Complete Operating Deflection Shapes of an Excited Workpiece in Thermal Environments via an Improved Continuously Scanning Laser Doppler Vibrometer with a two-dimension Scan Scheme

Abstract

Abstract—It is significant to optimize the efficiency and accuracy of operational modal analysis (OMA) in extreme operation. Modal parameters in thermal environments, especially complete operating deflection shapes (ODSs), was first reconstructed through an improved continuously scanning laser Doppler vibrometer (CSLDV) with a two-dimension scan (2D-S) scheme (CSLDV 2D-S) system. Before this work, the manual-moving laser Doppler vibrometer, which replaced heat resistant accelerometers, was used in thermal vibrational measurements to extract only a few dozens of measured points across the grid. Compared with a manual-moving laser Doppler vibrometer in thermal vibrational measurements, the CSLDV is able to sweep its laser spot along a scan path on the surface of a workpiece. An improved CSLDV 2D-S system is able to measure thousands of vibration points in a few seconds and reconstitute precise multi-ODSs through the demodulation method and arranging each single ODS according to the position of scan paths on the measured workpiece. Therefore, the complete ODSs can be meshed after interpolation, instead of rough mode shapes formed by the LDV.