A Noncontacting Approach for Full Field Strain Monitoring of Rotating Structures

Abstract

The threedimensional pointtracking (3DPT) measurement approach is used in conjunction with finite element (FE) method and modal expansion technique to predict fullfield dynamic response on a rotating structure. A rotating threebladed wind turbine rotor was subjected to different loading scenarios, and the displacement of optical targets located on the blades was measured using 3DPT. The outofplane measured displacement of the targets was expanded and applied to the FE model of the turbine to extract fullfield strain on the turbine. The sensitivity of the proposed approach to the number of optical targets was also studied in this paper. The results show that the dynamic strain on a structure can be extracted with a very limited set of measurement points (optical targets) placed on appropriate locations on the blades. It was shown that the proposed technique is able to extract dynamic strain all over the entire structure, even inside the structure beyond the line of sight of the measurement system. Because the method is based on a noncontacting measurement approach, it can be readily applied to a variety of structures having different boundary conditions.