The nanocrstalline (NC) metals have been reported to have high mechanical performance owing to it's small grain interior and a large volume fraction of grain boundary (GB) atoms. Small grain leads to the forbidden dislocation activities in grain interior while GB activities become dominant due to a higher volume fraction of GB atoms. Regarding the fatigue response to nanocrstalline metals, it has been reported that decreasing grain led to both significantly improvement on the fatigue-endurance limit and deleterious effect on the resistance to subcritical fatigue crack propagation. The increases endurance limit has been attributed to the greater resistance to fatigue crack initiation at near-surface regions. On the other hand, the less resistance to fatigue crack growth were resulted from less tortuous fatigue crack profiles supported by the deflection/closure theory. However, it has never been studied the influence of proceeding and pre-existing defects on the fatigue performance considering the difference response of NC structure from than coarse grain (CG) structure. In the present work, the influence of electrical discharge machining (EDM) and surface defects on the fatigue behavior of both conventional cold-rolled CG and electro-deposited (ED) NC Ni were investigated. The experimental results revealed considerable influence by EDM on the fatigue strength of NC Ni, while it has little or no affect on that for CG Ni. Specifically, EDM led to a 50 to 75% reduction in fatigue strength for NC Ni despite a relatively small depth of EDM affected material (~1% of width). Rationale for this effect can be attributed to grain growth, microcracks, and higher sulfur content at the GBs in the EDM affected zone. In addition, the pre-existing surface defects that appear to be due to impurity segregation near the electro-deposition substrate significantly reduced the fatigue resistance of ED NC Ni. In order to understand the fatigued behavior in NC Ni, crack tip grain structures were investigated using transmission electron microscope (TEM). Crack tip grain growth was observed at early state of crack propagation with low stress intensity factor (K ~ 6 MPa m 1/2). As K increased, the size of grain growth zone increased exponentially in width a crack propagation behavior transmitted from interganular to transgranular. It appears that this transmission is associated with grain growth. The coalesced grains due to grain rotation/GB diffusion created larger paths for more extended dislocation movement. Dislocation activities become less forbidden and the dislocation-slip mechanism can be dominant leading to a more plastically transgranular fracture. In addition to fatigue study of ED NC Ni, encrustation on ED NC Ti was investigated. The use of materials for medical applications in the urinary tract is hampered by the formation of calcium-based crystalline deposits, generally referred to as encrustation, that act as precursors to urinary stones. Anecdotal evidence suggests that titanium can possess encrustation-resistant properties in vivo and may be useful in urologic applications. To test the utility of coating surfaces with nanotructured titanium, several forms of materials were submersed in artificial urine with saturating concentrations of calcium for a period of 14 days. The specimens were then analyzed using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) to determine the extent of encrustation on the surface of the various samples. Our observations indicate that nanostructured titanium offers superior resistance to encrustation when compared to polyurethane, polyvinyl chloride or conventional coarser grained titanium. Further studies investigating the use of nanostructured titanium in urologic applications are warranted.

This book describes the main approaches for production and synthesis of nanostructured metals and alloys, taking into account the fatigue behavior of materials in additive manufactured components. Depending on the material type, form, and application, a deep discussion of fatigue properties and crack behavior is also provided. Pure nanostructured metals, complex alloys and composites are further considered. Prof. Cavaliere’s examination is supported by the most up-to-date understanding from the scientific literature along with a thorough presentation of theory. Bringing together the widest range of perspective on its topic, the book is ideal for materials researchers, professional engineers in industry, and students interested in nanostructured materials, fracture/fatigue mechanics, and additive manufacturing. Describes in detail the relevance of nanostructures in additive manufacturing technologies; Includes sufficient breadth and depth on theoretical modelling of fatigue and crack behavior for use in the classroom; Identifies many open questions regarding different theories through experimental finding; Contextualizes the latest scientific results for readers in industry.

The superior strength and large tensile plasticity of nanotwinned (nt) face-centered-cubic metals have been explained by different twin size-dependent dislocation mechanisms and their inherent strengthening/softening effects. Grain boundary (GB) plasticity generally induces softening in nanocrystalline metals; however, our current understanding of the role of GBs in plasticity of nt metals remains limited. Contradicting reports exist in literature on how twin size influences stress concentration at GB -- twin boundary (TB) intersections, which facilitates dislocation nucleation. In this thesis, molecular dynamics (MD) simulations and finite element analysis (FEA) were used to study the effects of GB plasticity and stress concentrations, on the mechanical behaviors of four different columnar-grained nt fcc metals. First, the extent of GB plasticity was found to be the same for different TB spacing (TBS). A special GB deformation mechanism, ductile cracking along GB was observed in nt Ni at small TBS, resulting from the higher GB plasticity of nt Ni. In addition, GB plasticity also depends on the strain rate, which contributes to strain rate sensitivity in nt fcc metals. Second, it was found that stress concentration at GB -- TB intersections decreases as TBS decreases in both anisotropic elasticity theory and atomistic simulations, which is contrary to past experimental results. Stress concentration at the intersection of two regions with different TBSs could be estimated simply by geometric average of stress concentrations in adjacent regions with homogeneous CTB distributions, suggesting that the paradox in stress concentration between experiments and our simulation may be related to the uneven TB distribution in experiments. Initial nucleation of twinning partials is predicted to occur at lower strain as TB spacing decreases, when the stress concentrations are smaller, because of a transition from stress-controlled to source-controlled dislocation nucleation. Therefore, this thesis shows that it is necessary to tailor the size and distribution of grains and nanotwins to achieve ideal mechanical properties in columnar-grained nt metals.

This the sixth volume of six from the Annual Conference of the Society for Experimental Mechanics, 2010, brings together 128 chapters on Experimental and Applied Mechanics. It presents early findings from experimental and computational investigations including High Accuracy Optical Measurements of Surface Topography, Elastic Properties of Living Cells, Standards for Validating Stress Analyses by Integrating Simulation and Experimentation, Efficiency Enhancement of Dye-sensitized Solar Cell, and Blast Performance of Sandwich Composites With Functionally Graded Core.

Nanotechnology is at the forefront of advances in medicine. Nanomedicine: Technologies and applications provides an important review of this exciting technology and its growing range of applications. After an introduction to nanomedicine, part one discusses key materials and their properties, including nanocrystalline metals and alloys, nanoporous gold and hydroxyapatite coatings. Part two goes on to review nanomedicine for therapeutics and imaging, before nanomedicine for soft tissue engineering is discussed in part three, including organ regeneration, skin grafts, nanotubes and self-assembled nanomaterials. Finally, nanomedicine for bone and cartilage tissue engineering is the focus of part four, with electrically active biocomposites as smart scaffolds investigated, as is cartilage and bone tissue engineering, regeneration and replacement. With its distinguished editor and international team of expert contributors, Nanomedicine: Technologies and applications is an indispensable guide for all those involved in the research, development and application of this exciting technology, whilst providing a comprehensive introduction for students and academics interested in this field. Provides an important review of nanomedicine technology and its growing range of applications Discusses key nanomedicine materials and their properties, including nanocrystalline metals and alloys, nanoporous gold and hydroxyapatite coatings Reviews nanomedicine for therapeutics and imaging and nanomedicine for soft tissue engineering