Multiaxial fatigue assessment of steels with non-metallic inclusions by means of adapted critical plane criteria

• Published in: Theoretical and applied fracture mechanics 2020-08, Vol.108, p.102585, Article 102585
• Main Authors: Machado, Pedro Vinícius Sousa, Araújo, Lucas Carneiro, Soares, Marcos Venicius, Reis, Luis, Araújo, José Alexander
• Format: Article
• Language: English
• Subjects: 4140 steel; Crack initiation; Fatigue strength; Fracture surfaces; Metal fatigue; Multiaxial fatigue; Non-metallic inclusions; Nonmetallic inclusions; Out-of-phase loads; Small defects
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2020.102585

•Critical plane models adapted to estimate the fatigue strength of naturally defective materials.•New tests under in phase and out of phase combined loadings were generated using an AISI 4140 steel.•Statistic of extreme was considered to calibrate the fatigue material parameters;•Fracture’s surface analysis showed good agreement between seen crack orientation and estimated. The goal of this research is to investigate the detrimental effect of non-metallic inclusions on the fatigue strength of the AISI 4140 steel under multiaxial loading conditions. In order to do so, two multiaxial fatigue models based on the critical plane approach are coupled with Murakami’s √area parameter. The proposed adapted multiaxial criteria are proved simple to calibrate. Experiments under combined push-pull and torsional loading in and out-of-phase are conducted and compared with the estimates provided by the proposed adapted models. The adaptation is conservative with errors around 20%. An analysis of the fracture surfaces is carried out to compare the estimated crack initiation planes with the observed ones.