In rheology, a Bingham plastic behaves as a solid until which threshold is exceeded?

In rheology, a Bingham plastic behaves as a solid until which threshold is exceeded?

• A. A threshold density
• B. A critical shear rate
• C. A given viscosity
• D. A yield stress

Answer: (D)

A Bingham plastic resists deformation until a finite yield stress is exceeded. Below that stress, the material behaves like a solid with essentially no flow. Once the applied shear stress surpasses the yield stress, it starts to flow and, above that threshold, the stress increases with shear rate roughly linearly, described by tau = tau_y + mu_p * gamma_dot, where mu_p is the plastic viscosity. This yield stress is a material property that reflects the internal structure holding the material together; it’s the exact threshold that marks the transition from solid-like to liquid-like behavior. The other options don’t match this onset mechanism: density doesn’t determine when flow begins, viscosity isn’t defined in the solid regime, and a fixed critical shear rate would imply flow starts at a specific rate regardless of stress, which isn’t how a Bingham plastic behaves.

A Bingham plastic resists deformation until a finite yield stress is exceeded. Below that stress, the material behaves like a solid with essentially no flow. Once the applied shear stress surpasses the yield stress, it starts to flow and, above that threshold, the stress increases with shear rate roughly linearly, described by tau = tau_y + mu_p * gamma_dot, where mu_p is the plastic viscosity. This yield stress is a material property that reflects the internal structure holding the material together; it’s the exact threshold that marks the transition from solid-like to liquid-like behavior. The other options don’t match this onset mechanism: density doesn’t determine when flow begins, viscosity isn’t defined in the solid regime, and a fixed critical shear rate would imply flow starts at a specific rate regardless of stress, which isn’t how a Bingham plastic behaves.