A brittle-fracture methodology for three-dimensional visualization of ductile deformation micromechanisms

2009 ◽  
Vol 61 (1) ◽  
pp. 20-23 ◽  
Author(s):  
C.C. Tasan ◽  
J.P.M. Hoefnagels ◽  
M.G.D. Geers
Keyword(s):  
Brittle Fracture ◽  
Three Dimensional ◽  
Ductile Deformation

Cleavage Planes of Icosahedral Quasicrystals: A Molecular Dynamics Study

2003 ◽  
Vol 805 ◽  
Author(s):  
Frohmut Rösch ◽  
Christoph Rudhart ◽  
Peter Gumbsch ◽  
Hans-Rainer Trebin
Keyword(s):  
Molecular Dynamics ◽  
Brittle Fracture ◽  
Crack Propagation ◽  
Three Dimensional ◽  
Propagation Direction ◽  
Mode I ◽  
Dynamic Crack ◽  
Fracture Surfaces ◽  
Icosahedral Quasicrystals ◽  
Crack Tip Plasticity

ABSTRACTThe propagation of mode I cracks in a three-dimensional icosahedral model quasicrystal has been studied by molecular dynamics techniques. In particular, the dependence on the plane structure and the influence of clusters have been investigated. Crack propagation was simulated in planes perpendicular to five-, two- and pseudo-twofold axes of the binary icosahedral model.Brittle fracture without any crack tip plasticity is observed. The fracture surfaces turn out to be rough on the scale of the clusters. These are not strictly circumvented, but to some extent cut by the dynamic crack. However, compared to the flat seed cracks the clusters are intersected less frequently. Thus the roughness of the crack surfaces can be attributed to the clusters, whereas the constant average heights of the fracture surfaces reflect the plane structure of the quasicrystal. Furthermore a distinct anisotropy with respect to the in-plane propagation direction is found.

Geometry of the allochthonous Daly Bay Complex, Northwest Territories: a model constrained by geology and a three-dimensional gravity interpretation

1995 ◽  
Vol 32 (9) ◽  
pp. 1292-1302
Author(s):  
Terence M. Gordon ◽  
Donald C. Lawton
Keyword(s):  
Three Dimensional ◽  
Outer Part ◽  
Complex Form ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Lower Grade ◽  
Crustal Material ◽  
Tectonic Event ◽  
Granulite Facies Metamorphism ◽  
Dimensional Gravity

The Daly Bay Complex is one of several metamorphic complexes making up the Aqxarneq gneisses north of Chesterfield Inlet in central District of Keewatin. Granulite-facies metamorphism (0.55 GPa, 750 °C) and ductile deformation have affected all of the rocks in the complex. A 1–15 km wide, inward-dipping, ductile shear zone forms the outer part of the complex and contains strongly deformed equivalents of rocks in the core. Mesoscopic structures and metamorphic mineralogy suggest the Daly Bay Complex was emplaced into the surrounding lower grade rocks by northward-directed thrusting. A three-dimensional gravity model, constrained by structural observations and 1091 surface density measurements, shows that the relatively dense rocks of the complex form a spoon-shaped structure with a long axis trending northwest–southeast. It is approximately 50 km by 120 km in lateral extent and reaches a maximum depth of about 9 km. The thin-skinned geometry of the Daly Bay Complex supports the notion that the crust in central Keewatin between the Daly Bay Complex and Baker Lake comprises a series of undulating imbricated gneiss sheets of middle and lower crustal material, which were juxtaposed by a major tectonic event sometime between 2.5 and 1.9 Ga. The interpreted basal décollement is comparable to seismic features in many orogens, and a predictable consequence of increased ductility with depth in the crust.

scholarly journals Micromechanical Modeling of Brittle Fracture of French RPV Steel: A Comprehensive Study of Stress Triaxiality Effect

2008 ◽  
Author(s):  
Jean-Philippe Mathieu ◽  
Olivier Diard ◽  
Karim Inal ◽  
Sophie Berveiller
Keyword(s):  
Brittle Fracture ◽  
Low Temperatures ◽  
Mean Field ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Micromechanical Modeling ◽  
Multiscale Approach ◽  
Local Approach ◽  
Rpv Steel ◽  
Probability Of Fracture

The present study describes a multiscale representation of mechanisms involved in brittle fracture of a french Reactor Pressure Vessel (RPV) steel (16MND5 equ. ASTM A508 Cl.3) at low temperatures. Attention will be focused on the representation of stress heterogeneities inside the ferritic matrix during plastic straining, which is considered as critical for further micromechanical approach of brittle fracture. This representation is tuned on experimental results [1]. Modeling involves micromechanical a description of plastic glide, a mean field (MF) model and a realistic three-dimensional aggregates Finite Element (FE) simulation, all put together inside a multiscale approach. Calibration is done on macroscopic stress-strain curves at different low temperatures, and modeling reproduces experimental stress heterogeneities. This modeling allows to apply a local micromechanical fracture criterion of crystallographic cleavage for triaxial loadings on the Representative Volume Element (RVE). Deterministic computations of time to fracture for different carbide sizes random selection provide a probability of fracture for an Elementary Volume (EV) consistant with the local approach. Results are in good agreement with hypothesis made by local approach to fracture. Hence, the main difference is that no phenomenological dependence on loading or microstructure is supposed for probability of fracture on the EV: this dependence is naturally introduced by the micromechanical description.

