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，所有这些过程都明显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会导致从韧性到脆性断裂行为的转变，该项目的目的是分析复杂的速度依赖性切削过程中的变形和断裂模型的基础上，并在实验和数值模型中描述从韧性到脆性的转变。实验研究进行了两个粘弹性天然产物为基础的模型系统，其中一个系统是基于水合蛋白质基质和第二个系统是基于糖。分析了它们在不同温度和速度下的变形和断裂。实验无法达到的应变率范围将通过应用温度-时间叠加，TTS。实验和TTS确定的参数，然后建立在大变形的速度和温度依赖的变形行为的数值模拟的基础上，使用粘弹性材料模型。确定的断裂韧性将是一个相场模型的基础上开发的速度依赖性的断裂行为模拟，特别强调被放在从韧性到脆性破坏在高速的过渡。将该相场模型与粘弹性材料模型相结合，应用于切削过程的模拟，并在较大的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性。此外，还将对真实的天然材料进行试验，以验证试验结果及其可移植性。因此，该应用项目基于对速度相关变形和断裂行为的试验分析，生成了切削过程的数值模型，这是未来天然材料切削系统工艺开发和工艺参数优化的基础。此外，提供了用于通过实验和TTS对材料行为进行组合的直接-间接分析的例程，其可以进一步用于分析也在切割期间发生的热机械效应。

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.