Servo-hydraulic Testing Machine
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Servo-hydraulic testing machine
Fundamentals
In servo-hydraulic high-speed testing machines (see also: high-speed tensile test), the load on the test specimen is not applied according to the principle of force coupling, as is the case in quasi-static tensile tests, but according to the principle of energy transfer. This means that the kinetic energy is suddenly introduced into the test specimen as deformation work [1, 2] (see: servo-hydraulic drive for materials testing machines). The selected test speed is achieved via a run-up distance, whereby a run-up bolt is clamped to the test specimen. At the end of the run-up distance, the test specimen is coupled in a force-fit manner.
The Figure shows a schematic diagram of a servo-hydraulic testing machine. This testing machine can achieve a maximum test speed of 20 m/s and a maximum load of 25 kN.
| Figure: | Schematic diagram of the Instron VHS 25/25-20 servo-hydraulic testing machine [3, 4] |
Experimental procedure
The procedure for the high-speed tensile test differs from that of the quasi-static experiment in that there is no direct coupling between the test specimen and the piston rod. Once the desired test speed has been reached over the run-up distance, the energy of the system is suddenly transferred to the test specimen [1]. In order to minimise the vibrations occurring during the sudden load (see: impact loading plastics), a damping disc made of 4 mm thick leather was used in the run-up section. The force was measured using a piezoelectric force transducer, and the elongation of the test specimen was determined using an inductive displacement transducer (LVDT).
See also
- Material testing machine
- High-speed tensile test
- Crosshead speed
- Drives materials testing machines
- Impact loading high-speed testing
Referecnces
| [1] | Bardenheier, R., Rogers, G.: Dynamic Impact Testing. Instron Ltd., High Wycombe, UK (2003) |
| [2] | Bardenheier, R., Borsutzki, M.: Anforderungen an Hochgeschwindigkeitsprüfsysteme zur Ermittlung von Kennwerten an Blechwerkstoffen. In: Buchholz, O. W., Geisler, S. (Eds.): Herausforderung durch den industriellen Fortschritt – Proceedings Werkstoffprüfung (2003) pp. 78–87, (ISBN 3-514-00703-9; see AMK-Library under M 11) |
| [3] | Bardenheier, R.: Dynamic Impact Testing – VHS High Rate Testing Systems. Instron Ltd., High Wycombe, UK (2005) |
| [4] | Stahl-Eisen-Prüfblätter (SEP) 1230 (2007-02): The Determination of Mechanical Propertiesof Sheet Metal at High Strain Rates in High Speed Tensile Tests |
Weblinks
Wikipedia – The Free Encyclopedia: Materials Testing Machine https://en.wikipedia.org/wiki/Universal_testing_machine