Fundamentals of Piezoelectricity and Piezo Actuators

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Fundamentals of Piezoelectricity and Piezo Actuators

 

The product You were Looking for was moved Click Here for new Address Fundamentals ... (cont.) Mechanical Considerations for Dynamic Operation of PZTs Dynamic Forces Every time the PZT drive voltage changes, the piezo element changes its dimensions. Due to the inertia of the PZT mass (plus any additional load), a rapid change will generate a force (pushing or pulling) acting on the piezo. The maximum force that can be generated is equal to the blocked force, described by: (Equation 8) Maximum force available to accelerate the piezo mass plus any additional load. where: DL0 = max. nominal displacement without external force or restraint [m] kT = PZT actuator stiffness [N/m] Tensile forces must be compensated for by a mechanical preload (inside the actuator or external) in order to prevent damage to the ceramics. Preload should be around 20% of the compressive load limit, with soft preload springs—soft compared to the PZT stiffness (1/10 or less). In sinusoidal operation with frequency f and amplitude DL/2, peak forces can be expressed as: (Equation 9) Dynamic forces on a PZT in sinusoidal operation at frequecy f. where: Fdyn = dynamic force [N] meff = effective mass [kg] DL = peak-to-peak displacement [m] f = frequency [Hz] The maximum permissible forces must be considered when choosing an operating fequency. Example: Dynamic forces at 1000 Hz, 2 μm peak-to-peak and 1 kg load reach approximately ± 40 N. Fig. 22. Recommended guiding for large masses.