COMPENSATION OF FREQUENCY RESPONSE FUNCTION MEASUREMENTS BY INVERSE RCSA
1 online resource (86 pages) : PDF
University of North Carolina at Charlotte
The stability lobe diagram is a graphical device used to select stable cutting conditions in machining. The generation of the stability lobe diagram requires the tool-holder-spindle-machine frequency response function (FRF). Therefore, the accuracy of the stability lobe diagram depends on the accuracy of the measured FRF. Impact testing is a widely used technique to measure FRFs. Due to its setup simplicity, an accelerometer is often used to measure the structure’s response that corresponds to the force impact. However, the use of an accelerometer causes mass loading, which leads to a shift in the measured natural frequency of the system. The objective of this study is to understand the effect of accelerometer mass loading and cable damping on FRF measurements and to compensate it using the inverse receptance coupling substructure analysis (IRCSA) approach. Impact testing was completed for: 1) two steel rods of different diameters at multiple overhang lengths with clamped-free boundary conditions; and 2) two thin aluminum ribs of different lengths and thicknesses with clamped-clamped-clamped-free boundary conditions. The FRFs were measured using both accelerometers and a vibrometer, where the latter provided a non-contact measurement reference with no mass loading. Using IRCSA, a model of the accelerometer-cable FRF was decoupled from the measured FRF to compensate for mass loading and cable damping. The resultant IRCSA FRF was then compared against the vibrometer FRF to verify the compensation technique. The natural frequency agreement after compensation was shown to be at the tenths of a percent level in all cases.
ACCELEROMETERFREQUENCY RESPONSE FUNCTIONMASS LOADINGRCSARECEPTANCE
Elliott, GloriaTarbutton, Joshua
Thesis (M.S.)--University of North Carolina at Charlotte, 2017.
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