Part 1: Indexing Fracture Toughness Data: Results from the MPC Cooperative Test Program on the Use of Precracked Charpy Specimens for ---Determination

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 (PCCV) 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 E1921-97 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 E1921. The -100°C temperature is the optimum 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.

Part 2: Indexing Fracture Toughness Data: Fracture Data Analysis using ASTM Standards E1921-97 and E1921-02

The Japanese KIR Committee conducted a large-scale fracture toughness testing program for Japanese pressure vessel steels in 1997. Included in this program are a large number of crack initiation test data (KIC). In this project, the fracture toughness in the transition temperature region was evaluated on 24 pressure vessel steels. The test materials represented low, medium and high toughness heats of SA508, SA533 and weld metals long with a SA302B heat and two carbon steel heats. Static, dynamic and crack arrest toughness results were obtained on 1T compact fracture toughness specimens and in some cases on full thickness specimens. The objective of this study described in this paper is to analyze this database using ASTM Test Method for Determination of Reference Temperature, T₀, for Ferritic Steels in the Transition Range (E1921-97) and the proposed E1921-02.

This study showed that the proposed procedures for the determination of T₀ for data sets in which the test temperatures are distributed over the transition temperature region work well for both static dynamic fracture toughness results. This procedure also worked well for some of the crack arrest fracture toughness results. Some of the crack arrest results were close to or on the lower shelf and the procedure did not work as well. The distributed temperature procedure, which includes the lower shelf, was used for these results and it was found that this procedure worked well. This procedure appears to generate the same result as the procedure being proposed by the ASTM when there is sufficient data in the transition region.

Part 3: Indexing Fracture Toughness Data: Fracture Toughness Data Analysis using the Master Curve Method

The Japanese KIR Committee conducted a large scale fracture toughness testing program for Japanese pressure vessel steels. The fracture toughness data, which has been analyzed in this paper, was developed under the KIR Project. Previous publications of the results from this program concluded that this database is conservatively lower bounded by the existing ASME Boiler and Pressure Vessel Code KIR curve. An alternative KIR curve based on this database was incorporated into ASME Code by Code Case N-610. The objective of this paper is to analyze this database using a new technology in handling fracture toughness, generally referred to by the Master Curve method [ASTM E1921]. This large data analysis was performed to verify the applicability of the Master Curve method. This paper presents an application of the Master Curve method to twenty-four modern Japanese KIR data sets completed in 1993.

The results affirm that the reference temperature T₀ is the superior indexing parameter for fracture toughness of ferritic steels compared to the currently used RTNDT approach. The results also provide a valuable source for establishing the dynamic fracture toughness data trend.