Bingham plastic model

Definition

The Bingham plastic model describes a type of non-Newtonian fluid that behaves as a solid until a certain yield stress is exceeded, after which it flows like a viscous fluid. This model is crucial for understanding how certain materials, such as toothpaste or mud, require an initial force to start flowing, making it distinct from Newtonian fluids, which flow readily under any applied stress.

5 Must Know Facts For Your Next Test

1. The Bingham plastic model is characterized by two key parameters: the yield stress and the plastic viscosity, which defines the flow behavior once the yield stress is exceeded.
2. Common examples of Bingham plastics include materials like toothpaste, mayonnaise, and drilling mud, which do not flow until sufficient force is applied.
3. In practical applications, understanding the yield stress is critical for processes like pumping and mixing, where overcoming this threshold can influence efficiency.
4. The Bingham plastic model simplifies complex flow behavior into manageable equations, allowing engineers to predict how these materials will behave under various conditions.
5. For many Bingham plastics, the relationship between shear stress and shear rate is linear after the yield point, differentiating them from other non-Newtonian fluids like shear-thinning or shear-thickening fluids.

Review Questions

• How does the Bingham plastic model differentiate between solid-like and fluid-like behavior in materials?
  • The Bingham plastic model distinguishes between solid-like and fluid-like behavior through the concept of yield stress. Below this yield stress, the material behaves like a solid and does not flow. Once the applied stress exceeds this threshold, the material starts to flow as a viscous fluid. This behavior is important in applications where an initial force is needed to initiate movement, as seen in products like toothpaste.
• Discuss the significance of yield stress in the context of Bingham plastics and its impact on engineering applications.
  • Yield stress is a crucial parameter in the Bingham plastic model because it dictates the conditions under which a material transitions from a solid state to a flowing state. In engineering applications such as drilling or food processing, accurately measuring and managing this yield stress allows for more efficient design of equipment and processes. Understanding how to apply sufficient force to overcome yield stress can lead to better control over material handling and processing.
• Evaluate the implications of using the Bingham plastic model over other non-Newtonian models for predicting fluid behavior in industrial applications.
  • Using the Bingham plastic model has significant implications for predicting fluid behavior in industrial settings. Unlike other non-Newtonian models that may account for continuous changes in viscosity with shear rate, the Bingham plastic model provides clear thresholds with defined parameters such as yield stress and plastic viscosity. This simplicity can enhance predictability and facilitate easier calculations in designs involving materials like slurries or pastes. However, it may oversimplify some materials' behaviors, necessitating careful selection of models based on specific application needs.

Related terms

Yield Stress:

The minimum stress needed to initiate flow in a Bingham plastic material.

Viscoplasticity: A property of materials that exhibit both viscous and plastic characteristics when deformed.

Non-Newtonian Fluids:

Fluids whose viscosity changes with the applied shear rate or stress, unlike Newtonian fluids, which have a constant viscosity.