Discussion on determination of J-integral and comparison of different test standards

According to different fracture toughness test standard, J-Resistance curve tests were conducted at-5℃ in welded joints of X56 pipeline steel in the multiple specimen method and the test result were compared.According to the double P-V curves of each weld metal and heat affected zone specimen obtained from the two notch opening displacement the load-line displacement and the value of J were calculated. Finally, the best fited curve was determined the valid data points according to GB2038-91 and BS7448, respectively.The result indicates that BS7448 is superior to GB2038-91 on blunt line, exclusion lines and so on.J-Resistance curves and J_0.2 was obtained. But there are no valid data points according to GB2038-91 and no further calculation.