Finite-deformation analysis of the crack-tip fields under cyclic loading

Abstract

a b s t r a c tThe plane-strain crack subjected to mode I cyclic loading under small scale yielding was analysed. The influence of the load range, load ratio and overload on the near-tip deformation-, stress-and strain-fields was studied. Although the near-tip zones of appreciable cyclic plastic flow for all loading regimes matched closely one another, when scaled with (DK/r Y ) 2 , the activities of plastic flow within them manifested dependence on K max and K min , as well as on overload. Cyclic trajectories of the crack-tip opening displacement (CTOD) converged to stable self-similar loops of the sizes proportional to DK 2 and positions in CTOD-K plane dependent on the maximum K along the whole loading route, including an overload. Computed near-tip deformation evidenced plastic crack advance, this way visualising of the Laird-Smith concept of fatigue cracking. This crack growth by blunting-resharpening accelerated with rising DK and was halted by an overload. Crack closure upon unloading had no place. The affinities were revealed between computed near-tip stress-strain variables and the experimental trends of the fatigue crack growth rate, such as its dependence on K max and K min (or DK and K max ), and retardation by overload. Thus, the effects of loading parameters on fatigue cracking, hitherto associated with crack closure, are attributable to the stress-strain fields in front of it as the direct drives of the key fatigue constituents -damage accumulation and bond breaking.

The Role of Overloading on the Reduction of Residual Stress by Cyclic Loading in Cold-Drawn Prestressing Steel Wires

“…In all cases, a number of cycles (N) of 10 was applied in accordance to the null effect of this parameter, accounting for the results presented in previous analyses [20,21]. Furthermore, papers [22,23] show how the crack tip advance due to local plasticity appears during the first loading cycles. Prestressing steel wires can undergo overloading during their life in-service [24].…”

Finite element meshes for optimal modelling of plasticity induced crack closure

“…However, the application of these elements in the simulation of PICC presents several difficulties and does not seem to be the solution. An alternative would be the simulation of finite crack tip radius [65]. In fact, real cracks have (small) finite tip radius, which increase with loading.…”

Application of digital image correlation for estimation of fatigue crack closure level

“…According to the proposed formulation, it is important to measure the size of the plastic zone ahead of the crack tip and construct a crack propagation theory based on the plastic zone ahead of the crack tip. The data related to the estimation of the strain field behind and ahead of the crack tip can be found in [12][13][14][15].…”