Modal testing of complex hardened structures

Abstract

A new testing method is being developed by the Air Force Research Lab to excite a desired multi-dimensional response in a structure using tuned resonances. The structure consists of a Aluminum plate and a perpendicular shelf. The test article is excited through the use of either an impact hammer or pyrotechnics (e.g., a pyrotechnic plunger) which in turn inputs a specific frequency profile. The dynamic response of the plate and shelf spans the entire spectrum from low (10 Hz) to high (10 kHz) frequency as well different peak amplitudes (i.e., accelerations). They are captured by a variety of instrumentation methods including modal accelerometers, laser vibrometers, and a digital image correlation system. The location of the shelf as well as its material and stiffness properties is modified to reproduce the design objective (frequency response functions with the desired amplitude and phase spectrum). These modifications are achieved through interpretation of modal data. ©2010 Society for Experimental Mechanics Inc.