Single Specimen Tests for <i>J</i>Ic Determination

A JIc test procedure using a single deeply cracked specimen is proposed. The crack extension is measured by partially unloading the specimen to determine the elastic compliance. JIc tests were made using ASTM A469 steel. Compact specimens from 1/2T to 5T were tested. No size effect was found. Results from two independent laboratories are presented and are in agreement. The errors due to simple formulation of JI calculation, periodic partial unloading, and simplified analysis for the extension of deep cracks in compact specimens are explored. The measurement point of crack extension for establishing JIc is discussed. The results indicate that a practical and effective single specimen test procedure has been developed.