Boundary element analysis of stress singularity in dissimilar metals by friction welding

정남용,C.-H. Park 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.9

Friction-welded dissimilar metals are widely applied in automobiles, rolling stocks, machine tools, and various engineering fields. Dissimilar metals have several advantages over homogeneous metals, including high strength, material property, fatigue endurance, impact absorption, high reliability, and vibration reduction. Due to the increased use of these metals, understanding their behavior under stress conditions is necessary, especially the analysis of stress singularity on the interface of friction-welded dissimilar metals. To establish a strength evaluation method and a fracture criterion, it is necessary to analyze stress singularity on the interface of dissimilar metals with welded flashes by friction welding under various loads and temperature conditions. In this paper, a method analyzing stress singularity for the specimens with and without flashes set in friction-welded dissimilar metals is introduced using the boundary element method. The stress singularity index (λ ) and the stress singularity factor ( Γ ) at the interface edge are computed from the stress analysis results. The shape and flash thickness, interface length, residual stress, and load are considered in the computation. Based on these results, the variations of interface length (c) and the ratio of flash thickness (2 1t t ) greatly influence the stress singularity factors at the interface edge of friction-welded dissimilar metals. The stress singularity factors will be a useful fracture parameter that considers stress singularity on the interface of dissimilar metals.

A Review on Welding of Dissimilar Metals in Car Body Manufacturing

Md. Abdul Karim,Yeong-Do Park 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.1

This paper presents a comprehensive study of the metallurgical challenges of welding dissimilar metals. It also describes the important factors in dissimilar welding which need to be considered for automotive applications. It further investigates effective approaches to overcome these present challenges. Steels, aluminum alloys, and magnesium alloys are widely used metals in car bodies. However, it is difficult to weld these dissimilar metals and achieve good joint quality, due to their inherent disparate properties. The formation of brittle, crack sensitive and corrosion susceptible intermetallic phases is the main obstacle to dissimilar weld quality. Various approaches have been attempted by many researchers to enhance the performance of dissimilar welds. The most notable efforts include the application of interlayers, cover plate, least heat input, a combination of welding and mechanical joining, and alloying elements of filler metals. Based on considerations of joint performance, production cost and time, present industry infrastructure, and so on, the most effective and feasible approaches were identified which required the least amount of heat input, and the appropriate filler metal alloying elements.

스테인리스강 STS 316L과 탄소강 A516-70의 이종금속 GTA 용접부 특성에 대한 연구

김세철(Se Cheol Kim),신태우(Tae Woo Shin),문인준(In Joon Moon),장복수(Bok Su Jang),고진현(Jin Hyun Koh) 대한용접·접합학회 2015 대한용접·접합학회지 Vol.33 No.4

Characteristics of dissimilar metal welds between STS 316L and carbon steel ASTM A516 Gr.70 made with GTAW have been evaluated in terms of microstructure, ferrite content, chemical analysis, hardness and corrosion resistance. Three heat inputs of 9.00, 11.25, 13.00kJ/cm were employed to make joints of dissimilar metals with ER309 wire. Based on microstructural examination, the amount of vermicular type of δ-ferrite was increased with increasing heat input due to the increase of Creq /Nieq in the second layer of welds. Based on the EDX analysis of weld metals, Cr and Ni content in the 2nd layer increased while those content in the first layer of welds decreased with heat inputs. Cellular solidification mode in the 1st layer and dendritic solidification mode in the 2nd layer due to different cooling rates were prevailed, respectively. Heat affected zone which formed hard microstructure showed higher hardness than the weld metal. The salt spray test of dissimilar metals weld joints showed that the carbon steel surfaces only corroded. The weight loss rate due to corrosion increased up to 100hours but it decreased above 100 hours. There was little difference in the weight loss caused by corrosion regardless of heat inputs.

