Perform Nanoindentation on Al-Mg Alloy - Revision history

Yfwang09: /* Retrieve the Forth-Depth Curve of Nanoindentation */

2022-10-12T04:47:44Z

Retrieve the Forth-Depth Curve of Nanoindentation

← Older revision		Revision as of 04:47, 12 October 2022
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	[[Image:dislocation_analysis.png \| thumb \| 500px \| center \| Fig.6 dislocation nucleation during nanoindentation]]		[[Image:dislocation_analysis.png \| thumb \| 500px \| center \| Fig.6 dislocation nucleation during nanoindentation]]

	=== Retrieve the ~~Forth~~-Depth Curve of Nanoindentation ===		=== Retrieve the Force-Depth Curve of Nanoindentation ===

	As we discussed in section 3.3, the responsive force on the indenter is recorded in variable "f_indent[3]", the indentation depth is calculated and recorded in variable "v_depth". Therefore, we add the following lines before the "run" command in section 3.3, then we can retrieve the forth-depth curve from the simulation:		As we discussed in section 3.3, the responsive force on the indenter is recorded in variable "f_indent[3]", the indentation depth is calculated and recorded in variable "v_depth". Therefore, we add the following lines before the "run" command in section 3.3, then we can retrieve the forth-depth curve from the simulation:

Yfwang09 at 08:06, 18 May 2017

2017-05-18T08:06:37Z

← Older revision		Revision as of 08:06, 18 May 2017
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	<P ALIGN="CENTER">		<P ALIGN="CENTER">
	<FONT SIZE="+3" color="darkred"><STRONG>		<FONT SIZE="+3" color="darkred"><STRONG>
	~~Perform~~ Nanoindentation on Al-Mg Alloy using LAMMPS </STRONG></font></P>		Nanoindentation on Al-Mg Alloy using LAMMPS </STRONG></font></P>
	<DIV>		<DIV>
	<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>		<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>

Yfwang09 at 08:06, 18 May 2017

2017-05-18T08:06:19Z

← Older revision		Revision as of 08:06, 18 May 2017
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	<P ALIGN="CENTER">		<P ALIGN="CENTER">
	<FONT SIZE="+3" color="darkred"><STRONG>		<FONT SIZE="+3" color="darkred"><STRONG>
	Perform Nanoindentation on an Al-Mg Alloy </STRONG></font></P>		Perform Nanoindentation on Al-Mg Alloy using LAMMPS </STRONG></font></P>
	<DIV>		<DIV>
	<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>		<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>

Yfwang09 at 08:05, 18 May 2017

2017-05-18T08:05:47Z

← Older revision		Revision as of 08:05, 18 May 2017
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	<P ALIGN="CENTER">		<P ALIGN="CENTER">
	<FONT SIZE="+3" color="darkred"><STRONG>		<FONT SIZE="+3" color="darkred"><STRONG>
	Perform Nanoindentation on an ~~Aluminum~~-~~Magnesium~~ Alloy </STRONG></font></P>		Perform Nanoindentation on an Al-Mg Alloy </STRONG></font></P>
	<DIV>		<DIV>
	<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>		<P ALIGN="CENTER"><STRONG>Yifan Wang</STRONG></P>

Yfwang09: /* Generate the Sample of Al-Mg Alloy */

2017-05-18T08:01:57Z

Generate the Sample of Al-Mg Alloy

← Older revision		Revision as of 08:01, 18 May 2017
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	region BOX block -40.0 40.0 -40.0 40.0 -80.0 0.0 units lattice		region BOX block -40.0 40.0 -40.0 40.0 -80.0 0.0 units lattice

	Here the lattice constant 4.053 is the size after we consider the size effect, and 80 lattice distance is around 32.4nm. Note that if we change the indentation surface to other FCC planes ((110), (111), etc.), we should change the orientation in lattice definition, for example we take (110) plane as the indentation surface.		Here the lattice constant 4.053 is the size after we consider the size effect, and 80 lattice distance is around 32.4nm. Note that if we change the indentation surface to other FCC planes ((110), (111), etc.), we should change the orientation in lattice definition, for example if we take (110) plane as the indentation surface, the setting should be:

	lattice fcc 4.053 orient x 0.707 0 -0.707 orient y 0 1 0 orient z 0.707 0 0.707		lattice fcc 4.053 orient x 0.707 0 -0.707 orient y 0 1 0 orient z 0.707 0 0.707

Yfwang09: /* Thermodynamics */

2017-05-18T07:59:28Z

Thermodynamics

← Older revision		Revision as of 07:59, 18 May 2017
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	According to the phase diagram of Al-Mg alloy (Fig.1), the solubility of Mg in Al is smaller than 1% at room temperature. For our case, since the atomic concentration is 0.67%, we can generate the sample by first creating pure FCC Al metal, and then randomly exchange required Al atoms to Mg.		According to the phase diagram of Al-Mg alloy (Fig.1), the solubility of Mg in Al is smaller than 1% at room temperature. For our case, since the atomic concentration is 0.67%, we can generate the sample by first creating pure FCC Al metal, and then randomly exchange required Al atoms to Mg.

