Local stress in the vicinity of the propagating cleavage crack tip in ferritic steel

• Published in: Materials & design 2018-04, Vol.144, p.361-373
• Main Authors: Yanagimoto, Fuminori, Shibanuma, Kazuki, Suzuki, Katsuyuki, Matsumoto, Toshiyuki, Aihara, Shuji
• Format: Article
• Language: English
• Subjects: Cleavage fracture; Crack arrest; Local approach; Rapid crack propagation; Resistance to cleavage crack propagation; Steel
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2018.02.037

The objective of this research is to evaluate local tensile stresses in the vicinity of a propagating cleavage crack tip based on a combination of experiments and finite element analyses. Previous studies identified the local tensile stress as the most relevant factor in cleavage crack propagation and arrest behaviors in steels. However, there is no clear experimental evidence that the local tensile stress remains constant. This is because three dimensional effects are difficult to consider analytically and are thus ignored in the evaluation of local tensile stresses. Therefore, side-grooved specimens were employed to eliminate the three dimensional effect and make it possible to regard crack propagation as a two dimensional problem. Crack velocities were measured in isothermal experiments to determine local tensile stresses. Local tensile stresses were evaluated by finite element analyses for two steel samples at multiple temperatures and applied stress levels. The results show that the local tensile stresses were nearly constant for each steel. Thus, the local tensile stress can be considered the relevant material resistance property in cleavage crack propagation. This study yielded strong experimental evidence that the local fracture stress is well suited for use in describing cleavage crack propagation and arrest behavior in steels. [Display omitted] •Local stresses near a propagating cleavage cracktip in steel were investigated by using specimens to cancel 3D effects.•Local stresses were nearly constant, regardless of temperature, crack velocity, or crack length.•The results demonstrate the suitability of a local stress criterion for explaining crack propagation and arrest behaviors in steel.