The current version of E1921 contains Annex A1, which covers the determination of the reference temperature at elevated loading rates (dK/dt ? 2 MPa?m/s), T0,X. Section A1.6, Precision and Bias, presents repeatability and reproducibility statistics calculated from the results of an interlaboratory study conducted for the determination of To,X from instrumented impact tests on precracked Charpy-type specimens (dK/dt ? 105 MPa?m/s). Currently, no information is available concerning the determination of To,X by means of rapid-load J-integral fracture toughness tests, conducted in accordance with Annex A14 of Test Method E1820-20b using universal testing machines.
Between 2019 and 2021, the University of Stuttgart, MPA (U. Mayer) and the Fraunhofer-Institute for Mechanics of Materials, IWM (J. Tlatlik) launched and coordinated an interlaboratory study (ASTM ILS #1547) on the determination of To,X at elevated loading rates, using three materials (a German reactor pressure vessel steel, base and weld, and a high strength steel) and two specimen types (C(T) and SE(B)). Six experienced laboratories participated in this exercise, producing test results at loading rates between 103 MPa?m/s and 104 MPa?m/s. The ILS results have been analyzed according to ASTM E691-18 (Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method) and an ASTM Research Report will be made available after this revision has been approved.
It is proposed to add a new part to Section A1.6, covering the repeatability and reproducibility statistics obtained from the analysis of ILS #1547. All the sub-sections of A1.6 will be appropriately renumbered.
The proposed added test is highlighted in yellow below. Note that this change was previously balloted, and received a negative vote that was deemed persuasive. The rationale of this negative vote was that the added section (A1.6.2) was too long, and should be condensed. In the version presented below, the contents have been considerably shortened, by collecting all precision information in a single table (TABLE A1.2) instead of multiple tables.
NOTE: users should be reminded that the specific values of repeatability and reproducibility statistics provided in Precision and Bias sections of ASTM Test Methods, are just indicative and only relevant to the specific conditions of the interlaboratory studies considered (materials, specimens, temperatures, etc.). They should not be used as intrinsic measures of precision for the test method under consideration.