High-speed digital image correlation measurements of random nonlinear dynamic response

Abstract

Future United States Air Force (USAF) high-speed vehicles will require innovative, non-contacting full-field measurement techniques to validate analysis and design practices. In this experimental investigation, the authors explore the feasibility of using high-speed 3D digital image correlation (DIC) to measure the geometrically nonlinear and stochastic response of a compliant panel representing thin-gauge aircraft-like structure. Existing measurement techniques typically employed for this application include laser vibrometry, accelerometers, and discrete strain gages. However, these approaches are limited to a few points or direct contact resulting in altered structural response. The possibility of full-field noncontact displacement and strain measurement is an attractive alternative for this type of dynamic response testing, particularly as one is not limited to predetermined sensor location. The technical challenges of using DIC for this application include extending the technique from quasi-static or extremely short duration transient dynamic measurement technique to steady-state, long-duration (seconds of data) random response. Multiple, long-time sample records are desired for ensemble averaging, and correspondingly high sample rates generate appreciable volumes of digital images never before attempted with this type of analysis. DIC displacement and strain results are compared to the more traditional measurement methods to establish accuracy. Results demonstrate the feasibility of using DIC for nonlinear dynamic displacement and strain response measurements. The ability to obtain full-field displacement data was beneficial towards identification and differentiation of the dynamic panel response from the inherent dynamic response of the experimental facility.