Engineering Commons^™

Mechanical Properties Of Bone Due To Sost Expression: Nanoindentation Assessment Of Murine Femurs, Amir Rafie

Master's Theses

In the human genome, the SOST gene codes for a protein sclerostin. Sclerostin is an osteocyte-expressed negative regulator of bone formation. When the SOST gene is not coded, bone formation is reduced in individuals during skeletal maturation. This study utilizes nanoindentation methods to test for the mechanical properties of bones that both express and do not express the SOST gene. 100 transgenic murine femurs were obtained from Lawrence Livermore Labs in the form of 6 and 8 month SOST transgenic mice, 6 and 12 month SOST knockout mice, and wild type control littermates for each of the 4 age groups. …

A Tensile Deformation Model For In-Situ Dendrite/Metallic Glass Matrix Composites, J. W. Qiao, T. Zhang, Fuqian Yang, P. K. Liaw, S. Pauly, B. S. Xu

Chemical and Materials Engineering Faculty Publications

In-situ dendrite/metallic glass matrix composites (MGMCs) with a composition of Ti₄₆Zr₂₀V₁₂Cu₅Be₁₇ exhibit ultimate tensile strength of 1510 MPa and fracture strain of about 7.6%. A tensile deformation model is established, based on the five-stage classification: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (yield platform), (4) plastic-plastic (work hardening), and (5) plastic-plastic (softening) stages, analogous to the tensile behavior of common carbon steels. The constitutive relations strongly elucidate the tensile deformation mechanism. In parallel, the simulation results by a finite-element method (FEM) are in good agreement with the experimental findings and theoretical calculations. The present study gives a mathematical model to clarify …

Effect Of Architecture And Porosity On Mechanical Properties Of Borate Glass Scaffolds Made By Selective Laser Sintering, Krishna C. R. Kolan, Ming-Chuan Leu, Greg Hilmas, Taylor Comte

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The porosity and architecture of bone scaffolds, intended for use in bone repair or replacement, are two of the most important parameters in the field of bone tissue engineering. The two parameters not only affect the mechanical properties of the scaffolds but also aid in determining the amount of bone regeneration after implantation. Scaffolds with five different architectures and four porosity levels were fabricated using borate bioactive glass (13-93B3) using the selective laser sintering (SLS) process. The pore size of the scaffolds varied from 400 to 1300 μm. The compressive strength of the scaffolds varied from 1.7 to 15.5 MPa …

Engineering Properties Of Oil Palm Shell Lightweight Concrete Containing Fly Ash, Hilmi Mahmud

Hilmi Mahmud

The effect of cement replacement with type F fly ash at 0%, 10%, 30% and 50% on some engineering properties of an oil palm shell (OPS) high strength lightweight concrete was investigated. The properties studied include workability, density, compressive strength, splitting tensile strength, flexural strength, water absorption and drying shrinkage. The effect of initial water curing periods of 2, 4 and 6. days after demoulding and air drying environment on the 28-day compressive strength was also investigated. The test results showed that even with 50% substitution of cement with fly ash, a low cost grade 30 OPS lightweight concrete can …

Sol-Gel Derived Biodegradable And Bioactive Organic-Inorganic Hybrid Biomaterials For Bone Tissue Engineering, Bedilu A. Allo

Electronic Thesis and Dissertation Repository

Treatments of bone injuries and defects have been largely centered on replacing the lost bone with tissues of allogeneic or xenogeneic sources as well as synthetic bone substitutes, which in all lead to limited degree of structural and functional recovery. As a result, tissue engineering has emerged as a viable technology to regenerate the structures and therefore recover the functions of bone tissue rather than replacement alone. Hence, the current strategies of bone tissue engineering and regeneration rely on bioactive scaffolds to mimic the natural extracellular matrix (ECM) as templates onto which cells attach, multiply, migrate and function.

In this …

Scandia And Ceria Stabilized Zirconia Based Electrolytes And Anodes For Intermediate Temperature Solid Oxide Fuel Cells: Manufacturing And Properties, Yan Chen

Electronic Theses and Dissertations

Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement. Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in …

Electrodeposition Of Lead-Free Solder Alloys

A.S. Md Abdul Haseeb

Purpose - The purpose of this paper is to enhance the understanding on the electrodeposition of various lead (Pb)-free solder alloys, so that new studies can be carried out to solve processing issues. Design/methodology/approach - The paper reviews the available reports on the electrodeposition of tin (Sn)-based solder systems and identifies the challenges in this area. Findings - Compositional control remains a major challenge in this area, where the achievement of desired composition for binary and ternary alloys is subjected to uncertainties. The use of chelating agents in the bath and optimization of parameters can assist the achievement of near-desired …

Failure Analysis Of Superheater Tube Supports Of The Primary Reformer In A Fertilizer Factory

A.S. Md Abdul Haseeb

Eutectic Sn-Bi alloy is gaining considerable attention in the electronic packaging industry because of its favorable properties such as low melting temperature, good wettability, and good mechanical properties. Miniaturization of electronic devices requires small solder bumps, a few tens of micrometers in diameter. Electrodeposition is a reliable technique for the deposition of small volume of solder. This work focuses on the formation of eutectic Sn-Bi solder by reflowing a metal stack containing sequentially electrodeposited Sn and Bi layers. The effects of layering sequence on the composition and microstructure of the resulting alloy is investigated. Irrespective of the layering sequence, a …

Structural Origin Of Mechanical Prowess In Conch Shells, Haoze Li

Theses and Dissertations

Conch shells are natural nanocomposites with an exquisite multiscale hierarchical architecture which exhibit coupled ultrahigh mechanical strength and toughness. What materials design strategy renders conch shells such mechanical prowess? In this study, micro/nanoscale structural and mechanical characterization of conch shells (Busycon carica) has been carried out. We demonstrate, for the first time, direct evidence that the previously claimed single-crystal third-order lamellae - the basic building blocks in conch shells are essentially assembled with aragonite nanoparticles of the size ranging from 20 to 45 nm. The third-order lamellae exhibit not only elasticity but also plasticity with the strain up to 0.7% …

Welding Parameters, Distortion And Mechanical Properties Of Aa7075 Lap Joints In Ssfsw, Hejun Yu

Theses and Dissertations

Friction Stir Welding (FSW), first invented by The Welding Institute of UK (TWI) in 1991, is a solid state welding process which was initially applied to welding Aluminum Alloy. FSW has wide application in industrial sectors. Stationary shoulder friction stir welding (SSFSW) was first developed to weld low thermal conductivity Ti-based alloys, which are hard to weld using conventional friction stir welding. Previous literatures showed SSFSW can produce uniform temperature distribution through thickness during the welding process. Since SSFSW is still under study phase, its advantages and disadvantages are not yet well defined. It is important to study the characteristics …