W H I T E P A P E R
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The bilinear elastoplastic model with failure
When using the bilinear elastoplastic model, you can add a failure criterion. When the failure
option is enabled, a sudden drop on the moment value happens when the angular deformation
reaches the limiting value that controls the elastic-elastoplastic regime transition.
The bilinear elastoplastic model allows you to model the loss of joint stiffness without rupture,
i.e., without element separation. This model can be used, for example, to model green tree twigs
or branches. The behavior of the fiber before and after failure can be seen in Video 3 below.
Griffith surface energy criterion for breakage
With the Griffith surface energy criterion, rupture occurs when the tensile stress at the joint is
greater than the fracture stress, σ
n
f
(as shown in Figure 8). The fracture stress, by its turn, is
related to the surface energy.
What if you want the flexible fibers to break?
In Rocky DEM, flexible fibers can break according to two different criteria, as explained below.
Video 3. Fiber modeled using the bilinear elasto-plastic model with the failure criterion.
Figure 8. Griffith surface energy criterion for breakage.
