Modelling of nanometric cutting in metals using MD simulations
(2022) FMEM01 20221Mechanics
- Abstract
- This master thesis project has been done within the Mechanics department of Lunds Tekniska Högskola (LTH). It studies the nanometric cutting process of a single crystal copper workpiece by a cubic diamond tool using Molecular Dynamics (MD) simulations
on the software LAMMPS.
Several simulations are computed in order to study the influence of different factors. In a first place, several tool models are used: one cylindrical shell stiff tool, one cylindrical stiff tool and one cylindrical tool whose atoms are modelled with a Tersoff potential. For these simulations there is first a relaxation of the workpiece and the tool using an NVT ensemble and then the cutting is computed with an NVE one. Because important oscillations are observed,... (More) - This master thesis project has been done within the Mechanics department of Lunds Tekniska Högskola (LTH). It studies the nanometric cutting process of a single crystal copper workpiece by a cubic diamond tool using Molecular Dynamics (MD) simulations
on the software LAMMPS.
Several simulations are computed in order to study the influence of different factors. In a first place, several tool models are used: one cylindrical shell stiff tool, one cylindrical stiff tool and one cylindrical tool whose atoms are modelled with a Tersoff potential. For these simulations there is first a relaxation of the workpiece and the tool using an NVT ensemble and then the cutting is computed with an NVE one. Because important oscillations are observed, these simulations are repeated with an additional drag function and then with an NPT ensemble using a beam periodic in two dimensions rather than one like before. Even if the latter ensemble do not solve all the oscillations
problem, it is relevant enough to be used as a base to test other parameters.
A multi-layer cutting is also simulated with a shell stiff tool after an NVT ensemble without drag function. This simulation repeats the cutting process three times in a row on the same workpiece with the same cutting depth for every layer. It is found that the forces and the temperature increase layer after layer.
In a second place, the simulations are only performed with a tool whose atoms are modelled with a Tersoff potential, with an NPT relaxation and a two-dimensional periodic beam. Other factors are now studied such as the cutting depth, the tool radius, the workpiece height or the crystallographic orientation of the atoms in the beam. It is shown that the parameters that tend to create a bigger pileup, like deeper cutting depth d or smaller radius r are increasing the cutting forces and the temperature. (Less) - Popular Abstract
- Because of the nanometric scale involved, this project cannot rely on classical theories of continuum mechanics but uses instead molecular dynamics to model the cutting of a piece of copper by a diamond tool.
In this master thesis project, a Molecular Dynamics simulator called LAMMPS was used to model the behaviour of atoms in a copper workpiece and in a diamond tool. This software models the copper-copper interactions in the workpiece, the carboncarbon interactions in the tool and the copper-carbon interactions at the contact zone between these two parts. Because of the large number of atoms involved and the number of timesteps needed to model the whole cutting process, the code needed several days or weeks to run.
A previous study... (More) - Because of the nanometric scale involved, this project cannot rely on classical theories of continuum mechanics but uses instead molecular dynamics to model the cutting of a piece of copper by a diamond tool.
In this master thesis project, a Molecular Dynamics simulator called LAMMPS was used to model the behaviour of atoms in a copper workpiece and in a diamond tool. This software models the copper-copper interactions in the workpiece, the carboncarbon interactions in the tool and the copper-carbon interactions at the contact zone between these two parts. Because of the large number of atoms involved and the number of timesteps needed to model the whole cutting process, the code needed several days or weeks to run.
A previous study had already modeled the cutting of a copper piece for the same type of geometry but without having modeled the interactions of the carbon atoms within the diamond tool. The very first simulations have therefore served to highlight the importance of modeling these interactions to get a result closer to reality.
Then, the influence of several parameters was studied, like the cutting depth, the height of the workpiece or the tool radius. It turns out that the more dislocations there are in the workpiece, the more rigid it becomes and consequently the forces required to perform the cut and the temperature of the material increase. These results were observed on a software program called OVITO, acronym for Online Visualisation Tool, which allowed to visually see the evolution of material parameters during the cutting process, which was quite convenient.
Another calculation simulated three consecutive cuts of the same material, and this also highlighted the fact that the forces and temperatures involved increase cut after cut, which is an important element to take into account during machining processes.
Future work can continue the results of this master thesis and study more parameters, such as the orientation of atoms in the copper workpiece and the diamond tool, which was already studied briefly in this project but which deserves a more thorough study. The addition of grains in the structure of the studied materials could also be interesting in order to model them in a more realistic way. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9102580
- author
- Gautier, Damien LU
- supervisor
-
- Per Hansson LU
- organization
- course
- FMEM01 20221
- year
- 2022
- type
- H1 - Master's Degree (One Year)
- subject
- keywords
- Nanometric cutting, Molecular Dynamics
- language
- English
- id
- 9102580
- date added to LUP
- 2022-11-04 07:50:50
- date last changed
- 2022-11-04 07:50:50
@misc{9102580,
abstract = {{This master thesis project has been done within the Mechanics department of Lunds Tekniska Högskola (LTH). It studies the nanometric cutting process of a single crystal copper workpiece by a cubic diamond tool using Molecular Dynamics (MD) simulations
on the software LAMMPS.
Several simulations are computed in order to study the influence of different factors. In a first place, several tool models are used: one cylindrical shell stiff tool, one cylindrical stiff tool and one cylindrical tool whose atoms are modelled with a Tersoff potential. For these simulations there is first a relaxation of the workpiece and the tool using an NVT ensemble and then the cutting is computed with an NVE one. Because important oscillations are observed, these simulations are repeated with an additional drag function and then with an NPT ensemble using a beam periodic in two dimensions rather than one like before. Even if the latter ensemble do not solve all the oscillations
problem, it is relevant enough to be used as a base to test other parameters.
A multi-layer cutting is also simulated with a shell stiff tool after an NVT ensemble without drag function. This simulation repeats the cutting process three times in a row on the same workpiece with the same cutting depth for every layer. It is found that the forces and the temperature increase layer after layer.
In a second place, the simulations are only performed with a tool whose atoms are modelled with a Tersoff potential, with an NPT relaxation and a two-dimensional periodic beam. Other factors are now studied such as the cutting depth, the tool radius, the workpiece height or the crystallographic orientation of the atoms in the beam. It is shown that the parameters that tend to create a bigger pileup, like deeper cutting depth d or smaller radius r are increasing the cutting forces and the temperature.}},
author = {{Gautier, Damien}},
language = {{eng}},
note = {{Student Paper}},
title = {{Modelling of nanometric cutting in metals using MD simulations}},
year = {{2022}},
}