Recent Enhancements to Determine Flow Stress Data in High Speed Compression Tests*

The accuracy in numerical simulation and physical models is increasing continually. For this reason, the attention to the measurement of flow stress fields at hot forming condi-tions rises presently. The determination of flow curves at small and middle strain rates up to 100 /s has become a standard procedure. In the wide range between strain rates of 100 /s up to 500 /s no accurate experimental data of compression tests by the use of servo-hydraulic testing systems exists to date. In this context, the IBF investigated how compression tests especially on servo hydraulic testing-machines can be developed in order to expand the range of flow-curve fields clearly above 100 /s with strains up to ϕ = 0.7. The maximum tool speed of the IBF testing machine is 3000 mm/s. This presentation shows the advances realised in this field. During the research ac-tivities, the existing servo-hydraulic high-speed testing machine has been optimised and new post processing techniques have been developed. Hence, valid flow stress values can now be determined up to strain rates of 300 /s in compression tests on the utilised servo hydraulic testing system. Present investigations have the aim to determine abso-lutely reliably flow stress data even for strain rates up to 500 /s. Keywords