Fracture toughness determination of P91 steel according to ASTM E1820 and ISO 12135

Purpose: This paper attempts to discuss the problems associated with the determination of fracture toughness values for P91 steels according to the tests standards ASTM E1820 and ISO 12135. Design/methodology/approach: The most applied standards for fracture toughness values determination in the ductile region are ASTM E1820 and ISO 12135. Both standards are intended to determine fracture toughness values in the ductile region. However, there are remarkable differences which leads to different values of obtained fracture toughness parameters such as JIC or CTOD. Findings: Within this work the P91 steel was characterized by fracture mechanics and fracture toughness parameters according to the test standards ASTM E1820 and ISO 12135 were determined. It was shown that despite of the fact that both test standards are designed to provide engineering fracture toughness for ductile crack initiation the evaluated fracture toughness values differ strongly depending to the applied standard. Research limitations/implications: For establishing ultimate load limitations and assessing the integrity for a large number of engineering structures of multifarious types a fracture mechanic has attained a great attention. Originality/value: Fracture toughness is one of the most important mechanical properties.