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정윤철(Yoon-Chul Jung),박정수(Jung-Soo Park),신형섭(Hyung-Seop Shin),최광(Kwang Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this study, the similar and dissimilar friction stir spot welding of Mg-alloy and Al-alloy sheets have been tried using an apparatus devised with a CNC milling machine to give a precise control of the friction time and the plunge depth. The shape and volume of weld parts formed on the specimen were investigated. The history of temperature distribution and the related variation of vertical load during spot welding were measured by using an Infrared Thermal Imager(THERMA CAM™ SC2000) and a loadcell located below the specimen fixture, respectively. In order to investigate the influence on the weld strength, the layer sequence of lap-joint configuration was changed. The micrographic observation has been done to characterize the friction stir spot welding of Mg-alloy and Al-alloy sheets. Tensile shear test was also performed to evaluate the fracture load of the welded specimen.
정윤철(Yoon-Chul Jung),박정수(Jung-Soo Park),신형섭(Hyung-Seop Shin),최광(Kwang Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In this study, the friction stir spot welding of Mg-alloy sheets has been tried using an apparatus devised with CNC milling machine to give a precise control of the friction time and the plunge depth. The shape and volume of the protrusion formed depending on the probe shape and plunge depth were investigated. The history of temperature distribution the related variation of vertical load applied to specimen during welding by using an Infrared Thermal Imager(THERMA CAM™ SC2000) and loadcell located below the fixture of specimen respectively. In order to characterize the friction stir spot welding of Mg alloy sheets, the micrographic observation has been done. Tensile shear test is also performed to evaluate the fracture force of the welded specimen.
마그네슘합금(AZ31B) 판재의 마찰교반 점용접시 접합특성에 미치는 툴 속도의 영향
신형섭,정윤철,최광,Shin, Hyung-Seop,Jung, Yoon-Chul,Choi, Kwang 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.2
In this study, the friction stir spot welding (FSSW) of Mg alloy sheets has been tried using an apparatus devised with a CNC milling machine to give the precise control of joining condition including tool speed. The probe tool used is made of hard metal and composed of cylindrical shoulder and pin parts. The variation of morphologies formed after the friction stir spot welding depending on the plunge speed of the tool were investigated at each rpm of tool. The history of the temperature distribution and the vertical load induced during the spot welding with friction time were measured by using an Infrared Thermal Imager (THERMA CAMTM SC2000) and a loadcell located below the specimen fixture, respectively. Tensile-shear tests were also performed to evaluate the fracture load of welded specimens. In order to characterize the friction stir spot welding of Mg alloy sheets, the variation of the fracture load was discussed on micrographic observations, temperature distribution during the FSSW according to the plunge speeds of tool.
벌크 비정질 금속의 마찰접합에 미치는 접합계면 온도의 영향
박정수(Jung-Soo Park),정윤철(Yoon-Chul Jung),신형섭(Hyung-Seop Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This study aims to investigate the how the temperature distribution at the joining interface influence on the weld characteristic of dissimilar friction welding of bulk metallic glasses(BMG) to crystalline metals. An infrared thermal imager (FLIR-ThermaCam SC-2000) was used to measure the temperature distribution at joining interface of the specimens during friction welding. Understanding the temperature distribution on the joining interface is important, because not only it determines whether the friction welding will be implemented successfully or not, but also it influences the residual stress, the crystallization of amorphous phase, and the eventually strength of the welds. A successful welding is achieved by using a friction welding apparatus which incorporates a pneumatic actuator and gripper to give a precise control of the friction time and pressure. The shape of the protrusion formed at the weld interface were examined. A Zr??Cu₄?Al₁? bulk metallic glasses and crystalline metals of Ti-alloys and Al-alloys were adopted as samples. In order to characterize the friction welded interface, the micrographic observation and the X-ray diffraction analysis on the weld cross-section were carried out. The obtained results were disussed based on the temperature distribution measured at the weld interface A successful joining of the bulk metallic glasses(BMG) to crystalline metals could be obtained for certain pairs of the material combination through the precise control of friction conditions. The residual strength after welding was evaluated by the four-point bending test and compared with the cases of friction welding to similar materials.
