• Title/Summary/Keyword: Fatigue StrengthWelding Residual Stress

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A Study on Fatigue Crack Growth Parameters for Fatigue Life Assessment based on Fracture Mechanics (파괴역학 기반 피로 수명 평가를 위한 피로 균열 진전 파라미터에 관한 연구)

  • Kim, Hyeon-Su;Park, Tae-Jong;Lee, Dong-Ju;Shin, Sang-Beom;Kim, Myung-Hyun
    • Journal of Welding and Joining
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    • v.35 no.1
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    • pp.61-67
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    • 2017
  • Recent studies on the fatigue assessment of high strength steel weld based on the fracture mechanics have frequently raised the problems related to the conservatism in the fatigue crack growth rate specified in the relevant design code. The purpose of this study is to evaluate the effect of the fatigue crack growth parameter on the fatigue life for the low carbon steel weld. In order to do it, the fatigue tests with the constant stress ratio were performed to evaluate the fatigue crack growth rate in the butt weld of SM490. And the fatigue crack growth parameters of the weld were evaluated in accordance with ASTM E647. From the comparative fatigue assessment results, it was found that the fatigue crack growth rate specified in the relevant design code was too conservative to estimate the residual fatigue life of welded structure. So, in order to get the more reliable results, it was recommended that the fatigue life estimation based on the fracture mechanics be performed with the fatigue crack growth parameter specified by test.

A Study on the Mechanical Properties of Gas Pressure Welded Splices of Deformed Reinforcing Bar (가스압접 이형철근의 기계적 강도 특성 연구)

  • Jeon, Juntai
    • Journal of the Society of Disaster Information
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    • v.11 no.4
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    • pp.520-526
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    • 2015
  • Reinforcing bar splices are inevitable in reinforced concrete structure. In these days, there are three main types of splices used in reinforced concrete construction site - lapped splice, mechanical splice and welded splice. Low cost, practicality in construction site, less time consuming and high performance make gas pressure welding become a favorable splice method. However, reinforcing bar splice experiences thermal loading history during the welding procedure. This may lead to the presence of residual stress in the vicinity of the splice which affects the fatigue life of the reinforcing bar. Therefore, residual stress analysis and tensile test of the gas pressure welded splice are carried out in order to verify the load bearing capacity of the gas pressure welded splice. The reinforcing bar used in this work is SD400, which is manufactured in accordance with KS D 3504. The results show that the residual stresses in welded splice is relatively small, thus not affecting the performance of the reinforcing bar. Moreover, the strength of the gas pressure welded splice is high enough for the development of yielding in the bar. As such, the reinforcing bar with gas pressure welded splice has enough capacity to behave as continuous bar.

Evaluation of Mechanical Test Characteristics of Fillet Welding (필릿 용접의 기계적 시험 특성 평가)

  • Cho, Byung-Jun;Lee, Soung-Jun;Rhim, Jong-Guk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.2
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    • pp.535-541
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    • 2020
  • FCAW is used mainly in the welding of carbon steel and alloy steel because it can be welded in all positions and can obtain excellent quality at sites with variable working conditions. Recently, many studies in Korea have estimated the fatigue strength, residual stress, and deformation, and to develop a fillet welding process. On the other hand, there have been few studies of the mechanical properties based on the strength, macro and magnetic particle test results for fillet welding. This study shows the following results through fillet welding, macro testing and strength testing using SM490A (solid-structure rolled steel) for thick plates using SS400 (rolled steel) for the upper plate and FCAW. The hardness test, macro test and magnetic particle test were then conducted. The hardness tests showed that all result values were smaller than the KS B 0893 standard values of 350Hv. The macro-test showed that each type of welded part was in a normal organic state and that there were no internal errors, bubbles, or impurities on the front of the welded part. Therefore, there were no concerns about lamination. The magnetic particle examination showed no problems.