Publications

Nonlinear system identification using digital image correlation

Roettgen, D.; Jones, E.; Brink, Adam R.; Reu, P.; Rohe, D.; Wagner, J.

Mechanical and aerospace structures often contain nonlinearities arising from frictional contact at joints. In order to calibrate response predicting models, these nonlinearities must be experimentally quantified to provide information about the type and strength of nonlinearity. For amplitude dependent nonlinearities, such as frictional contact, the nonlinear response is obtained by gathering ring down accelerometer data from impact testing with varying amplitudes. These accelerations are then spatially filtered to obtain a single degree-of-freedom response, which is used to identify a pseudo-modal model. This work examines a small test article with embedded frictional nonlinearities, in which accelerometers cannot be placed. Using a laser doppler vibrometer (LDV) to determine linear mode shapes and digital image correlation (DIC) to obtain response data during various amplitude hammer strikes, the nonlinearity in this small system is quantified.