What Does Yield Point (YP) Mean?
Yield point is generally defined as the elastic limit at which a material will lose its elasticity and deform permanently. For drilling fluids, yield point refers to the resistance of initial flow of the fluid or in other words, the stress required to start the movement of the fluid. It is a parameter of the Bingham plastic model.
The forces of attraction between the colloidal particles in the drilling fluid will prevent the fluid from flowing until the required stress is applied.