New tools for structural testing: Piezoelectric impact hammers and acceleration rate sensors

Small size ultra-high precision mechanical systems demand special testing methodologies, such as a better high frequency response, a precise impact position, an extremely high repeatability, etc. Utilizing the fact that signals obtained from piezoelectric sensing elements are strongly influenced by the interfacing circuitry, piezoelectric sensors which can measure acceleration rate were developed. Both analytical and experimental results indicate that acceleration rate sensors can detect the arrival of realistic shock earlier than that of conventional accelerometers. An ultra-high precision high speed piezoelectric impact system with an on-line loadcell was also modeled, designed, and built. The sensitivity of this on-line loadcell was calibrated by using a standard quartz loadcell. This innovative high speed impact hammer system was found to have a timing accuracy in the range of micro-seconds and a positioning accuracy in the range of micrometers. Finally, modal testing was performed by combining the impact hammer system and acceleration rate sensors. © 1997 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.