A brief review of recent three-dimensional studies of brittle fracture

2016 ◽  
Vol 19 (1) ◽  
pp. 6-20 ◽  
Author(s):  
Z. He ◽  
A. Kotousov ◽  
F. Berto ◽  
R. Branco
Keyword(s):  
Brittle Fracture ◽  
Three Dimensional

scholarly journals Defects in olivine

2021 ◽  
Vol 33 (3) ◽  
pp. 249-282
Author(s):  
Sylvie Demouchy
Keyword(s):  
Upper Mantle ◽  
Materials Science ◽  
Three Dimensional ◽  
Ductile Deformation ◽  
Dislocation Slip ◽  
Crystalline Solid ◽  
Igneous Petrology ◽  
Planar Defects ◽  
Interface Defects ◽  
Point Line

Abstract. Olivine, a ferromagnesian orthosilicate, is the most abundant mineral in Earth's upper mantle and is stable down to the olivine–wadsleyite phase transition, which defines the 410 km depth mantle transition zone. Olivine also occurs in crustal environments in metamorphic and hydrothermal rocks and is expected to be the major mineral constituent of the Martian and Venusian mantles. The olivine atomic structure is also used in materials science to manufacture lithium batteries. Like any other crystalline solid, including minerals, olivine never occurs with a perfect crystalline structure: defects in various dimensions are ubiquitous, from point, line, and planar defects to three-dimensional (3-D) inclusions. In this contribution, I review the current state of the art of defects in olivine and several implications for key processes occurring in Earth's mantle. Intrinsic and extrinsic point defects are detailed, exemplifying the astonishing diversity of atomic impurities in mantle-derived olivine. Linear defects, one of the key defect types responsible for ductile deformation in crystalline solids, are examined in light of recent progress in 3-D transmission electron microscopy, which has revealed an important diversity of dislocation slip systems. I summarize the principal characteristics of interface defects in olivine: the free surface, grain and interface boundaries, and internal planar defects. As the least-studied defects to date, interface defects represent an important challenge for future studies and are the main application of numerical simulation methods in materials science. I provide an overview of melt, fluid, and mineral inclusions, which are widely studied in volcanology and igneous petrology. Special attention is given to new crystalline defects that act as deformation agents: disclinations (rotational defects) and the potential occurrence of disconnections in olivine, both of which are expected to occur along or near grain boundaries. Finally, I detail outstanding questions and research directions that will further our understanding of the crystalline specificities and paradoxes of olivine and olivine-rich rocks and ultimately their implications for the dynamics of Earth's upper mantle.

Insights into a dextral transtensional shear zone in NW Anatolia, Turkey: Preliminary results from the three dimensional strain and kinematic analyses of the Marmara Granitoid. 

2021 ◽  
Author(s):  
Salim Birkan Bayrak ◽  
Alp Ünal ◽  
Işıl Nur Güraslan ◽  
Ömer Kamacı ◽  
Erdinç Yiğitbaş ◽  
...  
Keyword(s):  
Shear Deformation ◽  
Simple Shear ◽  
Boundary Migration ◽  
Pure Shear ◽  
Three Dimensional ◽  
Ductile Deformation ◽  
Kinematic Vorticity ◽  
Strain Ellipsoid ◽  
Kinematic Analyses ◽  
Mean Trend

