Determination of fracture toughness of 2.25Cr1Mo0.25V steel based on acoustic emission technique

Abstract

The correct determination of fracture toughness is dependent on the accurate measurement of the point of crack initiation. In this research work, the AE technique is used to accurately detect the point of crack initiation and determine the initiation fracture toughness value JAE of 2.25Cr1Mo0.25V steel. Moreover, conventional standard procedures such as the J-R curve and stretch zone methods are also used to determine the fracture toughness JQ and JSZW values, respectively. Multiple AE parameters involving the entropy, peak amplitude, count, and energy are extracted from AE signals to identify the damage progression during fracture toughness tests. The results show several critical points associated with the point of plastic yielding, the onset of crack initiation, and the rapid crack growth and final fracture can be accurately identified by AE characteristics. Furthermore, the point of crack initiation recognized by AE is used to determine the JAE value. The fracture toughness JAE values of different specimens are also compared with the corresponding JQ and JSZW values. The JAE values are found to be about 20% lower than the JQ values but are significantly larger than the JSZW(2D) and JSZW(3D) values. It is believed that the fracture toughness parameter JAE determined by the AE technique can provide an important reference for evaluating the fracture toughness of engineering materials.