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

切削的特点是变形、断裂和摩擦过程的复杂相互作用。在粘弹性材料的情况下，所有这些过程都很大程度上取决于所施加的切削速度。切削速度的增加或切削温度的降低可能导致从韧性断裂行为向脆性断裂行为转变。提出的项目的目的是在模型的基础上分析复杂的速度依赖的切削过程中的变形和断裂，并在实验和数值模型中描述从韧性到脆性的转变。实验研究针对两种基于粘弹性天然产物的模型系统进行，其中一种系统基于水合蛋白基质，另一种系统基于糖。它们的变形和断裂行为将在不同的温度和速度下进行分析。实验上无法达到的应变速率范围将通过应用温度-时间叠加（TTS）获得。然后，通过实验和TTS确定的参数为使用粘弹性材料模型进行大变形时速度和温度相关变形行为的数值模拟奠定了基础。确定的断裂韧性将成为相场模型的基础，该模型将用于模拟与速度相关的断裂行为，特别强调在高速下从韧性破坏到脆性破坏的转变。结合粘弹性材料模型，该相场模型将用于模拟切削过程，并在大速度范围内进行切削试验。模拟运行和实验切割序列将最终评估速度依赖关系。将对真实的天然材料进行额外的测试，以验证结果及其可转移性。因此，应用项目生成了切削过程的数值模型，这是未来系统工艺开发和优化天然材料切削工艺参数的基础，该模型基于对速度相关变形和断裂行为的实验分析。此外，还提供了通过实验和TTS对材料行为进行直接-间接联合分析的程序，该程序可进一步用于分析切削过程中也发生的热机械效应。

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.