Kinks localized shearing

Inelastic shearing of atoms relative to one another is the mechanism that determines hardness. The shearing is localized at dislocation lines and at kinks along these lines. The kinks are very sharp in covalent crystals where they encompass only individual chemical bonds. On the other hand, in metal crystals they are often very extended. In metallic glasses they are localized in configurations that have a variety of shapes. In ionic crystals the kinks are localized in order to minimize the electrostatic energy. 

Some modes may dominate for example, for large bending strains in a flexible structure, fibre fracture in tension and fibre kinking in compression wdl dominate near both surfaces. Matrix cracks can cause delamination when they reach a ply interface. If the structure is stiff enough to resist with a significant force, then local indentation damage, and shear-driven delamination in the interior, wdl occur. Figure 9.2 shows schematically the different modes of fadure in three zones of a laminate. The peanut shape deformations (3) have this shape because the compression under the impact force suppresses the delaminations. 

Clear evidence exists that beyond the linear regime the synthetic thermostat influences the results. The role of the heat removing mechanism becomes especially important at high shear rates where the assumption of the linear velocity profile (iyyi is incremented in the position equation of equations 27) of the SLLOD shear flow is unrealistic. To allow the formation of kink instabilities in the velocity profile (turbulent flow) the simple thermostating scheme of equations (27) mast be replaced by a profile unbiased thermostat which makes no assumption about the local streaming velocity. ... 

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