Isotropic and kinematic ahrdening(metals)

[shalini.singh]

I've been trying to figure out difference between isotropic and kinematic hardening (modeling plasticity in metals).

As I see,kinematic hardening can model reversible nbehaviour of metals (Bauschinger effect).

In isotropic hardening, the yield surface increase in size, but remain the same shape, as a result of plastic straining.

That is, if the yield surface is represented by a cylinder of radius "A" then an increase in the radius denotes an increase in the yield stress as a result of plastic straining.

However,this cannot capture Bauschinger effect as when unloaded and reloaded in compression (if earlier was loaded in tension) there is no sign of reduction in palstic limit.

As I see, in kinematic hardening there the yield surface translates from its original position (thus there being a change in center of cylinder) which makes the difference.

Can anyone explain this more clearly (or correct me)-with a physical intuition?

 

[Navin A S]

Kinematic hardening is a more sophisticated model of plasticity in metals that takes into account the reversible behavior of metals. This reversible behavior is known as the Bauschinger effect, which is caused by a combination of strain hardening and strain softening due to the microstructure of the material. In kinematic hardening, the yield surface is shifted (translated) from its original position as a result of plastic straining. This shift in the yield surface results in a change in the center of the cylinder, as well as an increase in the radius. This shift in the yield surface allows for an increase in the yield stress when the material is reloaded in compression after being loaded in tension. This captures the Bauschinger effect, as the yield stress does not decrease after an unloading/reloading cycle. In contrast, isotropic hardening does not capture the Bauschinger effect, as the yield surface only increases in size, but remains the same shape. Thus, when the material is unloaded and then reloaded in compression, there is no increase in the yield stress, which does not match the behavior of real metals.