Science Buddies: "Ask an Expert"

Hi, for my project, I'm testing the shear strength of a material with the properties of a Bingham plastic. I have looked up what it is and have found the equation descibing its shear stress. However, I do not understand what it means. Any help you could give me on this would be greatly appreciated.

Thanks!

Hi,

In a normal Newtonian fluid, fluid is directly proportional to pressure (shear stress) applied.

In a Bingham plastic there is no flow until a certain physical shear stress is exceeded, then flow is proportional to the shear stress applied minus the critical shear stress. In physical terms the material behaves like a solid until the applied shear stress exceeds the critical shear stress, then behaves like a fluid with an applied apparent shear stress being like the actual shear stress ,inus the critical shear stress.

It has been suggested a gppd physical model is toothpaste coming out of a tube of toothpaste.See:
http://en.wikipedia.org/wiki/Bingham_plastic

I hope this helps. If not search google.com for “bingham plastic” and start reading the web pages listed there.

Best regards,

Barrett L Tomlinson