doi: 10.1111/j.1460-2695.2006.01041.x High-temperature fatigue crack growth in Inconel 718 subjected to high strain amplitudes M. ANDERSSON 1 , C. PERSSON 1 and S. MELIN 2 1 Division of Materials Engineering, 2 Division of Mechanics, Lund University, SE-221 00 Lund, Sweden Received in final form 2 May 2006 ABSTRACT Fatigue crack growth experiments in Inconel 718 subjected to high strain amplitudes at 650 ◦ C have been conducted. In the study the effects of load amplitude, ratio and frequency have been investigated. It was found that crack growth is a mixture of cyclic and time dependent mechanisms, depending on the load frequency. The load frequency was also found to have a strong influence on the crack growth rate. Also, crack closure was found to play an important role. By using an effective J-integral and including a frequency compensation term it was possible to summarize crack growth data into an empirical life prediction law, which seems to be in reasonable agreement with data from other studies. Keywords crack closure; frequency effects; high strain fatigue. NOMENCLATURE a = crack depth A L = uncracked cross-section area B = specimen thickness c = half crack width E = elastic modulus G = energy release rate range J = J-integral range J eff = effective J-integral range K = stress intensity range K eff = effective stress intensity range L = specimen gage length PD = potential drop value P = applied force R ε = load ratio U = effective part of the load cycle U e = elastic strain energy U p = plastic strain energy U ε = total strain energy U  = area under the load displacement curve V = global displacement W = specimen width η = dimensionless function to calculate J ε = global strain ε min = minimum global strain ε max = maximum global strain ε op = global strain at crack opening Correspondence: M. Andersson. E-mail: michael np andersson@yahoo.se c  2006 Blackwell Publishing Ltd. Fatigue Fract Engng Mater Struct 29, 863–875 863