scholarly journals On the Origin of Plastic Deformation and Surface Evolution in Nano-Fretting: A Discrete Dislocation Plasticity Analysis

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6511
Author(s):  
Yilun Xu ◽  
Daniel S. Balint ◽  
Daniele Dini
Keyword(s):  
Collective Motion ◽  
Surface Modifications ◽  
Deformation Mechanisms ◽  
Surface Evolution ◽  
Crystalline Materials ◽  
Damage And Failure ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Contact Size ◽  
Insight Into

Discrete dislocation plasticity (DDP) calculations were carried out to investigate a single-crystal response when subjected to nano-fretting loading conditions in its interaction with a rigid sinusoidal asperity. The effects of the contact size and preceding indentation on the surface stress and profile evolution due to nano-fretting were extensively investigated, with the aim to unravel the deformation mechanisms governing the response of materials subjected to nano-motion. The mechanistic drivers for the material’s permanent deformations and surface modifications were shown to be the dislocations’ collective motion and piling up underneath the contact. The analysis of surface and subsurface stresses and the profile evolution during sliding provides useful insight into damage and failure mechanisms of crystalline materials subject to nano-fretting; this can lead to improved strategies for the optimisation of material properties for better surface resistance under micro- and nano-scale contacts.

Climb Enabled Discrete Dislocation Plasticity of Superalloys

2015 ◽  
Vol 651-653 ◽  
pp. 981-986 ◽  
Author(s):  
Can Ayas ◽  
Vikram Deshpande
Keyword(s):  
Vacancy Concentration ◽  
Concentration Field ◽  
Point Sources ◽  
Deformation Mechanisms ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Plastic Matrix ◽  
Elastic Particles

Ni-based superalloys comprising of elastic particles embedded in a single crystal elastic-plastic matrix are usually subject to loading at elevated service temperatures. In order to enhance the understanding of high temperature deformation mechanisms a two dimensional discrete dislocation plasticity framework wherein the dislocations movement that incorporates both glide and climb is formulated. The climbing dislocations are modelled as point sources/sinks of vacancies and the vacancy diffusion boundary value problem is solved by superposition of the vacancy concentration fields of the point sources/sinks in an infinite medium and a complementary non-singular solution that enforces the relevant boundary conditions. The vacancy concentration field along with the Peach-Kohler force provides the climb rate of the dislocations.

scholarly journals Discrete dislocation plasticity analysis of loading rate-dependent static friction

2016 ◽  
Vol 472 (2192) ◽  
pp. 20150877 ◽  
Author(s):  
H. Song ◽  
V. S. Deshpande ◽  
E. Van der Giessen
Keyword(s):  
Loading Rate ◽  
Static Friction ◽  
Contact Length ◽  
Point Of View ◽  
Size Dependent ◽  
Rate Dependent ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Shear Yield ◽  
Contact Size

From a microscopic point of view, the frictional force associated with the relative sliding of rough surfaces originates from deformation of the material in contact, by adhesion in the contact interface or both. We know that plastic deformation at the size scale of micrometres is not only dependent on the size of the contact, but also on the rate of deformation. Moreover, depending on its physical origin, adhesion can also be size and rate dependent, albeit different from plasticity. We present a two-dimensional model that incorporates both discrete dislocation plasticity inside a face-centred cubic crystal and adhesion in the interface to understand the rate dependence of friction caused by micrometre-size asperities. The friction strength is the outcome of the competition between adhesion and discrete dislocation plasticity. As a function of contact size, the friction strength contains two plateaus: at small contact length ( ≲ 0.6   μ m ) , the onset of sliding is fully controlled by adhesion while for large contact length ( ≳ 10   μ m ) , the friction strength approaches the size-independent plastic shear yield strength. The transition regime at intermediate contact size is a result of partial de-cohesion and size-dependent dislocation plasticity, and is determined by dislocation properties, interfacial properties as well as by the loading rate.