박성수(Sung Su Park),정윤철(Yoon Chul Jung),최준홍(Joon Hong Choi),신형섭(Hyung Seop Shin) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4
고 변형률속도하에서 고무기 재료의 변형거동의 이해는 방호체계나 장갑과 같은 충격에 잘 견딜 수 있어야 하는 분야에서 중요하게 여겨지고 있다. 본 연구의 목적은 테일러 충격시험 동안 고무기 재료들의 총체적인 변형거동을 조사하는 것이다. 테일러 충격시험은 20 ㎜ 에어건을 사용하여 충격속도 150~250 m/s의 범위에서 수행되었다. 8 채널의 고속영상장치는 충격시험 동안 고무기 재료 발사체의 변형거동을 일련의 사진으로 제시한다. 선택된 재료들에 따라 다양한 변형과 파괴거동을 보여주고 있다 게다가, 충격 동안 고속영상장치로부터 얻어진 사진을 바탕으로 변형된 발사체 형상을 영상데이터화 함으로써 동적 변형의 양적인 접근이 가능하게 되었다. 그리고, 고무기 재료들의 동적 강도에 대한 첨가제의 영향 또한 조사하였다. The understanding of the deformation behavior of rubber materials under high loading-rate conditions will be important considering in their impact-resistant applications such as protective shields and transparent armor. The objective of this work is to investigate the overall deformation behavior of rubber materials during Taylor impact test. Taylor impact tests of rubber materials were carried out in the velocity range between 150~250 m/s using the 20 ㎜ air gun. A 8-ch High-speed photography system provided a series of images representing the deformation behavior of rubber projectile during impact. Depending on materials adopted, they showed a variety in deformation and fracture behaviors. Additionally, the quantitative approach of dynamic deformation analysis through digitizing the deformed shape of projectile using high-speed photographs taken during impact was tried. The influence of additive filler on the dynamic strength of rubber materials will be also examined.
슬리브드 폴리머 발사체의 충격시 벌징 거동 패턴에 미치는 코어 재료의 영향
박성택(Sung-Taek Park),정윤철(Yoon-Chul Jung),신형섭(Hyung-Seop Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In the present study, the deformation behavior of both of metal and polymer combination on impact was investigated. They have showed a different deformation behavior when the co-axially combined projectile was impacted on rigid target. The theory according to Taylor's simplified approach assumes an ideally rigid-plastic material model exhibiting rate-independent behavior and simple one-dimensional wave propagation concepts that neglect radial inertia. In the case of impact with polymeric materials, elastic strain in general are not negligible compared with plastic strain; and the rigid-plastic material behavior assumed by Taylor for metallic materials cannot be applied any more. Since, the sleeve and the core materials have widely different mechanical properties, they will produce a significant difference of mechanical impedance with each other. Therefore these impedance mismatch influences on the deformation behavior sleeved polymer projectile on impact. As a result, sleeved projectiles will generate a very interesting impact behavior. Therefore, the according to sleeved metal material and core polymer material can see expected. The objective of this study was to investigate the factors which influences on deformation behavior pattern of sleeve materials surface.
Jin-Rok Kim(김진록),Sung-Ho Yoon(윤성호),Yun-Chul Jung(정윤철),Chang-Hee Suh(서창희),Tae-Ha Kwon(권태하) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.7
In order to improve fatigue life of transmission gear carburizing is normally used. Carburizing is a very good process to achieve low cost and high performance. The machined gears are heated up to carburizing temperature and then cooled rapidly in an oil bath to produce high surface hardness. The gears may undergo excessive thermal distortion during heating and rapid cooling. In order to predict the distortion during heating and rapid cooling, a coupled thermo-mechanical simulation is needed. In the current research, the simulation of heating and cooling was performed. The results show that the thermal distortion and the residual stresses are well predicted by the coupled simulation. In addition, induction heating and rapid cooling simulation is carried out to predict the thermal distortion. The amount of distortion is compared. It is shown that induction heating is very effective to reduce thermal distortion.
신형섭(Hyung-Seop Shin),박정수(Jung-Soo Park),정윤철(Yoon-Chul Jung) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.7
The friction welding of Zr-based bulk metallic glass (BMG) rods and tubes to similar BMGs, and to crystalline metals were performed. An infrared thermal imager (FLIR-Thermal Cam SC-2000) was used to measure the temperature distribution at joining interface of the specimens during friction welding. All BMGs adopted in this study showed a successful friction joining to similar BMG. The shape of the protrusion formed at the weld interface were examined. In order to characterize the friction weld interface, the micrographic observation and the X-ray diffraction analysis on the weld cross-section were carried out. The obtained results were discussed based on the temperature distribution measured at the weld interface A successful joining of the BMGs to crystalline metals could be obtained for certain pairs of the material combination through the precise control of the friction condition. The residual strength after dissimilar friction welding of BMG was evaluated by the four-point bending test and compared with the cases of friction welding to similar materials.