The Interaction of a Circular Dislocation Pile-up with a Short Rigid Fiber: a 3-D Dislocation Dynamics Simulation

2001 ◽  
Vol 683 ◽  
Author(s):  
Tariq A. Khraishi ◽  
Hussein M. Zbib
Keyword(s):  
Boundary Condition ◽  
Metal Matrix ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Dynamics Analysis ◽  
Matrix Composites ◽  
Dislocation Loops ◽  
Pile Up ◽  
Surface Loops ◽  
Distributed Dislocations

ABSTRACTThis paper presents a dislocation dynamics simulation of the interaction of a circular dislocation pile-up with a short rigid fiber, say as in metal-matrix composites. The pile-up is composed of glide dislocation loops surrounding the fiber. This problem is treated here as a boundary value problem within the context of dislocation dynamics. The proper boundary condition to be enforced is that of no or zero elastic displacements at the fiber's surface. Such a condition is satisfied by a distribution of rectangular dislocation loops, acting as sources of elastic displacements, meshing the fiber's surface. Such treatment is similar to crack modeling using distributed dislocations and falls under the category of “generalized image stress analysis.” The unknown in this problem is the Burgers vectors of the surface loops. Once those are found, the Peach-Koehler force acting on the circular dislocation loops, and emulating the fiber's presence, can be determined and the dynamical arrangement of the circular pile-up evolves naturally from traditional dislocation dynamics analysis.

Dislocation Dynamics Simulation of Interaction between Prismatic Dislocation Loops and Voids in Irradiated Thin Films

2016 ◽  
Vol 725 ◽  
pp. 189-194
Author(s):  
Ying Ying Cai ◽  
Jia Pei Guo ◽  
Yi Ping Chen
Keyword(s):  
Thin Films ◽  
Radiation Damage ◽  
Image Force ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Dislocation Loops ◽  
Principle Of Superposition ◽  
Dislocation Glide ◽  
Calculation Results ◽  
Materials Used

At the microscopic scale fast neutron irradiation brings about a high density of small point defect clusters in the form of dislocation loops and voids. And such radiation damage is of primary importance for materials used in nuclear energy production. In the present investigation emphasis is placed on the understanding of the mechanisms involved in the evolution of prismatic dislocation loops by glide in the presence of external free surfaces and those of the voids and in the interaction between dislocation loops and voids within irradiated thin films, so as to simulate in situ Transmission Electron Microscopy (TEM) images of dislocations, which is an indispensable tool for extracting information on radiation damage. By employing 3D dislocation dynamics based on isotropic elacticity and principle of superposition, the calculation results show that the image force is determined by the distance of the dislocation loop from the external and void surfaces and scales with the film thickness; the dislocation glide force is determined by the image stress as well as the loop–loop interaction stress which is in turn governed by the loop spacing. It is also shown that the presence of voids in the thin films has a strong influence on the behaviours of prismatic dislocations.

Thermally induced dislocation generation in Al/Al2O3 metal-matrix composites

1991 ◽  
Vol 49 ◽  
pp. 588-589
Author(s):  
Kenneth S. Vecchio
Keyword(s):  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Internal Stresses ◽  
Frictional Stress ◽  
Matrix Composites ◽  
Matrix Interface ◽  
Dislocation Loops ◽  
Thermally Induced ◽  
The Matrix ◽  
Induced Dislocation

It has been well documented that when a large difference in the coefficients of thermal expansion (CTE) exist between the matrix and reinforcement in metal-matrix composites (MMCs) internal stresses can develop which are sufficiently high to generate dislocations at the reinforcement/matrix interface. Numerous observations have been made of this phenomenon via TEM which have shown a variety of different dislocation substructures and dislocation punching mechanisms. An important consequence of this phenomenon is that the metal matrix becomes strain hardened as the dislocation density increases, thereby reducing subsequent plastic flow of the matrix. One notable feature of the dislocation punching mechanism is that prismatic dislocation loops are commonly observed emanating from the interface. In two recent studies it was found that dislocations were not emitted immediately upon cooling, but rather at some lower critical temperature. A number of microstructural and processing parameters can affect the thermally-induced dislocation substructure such as: a) differences in CTEs, b) lattice frictional stress, c) vol.% particulate, d) particle/matrix interface morphology, e) quench temperatures (ΔT effect), and f) thermal-cycling (e.g. reheating and requenching).