이종 금속의 아크 스폿 용접성 및 접합부 형상 예측에 관한 연구

김기순,장경복,강성수 대한용접접합학회 2000 대한용접·접합학회지 Vol.18 No.2

In this study, the lap welding between austenitic stainless steel and carbon steel was carried out using arc spot welding process and weldability of welded specimens was estimated. From the tensile-shear strength test, micro Vickers harness test, and microstructure observation, specimen of $psi6.5mm$(hole of upper plate) showed the best results in terms of tensile-shear strength and nugget shape. And there was an unmix zone in fusion boundary between the carbon steel base metal and bulk weld metal. This zone had very width with the hard microstructure. The shape of weld nugget in arc spot welding of dissimilar metal melds was predicted by searching thermal history of a weld joint through a three-dimensional finite element model. From the numerical analysis, predicted the shape of weld nugget showed good agreement with the experiment.

Laser Joining of Ti3Al-Based Alloy to Ni-Based Superalloy using a Titanium Interlayer

Xiao-Long Cai,Da-Qian Sun,Hong-Mei Li,Hong-Ling Guo,Yan Zhang,Ying-ying Che 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.8

Joining Ti3Al-based alloy to Ni-based superalloy is of great interest for applications in the aerospace fields. Direct welding of these two materials was very difficult and the joint usually fractured during laser welding which cannot form an effective welding joint. In this work, a pure titanium interlayer with a thickness of 0.4 mm was used between the base metals. The results indicated that the addition of titanium interlayer has a great effect on the joint performance. No macrocracks were found through the whole joint. The average room-temperature tensile strength of the joint with titanium was 177 MPa which still much lower than the two base metals. The weak link of the dissimilar joint was the Ti3Al/weld interface. The presence of Ti2Ni, α2-Ti3Al and AlNi2Ti brittle intermetallic compounds in the Ti3Al/weld interface deteriorated the joint properties.

Influence on properties of base metal after elimination of lifting-lug member in a dissimilar welding between steel base and steel lifting lug

Park, Jeongung,An, Gyubaek,Lee, Haewoo The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.2

The increasing demands of lifting lugs can be attributed to the rapid advancement of shipbuilding and offshore-structure production technologies and an exponential increase in the size of the block units of ship structures. Therefore, to ensure safety during the transportation and turnover of large blocks, it is important to determine the structural integrity and position of lifting lugs. However, because the manufacturing cost and availability of lugs are important considerations, low cost and easily obtainable steel compositions of grades different from those of the blocks are often used as alternatives. The purpose of this study is to investigate the effect of a lifting-lug metal on the physical properties of a base metal in a dissimilar welding between the base metal and lifting lug. The effect was evaluated by observing the metal microstructures and determining the hardness and dilution values on the cross-sectional surface of the lifting lug. According to the results of the metal microstructures, impact, hardness, and emission spectrochemical analysis at the surface from where the lug was removed confirmed that the chemical composition of the lifting-lug metal did not influence the physical properties of the base metal.

Al/Fe 이종금속 접합부의 부식특성

강민정,김철희,김준기,김동철,김종훈,Kang, Minjung,Kim, Cheolhee,Kim, Junki,Kim, Dongcheol,Kim, Jonghoon 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.4

The use of light-weight Al alloys in the automotive industry is increasing to meet requirements for fuel efficiency and emission reduction. Joining Al alloy to the conventional steel sheet is also very important issue with the increased use of Al alloy, and several joining processes have been introduced to enhance joining strength between dissimilar metals. This paper deals with a galvanic corrosion in the dissimilar metal joining. Salt spray tests up to 2000 hours were conducted on a self-piercing rivet, spot welded, adhesive bonded and weld-bonded joints, and cross-sections and tensile shear strength according the salt spray duration were analyzed at every 500-hour. Self-piercing rivet joint had relative low initial strength but the joint strength did not change regardless of the salt spray duration. The strength of other joints (spot welded, adhesive bonded and weld-bonded joints) decreased with the increase of salt spray duration and the corrosion behaviour of each joint was discussed.

