Active Standard: E1921 - 13a
This ballot item adds additional quality assurance (QA) measures to help assure that the KJc values measured on each specimen are sufficiently accurate. The principal changes are to allow methods other than visual measurement to determine the starter crack length in the test, to move the requirement for the accuracy of the calculated crack length determined during the test from Section 8.6.3 to Section 8.6.2, and provide guidance to the user on what value of E to use in the calculated crack length. Additional guidance and requirements are provided for analyzing the post-test results in 8.8.2. There is then an additional accuracy check between the calculated crack length and the post-test measured crack length in 8.9.1 which is consistent with current requirements in E1820. Clarification on the value of E to use for the conversion of Jc to KJc is also provided. Additional reporting requirements are also proposed to implement these revisions. The following specific modifications to Sections 8.2, 8.6.2, 8.6.3, 8.7.4, 8.9.1, 9.5.1, and 11.1 are proposed to enact these additional QA requirements. In Section 8.2, it is proposed to allow the pre-test crack length to be estimated using techniques other than visual. In Section 8.6.2, it is proposed to move the repeatability check for the initial unloading/reloading sequence and the pretest crack length accuracy check from Section 8.6.3. Additionally, guidance for the value of E to use for the compliance expressions to perform this check is also provided in 8.6.3 as is criteria for adjusting the E value in order to accurately predict the precrack length. This guidance was copied directly from the surface crack testing standard (ASTM E2472) for consistency. Additionally, recommendations are provided for correcting the test setup if the accuracy and precision requirements are not met. Finally, the equation for Bn is proposed to be eliminated from this section. It is proposed to delete Section 8.7.4 because the proposed revisions in this ballot replace those requirements currently within this section. It is proposed to add a new Section 8.8.2 to require that the fatigue precrack for each test be estimated after the test. Unique values of E can be used for each test to accurately estimate the optically-measured fatigue crack length. Requirements for estimating the crack length within 5% using E values that differ by no more than 10% from the theoretical value are also provided. The requirement for estimating the crack length measurement post-test within 5% is also added to Section 8.9.1 for consistency. Finally, it is required that a single value of E be used at each test temperature for the Jc to KJc conversion in Section 9.5.1. Additional reporting requirements are added in Section 11.1 for the theoretical elastic modulus, E, value used to convert Jc to KJc at each test temperature and the individual values of E (Ei) and the associated calculated crack sizes for each test.
Negative Votes Need Resolution