The Materials Properties Council (MPC) conducted a cooperative testing program with the objective of developing a set of data to be used in the evaluation of the use of the precracked Charpy specimen for the determination of T0. This paper reports on the results of this program.
A total of nine laboratories from four countries participated in the cooperative testing program. Each of the laboratories conducted experiments in accordance with the published version of ASTM Standard Test Method E 1921-97 in order to obtain the T0 values. T0 was determined from data obtained at three test temperatures, -120°C, -100°C and -75°C. These temperatures were chosen to test the requirements of E 1921. The -100°C temperature is theoptimum test temperature for this size specimen, while -75°C is a marginal test temperature because there would be a number of tests which would be invalid. The -120°C temperature is below the optimum test temperature and may require a large number of tests to obtain T0,or result in an invalid data set.
Over 250 fracture toughness tests were conducted on the specimens fabricated from the weld metal used in this program, with 60 or more tests at each test temperature. These results have been analyzed and the T0 temperature determined for each of the three primary test temperatures. The effect of number of specimens at the individual test temperatures has been determined. These results are compared with the T0 results for larger size specimens also available for the test material.