Plasticity and asperity-induced fatigue crack closure under mixed-mode loading

Influence of a static torque on plasticity and asperity-induced closure effects during fatigue crack growth in bainitic steel cylinders loaded in push-pull

“…The reason for this difference is not clear. It is not an effect of the constitutive equations used in the present study, since the same crack growth simulations under cyclic mode I plus static mode II as in [21] run with these equations retrieved the reduction of PICC found in the previous study.…”

“…A static mode II superimposed on cyclic mode I has been reported by Stanzl et al [20] to reduce the growth rate of long cracks, for zero or negative R ratios, in a chromium steel, but to increase it for short cracks. This was rationalized by Doquet et al [21] who showed that a static mode II has opposite effects on RICC (which it increases, due to a permanent shift of crack faces asperities) and on PICC (which it reduces, especially for zero or negative R ratios).…”

“…steady mode III [13][14][15][16][17], steady mode II [18][19][20][21] or a combination of both [22][23][24][25][26], on mode I fatigue crack growth.…”

Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 1: Sequential Mode I and Mode II Loading

“…In particular, the branch crack growth rates of RP were plotted against ∆K I (Figure 11). These rates were expressed as da dN = 1.11 × 10 −11 (∆K I ) 2.40 (12) for RP5 and as da dN = 2.64 × 10 −10 (∆K I ) 1.95 (13) for RP6. As can be seen, the crack growth rate differs considerably depending on ∆K II /∆K I , and increasing in the ∆K II /∆K I increases the crack growth rate.…”

“…They also investigated the role of plasticity and crack face friction via finite element analysis (FEA) and concluded that the maximum growth rate criterion rationalized the crack path observed in the non-proportional loadings. Doquet et al [12] investigated through FEA the influence of static and 90 • out-of-phase cyclic mode II loading superimposed to the cyclic mode I on the plasticity-and asperity-induced closure for an aluminum alloy. The applied mode II could either increase or decrease ∆K Ieff depending on the stress ratio and loading path; in some cases, it had opposite effects on the two closure mechanisms.…”