Quasi-static crack tip fields in rate-sensitive FCC single crystals |
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Authors: | P BISWAS R NARASIMHAN |
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Affiliation: | 1.Global General Motors R&D, India Science Lab, GM Technical Centre (India),Bangalore,India;2.Department of Mechanical Engineering,Indian Institute of Science,Bangalore,India |
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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 10`1]]10\overline 1] direction. Solutions corresponding to different stress intensity rates (K)\dot]\dot{{K}}, T-stress values and strain rate exponents m are obtained. The results show that the stress levels ahead of the crack tip increase with (K)\dot]\dot{{K}} 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. |
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