Application of unified fatigue damage approach to compression-tension region

A Unified Approach to fatigue crack growth developed earlier is extended to include the fatigue behavior over the entire load ratio (R) regime, from c ompression-tension to tension-tension. This approach provides a self consis tent description of cyclic damage using the two loading parameters, Delta K and K-max, applicable over the entire crack growth regime. Crack growth be havior in the R>0 regime has been classified into five distinct classes. Th is classification is extended here to include the negative R-ratio region. When compression loads are included with the tension cycle, each classifica tion is further divided into three additional subsets, reflecting a charact eristic change in crack growth mechanisms. The current overall classificati on provides a methodology for understanding the combined effects of tension and compression loads on crack tip forces and their effect on material cra ck growth resistance. Like wise the role of environmental effect will also be altered in the presence of compressive forces. (C) 1999 Published by Els evier Science Ltd. All rights reserved.