Application of the Dissipated Energy Concept in Fatigue Endurance Limit Testing (05-0174)
Shihui Shen, Pennsylvania State University
Samuel H. Carpenter, University of Illinois, Urbana-Champaign

A fatigue endurance limit has been postulated to exist in HMA pavement performance. It cannot be observed and studied using traditional phenonenological approaches as seen by the totally different fatigue behavior at low strain/damage levels close to the fatigue endurance limit. The Ratio of Dissipated Energy Change (RDEC) succeeds in defining and investigating the existence of a fatigue endurance limit with a unique relationship between Plateau Value (PV) and fatigue life (Nf), regardless of strain/damage levels, mixture types, loading modes, and other testing conditions. The major problem in the study of a fatigue endurance limit is the extraordinary long time required to conduct a test. After examining the uniqueness of PV, this paper applied the PV to the study of a fatigue endurance limit to validate a shortened laboratory testing procedure Statistical analysis shows that the shortened test can predict the PV with sufficient accuracy. By applying the unique relationship between PV and Nf, the extremely long fatigue life under low strain/damage condition can be predicted without conducting millions of loading cycles. Thus the energy based fatigue endurance limit PVL can be more easily established.