Evaluation of the digital image correlation method for the measurement of vibration mode shapes

Digital Image Correlation (DIC) is a modern non-contact, full-field optical technique that is being used for the measurement of static and dynamic displacement problems, material testing and fracture mechanics. In particular, three dimensional DIC is able to measure the out-of-plane vibration mode shapes and deformation of a vibrating structure. Thus, this technique can potentially provide an important validation tool between measured and predicted results. This paper presents some preliminary evaluation results from using the DIC measurement approach. The DIC method was implemented using two low-speed charge-couple device cameras and a phase-locked measurement technique synchronised to the excitation. A 1.2mm thick steel plate with clamped boundary conditions was chosen as the test sample. Resonant frequencies and mode shapes were compared to predictions made using a Finite Element analysis and the experimental Chladni method of visualizing vibrating mode patterns. This comparison reveals some of the advantages and limitations of the DIC method for vibration mode shape analysis