TOUGHNESS GIVEN BY ACCUMULATED WORK IN LEFM - POSSIBLE IMPLICATIONS FOR ELASTOPLASTIC J(R) RESISTANCE CURVES

J(R) vs. Delta a curves are often determined from the accumulated work U-acc operated on by an eta/Bb factor, and rising J(R) curves are sai d to indicate increased resistance to fracture. It seems to have been overlooked, however, that Krafft G(R) resistance curves in lefm are no t obtained in this way from U-acc. Indeed the concept of accumulated w ork during propagation does not appear in the lefm literature. This pa per investigates U-acc in lefm and derives relations for eta U-acc/Bb vs. Delta a/b for the compact tension and 3-point notched bend testpie ces. For fracture at constant G(c) a series of quasi-linear plots is p redicted: all have G(c) as their ordinate intercept with slopes which are multiples of G(c), individual values depending on the starting (a/ W). Note that eta U-acc/Bb does not indicate current toughness directl y during globally-elastic crack propagation; the ordinate values not c oinciding with the known toughness G(c) (or R, K-c etc)even in cases w here there is ''real'' G(R) behaviour in the Irwin-Krafft sense.