Ductile fracture modeling based on a mesh objective element removal technology
Other conference contribution, 2014
The phenomenological Johnson-Cook continuum and failure models constitute a simple ap-
proach to the modelling of ductile fracture in metals. Even though the model is simple, it catches
the material behavior at high speed/temperature with a relatively few material parameters. This
is an obvious advantage, in addition to its widespread use in commercial softwares, which makes
it so often used in many applications, and, in particular, machining simulations of metal cutting
processes. Even though there are advantages with the model, a major drawback from our expe-
rience1 is that the JC–material model exhibits a significant mesh size dependence in orthogonal
machining simulations.
In order to overcome this difficulty a mesh objective element removal technology is devised
based on a smeared out type of dissipation concept to represent the fracture energy. The tech-
nology is investigated for the ductile failure modeling of the pearlite phase in a cast iron mi-
crostructure with the objective to obtain a mesh size independent computational tool. In order
to obtain mesh objective element deletion, an element removal criterion is defined on the plastic
strain energy prior to fracture state is considered as fracture energy. A fracture state is achieved
in a gauss-point when the accumulated effective plastic strain equals the fracture strain, com-
puted with the Johnson-Cook fracture model. Then a total scaled fracture dissipation energy is
computed based on the current accumulated dissipation. The figures below show the model set
up, a shear loaded plate, and the computed reaction force, where vertical displacements are pre-
scribed, for different mesh sizes. Indeed, our experience is that the model exhibits a significant
mesh size dependence without the proper scaling of the energy dissipation.
element removal technology
mesh size dependence
Johnson-Cook
ductile failure modeling