Date of Award

Fall 2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Gene Hou

Committee Member

Sebastian Bawab

Committee Member

Timothy Coats

Call Number for Print

Special Collections; LD4331.E56 D385 2011

Abstract

High speed performance crafts are subjected to repeated impact loads in open seas. In this study, an attempt is made to investigate the dynamic response of onboard equipment under an impact environment generated by a 6 degree-of-freedom (DOF) motion simulator. An aluminum frame is used to represent onboard equipment, which is mounted on the 6 DOF motion simulator at various orientations and with varying amounts of additional weight. A series of 15 single-axis drop tests are conducted with the DOF motion simulator to study the effects of these impact loads on the onboard equipment. The test data is analyzed to characterize the response produced by the 6 DOF machine and its effect on the test frame.

A finite element model of the aluminum frame is created in FEMAP. Transient analysis using base excitation in NX NASTRAN is implemented to simulate the experimental drop tests. The response of the frame is recovered from the analysis and validated against the experimental data using frequency and transient response comparison techniques. In the process, important modeling parameters are determined to aid in the analysis validation. Russell error measures were used to show that the analysis results compared well to the test data recovered at the top of the frame with magnitude, phase, and comprehensive measures below an acceptable value for shock, 0.25.

The validated model is used to explore the coupling of finite element analysis (FEA) and multi body dynamics (MBD). A MBD model of the entire 6 DOF machine is used to recreate the experiments and determine the velocity at the base of the equipment which, in tum, is used to drive the validated FEA model. The experimental results are then compared to the response of the FEA model driven by the MBD model. The FEA model driven by the MBb model output compared well to the test data. It is shown that the analysis can be broken up into these two steps effectively. The results from this study serve as a stepping stone to the eventual coupling of MBD analysis and finite FEA in one program capable of simulating both.

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DOI

10.25777/z345-m238

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