Effect of a graded layer on the plastic dissipation in mixed-mode fatigue crack growth along plastically mismatched interfaces

The stress ratio effect on plastic dissipation during fatigue crack growth

“…The load values were obtained by the load cell of the fatigue machine, while the displacement was measured from DIC results at a location defined hereafter. Theoretically the energy dissipation could be calculated with: = ∫ (2) in which F represents the total force on the specimen and u represents the displacement values in the direction parallel to the load direction in the far field where the displacement distribution is nearly uniform. However, it is not possible to measure the dissipated energy with the displacement directly from the far field away from the crack area.…”

“…The material properties are simulated with the nonlinear kinematic hardening model in ABAQUS, using the full range stress-strain relation for 2024-T3 obtained from [18]. In this paper the simulation method follows the similar way as the simulation work presented in [1][2][3][4][5][6]12]. In the FEA model, a stationary crack with no crack propagation is used to model the fatigue crack because the crack growth in one fatigue cycle is very small, and its influence is quite limited and could be neglected.…”

“…There is literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] on the topic of the plastic energy dissipation during the fatigue crack propagation. Most of the papers aim at finding the relation between the plastic energy dissipation per cycle (dW/dN) and da/dN, and their work could be summarized as:…”

“…There are some differences among the studies mentioned above, mainly in the definitions and in the method of obtaining those values of dW/dN and dW/da. Klingbeil et al [1][2][3][4][5][6] relate the fatigue crack growth to the static crack propagation and claim that dW/da is a material property and its value should be equal to the static fracture toughness G c . Then, dW/dN is the total plastic dissipation energy per cycle per unit width.…”

“…Besel et al [16][17] study AA2024-T3 plastic dissipation with digital image correlation (DIC) method and coupled FE simulation. From the work mentioned above, although with some slight differences, there seems to be a contradiction between the work of [1][2][3][4][5][6]15] and [12][13]: some researchers seem to believe that the dW/da value is a material property, MATEC Web of Conferences 165, 13002 (2018) https://doi.org/10.1051/matecconf/201816513002 FATIGUE 2018 but the others disagree with this. Therefore the research questions in this paper are as follows:…”