Energy description of fatigue crack growth process - theoretical and experimental approach

Abstract

The aim of the paper is the presentation of the energy methods in description of the fatigue crack growth rate (FCGR) process in structural steel components. In the literature and engineering practice, the ΔK – approach is preferred in construction of the FCGR diagrams. One of the main disadvantages of force approach, is a mean stress effect, reflected in a well-known stress R-ratio effect on FCGR. The second disadvantage seems to be inconsistency in closure estimation with ΔK and description only in the linear-elastic range. In this paper, two energy approaches are presented – ΔH and ΔJ. The kinetic equations based on energy parameters, describe synonymously the kinetics of fatigue crack growth under uniaxial fatigue loading. It has been demonstrated, that the energy description – based on dissipated strain energy density – ΔH is independent from R-ratio. All theoretical and numerical calculations based on ΔJ, ΔH strain energy density parameters were compared with experimental results obtained for different type of alloys.