Author: Edwin Fishman
Title: The Natural Response of Uniform in Air and Partially Submerged in a Quiescent Water Body
Date/time: April 24th at 10:00am
Location: 3179K Aerospace Engineering Conference Room, Glenn L. Martin Hall.
Committee members:
Professor James Duncan, Advisor & Chair
Professor Miao Yu
Professor Kenneth Kiger
Abstract:
The free vibration of three aluminum plates (.4 m wide, 1.08 m long) oriented horizontally is studied experimentally under two fluid conditions, one with the plate surround by air and the other with the bottom plate surface in contact with a large undisturbed pool of water. Measurements of the out of plane deflection of the upper surfaces of the plates are made using cinematic Digital Image Correlation (DIC) over the center portion of the surface and optical tracking of the center point. Three plate geometries and boundary conditions are studied: A uniform plate with 6.35 mm thickness pinned at the two opposite narrrow ends (UP), a uniform plate with 4.83 mm thickness simply supported at one narrow end and clamped at the opposite end (UC), and a stepped plate with thickness varying from 12.7 mm to 6.35 mm pinned at two opposite narrow ends (SP). The plate’s free response is induced using an impact hammer at three locations along the center-line of the plate. Video frames of the plate’s motion are collected from stereoscopic cameras and processed using DaVis-Strainmaster and MATLAB to extract full-field displacements as a function of time. 2-degree-of-freedom displacements of the plate center are collected from tracking the center target’s motion. Time and frequency response plots are presented for comparison between the half-wet and air cases and analysis of their dynamics. It is found that the added mass of the water results in lower measured natural frequencies and modified mode shapes. These results are compared to mode shapes/frequencies produced in Creo Simulate and found to agree. Further experiments are discussed.