Ductile fracture modeling based on a mesh objective element removal technology

• 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 catchesthe material behavior at high speed/temperature with a relatively few material parameters. Thisis an obvious advantage, in addition to its widespread use in commercial softwares, which makesit so often used in many applications, and, in particular, machining simulations of metal cuttingprocesses. 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 orthogonalmachining simulations.In order to overcome this difficulty a mesh objective element removal technology is devisedbased 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 orderto obtain mesh objective element deletion, an element removal criterion is defined on the plasticstrain energy prior to fracture state is considered as fracture energy. A fracture state is achievedin 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 iscomputed based on the current accumulated dissipation. The figures below show the model setup, 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 significantmesh size dependence without the proper scaling of the energy dissipation.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Produktionsteknik, arbetsvetenskap och ergonomi (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Production Engineering, Human Work Science and Ergonomics (hsv//eng)

Keyword

element removal technology

mesh size dependence

Johnson-Cook

ductile failure modeling

Publication and Content Type

kon (subject category)

vet (subject category)