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감동혁(Dong-Hyuck Kam),김영민(Young-Min Kim),김철희(Cheolhee Kim) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.1
Recent developments of Laser metal 3D deposition with wire feeding are reviewed which provide an alternative to powder feeding method. The wire feeding direction, angle and position as well as laser power, wire feeding rate, and deposition speed are found to be key parameters to make quality deposition with high throughput. When compared with the powder feed, the wire feed shows higher material efficiency, higher deposition rate, and smoother surface. Large elongated columnar grains which have epitaxial growth across deposit layers are observed in deposit cross sections. The growth direction is parallel to the thermal gradient during the deposit process. Tensile properties are found to be dependent on the direction due to the anisotropic deposit property. A real-time feedback control is demonstrated to be effective to improve the deposition stability.
CFRP-Aluminum 이종소재의 Self-Piercing Rivet 접합
전남기(Nam-Ki Jeon),이세헌(Sehun Rhee),감동혁(Dong-Hyuck Kam) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.3
In response to the environmental regulations and market forces for fuel economy, automotive industry has continued trying to apply lightweight multi-materials for weight reduction. Carbon fiber reinforced plastics (CFRP) is one of the most attractive structural materials because of its high strength to weight ratio. CFRP-metal dissimilar joints are inevitable to realize a variety of CFRP-metal hybrid designs. However, conventional fusion joining methods for metals are not applicable to CFRP-metal dissimilar joints. In this study, considering the process productivity and the joint reliability, self-piercing rivet (SPR) is investigated to join CFRP and aluminum panels. The SPR joint quality such as head height, interlock, bottom thickness is considered to find an optimal combination of the processing parameters, which include rivet, die, and punch force. In the tensile lap shear test of CFRP-aluminum SPR joints, the first fracture load is found to be a better parameter for representing the joint quality over the max fracture load because of the discontinuous property of CFRP panel. The first fracture load achieved in this study is up to 4.4 kN for SPR lap joint with 1.8 mm thickness CFRP upper and 2.0 mm Al5083-O lower.
808 ㎚ 조명 레이저 및 광학 필터를 이용한 아크 용접 현상 고속촬영 기법
이태현(Tae Hyun Lee),오제훈(Je Hoon Oh),감동혁(Dong-Hyuck Kam) 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.5
In this study, high-speed photography was performed for Gas Metal Arc Welding using an 808 nm diode laser and an optical filter. A Neutral Density(ND) filter and an 808 bandpass filter were used to an excluded arc light. We observed that the applied ND filter succeeded in capturing the drop transfer, but the arc image could not be excluded. When considering the spectral distribution of the arc, the 808 nm diode laser is suitable for recording a high speed camera sensor. The Full Width Half Maximum (FWHM) 3 nm of 808 nm bandpass filter is suitable for removing the arc spectrum signal. By combining an 808 nm diode laser and an 808 nm bandpass filter, we obtained a clear image of the drop transfer without the arc light.
알루미늄 제진판재와 1.5 ㎬ HPF 강재 이종소재 기계적 체결 특성 평가
주진혁(Jin Hyeok Joo),조경환(Keong Hwan Cho),오제훈(Je Hoon Oh),감동혁(Dong Hyuck Kam) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.5
In this study, the mechanical properties of aluminum vibration damping sheet and 1.5 ㎬ HPF steel sheet (SABC1470) dissimilar joining were evaluated. Joint methods of self piercing rivet (SPR), bolt/nut, flow drill screw (FDS), and blind rivet were compared to evaluate joint characteristic. In SPR Joining, buckling failure was occurred in SPR rivet caused by the strength of the 1.5 ㎬ HPF steel. So that, SPR hybrid joining was selected with a Al5052 alloy additional plate in lower sheet for formability and pre-hole processed on 1.5 ㎬ HPF steel in upper sheet. Through optimized of SPR die, the tensile shear load of the SPR hybrid joining was measured 7.53 kN. In FDS joining, failure of fastener was occurred due to the high strength of the 1.5 ㎬ HPF steel. FDS joining was available after pre-hole process on the 1.5 ㎬ HPF steel. However, delamination of the aluminum damping plate was observed and the tensile shear load was measured 3.14 kN. In bolt/nut joining, tensile shear load was measured depending on process variable (combination of plate, washer and tightening torque) and maximum tensile load was measured 5.43 kN. In blind rivet joining, the maximum tensile shear load was measured 3.64 kN, when the Al vibration damping sheet was placed on the upper plate. The large area of the blind rivet head released the concentration of stress on Al vibration damping sheet. As a result, SPR hybrid joining is considerable method because pre-hole processing is minimized and tensile shear load is higher than the other method.
A study on the Corrosion Properties of a Dissimilar Self-Piercing Rivet with CFRP-Steel joints
Ji-Ung Kim(김지웅),Jin-Hee Bae(배진희),Chanyoung Jeong(정찬영),Dong-Hyuck Kam(감동혁),Cheolhee Kim(김철희),Yeong-Do Park(박영도) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
Self-Piercing Rivet (SPR) is able to joint several kinds of metal and non-metal supports together as new performing technology. The combined effect of joint configuration and environmental conditions could have detrimental effects both a corrosion and a mechanical behavior with dissimilar material SPR joints. The corrosion properties of a Self-Piercing Rivet joint of carbon fiber reinforced plastic (CFRP) laminate and galvannealed steel (590 MPa) joint by an Almac-coated rivet were investigated. The aiming of this experiment, dissimilar joints were exposed to salt-spray environmental conditions according to KS D 9502 standard that is a neutral salt-spray method for 60 days. Furthermore, it was conducted to both open-circuit potential test and potentio-dynamic test in 3.5 wt% NaCl solution. Meanwhile, the tests of tensile shear were carried out in order to evaluate the mechanical performances of the riveted joints during the salt spray exposition. The results show that the mechanical performance of the SPR joints progressively was decreased as function of increasing exposure time. The corrosion behavior was confirmed by the SEM/EDS analysis after the exposure of the joint in the chamber.
아크열원 DED 공법의 STS 316L 와이어송급 적층공정 및 기계적물성 평가
이태현(Tae Hyun Lee),강민정(Minjung Kang),오제훈(Je Hoon Oh),감동혁(Dong-Hyuck Kam) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.3
Additive manufacturing of novel metals has received much attention as an alternative to traditional subtractive manufacturing because of its high material efficiency (cost reduction in terms of material efficiency or the Buy-to-Fly ratio), shorter lead time and higher design flexibility (new design possibilities). When compared with the laser and powder additive manufacturing, the arc and wire additive manufacturing is known to have higher material efficiency, higher deposition rate, and cheaper investment and maintenance. Therefore, in this work, we used cold metal transfer (CMT) gas metal arc welding (GMAW) for arc and wire additive manufacturing of STS 316L and perform a parametric study. It was found that the cooling time for the interpass temperature to cool down to 350℃ is dependent on the number of the deposition layer and the travel speed. We also investigate the effect of the travel speed, the travel direction, the contact tip to work distance (CTWD) and number of the deposition layer on the characteristics of the deposited sample. The spatial inconsistencies of the tensile strength and the hardness are observed to increase as the travel speed is increased. Finally, we find that anisotropic metallurgical properties are observed throughout the deposited STS 316L.