• Title/Summary/Keyword: Fillet welding

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Investigation on Ultimate Strength of STS304L Stainless Steel Welded Connection with Base Metal Fracture Using Finite Element Analysis

  • Lee, HooChang;Kim, TaeSoo;Hwang, BoKyung;Cho, TaeJun
    • International journal of steel structures
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    • v.18 no.4
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    • pp.1139-1152
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    • 2018
  • Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

Evaluation of Buckling Load and Specified Compression Strength of Welded Built-up H-section Compression Members with Residual Stresses (잔류응력의 영향을 고려한 조립 H-형강 부재의 좌굴하중 및 설계압축강도 평가)

  • Lee, Soo-Keuon;Yang, Jae-Guen;Kang, Ji-Seok
    • Journal of Korean Society of Steel Construction
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    • v.29 no.1
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    • pp.81-88
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    • 2017
  • Residual stress is defined as stress that already exists on a structural member from the effects of welding and plastic deformation before the application of loading. Due to such residual stress, welded H-section compression members under centroidal compression load can undergo buckling and failure for strength values smaller than the predicted buckling load and specified compressive strength. Therefore, this study was carried out to evaluate the effect of residual stress from welding on the determination of the buckling load and specified compressive strength of the H-section compression member according to the column length variation. A three-dimensional nonlinear finite element analysis was performed for the H-section compression member where the welded joint was fillet welded by applying heat inputs of 3.1kJ/mm and 3.6kJ/mm using the SAW welding method.

Reflow Behavior and Board Level BGA Solder Joint Properties of Epoxy Curable No-clean SAC305 Solder Paste (에폭시 경화형 무세정 SAC305 솔더 페이스트의 리플로우 공정성과 보드레벨 BGA 솔더 접합부 특성)

  • Choi, Han;Lee, So-Jeong;Ko, Yong-Ho;Bang, Jung-Hwan;Kim, Jun-Ki
    • Journal of the Microelectronics and Packaging Society
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    • v.22 no.1
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    • pp.69-74
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    • 2015
  • With difficulties during the cleaning of reflow flux residues due to the decrease of the part size and interconnection pitch in the advanced electronic devices, the need for the no-clean solder paste is increasing. In this study, an epoxy curable solder paste was made with SAC305 solder powder and the curable flux of which the main ingredient is epoxy resin and its reflow solderability, flux residue corrosivity and solder joint mechanical properties was investigated with comparison to the commercial rosin type solder paste. The fillet shape of the cured product around the reflowed solder joint revealed that the curing reaction occurred following the fluxing reaction and solder joint formation. The copper plate solderability test result also revealed that the wettability of the epoxy curable solder paste was comparable to those of the commercial rosin type solder pastes. In the highly accelerated temperature and humidity test, the cured product residue of the curable solder paste showed no corrosion of copper plate. From FT-IR analysis, it was considered to be resulted from the formation of tight bond through epoxy curing reaction. Ball shear, ball pull and die shear tests revealed that the adhesive bonding was formed with the solder surface and the increase of die shear strength of about 15~40% was achieved. It was considered that the epoxy curable solder paste could contribute to the improvement of the package reliability as well as the removal of the flux residue cleaning process.

An Experimental Study on Block Shear Fracture of Base Metal in Ferritic Stainless Steel Welded Connection (페라이트계 스테인리스강 용접접합부의 모재 블록전단파단에 관한 실험적 연구)

  • Kim, Tae Soo
    • Journal of Korean Society of Steel Construction
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    • v.28 no.5
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    • pp.303-312
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    • 2016
  • Many researches on the application of stainless steels as structural steels have been performed thanks to their material properties such as superior ductility and corrosion resistance. Ferritic stainless steels(STS430) with little or no nickel have been used increasingly in building structure because it is inexpensive compared to austenitic stainless steels(STS304) with nickel, but provide performances similar to the austenitic stainless steel. This paper deals with block shear fracture behavior of base metal in stainless steel welded connection. Although the block shear fracture behavior for welded connection due to stress triaxiality is different from that of bolted connection, the block shear strength of welded connection in current design specifications has been predicted based on that of bolted connection. The main parameters are weld length and welding process(Arc and TIG welds). The ultimate strengths of TIG welded specimens were higher than those of arc welded specimens and current design predictions by AISC, EC3 etc. were compared with test strengths.

An Estimation of the Fatigue Behavior on the Cruciform Type Specimen by Variation of the Stress Ratio (응력비 변화에 따른 십자형 접합부의 피로거동 평가)

  • 김태봉;서상구;우상익
    • Journal of the Korean Society of Safety
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    • v.15 no.1
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    • pp.140-145
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    • 2000
  • This paper was composed with fatigue test of the cruciform specimens, as load carrying and non-load carrying type. It also has performed computational analyses for geometric condition of the fillet welding bead. As test results, the effect of stress ratio in the specimen was insignificant. Stress ranges were varied with R=0.1~0.2. The fatigue cracks that were found in the load carrying type specimens and most specimens welded with contact were developed at the end of welds. The fatigue strength of specimen that have fractured in maternal plate was found about ${\Delta}\sigma_c$=63.5MPa. It's about 24% less than that of the non-load carrying type specimens having about ${\Delta}\sigma_c$=83.8MPa. A category of the Fatigue design specifications which provide for cruciform details was defined grade C as a stress of the maternal member. And then, the fatigue strength to be transformed into the maternal stress was found about 78.27 MPa, it tends to be less than that of allowable fatigue strength.

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Initial Imperfection and Axial Strength of Struts with Octagonal Hollow Section fabricated from HR Plate (열연강판 팔각강관 버팀보의 초기편심과 축방향 압축강도)

  • Jo, Jae Byung
    • Journal of Korean Society of Steel Construction
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    • v.27 no.1
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    • pp.23-30
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    • 2015
  • Developed in this study were Octagonal-hollow-section(OHS) struts, whose compressive strengths against flexural and local buckling is higher than H-shape or rectangular-hollow-section(RHS) struts with the same unit weight. OHS members are also advantageous in handling and storing compared to circular hollow sections(CHS). OHS members were fabricated from HR Plates by cold forming and fillet welding. 5 numbers of 20m long OHS struts were assembled, each of which consist of two 9.6m long OHS member and two end connection elements made of cast iron. The compressive strength of the OHS strut was evaluated by comparing the test results, design codes and FEM analysis each other. Test results show that all of the struts have almost same or larger compressive strength than Korean Road Bridge Design Code(KRBDC) (2012). The initial imperfections can be estimated by using measured strains and are turned out to be less than L/450 for all the struts tested. The results of FEM analysis show that the variation of initial imperfection has less effects on the compressive strength for struts with vertical surcharge than for those with self-weight only, while the strength decreases as the initial imperfection increases. As the result of this study, the allowable initial imperfection for 20m long OHS struts is recommended to be less than L/350 on job sites.

Effects of Geometry of Reactor Pressure Vessel Upper Head Control Rod Drive Mechanism Penetration Nozzles on J-Groove Weld Residual Stress (원자로 상부헤드 제어봉구동장치 관통노즐 형상이 J-Groove 용접잔류응력에 미치는 영향)

  • Kim, Ju-Hee;Kim, Yun-Jae;Lee, Sung-Ho;Hur, Nam-Young;Bae, Hong-Yeol;Oh, Chang-Young;Kim, Ji-Soo;Park, Heung-Bae;Lee, Seung-Geon;Kim, Jong-Sung;Huh, Nam-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1337-1345
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    • 2011
  • In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor$r_o$/t, geometry of fillet, and adjacent nozzle.