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Full-Text Articles in Mechanical Engineering

Microstructural Characterization Of Shear Transformation Zones And Modeling Indentation Size Effect In Amorphous Polymers, Leila Malekmotiei Jun 2018

Microstructural Characterization Of Shear Transformation Zones And Modeling Indentation Size Effect In Amorphous Polymers, Leila Malekmotiei

LSU Doctoral Dissertations

The first aim of this work is developing a procedure for experimental and analytical characterization of nano-scale microstructures which mediate large scale deformation in amorphous polymers. Glassy polymers are extensively used as high impact resistant, low density, and clear materials in industries. Nevertheless, their response under severe loading conditions is yet to be appropriately unraveled. Due to the lack of long-range order in the microstructures of glassy solids, their plastic deformation is different from that in crystalline solids. Shear Transformation Zones (STZs) are believed to be the main plasticity carriers in amorphous solids and defined as the localized atomic or …


A Nanoindentation Study Of The Fatigue Properties Of Al/A-Si Core-Shell Nanostructures, Jason Steck May 2018

A Nanoindentation Study Of The Fatigue Properties Of Al/A-Si Core-Shell Nanostructures, Jason Steck

Mechanical Engineering Undergraduate Honors Theses

Nanostructure-textured surfaces can reduce friction and increase the reliability of micro- and nanoelectromechanical systems (NEMS/MEMS). For MEMS incorporating moving parts, the fatigue properties of nanostructures pose a challenge to their reliability in long-term applications. In this study, the fatigue behavior of hemispherical Al/a-Si core-shell nanostructures (CSNs), bare hemispherical Al nanodots, and a flat Al/a-Si layered thin film have been studied using nanoindentation and nano-scale dynamic mechanical analysis (nano-DMA) techniques. Fatigue testing with nano-DMA shows that the deformation resistance of CSNs persists through 5.0 × 104 loading cycles at estimated contact pressures greater than 15 GPa. When the a-Si shell …


Surface Modification Of Titanium For Hard-Tissue Engineering Applications, Murali Krishna Duvvuru Jan 2018

Surface Modification Of Titanium For Hard-Tissue Engineering Applications, Murali Krishna Duvvuru

Graduate Research Theses & Dissertations

Titanium (Ti) and its alloys are widely used in dental and orthopedic applications due to their advantages such as biocompatibility, excellent corrosion resistance and mechanical properties like low Young’s modulus, low density and high strength as compared to other metallic implants. However, lack of interaction with host tissue (e.g. bioinertness), higher modulus of elasticity as compared to that of bone and resultant stress shielding cause fibrous tissue formation around the implant where the interaction with tissue is minimized. These will eventually cause the implant loosening and revision surgery is needed. Surface modification of Ti by increasing surface roughness and/or incorporation …