Author ORCID Identifier

https://orcid.org/0000-0002-2400-7958

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department

Mechanical Engineering

First Advisor

Dr. David W. Herrin

Abstract

Blocked force determination is an alternative to the more routine method of inverse force determination using classical transfer path analysis. One advantage of determining blocked forces is that there is no need for the source to be detached or isolated from the system. Another advantage is that calculated blocked forces are appropriate when modifications are made on the receiver side of the interface. This insures that the blocked forces are suitable for utilization in analysis models where receiver system modifications are considered. Difficulties in using the approach arise when interface locations are difficult to instrument. This thesis demonstrates that blocked forces may also be determined along a continuous interface offset from bolted connections or isolators making the method more convenient to use. This offset interface strategy is demonstrated for plate and shell structures using both simulation and measurement. Recommendations are made for selecting the number of forces and blocked force locations along this offset interface.

The number of blocked forces required will be prohibitive at higher frequencies since the structural wavelength is inversely proportional to the square root of frequency. An uncorrelated blocked force method is applied at high frequencies and the predicted results are validated for different structural systems. It is shown that predicted results in one-third octave bands are accurate using the uncorrelated assumption, and that uncorrelated forces can be used to predict the effect of modifications on the receiver side of the interface.

Similar approaches are then used for the analogous acoustic case where acoustic blocked sources are positioned on a cross-sectional plane inside a duct. It is demonstrated that correlated and uncorrelated assumptions can be used to predict the sound pressure level downstream of the source at low and high frequencies respectively. This is the case even if the duct system downstream of the cross-sectional plane is modified. The approach seems promising for simulating acoustic sources in heating, ventilation, and air conditioning ducts above the plane wave cutoff frequency.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.070

Share

COinS