No abstract

No abstract

This paper investigates numerically welding residual stress distributions of a tube with J-groove weld in control rod drive mechanisms of a pressurized nuclear reactor vessel. Parametric study is performed for the effect of the tube location, tube dimensions and material's yield strength. It is found that residual stresses increase with increasing the inclination angle of the tube, and the up-hill side is the most critical. For thicker tube, residual stresses decrease. For material's yield strength, both axial and hoop residual stresses tend to increase with increasing the yield strength of Alloy 600. Furthermore, axial stresses tend to increase with increasing yield strength of Alloys 82/182.

Recently, there have been the increase of ship size and the development of oil and gas in arctic region. These trends have led to the requirements such as high strength, good toughness at low temperature and good weldability for prevent of brittle fracture at service temperature. There has been the key issue of crack arrestability in large size structure such as container ship. In this report for the first time, crack arrest toughness of thick steel plate welds was evaluated by large scale ESSO test for estimate of brittle crack arrestability in thick steel plate. For large structures using thick steel plates, fracture toughness of welded joint is an important factor to obtain structural integrity. In general, there are two kinds of design concepts based on fracture toughness: crack initiation and crack arrest. So far, when steel structures such as buildings, bridges and ships were manufactured using thick steel plates (max. 80~100mm in thickness), they had to be designed in order to avoid crack initiation, especially in welded joint. However, crack arrest design has been considered as a second line of defense and applied to limited industries like pipelines and nuclear power plants. Although welded joint is the weakest part to brittle fracture, there are few results to investigate crack arrest toughness of welded joint. In this study, brittle crack arrest designs were developed for hatch side coaming of large container ships using arrest weld, hole, and insert technology.

This study evaluated the brittle Crack Arrest Temperature (CAT) through an isothermal crack arrest test. Generally, the embrittled zone is required in a CAT test. According to conventional studies, the test method consists of arresting a double tension–type brittle crack with an Electron Beam melt-run, which acts as a crack initiator and crack runway. However, conventional CAT test methods have disadvantages in that they need additional processes to create an embrittled zone with Electron Beam Welding (EBW). A Local Temperature Gradient (LTG) system is developed to overcome the limitations of the conventional EBW embrittlement CAT test method. LTG systems do not require additional EBW to develop a brittle zone to initiate a brittle crack. In a LTG system, the LTG method is proposed instead of EBW to create the embrittled zone. The LTG system is free of flaws. In EBW, it is impossible to perform accurate CAT tests because the presence of defects affects the brittle crack arrest. In this study, a new CAT test method is introduced to evaluate brittle CATs more easily. Furthermore, both test methods were compared for the same specimens to verify the validity of the test method.