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Atomistic simulations have been used to study the effect of various types of point defects on the mechanical response of FCC single crystals in nanoindentation and uniaxial tests. To study the effect of spatial distribution of defects in nanoindentation testing, various point defects were located in different relative positions to the indenter. When the defect position was close to the regions of high shear stresses the nucleation of dislocations was related to the location of the defect; however homogeneous nucleation of dislocations was also observed for defect-containing crystals. The effect of the point defects was independent of the indenter size, and the applied pressure needed to initiate plasticity, when compared to defect-free crystals, was a reduction of approximately 10%, 20%, 20% and 50% for a single vacancy, di-vacancy, self-interstitial atom and stacking fault tetrahedron (SFT), respectively. The stochastic nature of the pop-in loads was further explored for different orientations using molecular dynamics and complementary nanoindentation experiments on (100), (101) and (111) single crystals of copper and Ni200. The sensitivity of the crystal to the presence of internal structural defects depends strongly on its crystallographic orientation. The simulations suggest that the first event observed experimentally may not correspond to the first plastic deformation event. Anisotropy effects were also studied for various orientations in uniaxial tests in the presence of a centered SFT. Both the normal stresses to the slip plane and the relative values of Schmid factor in compression and tension affect the observed compression/tension yield asymmetry. The reduction in yield stress was found to be larger in compression than in tension for almost all orientations. The simulations suggest that compression is a more reliable experimental tool for studying the effect of structural defects on the mechanical behavior of the FCC crystals, while tension may be more useful to determine size effects in deformation. Finally, simulations at high temperatures showed that internal defects are capable of reducing the temperature sensitivity of yielding in various crystal orientations, especially when the stress field is mainly compressive like those in nanoindentation and compression tests.
Molecular dynamics simulation is a significant technique to gain insight into the mechanical behavior of nanostructured (NS) materials and associated underlying deformation mechanisms at the atomic scale. The purpose of this book is to detect and correlate critically current achievements and properly assess the state of the art in the mechanical behavior study of NS material in the perspective of the atomic scale simulation of the deformation process. More precisely, the book aims to provide representative examples of mechanical behavior studies carried out using molecular dynamics simulations, which provide contributory research findings toward progress in the field of NS material technology.
Research in the area of nanoindentation has gained significant momentum in recent years, but there are very few books currently available which can educate researchers on the application aspects of this technique in various areas of materials science. Applied Nanoindentation in Advanced Materials addresses this need and is a comprehensive, self-contained reference covering applied aspects of nanoindentation in advanced materials. With contributions from leading researchers in the field, this book is divided into three parts. Part one covers innovations and analysis, and parts two and three examine the application and evaluation of soft and ceramic-like materials respectively. Key features: A one stop solution for scholars and researchers to learn applied aspects of nanoindentation Contains contributions from leading researchers in the field Includes the analysis of key properties that can be studied using the nanoindentation technique Covers recent innovations Includes worked examples Applied Nanoindentation in Advanced Materials is an ideal reference for researchers and practitioners working in the areas of nanotechnology and nanomechanics, and is also a useful source of information for graduate students in mechanical and materials engineering, and chemistry. This book also contains a wealth of information for scientists and engineers interested in mathematical modelling and simulations related to nanoindentation testing and analysis.
An overview of recent developments in high performance computing and simulation, with special emphasis on the industrial relevance of the presented results and methods. The book showcases an innovative combination of the state-of-the-art modeling, novel numerical algorithms and the use of leading-edge high-performance computing systems.
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.