Simulation of Ductile Fracture of Slabs Subjected to Dynamic Loading Using Cohesive Elements

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Abstract

Dynamic loading of elastic-plastic slabs is studied numerically using a finite element approach, where introduction of cohesive elements enables fracture. For the bulk material, J(2)-flow theory is chosen as constitutive model, whereas the behavior of the cohesive elements is described by an irreversible cohesive law. The fracture behavior is governed solely by the cohesive elements, which are incorporated in the original mesh after a certain deformation state is reached. It is found that cohesive elements that are introduced early in the simulation are able to sustain the shape of the slab, so that necking and specimen fracture may occur at a location that does not coincide with the position of the first developed cohesive zone. This is an important feature, especially in the case of multiple necking. The influence of introducing cohesive elements on the deformation behavior is studied by comparison of contour plots describing the time development of normalized strain rates. Numerical simulations where the insertion of cohesive elements is enabled are compared with corresponding results where the material model only consists of J(2)-flow theory. Differences in the simulated material response, such as delay in the onset of necking, indicate that depending on the aim of the study, introduction of cohesive elements will influence the observed results. In addition, the proportion of kinetic energy of the post-fracture fragment compared to the amount of input work as function of imposed loading velocity is studied along with the effect of changing specimen aspect ratio.

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Subject classification (UKÄ) – MANDATORY

  • Applied Mechanics

Keywords

  • cohesive zones, ductile fracture, dynamic loading, finite elements, time, history
Original languageEnglish
Pages (from-to)871-892
JournalInternational Journal of Damage Mechanics
Volume21
Issue number6
Publication statusPublished - 2012
Publication categoryResearch
Peer-reviewedYes