Date of Award

Fall 1991

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Engineering Mechanics

Committee Director

Ramamurthy Prabhakaran

Committee Member

Stephen G. Cupschalk

Committee Member

Zia Razzaq

Call Number for Print

Special Collections; LD4331.E57R35

Abstract

Structural defects such as cracks can cause catastrophic failure in engineering components or structures. There are many techniques to measure the crack growth in materials and are commercially available. In this thesis, bondable crack length measurement gages have been investigated and these gages give electrical signal as the output and measure the crack length continuously. Silver paint, nickel powder impregnated epoxy and carbon powder impregnated polymer composite gages are investigated and tests are conducted by resistance measurement method with simple instrumentation and by potential drop method with a constant current output source. Rectangular shape gages have been investigated and as the sensitivity is low for this shape at small crack lengths, other modified shapes have been developed. Tapered width, tapered thickness and optimized shape gages are investigated to improve the sensitivity of the gages and tests are conducted. Dual sensitivity of the gages may cause errors and so experiments are conducted to study the changes in the resistance of the gages due to changes in temperature. Experiments are also conducted for the rectangular shape and for the other modified shapes using the direct current potential drop method and the performance of the gages is investigated.

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DOI

10.25777/aghj-hq51

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