Experimental and computational analysis of rate dependence during cutting of viscoelastic natural product-based model systems

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Cutting is characterized by a complex interplay of deformation, fracture and friction processes. In the case of viscoelastic materials, all these processes depend significantly on the applied cutting velocity. The increase of cutting velocity or the reduction of temperature at cutting may consequently lead to a transition from ductile to brittle fracture behavior.The aim of the proposed project is to analyze the complex velocity-dependent cutting process with respect to deformation and fracture on a model basis and to describe the transition from ductile to brittle both in the experiment and in a numerical model. The experimental investigations are carried out for two viscoelastic natural product-based model systems, where one system is based on a hydrated protein matrix and the second system is based on sugar. Their deformation and fracture be-havior will be analyzed at various temperatures and velocities. Experimentally unreachable strain rate ranges will be accessed by applying temperature-time superposition, TTS. The parameters de-termined experimentally and by TTS then build the basis for the numerical modeling of the velocity- and temperature-dependent deformation behavior at large deformations using a viscoelastic material model. The determined fracture toughness will be the basis for a phase-field model to be developed for simulating the velocity-dependent fracture behavior, with special emphasis being placed on the transition from ductile to brittle failure at high velocities. In combination with the viscoelastic material model, this phase field model will be applied to simulate cutting processes and cutting tests will be carried out over a large velocity range. Simulation runs and experimental cutting sequences will finally be evaluated with regard to velocity dependency. Additional tests on real natural material will be carried out to validate the results and their transferability.Therefore, the applied project generates a numerical model of the cutting process which is the basis for a future systematic process development and optimization of the process parameters for the cutting of natural materials, based on the experimental analysis of the velocity-dependent defor-mation and fracture behavior. Furthermore, routines are provided for the combined direct-indirect analysis of the material behavior by means of experiment and TTS, which may further be used for analyzing thermomechanical effects that also occur during cutting.