Quasi-static crack tip fields in rate-sensitive FCC single crystals

Abstract

In this work, the effects of loading rate, material rate sensitivity and constraint level on quasi-static crack tip fields in a FCC single crystal are studied. Finite element simulations are performed within a mode I, plane strain modified boundary layer framework by prescribing the two term (K − T) elastic crack tip field as remote boundary conditions. The material is assumed to obey a rate-dependent crystal plasticity theory. The orientation of the single crystal is chosen so that the crack surface coincides with the crystallographic (010) plane and the crack front lies along [101] direction. Solutions corresponding to different stress intensity ratesK , T-stress values and strain rate exponents m are obtained. The results show that the stress levels ahead of the crack tip increase withK which is accompanied by gradual shrinking of the plastic zone size. However, the nature of the shear band patterns around the crack tip is not affected by the loading rate. Further, it is found that while positive T-stress enhances the opening and hydrostatic stress levels ahead of crack tip, they are considerably reduced with imposition of negative T-stress. Also, negative T-stress promotes formation of shear bands in the forward sector ahead of the crack tip and suppresses them behind the tip.

Lattice strains at cracks in single crystal titanium: Elastic distortion and GND contributions

“…The issue of anisotropy effects at the crack tip was recently investigated by Kartal et al [10] to evaluate the effects of crystallographic orientation and grain morphology on crack tip stress state and found that single crystal crack tip stresses largely remain independent of crystal orientation but that the plastic zone size and shape depends greatly upon it. Further studies include that by Biswas and Narasihman [11,12] who investigated crack tip fields in rate sensitive FCC single crystals; Lopez-Crespo et al [13,14] who address overload effects during fatigue crack growth in steel using synchrotron x-ray diffraction for both plane strain and stress conditions, and studies by Kaushik et al [15,16] on experimental and finite element simulations of notch tip fields in magnesium single crystals.…”