  In this paper we study the ductile breakup of tracer aggregates in an
incompressible, homogeneous, and isotropic three-dimensional turbulent flow.
The flow dynamics is studied by means of a direct numerical simulation, whereas
the Lagrangian velocities and stress statistics along trajectories are obtained
by particle tracking. We investigate the breakup dynamics under the hypothesis
that aggregates are able to deform and accumulate energy. Within this
framework, breakup occurs when the energy transferred to the aggregate by the
flow exceeds a critical value. We contrast our predictions for ductile breakup
with those obtained for brittle breakup. We observe that turbulence
intermittency is crucial for the breakup of brittle aggregates, while it
becomes less relevant for ductile aggregates. In the limit of highly ductile
aggregates the breakup rate is dictated by the mean properties of the flow. We
propose a simple model to capture this behaviour.
