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Piezo electric actuation servo-hydraulic valve

The upgraded product, the piezo-electric actuation servo-valve, will facilitate essential high strain rate testing and particularly testing in the intermediate strain rate, which is often the strain rate of seismic action. The available servo-hydraulic valves cannot generate and control high frequency loading, particularly when high loading – frequency and large stroke are combined. However, if the driving unit of the servo – valve, which is electromagnetic, is suitably substituted by an equivalent piezo-electric unit, the performance of the valve is enhanced. Although the principle seems simple and the relevant dynamic model is well defined, the implementation is partially effective due to the limited expansion of the piezo-actuator. IMMG had already proceeded in the implementation of this unit in the project but the expansion limitation of P?? powerful actuators (< 150 µm) did not allow the use of the improved valve in high strain rate testing, when high ductility was foreseen. During the first part of this project a prototype mechanism was developed which multiplies (by four) the small range stroke of the piezo-electric actuator. Numerical investigation supported the experimental work and optimised the dimensions of the elements of the multiplier. Also, preliminary tests on dummy specimens indicate that the valve performance should be adequate during the main tests, which simulates earthquake motion. The response time of the new valve is 1,5 msec and this reaction speed allows the interruption of a fast developing phenomenon like concrete fracture.

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22, Askiton str
152 36 Penteli
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