Eq. (7) of ASTM E1820-21 allows calculating the maximum stress intensity factor, K_MAX, that may be applied during the second precracking step (at least the final 50 % of the fatigue precrack). In eq. (7), use is made of K_F, which depends on the result of the test. If the result of the test is either J_Q, J_Qc, or J_Qu, the corresponding K_F is calculated by the use of eq. (8). However, if the result of the test is K_Q (conditional value of K_Ic for a Linear-Elastic Plane-Strain fracture toughness test conducted according to ASTM E399), then K_F = K_Q.
The changes proposed here aim at distinguishing the case where K_F = K_Q (adding a reference to ASTM E399) from the instances where the test result is a value of J-integral, which needs to be converted to the corresponding value of K. This will also provide a definition of K_Q, which is currently unavailable in E1820 (Annex A5 on K_Ic determination was removed years ago).