Fatigue crack propagation under non-proportional mixed mode loading

Influence of the loading path on fatigue crack growth under mixed-mode loading

“…3c. This curve also is similar to that obtained by Yu and Abel and consistent with some experimental observations on Al alloys, by Planck and Kuhn (1999) who , while for lower Rratios, mode II crack growth was observed, when K II was high enough.…”

“…Does the loading path have an intrinsic influence, or can all this influence be captured through appropriate corrections for closure and friction effects on stress intensity factors, that is, by the use of K effective I , K effective II , K effective III ? This problem is complex and no clear answer emerges from the literature on non-proportional mixedmode I and II (Gao et al 1983;Hourlier et al 1985;Wong et al 1996Wong et al , 2000Planck and Kuhn 1999;Yu and Abel 2000;Doquet and Pommier 2004) or mode I and III (Feng et al 2006). The latter concludes: "with identical loading magnitudes in the axial and torsional directions, the crack growth and crack profiles are strongly dependent on the loading path.…”

A review of asymptotic procedures in stress analysis: Known solutions and their applications

“…The concept of 'small-scale yielding', which must be satisfied for crack growth to be controlled by the stress intensity factor, is precisely this. In fact, there are stronger requirements on the nature of the stress state that the crack tip experiences: (a) if the T-stress is significant in proportion to the singular field at the position of the process zone front, that may have an influence on the fatigue performance; (b) if the crack tip is experiencing combined modes loading, each non-zero mode contributes to the local stress field and, if the ratio between the stress intensity factors varies during the loading cycle (the so-called 'non-proportional loading' regime), the crack may propagate in a way that is difficult to predict; the latter is the subject of current research [13]. Lastly, it is known that it is the range of plastic strain (rather than its maximum value) which is principally responsible for the rate of crack extension.…”

Precise 3D crack growth simulations

“…Today, crack propagation is analyzed by numerical simulation, which is based on the concepts mentioned above. A lot of studies on the numerical treatment of cracks have been done by Kuhn and his colleagues (Mews and Kuhn 1988;Schillig and Kuhn 1992;Russwurm and Kuhn 1991;Huber et al 1996;Plank and Kuhn 1999;Partheymüller et al 2000;Kolk and Kuhn 2006;Heyder and Kuhn 2006;Heyder et al 2005). Beside the numerical determination of stress intensity factors (Mews and Kuhn 1988), crack propagation has been simulated in 2D (Schillig and Kuhn 1992) in the late 1980s.…”

“…Furthermore, cracks in structures with elastic-plastic material behavior have been analyzed in 2D (Russwurm and Kuhn 1991) and 3D (Huber et al 1996). Then, experiments on crack propagation under non-proportional loading conditions have been performed (Plank and Kuhn 1999) and software for the 3D simulation of fatigue crack growth has been developed (Partheymüller et al 2000). Within the last years, a 3D crack growth criterion including the special treatment of surface breaking points of the crack front has been identified by the comparison of numerical simulations (Kolk and Kuhn 2006) and experimental analyses (Heyder and Kuhn 2006;Heyder et al 2005).…”