Creep damage evaluation via uniaxial miniature testing for multiaxially stressed Mod.9Cr–1Mo steel components

• Published in: The International journal of pressure vessels and piping 2021-12, Vol.194, p.104518, Article 104518
• Main Authors: Matsubara, Naoki, Sakane, Masao, Itoh, Takamoto, Kosaka, Rui
• Format: Article
• Language: English
• Subjects: Biaxial stress; Creep; Cruciform specimen; Damage evaluation; Miniature specimen; Mod.9Cr–1Mo steel
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2021.104518

In this study, creep damage in a biaxially creep-damaged Mod.9Cr–1Mo component has been examined via uniaxial miniature creep testing. Using cruciform specimens, biaxial tension creep tests were conducted at principal stress ratios (λ) of λ=0.0 and 1.0 at 923 K. The principal stress ratio is the ratio of the y-directional principal stress (σy) to the x-directional principal stress (σx) in a cruciform specimen (λ=σy/σx). The equi-biaxial creep test was interrupted at a half lifetime, and two miniature specimens were machined from the damaged cruciform specimen in the x- and y-direction. The applicability of the linear cumulative creep damage rule was assessed using the results of the miniature lifetimes. The linear cumulative creep damage rule gave an unconservative estimate to the remaining life of a biaxially damaged cruciform specimen. Using the hyperbolic constitutive relationship, the unconservative estimate according to the damage accumulation was explained. •The conventional creep damage evaluation method using uniaxial miniature creep testing gave an unconservative estimate.•The unconservative estimate was analyzed bythe multiaxial creep deformation using a hyperbolic constitutive equation.•The degree of unconservativeness was larger with a hyperbolic constitutive relationship than that with a Norton one.