A mesomechanics model of fatigue crack growth for nanoengineering applications

作者：Wnuk M P^*; Rouzbehani A

来源：Physical Mesomechanics, 2008, 11(5-6): 272-284.

DOI：10.1016/j.physme.2008.11.007

• fatigue
• fracture
• crack growth
• energy dissipation
• process zone
• deformation
• mesomechanics
• scaling effects
• discrete fracture

In this paper we present a model of a propagating fatigue crack based on energy dissipated within the process zone, This model heavily relies on the mesomechanical concepts applicable in the region immediately adjacent to the leading edge of the propagating crack. The model applied here, based on the cohesive crack concepts, seems to be a good approximation of the mesomechanical phenomena that govern nonlinear discrete deformation and fracture processes. The model suggests that the displacement just ahead of the crack tip is not zero, but it gradually approaches zero over a finite length, which measures the extent of the decohesion zone. Consequently, there is no singular stress at the crack tip. A certain distribution of the cohesive stress is used to model the finite stresses within highly nonlinear end zone preceding the crack. Such approach appears to be in agreement with Panin's concepts of the sequence of deformation and prefracture processes occurring at the mesomechanical level.
Analytical methods such as a power law and an exponential law were used to describe high cycle and low cycle fatigue processes, respectively. Numerical values for the ratio of the upper plateau to the threshold level of the cyclic R-curve derived from Wnuk's "final stretch" model of subcritical crack propagation are provided. The relations derived here and based on the principles underlying mechanics of fracture at nanolevels, can be used as a bridge between continuum description of material response to fracture and the more fundamental, microstructural representation of material behavior.

• 出版日期2008-12