An alternative approach to the Battelle 'Screening Criterion' for pipes with through-wall cracks

The Battelle 'Screening Criterion' is described, it being a way of ascertaining the validity of the limit moment, Mlim* as a lower bound for the experimental maximum value of the bending moment of a pipe with a through-wall crack (for instance in a four-point bending experiment). Therefore meeting this criterion allows the conservative application of net-section-collapse analysis. The Battelle Screening Criterion is found to be more difficult to meet if the J-integral value at initiation, Ji, is low; if the pipe mean radius, R, is high (that was expected); but also if the crack angle, 2α, is low; this last aspect is believed to be questionable. J-Estimation schemes such as GE/EPRI or R6 may be used to derive alternative criteria. When applied to an elastic/perfectly plastic material, both these procedures lead to a new screening criterion which, while similar to the Battelle expression, exhibits an inverse dependence on α. Data used by Battelle to validate its criterion can equally justify the alternative expression. Moreover, the physical meaning of the new criterion is simple; it simply states that, in order for M at initiation to reach Mlim, J must not exceed Ji for a smaller value of the applied moment. Although this new criterion seems promising, additional validation studies ought to be conducted. (author)