Brittle fracture of nickel by dynamic indentation

1992 ◽  
Vol 7 (8) ◽  
pp. 1973-1975 ◽  
Author(s):  
J.W. Hoehn ◽  
T. Foecke ◽  
W.W. Gerberich
Keyword(s):  
Electron Microscopy ◽  
Brittle Fracture ◽  
Fracture Process ◽  
Low Energy ◽  
Face Centered Cubic ◽  
Dynamic Indentation ◽  
Transgranular Cleavage ◽  
Energy Process ◽  
Face Centered ◽  
Scanning Electron

Cracks of up to 40 μm which are either transgranular cleavage or very low energy “ductile” cracks have been introduced into large-grained fcc Ni. The mechanism for introducing this brittle fracture was dynamic indentation. Optical and scanning electron microscopy together with use of selected area channeling patterns were used to confirm that the fracture process is transgranular. The results qualitatively support the hypothesis that dynamic cracks originating in a brittle film can propagate relatively large distances into a ductile face-centered-cubic substrate by a rapid, low energy process.

Full—Potential Lmto Calculation of Brittle Fracture in Titanium Carbide

1991 ◽  
Vol 253 ◽  
Author(s):  
D.L. Price ◽  
B.R. Cooper
Keyword(s):  
Brittle Fracture ◽  
Titanium Carbide ◽  
Fracture Process ◽  
Practical Interest ◽  
Full Potential ◽  
Metal Carbides ◽  
Lmto Method ◽  
Fracture Instability ◽  
Atomic Radii ◽  
The Ideal

ABSTRACTThe refractory transition metal—carbides commonly fail under stress by brittle fracture and the properties and nature of the fracture process are consequently of practical interest. We have calculated the fracture properties of titanium carbide under tensile stress using our full—potential LMTO method, a methodology which is closely related to multiple scattering theory (and includes a true interstitial region). The fracture calculation is accomplished by employing a repeated slab (or repeated cleavage separation) geometry. Within this geometry, the fracture process is simulated most simply by uniformly increasing the gap separation from zero to a distance on the order of a few atomic radii. A more sophisticated search for fracture instability involved stretching the ideal crystal and examining the separation energetics of the strained system.Results of these calculations will be reported both for the ideal, stoichiometric titanium carbide crystal and also for systems containing carbon vacancies. We will discuss therole of such defects in modifying the bonding behavior at the cleavage plane and the resulting effect on resistance to fracture.

Size effect analysis of quasi-brittle fracture with localizing gradient damage model

2021 ◽  
pp. 105678952098387
Author(s):  
Yi Zhang ◽  
Amit S. Shedbale ◽  
Yixiang Gan ◽  
Juhyuk Moon ◽  
Leong H. Poh
Keyword(s):  
Brittle Fracture ◽  
Size Effect ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Concrete Beams ◽  
Process Zone ◽  
Damage Zone ◽  
Damage Model ◽  
Lattice Models ◽  
Gradient Enhancement

The size effect of a quasi-brittle fracture is associated with the size of fracture process zone relative to the structural characteristic length. In numerical simulations using damage models, the nonlocal enhancement is commonly adopted to regularize the softening response. However, the conventional nonlocal enhancement, both integral and gradient approaches, induces a spurious spreading of damage zone. Since the evolution of fracture process zone cannot be captured well, the conventional nonlocal enhancement cannot predict the size effect phenomenon accurately. In this paper, the localizing gradient enhancement is adopted to avoid the spurious spreading of damage. Considering the three-point bend test of concrete beams, it is demonstrated that the dissipation profiles obtained with the localizing gradient enhancement compare well with those of reference meso-scale lattice models. With the correct damage evolution process, the localizing gradient enhancement is shown to capture the size effect phenomenon accurately for a series of geometrically similar concrete beams, using only a single set of material parameters.

scholarly journals Nonlocal Criteria for Brittle and Quasi-Brittle Fracture of Geomaterials and Rocks

2018 ◽  
Vol 56 ◽  
pp. 02003 ◽  
Author(s):  
Sergey Suknev
Keyword(s):  
Brittle Fracture ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Common Property ◽  
Process Zone ◽  
Material Structure ◽  
Fracture Criteria ◽  
Stress Concentrations ◽  
Stress Criterion ◽  
Nonlocal Criteria

Nonlocal criteria are used for prediction materials and rock mass failure near stress concentrations (pores, faults, openings, excavations). A common property of nonlocal fracture criteria is the introduction of the intrinsic material length characterizing its microstructure, which allows one to describe the size effect in conditions of stress concentration. At the same time the scope of their application is limited to cases of brittle or quasi-brittle fracture with a small fracture process zone. To expand the scope of the criteria for cases of fracture with a developed fracture process zone, it is proposed to abandon the hypothesis of the size of this zone as a material constant, associated only with the material structure. New fracture criteria are proposed, which are the development of the average stress criterion, and point stress criterion, and which contain a complex parameter that characterizes the size of the fracture process zone and accounts not only for the material structure, but also plastic properties of the material, geometry of the sample, and its loading conditions. Expressions are obtained for the critical pressure in the problem of the formation of tensile cracks under compression in the samples of geomaterials with a circular hole. The calculation results are in good agreement with the experimental data on the fracture of drilled gypsum plates.

Multiscale Fracture Model for Quasi-Brittle Materials

2011 ◽  
Vol 82 ◽  
pp. 160-165 ◽  
Author(s):  
Yuri V. Petrov ◽  
Vladimir Bratov
Keyword(s):  
Experimental Data ◽  
Brittle Fracture ◽  
Experimental Determination ◽  
Fracture Process ◽  
Strength Properties ◽  
Material Strength ◽  
Scale Level ◽  
Scale Levels ◽  
Real Scale

Fracture of quasi-brittle heterogeneous materials is steered by processes at several different scale levels. These processes can progress independently or affect each other. In order to model fracture of such materials one should account for all rupture processes contributing to overall fracture process. This paper is presenting structural-temporal approach for analysis of multiscale nature of brittle fracture. Notion of spatial-temporal cell for different scale levels is introduced. Problem of experimental determination of a fixed scale level is discussed. Possible interconnections of this scale level with higher and lower scale levels are discussed. It is shown that this can give a possibility to predict fracture on a higher (real) scale level having experimental data obtained on a lower (laboratory) scale. This possibility is of extreme importance for many applications where the possibility to evaluate material strength properties on real structure scale level does not exist (ex. geological objects, big concrete structures, trunk pipelines, etc.).

Energy Dissipation during Quasi-Brittle Fracture Associated with the Crack and the Fracture Process Zone Progression

2015 ◽  
Vol 665 ◽  
pp. 261-264 ◽  
Author(s):  
Jiří Klon ◽  
Václav Veselý
Keyword(s):  
Energy Dissipation ◽  
Brittle Fracture ◽  
Numerical Simulations ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Advance ◽  
Fracture Test ◽  
Notched Specimen ◽  
Nonlinear Zone

The paper presents an analysis with an attempt to capture the phenomenon of quasi-brittle fracture based on the record of the fracture test on a notched specimen via separation the energy amounts released for the crack advance and dissipated within the volume of the sizeable nonlinear zone at the crack tip – the fracture process zone (FPZ). The described approach is tested on selected data of published experimental campaigns accompanied with own conducted numerical simulations.

Sign in / Sign up

Export Citation Format

Share Document