The Use Of Piezoelectric Materials In Smart Structures

A piezoelectric material is basically a ceramic that outputs a voltage upon being mechanically strained. Sensors made of this material are sensitive enough to generate signals when subjected to low-amplitude mechanical waves such as sound waves traveling through solids. This makes them candidate materials for all kinds of exciting applications. For example, sensors mounted on a wing surface could detect ice formation on the wing using surface active waves. Since the velocity of sound in a given medium is a function of temperature, such sensors are also being used to actually measure temperature. It is important for students to be aware of this new generation of materials and to be familiar with the use of these materials for measuring fundamental quantities such as the velocity of sound. This experiment has been designed for use in an introductory mechanical or materials engineering instrumentation lab. Initial setup (after procuring all the materials) should take the lab instructor about 2 hours. A single measurement can be initiated and saved to disk in less than 3 minutes, allowing for all the students in a typical lab section to take their own data rather than share a single set of data for the entire class. This experiment is offered to a sophomore-level laboratory class in mechanical engineering that focuses on measurements, instrumentation and manufacturing and addresses the first two topics in that course. Introduction A piezoelectric material is basically a ceramic that outputs a voltage upon being mechanically strained. Sensors made of this material are sensitive enough to generate signals when subjected to low-amplitude mechanical waves such as sound waves traveling through solids. This makes them candidate materials for all kinds of exciting applications. For example, sensors mounted on a wing surface could detect ice formation on the wing using surface active waves. Since the velocity of sound in a given medium is a function of temperature, such sensors are also being used to actually measure temperature. It is important for students to be aware of this new generation of materials and to be familiar with the use of these materials for measuring fundamental quantities such as the velocity of sound. This experiment has been designed for use in an introductory mechanical or materials engineering instrumentation lab. Initial setup (after procuring all the materials) should take the lab instructor about 2 hours. A single measurement can be initiated and saved to disk in less than 3 minutes, allowing for all the students in a typical lab section to take their own data rather than share a single set of data for the entire class. P ge 8.182.1 Proceedings of the 2003 American Society for Engineering Education Annual Conference & Exposition Copyright © 2003, American Society for Engineering Education Approach Our experiment utilizes long single strand wire of different materials coiled on a cylindrical spool with the coils widely spaced to avoid interference. A piezosensor is connected to each coil at the same polar location and the electric signal is fed through an amplifier to an oscilloscope. A sound wavetrain is generated by a pencil lead break at one end of the wire and progresses through the length of the wire. The time lag between the wavetrain’s arrival at successive coils, and the reduction of the signal’s amplitude are a measure of fundamental material properties such as the velocity of sound and the attenuation factor for that material. The experiment enables students to interface concepts of physics, materials science and materials engineering and encourage them to develop scenarios for the practical application of novel materials. Equipment and supplies General supplies and measuring equipment commonly found in most physics/instrumentation labs are listed in Table 1. Materials/supplies that will need to be purchased specially for this experiment are listed in Table 2.