Bingham Plastic

Definition

A Bingham plastic is a type of non-Newtonian fluid that behaves like a solid until a certain yield stress is applied, after which it flows like a viscous liquid. This unique characteristic means that Bingham plastics require an initial force to start flowing, making them distinct from Newtonian fluids, which flow immediately under any applied shear stress. Understanding Bingham plastics is crucial for modeling materials like toothpaste or mud, where the yield stress defines the transition between solid and flow states.

5 Must Know Facts For Your Next Test

1. Bingham plastics are characterized by a linear relationship between shear stress and shear rate, but only after the yield stress is surpassed.
2. Common examples of Bingham plastics include materials like drilling mud, mayonnaise, and some types of slurries.
3. The mathematical model for a Bingham plastic can be represented as $$ au = au_y + eta rac{du}{dy}$$ where $$ au$$ is the shear stress, $$ au_y$$ is the yield stress, and $$eta$$ is the plastic viscosity.
4. In practical applications, understanding the yield stress of a Bingham plastic is crucial for predicting how materials will behave under different loading conditions.
5. Bingham plastics are often analyzed in engineering and material science for their unique flow properties, particularly in contexts where they need to be transported or processed.

Review Questions

• How does the behavior of Bingham plastics differ from that of Newtonian fluids under shear stress?
  • Bingham plastics differ significantly from Newtonian fluids in that they do not begin to flow until an applied shear stress exceeds a specific yield stress. In contrast, Newtonian fluids start flowing immediately with any increase in shear stress and maintain a constant viscosity. This means that while a Newtonian fluid will smoothly transition to flow at any level of force, a Bingham plastic will remain static until enough force is applied to overcome its yield point.
• What role does yield stress play in determining the flow characteristics of Bingham plastics in industrial applications?
  • Yield stress is critical in defining when a Bingham plastic will begin to flow, impacting its handling and processing in various industrial applications. For instance, if the yield stress is too high, it may be difficult to pump or mix the material without pre-treating it. Understanding yield stress allows engineers to design systems that can effectively manage the transition from solid to liquid behavior during operations like drilling or food processing.
• Evaluate how understanding the properties of Bingham plastics could influence material selection for specific engineering applications.
  • Understanding the properties of Bingham plastics can greatly influence material selection in engineering by ensuring that the chosen materials perform adequately under expected conditions. For example, selecting a material with appropriate yield stress can determine whether it behaves more like a solid or liquid during application processes such as transport or mixing. By carefully analyzing these characteristics, engineers can optimize performance, reduce waste, and improve safety across various industries where non-Newtonian behavior is present.

Related terms

Yield Stress: The minimum stress required to initiate flow in a material, characteristic of Bingham plastics and other non-Newtonian fluids.

Viscosity: A measure of a fluid's resistance to flow, which can change depending on the shear rate in non-Newtonian fluids.

Non-Newtonian Fluid: A fluid whose viscosity changes with the applied shear rate, unlike Newtonian fluids that have a constant viscosity.