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

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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.