A smart way to increase the frequency and degree of protection of piezoelectric ceramic transducers

The fragile nature of piezoelectric ceramic transducers (PCTs) is one of the largest problems in handling and using them. The various uses of PCTs in different applications and being subjected to different pressure loads expose PCTs to the risk of breakages. Additionally, to increase the natural frequency of any PCT, its thickness needs to be decreased. PCT thickness is usually designed to be half of an acoustic wavelength at its resonant frequency. Requirements for such physical changes complicate frequency adjustment of PCTs. To protect PCTs from breakage risks and to increase its frequency without decreasing thickness, this work suggests mounting the PCT on a rubber base. A high frequency SM211 7.2 MHz PCT was used in this experimental study. For comparisons, a PCT with standard bonding was used as reference. A three step procedure was used to prepare the rubber mounted emitter and receiver PCT in a new test setup. A scientific comparison between the standard response and the new setup response was performed, and the effects of various levels of static pressures and on various types of specimens were studied. Results showed that the frequency of the rubber mounted PCT increased from 7.2 MHz to 125 MHz, but the mode shape remained unchanged. The type of metal specimen used had no significant effect, but increasing the applied pressure increased the rms output voltage, with no effect on frequency.