A Dissipated Energy Approach to Fatigue Crack Growth in Ductile Solids and Layered Materials

Abstract

This paper summarizes recent work on a new theory of fatigue crack growth in ductile solids based on the total plastic energy dissipation per cycle ahead of the crack. The fundamental hypothesis of the theory proposes a unified criterion for crack extension under monotonic and fatigue loading, so that the fatigue crack growth rate is given explicitly in terms of the total plastic dissipation per cycle and the monotonic fracture properties of the material. The total plastic dissipation per cycle is obtained by 2-D elastic-plastic finite element analysis of a stationary crack under constant amplitude loading, for both mode I (C(T)) and general mixed-mode I/II specimen geometries. Both elastic-perfectly plastic and bi-linear kinematic hardening constitutive behaviors are considered, and numerical results for a dimensionless plastic dissipation per cycle are presented over a wide range of relevant mechanical properties and mixed-mode loading conditions. Results are further extended to include fatigue delamination of layered material systems, where either discrete mismatches or a continuous grading of mechanical properties can exist across the interface.

The stress ratio effect on plastic dissipation during fatigue crack growth

“…Finally, if we consider the contradiction between the work of [1][2][3][4][5][6]15] and [12][13], this paper is on the side of [12][13] stating that dW/da is variable. Considering that in the work done by Karlsson et al [7][8][9][10][11] and Zheng [14] the definitions of dW/dN are slightly different, further numerical details need be given in order to make a comparison between their work and the work in this paper.…”

“…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:…”