# Flow Stress

Flow stress is defined as the instantaneous value of stress required to continue deforming the material - to keep the metal flowing. It is the yield strength of the metal as a function of strain, which can be expressed:

Yf = Ken
• Yf = Flow stress, MPa
• e = True strain
• K = Strength Coefficient, MPa
• n = Strain hardening exponent

Hence, Flow stress can also be defined as the stress required to sustain plastic deformation at a particular strain.

The flow stress is a function of plastic strain.

Flow stresses occur when a mass of flowing fluid induces a dynamic pressure on a conduit wall. The force of the fluid striking the wall acts as the load. This type of stress may be applied in an unsteady fashion when flow rates fluctuate. Water hammer is an example of a transient flow stress.

The following properties that have an effect on flow stress: chemical composition, purity, crystal structure, phase constitution, exit microstructure, grain size, and heat treatment.

### Other articles related to "flow stress, stress":

Viscoplasticity - Strain-rate Dependent Plasticity Models - Flow Stress Models - Preston–Tonks–Wallace Flow Stress Model
... (PTW) model attempts to provide a model for the flow stress for extreme strain-rates (up to 1011/s) and temperatures up to melt ... The PTW flow stress is given by with where is a normalized work-hardening saturation stress, is the value of at 0K, is a normalized yield stress, is the hardening constant ... The saturation stress and the yield stress are given by where is the value of close to the melt temperature are the values of at 0 K and close to ...
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... The Mechanical Threshold Stress (MTS) model ) has the form where is the athermal component of mechanical threshold stress, is the component of the flow stress due to ... The strain hardening component of the mechanical threshold stress is given by an empirical modified Voce law where and is the hardening due to dislocation accumulation, is the ...
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... The general form of the equation for the flow stress is In this model, is the athermal component of the flow stress given by where is the contribution due to solutes ...

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