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Jaesuk Lee

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Mechanical Engineering

First Advisor

Kamyar Nikpur


Flaws exist in most machine parts and structures which under critical conditions can rapidly grow and cause the sudden rupture of the component. The catastrophic fracture can be prevented if an early warning, on-line real-time system is devised to trace the crack position and its severity. There are functional relationships between the vibrational frequency and the local compliance. The crack is one of the major elements which gives rise to the local flexibility of the component. Thus, an analysis of the vibrational response of the cracked component, furnishes sufficient information regarding the size and position of the propagating crack. Composite shell-like components are widely used in industry due to their high strength-to-weight ratios. However, these materials are usually susceptible to cracking. Identification of the cracks in composite shells is of great importance and is studied in the present thesis. The vibrational analysis of cracked shells reveals significant changes in the frequency spectrum and the coupling of vibrational modes, which provides promising tools to diagnose the crack and locate its approximate position.

Library of Congress Subject Headings

Shells (Engineering) -- Vibration

Strains and stresses

Fracture mechanics



Number of Pages



South Dakota State University