For larger forces, an additional term, describing the influence of the polarization changes, must be superimposed on the stiffness (k T). The equation DL N = F/k T is only valid for small forces and small-signal conditions. When an external force is applied to poled piezoceramics, the dimensional change depends on the stiffness of the ceramic material and the change of the remnant strain (caused by the polarization change). The polarization is affected by both the applied voltage and external forces. The poling process of piezoceramics leaves a remnant strain in the material which depends on the magnitude of polarization. This narrow definition is of limited application for piezoceramics because the cases of static, dynamic, large-signal and small-signal operation with open and shorted electrodes must all be distinguished. Stiffness is normally expressed in terms of the spring constant k T, which describes the deformation of the body in response to an external force. The stiffness of a solid body depends on Young’s modulus of the material. The PZT ceramic is especially sensitive to shear forces they must be intercepted by external measures (flexure guides, etc.).Īctuator stiffness is an important parameter for calculating force generation, resonant frequency, full-system behavior, etc. Preloaded elements are highly recommended for dynamic applications. PI offers a variety of piezo actuators with internal spring preload for increased tensile load capacity. Tensile loads of non-preloaded piezo actuators are limited to 5% to 10% of the compressive load limit. The load capacity data listed for PI actuators are conservative values which allow long lifetime. Parameters such aspect ratio, buckling, interaction at the interfaces, etc. For stacked actuators and stages (which are a combination of several materials) additional limitations apply. This value must never be approached in practical applications, however, because depolarization occurs at pressures on the order of 20 % to 30 % of the mechanical limit. PZT ceramic material can withstand pressures up to 250 MPa (250 x 10 6 N/m 2) without breaking. The mechanical strength values of PZT ceramic material (given in the literature) are often confused with the practical long-term load capacity of a piezo actuator. (Compressive Load Limit, Tensile Load Limit) More Video Animations of Piezo Motion Technologies Piezo Application Examples are found in the Piezo Blog Piezo Effect /Different Types of Piezo Actuators / Video The book addresses students, academic as well as industrial reseachers and development engineers who are concerned with piezoelectric sensors and actuators.Piezo Design: Forces & Stiffnes in Piezoelectric ActuationĪctuators | Piezo Motors | Piezo Transducer | Piezo Stages | Controllers | FSM In particular, the studied application areas are The book also deals with various applications of piezoelectric sensors and actuators. An optical approach is presented that allows the quantitative determination of the resulting sound fields. One focus of the book lies on piezoelectric ultrasonic transducers. Furthermore, a simulation-based approach is detailed which enables the reliable characterization of sensor and actuator materials. Different modeling approaches and methods to precisely predict the behavior of piezoelectric devices are described. It gives a comprehensive overview of piezoelectric materials such as quartz crystals and polycrystalline ceramic materials. This book introduces physical effects and fundamentals of piezoelectric sensors and actuators.
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