GKM+Types+of+flow

= WHAT IS BINGHAM PLASTIC, PSEUDOPLASTIC, DILANTANT, ANS YIELD STRESS? =

In the last article that i discussed about Newtonian and Non-Newtonian behave fluid. From there, we find that there are few terminology that we still not sure with. Now, lets have some explanation about these term. ( weird term again?)

Again, study this graph, i m sure now u can easily tell the different between what is Newtonian and what are non-Newtonian fluids. But the question now is, what are the terminology means? Bingham looks like Newtonian behave fluid!? and what is pseudoplastic? and so on...

As you know about the Newtonian fluid, from the graph, maybe it is quite obvious that why bingham plastic fluid looks so similar to Newtonian behaving fluid, but what is the different? Bingham plastic is a viscoplastic material that behave like a rigid in the low shear stress but flows as a smooth liquid upon a high shear stress. In short, Bingham plastic behave like a Newtonian fluid but it have a certain YIELD STRESS that have to be overcome. Well, this is a simpler definition but another question arise, what is yield stress. OK, yield stress is the minimum shear stress that have to be applied to the sample in order to overcome the cohesive force holds the structure of the material, so that the fluids flows! You can see that, once the shearing stress is applied, from the 0, the shear rate ( viscosity) is increase. However, for the Bingham plastic, it behave like a Newtonian fluid but only when a certain shear stress have applied. The DIFFERENCE is the Yield Stress. Of course, different Bingham plastic behave material will having a different value of Yield stress.

For Pseudo plastic material, it show a decreasing viscosity ( increasing in shear rate ) when the shear stress is increasing. The material is called pseudo plastic but the behavior is called SHEAR THINNING. Shear thinning behaving material are more common that SHEAR THICKENING in our daily life. Material shows shear thinning are ketchup and whipped cream.

Shear thickening meaning the material will increase in viscosity as the shear stress is increasing ( decreasing in shear rate). The example can be a constarch mix with water and u try to stir it... then you will find it is harder and harder to move the liquid.This behavior is called Dilatant!


 * Ok, now i would like to clarify again shear rate and shear stress... please do not confuse. Shear stress is the stress that applied to the material in perpendicular way. Shear rate is directly proportional to viscosity of a material. SO, increasing in shear stress meaning the stress applied is greater so it means the viscosity of the material should be higher! In other way... it also means the increasing of shear rate!** ( shear rate = k X viscosity, k= constant )

i hope i did not give any wrong information here, if you find anything wrong please let me know, THANKS and Thanks for reading..