Vickers hardness Subject

On the other hand materials deform plastically only when subjected to shear stress. According to Frenkel analysis, strength (yield stress) of an ideal crystalline solid is proportional to its elastic shear modulus [28,29]. The strength of a real crystal is controlled by lattice defects, such as dislocations or point defects, and is significantly smaller then that of an ideal crystal. Nevertheless, the shear stress needed for dislocation motion (Peierls stress) or multiplication (Frank-Read source) and thus for plastic deformation is also proportional to the elastic shear modulus of a deformed material. Recently Teter argued that in many hardness tests one measures plastic deformation which is closely linked to deformation of a shear character [17]. He compared Vickers hardness data to the bulk and shear... 

Similar to Brinell hardness, Vickers hardness has also been the subject of study to search for a possible relationship between hardness and other mechanical properties. Some semiempirical relationships were reported. Based on a study of a magnesium alloy AZ19 with a nominal composition of Mg-8% Al-0.7% Zn-0.2% Mn-0.002% Fe-0.002% Cu, the flow stress can be approximately calculated by Equation 3.26, where the Vickers hardness number has a nominal unit of kg/mm, and the flow stress is measured in MPa (Caceres, 2002). 

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