GKM+rheology2-newtonian&non-newtonian

= RHEOLOGY- NEWTONIAN AND NON-NEWTONIAN BEHAVE FLUID. =

hello, everyone, in this page, i would like to discuss about some other terminology under the topic rheology. Again, these term maybe still sound weird, but lets try to understand it by reading my summary.. haha

the last summary i talked about viscosity at the end of the discussion. i missed out something. that is, what are the factors that affect viscosity? Basically, shear rate, time of shearing, temperature and pressure are the factors that can affect the viscosity of a material. Well, i think there will be no problem on the term of temperature and pressure, but what is shear rate? u can refer to this link. >> shear rate in wikipedia. but there is something special about the word pressure here, it means shear stress instead of normal pressure that we known. shear stress is different from normal stress that applied perpendicularly. Shear stress means a stress which is applied parallel or tangential to the face of the material.( it is something like stirring in a simple sense, right? )

ok, now is the time to explain how these 4 factors come together to relate to the viscosity of a material. Basically, viscosity of a material is divided 2 categories which are Newtonian and Non-newtonian behavior.

The definition of Newtonian behavior is the shear viscosity doesnt vary with shear rate, which mean the viscosity is always constant with the time of shearing. So, the shear stress will fall immediately to 0 when a shearing is stopped. when shear again, the viscosity is still the same with the previous measured, meaning there is no relationship to the delay between measurements. Therefore, after knowing that the definition of Newtonian behavior, i think the definition of Non newtonian behavior is simple now. A material showing ANY deviation from the Newtonian is said to be Non Newtonian.



The example of Newtonian behave fluid are water, milk and honey... etc. From the graph, and refer to the definition above... we should able to identify the Newtonian and non-Newtonian behaved fluid. Bingham plastic Pseudo plastic and dilantant are the example of the non-Newtonian fluid.

In non-Newtonian behave fluid, there are 2 categories under it, time dependent and time independent behavior. Time independent non-Newtonian behave fluid is the fluid that show a viscosity which dependent on shear rate but independent of time, meaning no matter how long u stir the material, the viscosity remain the same unless you change a shear rate.So, the viscosity is only presented a specific shear rate and refer as "apparent viscosity" "shear viscosity" and "shear dependent viscosity". Base on this possibility that a fluid might show a TIME INDEPENDENT NON-NEWTONIAN behavior, when determine a viscosity of a material, it's viscosity shouldn't be measured at certain shear rate only. A full graph with different shear rate should be prepared instead of measuring a single point viscosity on certain shear rate. The Bingham, Pseudo plastic and Dilantant are showing Time independent non-Newtonian behavior. Therefore a time dependent non-Newtonian behave fluid is dependent on shear rate and time during which shear rate is applied. The example are Thixotropy and Rheopectic.

I think there are still some doubt about this topic. I will try to do another summary on the next article.. hahaha... next i might discuss what is YIELD STRESS, PLASTIC FLUID, BINGHAM FLUID AND THIXOTRPY AND RHEOPECTIC.