Development and verification of a constitutive approach for the determination of high-strain-rate flow curves by means of the cutting process

有限元模拟对于金属切割过程的分析、设计和优化的好处是毋庸置疑的，特别是在开发昂贵且耗时的刀具概念方面。此外，它不仅被越来越多地用于基础研究工作，也被越来越多地用于中型公司，以提高产品开发的效率。为了用有限元程序模拟真实的加工过程，需要一个可靠的本构材料定律。这必须能够准确地描述在极高应变(1-5)、应变率(10^-3-10^61/S)和温度(Thomologe=0.16-0.90)下的热机械材料流动行为。为了确定高应变率流动曲线，这是发展本构材料定律所必需的，通常使用特殊的材料试验方法。例如，这包括使用分离式霍普金森棒测试(SHBT)。SHPT是专门为高应变率变形而开发的，它基于弹性波理论，最大应变率可达10^41/S，其获得的应变率比切削过程中的应变率低两个数量级。因此，材料定律必须外推到更高的应变率，以进行有限元切割模拟，从而不能充分地再现切割材料的行为。此外，SHBT技术非常复杂、成本密集型和耗时。本研究工作的目的是基于Oxley剪切带理论、有限元切割模拟和反向模拟，开发、验证和提供一种简单、经济的本构方法，直接从切割过程确定高应变率流动曲线(&gt；10^4 1/S)。为了验证将要开发的方法，需要考虑不同的材料。

The benefit of the FE-simulation for the analysis, design and optimization of metal cutting processes is undisputed, especially in the development of costly and time-intensive tool concepts. Furthermore, it is increasingly used not only in basic research works but also from medium-sized companies to improve the efficiency of product development. In order to simulate real machining processes with FE codes, a reliable constitutive material law is required. This must be capable to exactly describe the thermo-mechanical material flow behavior at extremely high strains (1-5), strain rates (10^-3 - 10^6 1/s) and temperatures (Thomologe = 0.16 to 0.90). For the determination of high-strain-rate flow curves, which are essential for the development of constitutive material laws, special material testing methods are generally used. This includes, for example, the use of the Split Hopkinson Bar Testing (SHBT). SHPT, specially developed for high-strain-rate deformations, is based on the elastic wave theory and can maximum strain rates up to 10^4 1/s. The achieved strain rates with the SHBT are by two orders of magnitude smaller than those in the cutting process. Therefore, the material law must be extrapolated to higher strain rates for the FE-cutting simulation, whereby the cutting material behaviour cannot be adequately reproduced. In addition, the SHBT technique is very complicated, cost-intensive and time consuming. The objective of this research work is, based on the Oxley shear zone theory, the FE cutting simulation and the inverse modeling the development, validation, and supply of a simple and economical constitutive approach to determine high-strain-rate flow curves (>10^4 1/s) directly from the cutting process. To verify the approach to be developed, different materials are to be considered.