• 제목/요약/키워드: Two Spot Welding

검색결과 83건 처리시간 0.025초

Al합금 펄스 Nd:YAG 레이저 점 용접부의 균열 발생기구 (Mechanism of Crack Formation in Pulse Nd YAG Laser Spot Welding of Al Alloys)

  • 하용수;조창현;강정윤;김종도;박화순
    • Journal of Welding and Joining
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    • 제18권2호
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    • pp.213-213
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    • 2000
  • This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7NO1 spot-welded by pulse Nd: YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed: center line crack($C_{C}$), diagonal crack($C_{D}$), and U shape crack($C_{U}$). Also, HAZ crack($C_{H}$), was observed in the HAZ region, furthermore, mixing crack($C_{M}$), consisting of diagonal crack and HAZ crack was observed.White film was formed at the hot crack region in the fractured surface after it was immersed to 10%NaOH water. In the case of A5083 alloy, white films in C crack and $C_D crack region were composed of low melting phases, Fe₂Si$Al_8$ and eutectic phases, Mg₂Al₃ and Mg₂Si. Such films observed near HAZ crack were also consist of eutectic Mg₂Al₃. In the case of A7N01 alloy, eutectic phases of CuAl₂, $Mg_{32}$ (Al,Zn) ₃, MgZn₂, Al₂CuMg and Mg₂Si were observed in the whitely etched films near $C_{C}$ crack and $C_{D}$ crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Si in the case of A7N01 aooly, respectively.The $C_{D}$ and $C_{C}$ cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of $C_{M}$ crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The $C_{U}$ crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification. (Received October 7, 1999)

하이브리드 방식 (CNC+Laser)을 이용한 폴리머용접공정 (Hybrid (CNC+Laser) process for polymer welding)

  • 유종기;이춘우;김순동;최해운;신현명
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2009년 추계학술발표대회
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    • pp.4-4
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    • 2009
  • Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) was welded through a combination of a diode laser and CNC. Laser beam passed the transparent PC and was absorbed in an opaque ABS. Polymers were melted and welded by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead size and the specimen cross-section were analyzed, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was 3.75mm and the shear strength was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in CNC machining processes, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision. By combining two operations processes developed process gained 50% more efficiency.

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폴리머의 레이저 투과접합 시 접합부의 기계적 성질에 관한 연구 (A Study on the Mechanical Properties of Joints in Laser Transmission Joining of Polymers)

  • 차상우;김진범;윤석환;나석주
    • Journal of Welding and Joining
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    • 제25권2호
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    • pp.43-48
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    • 2007
  • Laser Transmission Joining (LTJ) of plastics is a process in which light of suitable wavelength is transmitted through a transparent substrate that is in contact with an absorbing one. In this paper, LTJ is investigated by preliminary experiments from the viewpoint of mechanical engineering. To understand transmitting characteristics of each polymer substrate, transmission rate, reflection rate and absorption coefficient of polymer are measured by using a laser power-meter. Characteristics of joining in the spot welding and seam welding are investigated by measuring the fracture load. Fracture load increases in accordance to the laser power and irradiation time. However, when the laser power is over 60W and irradiation time over 4seconds, fracture load decreases. This phenomenon is probably due to heat-softening of materials. Besides, cavities are generated at a joint by evaporation of water molecules, which can be suppressed by introduction of a gap between two substrates.

FATIGUE STRENGTH OF FILLET WELDED STEEL STRUCTURE UNDER OUT-OF-PLANE BENDING LOAD

  • Kang, Sung-Won;Kim, Wha-Soo;Paik, Young-Min
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.113-120
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    • 2002
  • The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

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Periprosthetic Acetabular Fracture after Total Hip Arthroplasty: A Report on Two Cases

  • Joonkyoo Kang;Chan Young Lee;Taek-Rim Yoon;Kyung-Soon Park
    • Hip & pelvis
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    • 제36권2호
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    • pp.155-160
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    • 2024
  • We report two cases of postoperative total hip arthroplasty periprostehtic fracture of the acetabulum which treated by open reduction with internal fixation without acetabular cup revision. From these cases, we should consider open reduction with internal fixation as the first treatment option in cases where spot welding of the cup to the host bone is observed.

