PSI - Issue 60

Vivek Srivastava et al. / Procedia Structural Integrity 60 (2024) 233–244 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 11. Schematic of primary-crack growth region (blue-box) in CT specimen and its branching into multiple secondary cracks at increasing crack length and ∆K; these cracks in A - A’ cross -sections manifested as PSCs signature pattern observed in fractography of ICCP condition

3.3 Fatigue life analysis Fatigue life analysis was carried out further to quantify the beneficial effect of retarded CFCGR due to ICCP protection on the fatigue life behaviour of this steel. Under the damage-tolerant design philosophy, stable crack growth fatigue life of a structural component is governed by the Paris law (equation 1). Critical crack length (a C ) at the point of final failure is governed by K max_C and maximum allowable stress (σ max_allowable ) in the material (equation 2). Maximum allowable stress was considered as 8 0% of yield strength (σ max_allowable = 355 MPa). Fatigue life analysis was carried out by integrating Paris law and using experimentally derived material constants (Table 3). Fatigue lives were calculated in a typical situation, where a large plate of the shipbuilding steel consisting an initial edge crack of 1 mm was applied a fatigue stress range equal to 100 MPa (Fig. 12). Fatigue life analysis results for FC and ICCP conditions are presented in Table 4. From above analysis, the beneficial effect of ICCP protection was clearly evident as the ICCP-protected specimen exhibited 2.45 times higher fatigue life as compared to the unprotected FC specimen. = ∆ … Equation (1) = 2 ( max _ max _ ) 2 … Equation (2)

Fig. 12. Schematic loading configuration for fatigue life analysis

Table 4. Fatigue life analysis results