Comparisons of creep constraint and fracture parameter C* of different types of surface cracks in pressurized pipes. (May 2019)

• Record Type: Journal Article
• Authors: Tan, X.M.; Wang, G.Z.; Tu, S.T.; Xuan, F.Z.
• Is Part Of: International journal of pressure vessels and piping. Volume 172(2019)
• Page Start: 360
• Page End: 372
• Publication Date: 2019-05
• Subjects: Creep constraint -- Fracture parameter C* -- Surface crack -- Pipe -- Finite element method; Pressure vessels -- Periodicals; Pipe -- Periodicals; Récipients sous pression -- Périodiques; Tuyaux -- Périodiques; Pipe; Pressure vessels; Periodicals; 681.76041
• DOI: 10.1016/j.ijpvp.2019.04.009
• Languages: English
• ISSNs: 0308-0161

Abstract

Abstract: The surface cracks in pressurized pipes include internal axial crack (IAC), internal circumferential crack (ICC), external axial crack (EAC) and external circumferential crack (ECC). The unified creep constraint parameter A c and fracture parameter C* for ICCs, EACs and ECCs have been calculated by three-dimensional finite element analyses. The A c solutions for ICCs with high aspect ratio (1.2 ≤ a/c ≤ 2) have been obtained, and the estimation method of A c for EACs and ECCs are given. The A c and C* of the four types of pipe cracks have been comparatively investigated. The results show that the four types of cracks have similar distributions of A c and C*, and the order of the constraint level and C* from high to low is IAC > EAC > ICC > ECC. Among all pipe cracks, the IACs and EACs with larger depth a / t and lower aspect ratio a/c have the highest constraint and C* levels, thus they are the most dangerous cracks. The ICCs and ECCs with smaller a / t and higher aspect ratio a/c have the lowest constraint and C* levels, hence they are relatively safer cracks. The IACs and EACs should be avoided as far as possible in manufacturing and service of high-temperature pipes. Highlights: Creep constraint A c and C* of different types of pipe cracks were comparatively investigated. The A c solutions for internal circumferential crack with high aspect ratio have been obtained. The estimation method of A c for external axial cracks and external circumferential crack are given. Axial cracks with larger depth and lower aspect ratio have the highest constraint and C* levels. Circumferential cracks with smaller depth and higher aspect ratio have the lowest constraint and C* levels.