Recommendations for a modification of ASTM E 1457 to include creep-brittlematerials

VAMAS Technical Working Area 19 on High Temperature Fracture of Brittle Mat erials has developed several new recommendations for determining and analys ing the creep crack extension behaviour of creep-brittle materials. These r ecommendations, most of which are also useful for creep-ductile materials, include: machining narrow starter notches for brittle materials; definition of creep crack initiation; definition of creep toughness; recommendations for conducting creep crack growth tests under the conditions of constant di splacement rates or stepwise increments in displacements and/or displacemen t rates, in addition to the usual constant force method; additional paramet ers for correlating the creep crack extension rate, such as stress intensit y factor, K, C-t parameter, Q* parameter, and rate of delta(5) type CTOD, ( delta)over dot(5); and criteria for the various correlation parameters. The se recommendations are presented in a form which should aid development of national and international standardization of creep crack extension test me thods, (C) 1998 Published by Elsevier Science Ltd. All rights reserved.