Figure 3. Extracted parameters from the yield loci.
In order to better understand the contribution of pure friction and
adhesion to the unconfined strength, it can be decomposed into tensile
strength (σt) and internal angle of friction (φ )
using the equation14,15 as:
\(\sigma_{u}=\frac{1+sin\varphi}{1-sin\varphi}\sigma_{t}\) (1)
The equation assumes linearized yield loci (τ and σ plot).
The linearized friction angle represents the pure frictional component
of the material. On the other hand, the tensile strength
(σt) represents the adhesive component of the material,
which is the strength required to ‘pull’ the material apart as shown in
Figure 4. The Flow function coefficient (FFc) is the ratio of the major
principal stress to the unconfined yield strength. Increasing values of
FFc relate to better flowability of the powder.