than before forging. The minimum forging temperature was found 40$0^{\circ}C$ to save heating time.

• 대한기계학회논문집
• /
• 제13권3호
• /
• pp.337-344
• /
• 1989

본 연구에서는 플래쉬(flash)를 가진 축대칭 리브-웨브형(rib-web type) 제품의 형단조가공을 해석하기 위한 UBET 프로그램을 개발하고 변형중의 경계 조건처리를 다르게 한 세 가지 유동모델에 대하여 소재의 유동상태와 단조하중을 계산하여 효과적인 유동모델을 제시하였다. 또한 체적은 같으나 반지름과 높이의 비가 다른 몇 가지 초기소재 형상에 대하여 변형에 따른 소재의 다이충만도 및 하중을 비교하여 적절한 초기소재의 형상을 찾고자 하였다. 본 연구에서 제시한 유동모델의 효율성을 검증하기 위하여 플라스씬(plasticine) 소재를 사용한 실험과 그 결과를 비교, 분석하였다.