Abstract
In this paper, interactions of double parallel cracks were studied by performing experiments and numerical simulations. Fatigue crack propagation tests were carried out to measure crack growth rates in the specimens with double parallel cracks or a single crack. Finite element method was adopted to calculate stress intensity factors at the crack tips. Results show that the double parallel cracks at different positions present a shielding effect or enhancement effect on crack growth rates and stress intensity factors. When the double parallel cracks are offset, crack interactions mostly behave as enhancement effects. Empirical formulas were obtained to calculate the stress intensity factor at the “dangerous” crack tip of the double parallel cracks. By modifying the material parameters in Paris equation of the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rates.
Highlights
Multiple cracks usually initiate in the weld joints, because the weld butt and fillet contain heterogeneous microstructures, leading to high residual stresses at weld toes [1,2,3]
Li et al [18] researched interactions of multiple offset parallel cracks, and results showed that crack interactions could afford either a shielding or enhancement effect on the stress intensity factor (SIF) and stress field determined by the relative positions and sizes of cracks
By modifying the material parameters in Paris equation for the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rate (CGR)
Summary
Multiple cracks usually initiate in the weld joints, because the weld butt and fillet contain heterogeneous microstructures, leading to high residual stresses at weld toes [1,2,3]. It is significant to investigate the interactions of multiple cracks in terms of CGRs. Crack interactions would change the stress field around the crack tips [11], leading to the values of the stress decreasing or increasing; the SIFs at crack tips receive a shielding or an enhancement effect [12,13,14]. Li et al [18] researched interactions of multiple offset parallel cracks, and results showed that crack interactions could afford either a shielding or enhancement effect on the SIFs and stress field determined by the relative positions and sizes of cracks. Crack growth rates of the double parallel crack and single crack specimens were obtained through the fatigue crack propagation tests. Experiments and simulation results showed that the CGRs and SIFs at crack tips received a shielding or enhancement effect. By modifying the material parameters in Paris equation for the single crack, the double parallel cracks are simplified into a single crack with the same CGRs
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