Publication Date

5-2024

Date of Final Oral Examination (Defense)

11-28-2023

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Civil Engineering

Department Filter

Civil Engineering

Department

Civil Engineering

Supervisory Committee Chair

Nick Hudyma, P.E., Ph.D.

Supervisory Committee Member

Bhaskar Chittoori, P.E., Ph.D.

Supervisory Committee Member

George Pujalte, M.D., C.A.Q.S.M., F.A.C.S.M, F.A.M.S.S.M., F.A.A.F.P.

Abstract

Bone is a complex natural material that presents many challenges to researchers interested in characterizing its mechanical properties. There are different techniques, such as drying, embalming, and freezing, to preserve bones for engineering and scientific study. There are advantages and disadvantages to these techniques, and there have been limited studies comparing the effect of preservation techniques on the mechanical and fracture properties. In this research, aged and fresh bovine bone specimens are tested in compression while monitoring acoustic emissions (AE). Three main aspects of testing are investigated: the force-displacement curves, acoustic emission activity, and fracture patterns observed in X-ray computed tomography (CT) scans.

Before compression testing, the ends of each bone specimen were potted in epoxy, CT scanned, encased in heat-shrink plastic, and an acoustic emission sensor was mounted to each specimen. During compression testing, force-displacement data is collected and synchronized to acoustic emission data. The tested bone specimen were CT scanned.

Pre-test CT scans showed that aged bones contained fractures that were produced by the aging (bleaching and boiling) processes. Aged bone specimens had higher failure forces and higher apparent stiffness values. The force-displacement curves show that aged bone specimens have a more brittle behavior. Aged bone specimens had greater numbers of acoustic emission events than fresh bone specimens. The AE events in fresh bone specimens were associated with lower energy and higher average frequencies. Acoustic emission events occur in aged bone specimens well before they occur in fresh bone specimens. In some instances, no acoustic emission event occurred until failure in fresh bone specimens. Post-test CT scans revealed that aged bone specimens had large multifragmentary fractures that propagated through the entire length of the specimen. The fractures produced in fresh bone specimens were contained within the lower and upper twenty percent of the specimen. The fresh bone specimens had circumferential fractures that were not observed in the aged bone specimens. These fractures were contained between the inner and outer dense cortical bone veneer of the specimens.

The data generated and presented show there is a clear difference in the behavior of aged and fresh bone specimens. These differences are demonstrated by force-displacement curves, acoustic emission data, and fracture types identified in CT scans. Deformation properties between fresh and aged bone specimens presented a clear distinction between the microcracks and crack propagation between fresh and aged bones. Overall, each aspect of this research showed clear differences in the failure behavior of fresh and aged bones. Although aged bone specimens and fresh bone specimens have less stringent handling and storage requirements than fresh bone specimens, these two specimen types have different mechanical and fracture properties.

DOI

https://doi.org/10.18122/td.2195.boisestate

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