Yield Stress
 

Hello folks,

can anybody explain or even pose a formular concerning yield stress? Is there a relation to shear rate and shear stress?

Cheers in advance

In general, the yield stress is the stress level beyond which when unloaded, the material does not return to its original unloaded state. This hysteretic response is termed plasticity (contrary to elasticity, where - upon a loading-unloading path, the material state, e.g., the stress and strain, follows the same path). Some materials yield (and yield models) is independent of the hydrostatic stress, and are therefore dependent on the deviatoric (crudely, shear) stress state, and in some cases (viscoplasticity) - on the deviatoric rate as well. The yield stress models are used to also relate a multidimensional stress state to a uniaxial state.