Influence on properties of base metal after elimination of lifting-lug member in a dissimilar welding between steel base and steel lifting lug

Jeong-ung Park,Gyubaek An,Hae Woo Lee 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.2

The increasing demands of lifting lugs can be attributed to the rapid advancement of shipbuilding and offshore-structure production technologies and an exponential increase in the size of the block units of ship structures. Therefore, to ensure safety during the transportation and turnover of large blocks, it is important to determine the structural integrity and position of lifting lugs. However, because the manufacturing cost and availability of lugs are important considerations, low cost and easily obtainable steel compositions of grades different from those of the blocks are often used as alternatives. The purpose of this study is to investigate the effect of a lifting-lug metal on the physical properties of a base metal in a dissimilar welding between the base metal and lifting lug. The effect was evaluated by observing the metal microstructures and determining the hardness and dilution values on the crosssectional surface of the lifting lug. According to the results of the metal microstructures, impact, hardness, and emission spectrochemical analysis at the surface from where the lug was removed confirmed that the chemical composition of the lifting-lug metal did not influence the physical properties of the base metal.

다중주물을 활용한 주얼리 제작에 관한 연구

이정수,김형성,Lee, Jung Soo,Kim, Hyeong Seong 한국결정성장학회 2012 한국결정성장학회지 Vol.22 No.5

이종(異種)금속을 접합 가공하는 모꾸메가네기법, 상감기법 등의 기존 제작 방식은 주얼리 대량생산에 있어 표현 및 제작 상 많은 제한이 따른다. 이를 극복하기 위하여 기존의 정밀주조기법과 CAD/CAM방식을 융합한 다중(多重)주물 제작기법을 제시하였다. 주얼리 원본제작에 있어 CAD/CAM을 활용하여 2차 원본은 1차 원본보다 5 % 작게 제작하였다. 1차 황동 주조물에 2차로 은을 주조하여 실험하였으며, 2차 주조 시 통상적 주조의 플라스크 온도 보다 약 $150{\sim}200^{\circ}C$ 높게 주조하였다. 다중주물 방식을 통하여 대량생산이 가능한 이종(異種)금속의 주얼리를 손쉽게 제작할 수 있었다. There are many restrictions in conventional ways of Jewelry mass production which are Mokume Gane, Inlaid Technology based on a joining work of dissimilar metals. To overcome this, Multi-Casting using both Jewelry-Casting and CAD/CAM has presented. In experiment on Muti-Casting, second original sample which was produced by CAD/CAM is 5 % smaller than first one. The first and second castings are brass and silver, respectively. When making second sample, the temperature of flask was about $150{\sim}200^{\circ}C$ higher than the standard temperature of flask when making castings. Through the Multi-Casting, it was found that there was no trouble making dissimilar metals Jewelry which can be mass produced.

Tensile and impact toughness properties of various regions of dissimilar joints of nuclear grade steels

K. Karthick,S. Malarvizhi,V. Balasubramanian,S.A. Krishnan,G. Sasikala,Shaju K. Albert 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.1

Modified 9Cr-1Mo ferritic steel is a preferred material for steam generators in nuclear power plants fortheir creep strength and good corrosion resistance. Austenitic stainless steels, such as type 316LN, areused in the high temperature segments such as reactor pressure vessels and primary piping systems. So,the dissimilar joints between these materials are inevitable. In this investigation, dissimilar joints werefabricated by the Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. Thenotch tensile properties and Charpy V-notch impact toughness properties of various regions of dissimilarmetal weld joints (DMWJs) were evaluated as per the standards. The microhardness distribution acrossthe DMWJs was recorded. Microstructural features of different regions were characterized by optical andscanning electron microscopy. Inhomogeneous notch tensile properties were observed across theDMWJs. Impact toughness values of various regions of the DMWJs were slightly higher than the prescribedvalue. Formation of a carbon-enriched hard zone at the interface between the ferritic steel andthe buttering material enhanced the notch tensile properties of the heat-affected-zone (HAZ) of P91. Thecomplex microstructure developed at the interfaces of the DMWJs was the reason for inhomogeneousmechanical properties