Issue 49

R. Suresh Kumar et alii, Frattura ed Integrità Strutturale, 49 (2019) 526-535; DOI: 10.3221/IGF-ESIS.49.49 529 Pipe bend data The data from literature includes the experimental study on FCG behaviour of a full-scale pipe bend of 219 mm outer diameter and thickness of 15.12 mm [5], made of carbon steel (SA333 Gr.6 grade) material. The schematic of the test pipe specimen is shown in Fig. 3. The cyclic test was carried out with a load ratio of 0.1, and other relevant data considered in the computational modelling of the FCG behaviour are presented in Tab. 2. The measured crack length as a function of the number of cycles is depicted in Fig. 4. Material Maximum Load F max (kN) Minimum Load F min (kN) a 0 (mm) 2C 0 (mm) SA350LF2 -150 -15 2.0 87.0 Table 2: Data used in modelling FCG in a pipe bend [5-6]. Figure 4: Benchmark data for pipe bend geometry [5] S TATIC ANALYSIS t the outset, static analysis has been carried out for both the plate as well as the pipe bend geometries, to check the correctness of the numerical model. These results are presented below: Plate specimen The plate geometry has been modelled using 3-Dimensional solid element along with the associated rigid loading connections for the application of the required bending moment. As already indicated that the maximum load of 22.5 kN is applied [4]. The mode-1 stress distribution under the application of the external load is shown in Fig.5. It is clear that the inner surface of the plate is under the maximum tensile stress (319 MPa), while the outer surface is under the maximum compressive stress (-290 MPa). Thus, for the FCG simulation, the crack is provided at the inner surface of the plate in the horizontal direction, as shown in Fig. 1. Pipe bend geometry The 219 mm outer diameter, 15.1 mm thick pipe bend with a radius of 219 mm is also modelled using 3-D solid element. The pipe bend is subjected to the maximum load of 150 kN [5]. Application of this force in the direction as indicated in Fig.6 with a moment arm of 485 mm, creates an in-plane bending moment in the pipe bend, which leads to a closing of the pipe bend, and thereby the pipe cross-section becomes oval. At this condition, the stress distribution responsible for the mode-I crack propagation is presented in Fig.6. It is clear that the preferred location and the orientation to insert the initial defect on the pipe bend is at the crown location along the longitudinal direction. A