A Local Damage Approach to Predict Crack Initiation in Type AISI 316L(N) Stainless Steel

Coupled FEM and experimental analysis to characterize initial crack growth regime in AISI 316L(N) stainless steel

“…The plain strain and plain stress 2D FEM analysis for crack blunting to predict the critical CTOD and load line displacement (LLD) for various a/W ratios and its experimental validation by means of stretch zone width (SZW) measurement have been discussed in detail by the Krishnan et al (2014). To carry out the FEM crack growth 391 Coupled FEM and experimental analysis analysis, the crack length (Δa) vs LLD data are required.…”

“…The presence of crack or notch produce high, locally concentrated strain and lead to formation ductile void which grow and link with neighboring voids and later coalesce with the crack or notch tip. Different microscopic crack initiation models based on critical stress, critical stress-modified critical strain along with size and spacing of void-nucleating sites have been used in literature for predicting crack initiation (Rice and Tracy, 1969;Rice and Johnson, 1970;McClintock, 1969;Krishnan et al, 2014). Different critical stress field based criteria adopted in the literature are, first, stress reaches the inherent strength (usually larger than ultimate tensile strength of the material) at a certain distance from the crack tip; and second, average stress along a certain distance (starting from the crack tip) reaches the inherent strength Madrazo et al (2013).…”

“…Elastic-plastic crack initiation parameters like initiation toughness (J i ), crack tip opening displacement (CTOD i ) are essential inputs for fracture analyses of crack or notch like stress raisers Matvienko 390 IJSI 6,3 (2013). The authors, in an earlier study, established a local damage approach based on critical strain (ε c ) at characteristics distance (l c ) as a criterion for crack initiation Krishnan et al (2014). Uniform strain from uniaxial tensile test as (ε u ) and 2× grain diameter as l c have been considered for FEM simulation of crack initiation parameters for 316L(N) SS material.…”

“…The FEM-based crack blunting analyses have been carried out as per earlier established procedure Krishnan et al (2014) and it has been vindicated by experimental results. Beyond initial blunting, CTOD/CTOA is evaluated using coupled experimental and FEM simulations and further, the established scheme has been applied for prediction of load-displacements response of the CT specimens with different a/W ratios.…”

“…Therefore, crack blunting is viewed as large deformation and simultaneous damage accumulation ahead of crack tip characterised with equivalent plastic strain. The more detailed theoretical overview and reasons for the above adopted crack initiation criterion have been discussed in Krishnan et al (2014).…”