In this paper the impact of recent changes in ASTM Test Method for JIc, a Measure of Fracture Toughness (E 813) are evaluated. JIc was determined from a large number of J-R curves using both the 1981 and the 1987 versions of ASTM E 813. The value of JIc is usually from 10 to 15% higher when measured according to the new version of the standard. The scatter in the measured JIc values was not affected by the revisions. Although the revisions to the standard removed a number of difficulties with its use, one problem still remains to be resolved. ASTM E 813 should be revised to include some guidance for correcting a0 so that the blunting line fits the data in the early portion of the J-R curve when a J-R curve from ASTM Test Method for Determining J-R Curves (E 1152-87) is used.
Fracture toughness testing of steels in the ductile-to-brittle transition region is complicated by a large amount of data scatter. There are many available methods of analyzing transition region toughness data with the objective of reducing the data scatter and arriving at a representative value for the lower bound toughness. Ten 1T and five 4T compact specimens of SA508 C12 pressure vessel steel given a special heat treatment were tested in the transition region, and the data were analyzed according to six of the available methods. Of three purely statistical methods, one based on a large collection of pressure vessel and rotor steel data is preferred. Of three analytical methods, one which subtracts the contributions of plasticity and crack growth from measured toughness is preferred.
Thermal-aged surveillance material was removed from two commercial reactor pressure vessels. The material from the first reactor vessel received a thermal exposure of approximately 103,000 hours at 282°C (540°F), while the material from the second reactor vessel received a thermal exposure of approximately 93,000 hours at 282°C (540°F). The surveillance material removed consisted of SA-508, Class 2 and SA-533, Grade B, Class 1, base metals; Mn-Mo-Ni/Linde 80 flux weld metals; and SA-533, Grade B, Class 1, correlation monitor material. Charpy V-notch impact specimens were fabricated from these materials and tested. In addition, selected thermal-aged specimens were annealed at 343°C (650°F) and 454°C (850°F) and impact tested. Unaged material was tested to establish baseline data for evaluating the thermal-aged material and thermal-aged/annealed material. Small variations in the impact properties were observed for all materials. Small increases in transition temperature were observed for the forging base metal and weld metal B surveillance materials, while the upper-shelf energies exhibited small decreases. The 454°C (850°F) anneal restored the upper-shelf energy for the forging base metal and weld metal B surveillance materials.
Fracture toughness testing of steels in the ductile-to-brittle transition region is complicated by a high degree of data scatter. Variations in the amount of ductile tearing prior to cleavage initiation often accompany the data scatter. Dynamic toughness testing is shown to be experimentally successful at reducing the incidence of prior ductile tearing. For the displacement rates tested, dynamic toughness values are at or above the lower-bound static toughness. Analysis of transition region toughness data using Weibull statistics, available energy analysis, and a constraint correction procedure is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.