Author: Mark J. McLean
Publisher:
ISBN: 9781303290800
Category :
Languages : en
Pages : 176
Get Book Here
Book Description
Furthermore, a single-crystal plasticity model was incorporated into a commercial finite element software package (ABAQUS) in order to investigate the development of the plastic zone in front of the notches created in the test specimen. It was found that the size of this zone was likely constrained by the specimen dimensions, which had a significant impact on the measured fracture toughness values.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1074
Get Book Here
Book Description
Author: Gary Steven Was
Publisher:
ISBN:
Category : Crystallography
Languages : en
Pages : 380
Get Book Here
Book Description
Materials Science Forum Vol. 46.
Author: Wanjun Cao
Publisher:
ISBN: 9781303478253
Category :
Languages : en
Pages : 195
Get Book Here
Book Description
Grain boundaries play a very important role in determining the mechanical properties of polycrystalline ceramics. In particular, the addition of certain dopants or impurities can cause significant changes in fracture path and fracture toughness. While substantial progress has been made in the past few decades, there remains an active debate about the fundamental mechanism of how the grain boundary segregation influences the mechanical properties. Prior studies have revealed limitations of the conventional macro-scale mechanical testing technique since dopants not only alter grain boundary structure they also influence the grain size, grain anisotropy and porosity that all contribute to the mechanical properties of polycrystalline bulk samples. Small-scale mechanical testing offers an opportunity to minimize the number of variables to obtain information about the mechanical properties of a single grain boundary, thus enabling direct correlations between grain boundary structures and mechanical properties. Three different micro-scale mechanical testing techniques--including Compression Splitting, Double Torsion and Micro-cantilever Deflection test methods--were examined and the Micro-cantilever Deflection test was selected for this project. At the beginning, tests were performed in single crystal magnesium aluminate spinel (MgAl2O4). Five distinct orientation cantilever specimens were prepared by Focused Ion Beam (FIB) technique and loaded by a dedicated in-situ nano-indentation system. Anisotropic finite element analysis was performed and the influence of the material's anisotropy on the stress intensity factor was determined. Orientation dependent fracture behaviors of different specimens were observed and associated with a mixed-mode loading condition and anisotropic mechanical properties of spinel single crystal. A maximum tensile stress fracture criterion for anisotropic materials was used to determine the fracture toughness values of fracture planes as the crack deflected at certain angles. Good agreement of fracture toughness values for {100} planes was obtained between the micron-scale measurements and macroscopic results available in the open literature. Lower bounds for the fracture toughness of {110} and {111} orientations were also obtained. After the technique had been validated, the Micro-cantilever Deflection test technique was then applied to test bi-crystal grain boundaries. The effect of ytterbium (Yb) on magnesium aluminate spinel (MgAl2O4) grain boundary structure and strength has been evaluated. Doped and updoped interfaces were characterized using atomic resolution High Angle Annular Dark Field (HAADF) imaging. Interface fracture toughness was determined using a micro-scale cantilever beam test. A 30% increase in fracture toughness was found to correlate with grain boundary Yb segregation. Finally, the Micro-cantilever Deflection beam deflection test was introduced to measure the fracture toughness and investigate fracture mechanisms of electrodeposited Ni-W coatings exposed to different heat treatment conditions. As deposited Ni-W films were found to be amorphous and to exhibit a ductile fracture behavior while after heat treatment nanocrystalline Ni-W exhibited a brittle fracture behavior. By introducing nano-scale sharp pre-cracks, the nanocrystalline Ni-W fracture surface exhibited an intergranular morphology that has never been reported before to our knowledge. In addition, the fracture path of nanocrystalline Ni-W was along boundaries of grain boundary agglomerates that can be directly correlated with an agglomerate cooperative motion model proposed in previous reports.
Author: Joshi Anne
Publisher:
ISBN:
Category :
Languages : en
Pages : 138
Get Book Here
Book Description
Author: John C. Riviere
Publisher: CRC Press
ISBN: 1420007807
Category : Science
Languages : en
Pages : 671
Get Book Here
Book Description
The original Handbook of Surface and Interface Analysis: Methods for Problem-Solving was based on the authors' firm belief that characterization and analysis of surfaces should be conducted in the context of problem solving and not be based on the capabilities of any individual technique. Now, a decade later, trends in science and technology appear
Author: Ian Christopher Elliott
Publisher:
ISBN:
Category : Copper
Languages : en
Pages : 0
Get Book Here
Book Description
Author: Ian Christopher Elliott
Publisher:
ISBN:
Category : Copper
Languages : en
Pages :
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 782
Get Book Here
Book Description
Author: Pavel Lejcek
Publisher: Springer Science & Business Media
ISBN: 3642125050
Category : Technology & Engineering
Languages : en
Pages : 249
Get Book Here
Book Description
Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.
