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Failure Assessment Diagrams of Semi-Elliptical Surface Crack with Constraint Effect

구속상태를 고려한 반타원 표면균열의 파손평가선도

  • Published : 1999.11.01

Abstract

In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

Keywords

Semi-Elliptical Surface Crack;J-Integral;T-Stress;Line-Spring Finite Element;Constraint;Failure Assessment Diagram;Failure Assessment Curve

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