scholarly journals Coupling Quantitative Dislocation Analysis with In Situ Loading Techniques: New Insight into Deformation Mechanisms

2017 ◽  
Vol 23 (S1) ◽  
pp. 764-765
Author(s):  
M.L. Taheri ◽  
G. Vetterick ◽  
A.C. Leff ◽  
M. Marshall ◽  
J. K. Baldwin ◽  
...  
Keyword(s):  
Deformation Mechanisms ◽  
Insight Into

scholarly journals Discrete Dislocation Plasticity

2005 ◽  
pp. 1115-1131 ◽  
Author(s):  
E. Van der Giessen ◽  
A. Needleman
Keyword(s):  
Discrete Dislocation ◽  
Dislocation Plasticity

A Discrete Dislocation Plasticity Analysis of Plane-Strain Indentation of a Single-Crystal Half-Space by a Smooth and a Rough Rigid Asperity

2010 ◽  
Author(s):  
X. Yin ◽  
K. Komvopoulos
Keyword(s):  
Single Crystal ◽  
Plane Strain ◽  
Half Space ◽  
Crystal Surface ◽  
Normal Load ◽  
Surface Profile ◽  
Dislocation Source ◽  
Discrete Dislocation ◽  
Dislocation Plasticity ◽  
Edge Dislocations

A discrete dislocation plasticity analysis of plane-strain indentation of a single-crystal half-space by a smooth or rough (fractal) rigid asperity is presented. The emission, movement, and annihilation of edge dislocations are incorporated in the analysis through a set of constitutive rules [1,2]. It is shown that the initiation of the first dislocation is controlled by the subsurface Hertzian stress field and occurs in the ±45° direction with respect to the normal of the crystal surface, in agreement with the macroscopic yielding behavior of the indented halfspace. For fixed slip-plane direction, the dislocation density increases with the applied normal load and dislocation source density. The dislocation multiplication behavior at a given load is compared with that generated by a rough indenter with a fractal surface profile. The results of the analysis provide insight into yielding and plastic deformation phenomena in indented single-crystal materials.

scholarly journals Analysis of the Crack Initiation and Growth in Crystalline Materials Using Discrete Dislocations and the Modified Kitagawa–Takahashi Diagram

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 358
Author(s):  
Kuntimaddi Sadananda ◽  
Ilaksh Adlakha ◽  
Kiran N. Solanki ◽  
A.K. Vasudevan
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Dislocation Dynamics ◽  
Internal Stresses ◽  
Stress Concentrations ◽  
Crystalline Materials ◽  
Discrete Dislocation ◽  
Continuous Crack ◽  
American Society

Crack growth kinetics in crystalline materials is examined both from the point of continuum mechanics and discrete dislocation dynamics. Kinetics ranging from the Griffith crack to continuous elastic-plastic cracks are analyzed. Initiation and propagation of incipient cracks require very high stresses and appropriate stress gradients. These can be obtained either by pre-existing notches, as is done in a typical American Society of Testing and Materials (ASTM) fatigue and fracture tests, or by in situ generated stress concentrations via dislocation pile-ups. Crack growth kinetics are also examined using the modified Kitagawa–Takahashi diagram to show the role of internal stresses and their gradients needed to sustain continuous crack growth. Incipient crack initiation and growth are also examined using discrete dislocation modeling. The analysis is supported by the experimental data available in the literature.

scholarly journals Discrete dislocation plasticity and crack tip fields in single crystals

2001 ◽  
Vol 49 (9) ◽  
pp. 2133-2153 ◽  
Author(s):  
E. Van der Giessen ◽  
V.S. Deshpande ◽  
H.H.M. Cleveringa ◽  
A. Needleman
Keyword(s):  
Single Crystals ◽  
Crack Tip ◽  
Crack Tip Fields ◽  
Discrete Dislocation ◽  
Dislocation Plasticity
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