The effect of operational modal analysis in strain estimation using the modal expansion

The stress history of a structure in operation is important for the remaining fatigue lifetime. The fatigue critical locations are, however, often inaccessible or placed at damaging spots where sensors are easily corrupted. Virtual sensing techniques can be applied to estimate strain in unmeasured points. The Modal Expansion/Modal Decomposition is one of these techniques. This technique uses the mode shape of the structure to decorrelate a measured spatial limited response so it can expand this decorrelated response with the strain mode shape to estimate the strain response of the entire structure. These mode shapes come from either an updated Finite Element Model or a modal analysis. The experimental mode shapes use an expansion procedure - like the Local Correspondence Principle. This paper studies the effect of using experimental mode shapes in strain estimation using the Modal Expansion and the Local Correspondence Principle.