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 conditions 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 phi = 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 activities, 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 absolutely reliably flow stress data even for strain rates up to 500 /s