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An alternative definition of the plasticity index has been given by Mikic. [32] Yield occurs when the pressure is greater than the uniaxial yield stress. Since the yield stress is proportional to the indentation hardness σ 0 {\displaystyle \sigma _{0}} , Mikic defined the plasticity index for elastic-plastic contact to be
The onset of plasticity in polycrystals is influenced by the number of available slip systems to accommodate incompatibilities at the grain boundaries. In the case of two adjacent, randomly oriented grains, one grain will have a larger Schmid factor and thus a smaller yield stress.
Both factors τ and σ are measured in stress units, which is calculated the same way as pressure (force divided by area). φ and λ are angles. The factor is named after Erich Schmid who coauthored a book with Walter Boas introducing the concept in 1935. [3]
Although shear thinning is generally not observed in pure liquids with low molecular mass or ideal solutions of small molecules like sucrose or sodium chloride, it is often observed in polymer solutions and molten polymers, as well as complex fluids and suspensions like ketchup, whipped cream, blood, [5] paint, and nail polish.
Pulse wave velocity (PWV) is the velocity at which the blood pressure pulse propagates through the circulatory system, usually an artery or a combined length of arteries. [1] PWV is used clinically as a measure of arterial stiffness and can be readily measured non-invasively in humans, with measurement of carotid to femoral PWV (cfPWV) being ...
The quadratic Hill yield criterion for thin rolled plates (plane stress conditions) can be expressed as + (+) (+) + = where the principal stresses , are assumed to be aligned with the axes of anisotropy with in the rolling direction and perpendicular to the rolling direction, =, is the R-value in the rolling direction, and is the R-value perpendicular to the rolling direction.
Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the crystal lattice: slip and twinning. Slip is a shear deformation which moves the atoms through many interatomic distances relative to their initial positions.
It is commonly used to demonstrate the pressure dependence of a yield surface or the pressure-shear trajectory of a stress path. Because r {\displaystyle r} is non-negative the plot usually omits the negative portion of the r {\displaystyle r} -axis, but can be included to illustrate effects at opposing Lode angles (usually triaxial extension ...