Dislocation Dynamics Simulation of Grain Boundary Effects on Yield Behavior of Metals

2004 ◽  
Vol 261-263 ◽  
pp. 741-746
Author(s):  
Akiyuki Takahashi ◽  
Naoki Soneda ◽  
A. Nomoto ◽  
G. Yagawa
Keyword(s):  
Boundary Condition ◽  
Grain Boundary ◽  
Dislocation Dynamics ◽  
Boundary Effects ◽  
Dynamics Simulation ◽  
Rigid Boundary ◽  
Yield Behavior ◽  
Grain Boundary Effects ◽  
Geometrical Effect ◽  
Dislocation Pileups

This paper describes dislocation dynamics simulation of grain boundary effects on yield behavior of metals, such as α-Fe bcc metal. Since the stress field arising from the grain boundary has not been well understood yet, the geometrical effect of the grain boundary can be handled in the simulation by the use of rigid boundary condition. The dislocation pileups can be observed near the grain boundary in the result of the DD simulation. And the yield stress in the crystal having the grain boundary becomes larger than that in the crystal having free surface. This result tells us that the Hall-Petch effect can actually describe well the effects of the grain boundary on the yield behavior of metals.

scholarly journals Research progress in molecular dynamics simulation of CNT and graphene reinforced metal matrix composites

2021 ◽  
Author(s):  
Changsheng Xing ◽  
Jie Sheng ◽  
Lidong Wang ◽  
Weidong Fei
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Metal Matrix Composite ◽  
Molecular Dynamic ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Carbon Nanomaterials ◽  
Dynamics Simulation ◽  
Research Progress ◽  
Matrix Composites

Abstract Carbon nanomaterials are considered as one of the ideal choices for high performance metal matrix composite reinforcements and one of the key directions of scientific research in recent years. Molecular dynamics simulation could be used conveniently to construct different composite material systems and study the properties of carbon nanomaterials reinforced metal matrix composites under different conditions. This review mainly introduces the molecular dynamic research progress of carbon nanotube (CNT) and graphene reinforced metal (Cu, Al, Ni) composites. The potential functions of the carbon nanomaterials reinforced metal matrix composite simulation systems are briefly introduced. The dependence of the mechanical properties of metal matrix composites on the sizes, volume fraction, and distribution states of CNT and graphene is detailed discussed. Finally, we briefly summarize the future development direction of the molecular dynamic simulation with respect to carbon nanomaterials reinforced metal matrix composites.

Electron Microscopy of Metal-Matrix Composites

1970 ◽  
Vol 28 ◽  
pp. 404-405
Author(s):  
A. Lawley ◽  
M. R. Pinnel ◽  
A. Pattnaik
Keyword(s):  
Electron Microscopy ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Critical Evaluation ◽  
Elastic Behavior ◽  
Matrix Composites ◽  
Directionally Solidified ◽  
Fracture Characteristics ◽  
Broad Program

As part of a broad program on composite materials, the role of the interface on the micromechanics of deformation of metal-matrix composites is being studied. The approach is to correlate elastic behavior, micro and macroyielding, flow, and fracture behavior with associated structural detail (dislocation substructure, fracture characteristics) and stress-state. This provides an understanding of the mode of deformation from an atomistic viewpoint; a critical evaluation can then be made of existing models of composite behavior based on continuum mechanics. This paper covers the electron microscopy (transmission, fractography, scanning microscopy) of two distinct forms of composite material: conventional fiber-reinforced (aluminum-stainless steel) and directionally solidified eutectic alloys (aluminum-copper). In the former, the interface is in the form of a compound and/or solid solution whereas in directionally solidified alloys, the interface consists of a precise crystallographic boundary between the two constituents of the eutectic.

TEM examination of 2014-SiC metal matrix composite

1988 ◽  
Vol 46 ◽  
pp. 726-727
Author(s):  
M. G. Burke ◽  
M. N. Gungor ◽  
P. K. Liaw
Keyword(s):  
Metal Matrix Composite ◽  
Metal Matrix Composites ◽  
Matrix Composite ◽  
Metal Matrix ◽  
Tensile Deformation ◽  
Microstructural Characterization ◽  
Thin Foil ◽  
Matrix Alloy ◽  
Matrix Composites ◽  
Ion Milling

Aluminum-based metal matrix composites offer unique combinations of high specific strength and high stiffness. The improvement in strength and stiffness is related to the particulate reinforcement and the particular matrix alloy chosen. In this way, the metal matrix composite can be tailored for specific materials applications. The microstructural characterization of metal matrix composites is thus important in the development of these materials. In this study, the structure of a p/m 2014-SiC particulate metal matrix composite has been examined after extrusion and tensile deformation.Thin-foil specimens of the 2014-20 vol.% SiCp metal matrix composite were prepared by dimpling to approximately 35 μm prior to ion-milling using a Gatan Dual Ion Mill equipped with a cold stage. These samples were then examined in a Philips 400T TEM/STEM operated at 120 kV. Two material conditions were evaluated: after extrusion (80:1); and after tensile deformation at 250°C.

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