PSI - Issue 42

Diego F. Mora et al. / Procedia Structural Integrity 42 (2022) 224–235 Diego F. Mora et. al./ Structural Integrity Procedia 00 (2019) 000 – 000

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XFEM

eXtended Finite Element Method

2. Simulation of the crack propagation 2.1. Falsire mock-up The PTS specimen used in FALSIRE to examine the crack growth behavior is a cylinder with geometry defined by inner diameter 400 i mm  = , outer diameter 800 o mm  = and length 800 L mm = as shown in Fig. 1. The test cylinder contains a 360° circumferential flaw with crack depth to wall thickness ratio ( / a wt ) of 0.1.

Fig. 1. Mock-up geometry (a) Top view; (b) Cross section.

The loading condition of the test specimen in Merkert (Merkert 2002) is shown in Fig. 2. It was first loaded with an axial tensile load of 15 F MN = and an internal pressure of 5 p MPa = . The thermal shock cooling is applied by injecting cold water at 23°C by means of two high-pressure pumps. Uniformly distributed nozzles along the whole length of the cylinder injected evenly the water to cool down the inner cylinder surface. Thus, a uniform hoop stress in the cylinder is generated. It is assumed that at the initial thermal condition, the material is stress free.

Fig. 2. Loading conditions. Cross section of the cylinder indicating the initial and final temperatures of 250°C and 23°C, respectively

2.2. Materials The vessel was fabricated with 17 MoV 8 4 mod steel whose thermophysical properties are summarized in Table 1 (Stumpfrock and Taylor 1999).