<p>Marmara Granitoid (MG) is an E-W trending sill-like magmatic body exposed in the center of the Marmara Island, NW Anatolia, Turkey. MG is lower Eocene in age and was concordantly emplaced into metamorphic basement rocks of Saraylar Marble and Erdek Complex. It is represented by a deformed granodiorite which widely displays protomylonitic-mylonitic textures with prominent foliation and lineation. Foliation planes display a mean dip direction-angle of 335/29 and mineral stretching lineations show mean trend-plunge of 286/34. Mica-fishes, rotated porphyroclasts and micro-faults are commonly observed and serve as shear gauges pointing out to a dextral movement. Mineral deformation thermometers such as myrmekite development, chessboard extinction, grain boundary migration (GBM), sub-grain rotation recrystallization (SGR), and bulging recrystallization (BLG) in quartz crystals indicate that solid-state deformation of the MG has experienced a high-temperature ductile deformation and superimposed ductile to brittle deformation.</p><p>Three-dimensional strain ellipsoid measurements are investigated on the MG in order to determine the relative amounts of pure shear and simple shear deformation and the mean kinematic vorticity number (W<sub>m</sub>). The image processing of quartz grains is used as strain markers to obtain the three-dimensional best-fit ellipsoids. The results show that, Lode’s ratio (ν) of the samples change between -0.010 and -0.650 and Flinn’s k-values range from 1.026 to 11.157 indicating to a general constrictional (prolate) deformation. The calculated kinematic vorticity numbers change between 0.429 and 0.958 which show that shear deformation of MG is mostly dominated by simple shear. All of these micro and meso structural properties and three-dimensional strain and kinematic analyses collectively suggest that MG has experienced a dextral transtensional deformation.</p>

French RPV Assessment — Contribution of Expertises in Mechanical Analyses

2002 ◽  
Author(s):  
G. Bezdikian ◽  
Y. Rouillon ◽  
J. Bourgoin
Keyword(s):  
Brittle Fracture ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Surveillance Program ◽  
Low Leakage ◽  
New Development ◽  
Safety Studies ◽  
Vessel Material ◽  
Vessel Integrity ◽  
Mechanical Studies

The process used by the French utility, concerning the Reactor Pressure Vessel assessment, applied on 54 PWR NPPs (3-loop and 4-loop Reactors), involves the verification of the integrity of the component by mechanical studies, in the most severe conditions of loading in relation with RTndt (Reference Nil Ductility Transition Temperature), and considering major parameters. This approach, is based on mechanical safety studies, to demonstrate the absence of risk of failure by brittle fracture. For these mechanical studies two major input data are necessary: 1 - the fluence distribution and the values during the lifetime in operation for each NPPs, 2 - the thermal-hydraulic evaluation and temperature distribution values in the downcomer. The main results must show significant margins against initiation of the brittle fracture. The flaws considered in this approach are shallow flaws beneath the cladding (subclad flaws) or in the first layer of cladding. The major tasks and expertises engaged by EDF are: • more precise assessment of the fluence and neutronic calculations, • better knowledge of the vessel material properties, including the effect of radiation, • the NDE inspection program based on the inspection of the vessel wall, with a special NDE tool to inspect the area in subcladding zone, • the evaluation of vessel integrity, the mechanical analysis of margins in major loading conditions. The principal actions conducted during recent years are: • the fuel management optimisation (low-leakage core design) and the new development to evaluate the fluence, • the data gathered from radiation specimen capsules, removed from the vessels (3 loop reactor), within the framework of the radiation surveillance program, and • the thermal-hydraulic-mechanical calculations based on finite element thermal-hydraulic computations and three dimensional elastic-plastic mechanical analyses.

Mechanisms of Material Removal in the Precision Production Grinding of Ceramics

1997 ◽  
Vol 119 (4A) ◽  
pp. 509-519 ◽  
Author(s):  
K. Subramanian ◽  
S. Ramanath ◽  
M. Tricard
Keyword(s):  
Plastic Deformation ◽  
Brittle Fracture ◽  
Material Removal ◽  
Systems Approach ◽  
Removal Rate ◽  
Ductile Deformation ◽  
Surface Generation ◽  
Grinding Wheel ◽  
Ceramic Grinding ◽  
Work Interaction

Grinding of ceramics is often treated as coarse grinding dominated by brittle fracture or fine grinding, at very low removal rates, dominated by plastic deformation. Through a set of experimental observations and analysis, it is shown that in grinding of ceramics the abrasive/work interaction can be treated similar to well known chip formation models. Such an approach permits the coexistence of ductile deformation and brittle fracture during the grinding of ceramics. When the grinding process is managed such that the brittle fracture is minimized, while maximizing the plastic deformation optimum results are achieved. In this regard it is conceivable to design ceramic grinding cycles, where the rough grinding cycle focuses on surface generation to achieve high material removal rate and productivity while minimizing brittle fracture and the finish grinding cycle focuses on surface generation which maximizes plastic deformation while still minimizing brittle fracture. While the above accounts for only one of four interactions in the grinding zone (viz) abrasive/work interaction, it is also necessary to address the other three interactions (viz) chip/bond, chip/work and bond/work interactions. The later considerations for ceramics grinding are identical to well established practices in metal grinding. When such grinding cycle optimization is carried out taking simultaneously into account the aspects of machine tool, grinding wheel, work material and operational factors, significant progress can be made in the grinding of ceramics. The results obtained through such systems approach are also described in this paper.

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