Zhu, WeidongYuan, Ke2025-02-132025-02-132024-01-0112963http://hdl.handle.net/11603/37662The objective of this work is to develop a novel general-purpose three-dimensional (3D) continuously scanning laser Doppler vibrometer (CSLDV) system for 3D vibration measurement of structures with arbitrarily curved surfaces. This work is motivated by the fact that 3D full-field vibration measurement is significant to structures, especially those with curved and complex surfaces such as turbine blades, vehicle bodies, and aircraft wings. Modal tests that obtain vibration components along three axes of a coordinate system can provide more information and locate defects on more complex structures than those that only obtain single-axis vibration, and can improve the accuracy of their structural health monitoring. 3D full-field vibration can also be used to identify dynamic characteristics of a complex structure and update its finite element model during structural analysis and product design where vibration must be determined in all its components. A triaxial accelerometer can be attached on a structure to measure its 3D vibrations, which can lead to mass loading, especially when multiple triaxial accelerometers are needed in modal tests of light-weight structures. A 3D scanning laser Doppler vibrometer (SLDV) system can be used to measure 3D vibration of a structure in a non-contact. However, it usually takes the 3D SLDV system a long time to obtain high spatial resolution, especially for structures with large surfaces, because laser spots must stay at one measurement point for enough time before they are moved to the next one to conduct more averages of measurement data when high frequency resolution is needed. The 3D CSLDV system proposed in this work can rapidly obtain 3D full-field vibration shapes, such as mode shapes and operating deflection shapes (ODSs) of a structure, in a non-contact way by sweeping three laser spots over its surface in a continuous and synchronous mode. The universality of the system lies in its capability to measure vibration of structures with various shapes, including flat, curved, and difficult-to-access areas, as well as structures under various excitation, including sinusoidal and random excitation. The major contributions of this work include: 1) developing a calibration method to achieve synchronous scanning of three laser spots, and improving it to fit measurement on curved surfaces and virtual surfaces behind a mirror; and 2) developing a signal processing method to identify modal parameters of structures under random excitation.application:pdfThis item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu or contact Special Collections at speccoll(at)umbc.eduText