잔류응력을 고려한 피로수명평가법의 적용성 검토(I) - 다양한 용접연결부에 대한 적용 - (Application of Fatigue Life Assessment considering Residual Stresses for Various Welded Details)

  • 한정우;이탁기;한승호;김재훈
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2002년도 춘계학술대회 논문집
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    • pp.125-129
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    • 2002
  • Authors had developed the model for the fatigue life assessment of welded details considering residual stress and its relaxation. The model consists of three ingredients; a hot-spot stress approach, a residual stress relaxation, and an equivalent stress. The equivalent stress is induced by stress ranges and the ratios between the applied mean stresses and the ultimate stress of material. Once being tuned with two specific fatigue tests by using load carrying cruciform joint, this model can be applied to many kinds of welded details which structural stress concentration factors are different from each other. This paper reports the application of the proposed model for various welded details including cover plate, longitudinal stiffener, gusset and side attachment. From the investigation of predicted results by using the proposed model it was shown that the ambiguous fatigue characteristics of the various details influenced widely by the welding residual stress are clarified, and also the model could be applied to assess fatigue life of general welded structures.

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접착-성형 공정의 개선을 통한 중첩된 박판간의 결합 (Improvement of Form-joining Process with the Aid of Adhesive for Joining of a Sheet Metal Pair)

  • 정창균;김태정;양동열
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 추계학술대회논문집
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    • pp.121-124
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    • 2003
  • A new form-joining process with the aid of an adhesive is proposed in which an epoxy adhesive is applied to a sheet metal pair, and before it cures the pair is clinched to cause the geometric constraint in the form of a protrusion. In order to reduce the forming load and the height of protrusions, a new die and punch set with a very small clearance was devised to reduce the depth of drawing and the forming load. Taguchi method was employed to find the optimal values of design parameters. To implement each case of the orthogonal array, the finite element method was used. The experiments showed that on the tensile-shear test, the bonding strength of the new form-joining process with an epoxy adhesive is approximately the same as that of the resistance spot welding; and in comparison with the other two form-joining processes with an epoxy adhesive, the height of protrusions was reduced by more than 65 percent and the forming load by 50 percent.

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高張力 鋼板과 亞鉛鍍金 鋼板間의 疲勞特性 II (Fatugue Chacrateristics of Spot Welding between High Strength Steel and Galvanized Steel Sheet (II))

  • 서창민;강성수
    • 대한기계학회논문집
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    • 제13권2호
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    • pp.229-235
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    • 1989
  • 본 연구에서는 편면도금 강판과 복합조직 고장력 강판간의 이종 용접재의 피로거동을 연구하고져 한다. 즉 유한요소법으로 응력분포를 조사하고 그 결과와 피로균열발생 위치를 비교 검토해 보고자 한다.

SM 45C강의 레이저 표면경화처리에 관한 연구 (A study on the laser surface hardening of SM 45C steel)

  • 나석주;김성도;이건이;김태균
    • 대한기계학회논문집
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    • 제11권1호
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    • pp.53-62
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    • 1987
  • 본 논문에서는 1 KW CW CO$_{2}$레이저 발생자장치를 사용하여 표면경화 처리 를 행할때 공정과 관련된 변수들이 용접부 및 표면경화층에 미치는 영향들을 이론과 실험을 통해서 규명하고, 이 결과들을 실제공정에 사용할 수 있는 기초자료로서 제시 하고자 한다. 이를 위해서 해석에 사용될 수 있는 유한요소법(Finite Element Meth- od)에 근거한 2차원 열유동 해석용 프로그램 및 데이타 처리 프로그램을 개발하고, 중 탄소강에 레이저 표면처리를 수행하여 실험 및 이론해석의 결과를 비교 검토하였다. 비교 검토하여 그 설정기준을 고찰하였다.

원격 CO2 레이저 용접이음에 대한 피로시험과 해석 (Fatigue Test of Remote CO2 Laser Welded Joints and Its Analysis)

  • 주석재;조군
    • 대한기계학회논문집A
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    • 제36권10호
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    • pp.1213-1219
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    • 2012
  • 원격 $CO_2$ 레이저는 렌즈와 거울을 사용하여 신속하게 레이저 빔을 편향시키므로 복잡한 패턴을 그리기 쉽다. 기존 점용접 시편과 원격 $CO_2$ 레이저 여러 가지 용접선 패턴 시편을 준비하여 정적인장시험과 동적피로시험을 수행하였다. 피로수명(피로파단까지 하중반복횟수)에 대한 피로강도(최대피로하중) 데이터를 얻었다. 수명 이백만 회일 때 피로강도는 대체로 정적 인장강도의 10%이었다. 그리고, 피로하중 수준에 따라 피로파괴형태가 달라지는 것을 발견하였다. 구조해석 결과 응력이 높은 부위와 피로균열 발생부위가 일치하는 것으로 확인되었다. 수명 이백만 회일 때 모든 용접선 패턴에 대하여 최대응력이 서로 비슷하여지는 것을 확인하였다.