Work Item
ASTM WK75167
Revision of E1820-20b Standard Test Method for Measurement of Fracture Toughness
Rationale
The current sections A9.6.6 and A11.6.6 of ASTM E1820 suggest the use of a relatively simple algorithm to iteratively solve a non-linear equation, which allows establishing the provisional values JQ and ?Q. Currently and many years, the required convergence/accuracy has been set at ±2 %, which could also be achieved by a graphical determination of the intersection. Nowadays, this level of convergence is totally obsolete, and very marginal effort is required to increase the accuracy to 0.1 %, or better. Using modern tools often embedded into various software packages, this level of accuracy is easily achieved and exceeded.
The modifications proposed here change the target convergence level from 2 % to 0.1 %, but also allow the user to use other numerical approaches should they wish to. Some examples (bisection method, false position (regula falsi), secant method, Newton method) are provided in a note. English unit equivalents are also provided in the equations. Finally, more consistency is now achieved between the structure of sections A9.6.6 (JQ determination) and A11.6.6 (?Q determination). Changes are indicated by Track Changes below.
This work item was already balloted four times between 2020-2022, and received several persuasive negatives. It has been edited based on technical discussions between the negative voters and the ASTM Technical Contact.
Work Item Status
Date Initiated: 12-11-2020
Technical Contact: Enrico Lucon
Item: 011
Ballot: E08 (21-02)
Status: Will Reballot Item
Item: 002
Ballot: E08 (21-01)
Status: Withdrawn From Balloting
Item: 001
Ballot: E08 (22-02)
Status: Will Reballot Item
Item: 022
Ballot: E08 (22-03)
Status: At Society Review