Mixed mode I/II crack propagation in stainless steel 316L sheets by large plastic deformations: Prediction of critical load by combining LEFM with fictitious material concept

• Published in: Engineering fracture mechanics 2021-04, Vol.247, p.107657, Article 107657
• Main Authors: Torabi, A.R., Sadeghian, H., Ayatollahi, M.R.
• Format: Article
• Language: English
• Subjects: Bearing strength; Brittle materials; Crack propagation; Criteria; Deformation; Ductile fracture; Ductile-brittle transition; Elastic analysis; Elasticity; Elastoplasticity; Failure analysis; Fictitious material concept (FMC); Fracture limit curve; Fracture mechanics; Fracture testing; Linear elastic fracture mechanics; Linear elastic fracture mechanics (LEFM); Load carrying capacity; Metal sheets; Mixed mode loading; Propagation modes; Square plates; Stainless steel; Stainless steels; Strain hardening
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2021.107657

•Ductile crack growth instance is studied in 316L steel under mixed mode loading.•Original fracture experiments are conducted for various mode mixity ratios.•The Fictitious Material Concept (FMC) is employed to avoid elastoplastic analysis.•The critical loads are well estimated by coupling FMC with MTS and GMTS criteria.•The ductile failure regimes are moderate-scale yielding and large-scale yielding. In this research, the load carrying capacity (LCC) of O-notched diagonally loaded square plate (DLSP) samples with pre-existing cracks emanating from the notch edge is investigated theoretically and experimentally under mixed mode I/II loading. The specimens are made of the stainless steel 316L, which is highly ductile and has great strain-hardening. In order to determine the LCC experimentally, several fracture tests are performed on DLSP specimens. Experimental observations reveal that these specimens experience significant plastic deformations at the onset of crack propagation. For theoretical prediction of the experimental LCCs, the Fictitious Material Concept (FMC) is first employed. By utilizing FMC, the stainless steel 316L with highly ductile behavior and great strain-hardening can be replaced with a virtual brittle material having linear elastic behavior. Then, by coupling FMC with two well-known stress based brittle fracture criteria in the field of the linear elastic fracture mechanics (LEFM), the LCCs of the cracked DLSP samples are estimated. In fact, by using FMC, complex and time-consuming elastoplastic failure analysis can be avoided and by performing only linear elastic analysis, the LCC of ductile DLSP specimens can be estimated. It is shown that combination of FMC with the maximum tangential stress (MTS) and the generalized MTS (GMTS) criteria is quite successful in predicting the crack growth instance in ductile DLSP specimens.