	[[Image:Al-Mg_phase_diagram.jpg \| ~~frame~~ \| center \| Fig.1 Phase Diagram of Aluminum-Magnesium (Murray, 1982)]]		[[Image:Al-Mg_phase_diagram.jpg \| thumb \| 500px \| center \| Fig.1 Phase Diagram of Aluminum-Magnesium (Murray, 1982)]]
	[[Image:Al-Mg_size_factor.jpg \| ~~frame~~ \| center \| Fig.2 Size Factors of Al-Mg solid solution (Cai&Nix, 2016)]]		[[Image:Al-Mg_size_factor.jpg \| thumb \| 500px \| center \| Fig.2 Size Factors of Al-Mg solid solution (Cai&Nix, 2016)]]

	However, the size factor of Mg as the solute in Al is not negligible (Fig.2). We have to consider the volume change of the sample by adding Mg into pure Al. There are two ways to account for the size effect:		However, the size factor of Mg as the solute in Al is not negligible (Fig.2). We have to consider the volume change of the sample by adding Mg into pure Al. There are two ways to account for the size effect:

Yfwang09: /* Retrieve the Forth-Depth Curve of Nanoindentation */

2017-05-18T07:58:50Z

Retrieve the Forth-Depth Curve of Nanoindentation

← Older revision		Revision as of 07:58, 18 May 2017
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	The force-depth curves for different indentation direction are shown below in Fig.7.		The force-depth curves for different indentation direction are shown below in Fig.7.

	[[Image:FD_curve_orientation.png \| 500px \| center \| Fig.7 Force-depth curve of nanoindation performed on different orientations]]		[[Image:FD_curve_orientation.png \| thumb \| 500px \| center \| Fig.7 Force-depth curve of nanoindation performed on different orientations]]

	In addition, because we have periodic boundary condition on both x- and y- direction, there are actually infinite indenter images exerting infinite force on the sample. Therefore, the sample is not touching the indenter at very beginning, and the actual indentation process started at finite indentation depth. In the results, we manually corrected the indentation depth so that it starts from the position where the indenter is exactly touching the sample.		In addition, because we have periodic boundary condition on both x- and y- direction, there are actually infinite indenter images exerting infinite force on the sample. Therefore, the sample is not touching the indenter at very beginning, and the actual indentation process started at finite indentation depth. In the results, we manually corrected the indentation depth so that it starts from the position where the indenter is exactly touching the sample.

Yfwang09: /* Retrieve the dislocation structure from MD simulation */

2017-05-18T07:58:41Z

Retrieve the dislocation structure from MD simulation

← Older revision		Revision as of 07:58, 18 May 2017
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	After we get the atom profiles during the simulation, we can perform the dislocation analysis and get the dislocation structure, as shown in Fig.6:		After we get the atom profiles during the simulation, we can perform the dislocation analysis and get the dislocation structure, as shown in Fig.6:

	[[Image:dislocation_analysis.png \| 500px \| center \| Fig.6 dislocation nucleation during nanoindentation]]		[[Image:dislocation_analysis.png \| thumb \| 500px \| center \| Fig.6 dislocation nucleation during nanoindentation]]

	=== Retrieve the Forth-Depth Curve of Nanoindentation ===		=== Retrieve the Forth-Depth Curve of Nanoindentation ===

Yfwang09: /* Loading and Unloading */

2017-05-18T07:58:29Z

Loading and Unloading

← Older revision		Revision as of 07:58, 18 May 2017
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	Fig.5 is a diagram showing the loading process of the nanoindentation.		Fig.5 is a diagram showing the loading process of the nanoindentation.

	[[Image:example_nanoindentation.png \| 150px \| center \| Fig.5 Loading of the nanoindentation process]]		[[Image:example_nanoindentation.png \| thumb \| 150px \| center \| Fig.5 Loading of the nanoindentation process]]

	In LAMMPS, the command used for indentation is "fix indent". This command can use the information of time steps and thus perform dynamic indentation during the MD simulation.		In LAMMPS, the command used for indentation is "fix indent". This command can use the information of time steps and thus perform dynamic indentation during the MD simulation.

Yfwang09: /* The Force Field for the Indenter */

2017-05-18T07:58:13Z

The Force Field for the Indenter

← Older revision		Revision as of 07:58, 18 May 2017
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	We have tested the K value ranging from 1 to 1000. Note that with this force field function, the indenter is not an elastic sphere. The effective elastic modulus of the indenter is shown in Fig.4. We can see that the K value does not have significant influence on the effective modulus of the indenter. In our simulation, we choose K = 1.0eV/Å for all the simulation.		We have tested the K value ranging from 1 to 1000. Note that with this force field function, the indenter is not an elastic sphere. The effective elastic modulus of the indenter is shown in Fig.4. We can see that the K value does not have significant influence on the effective modulus of the indenter. In our simulation, we choose K = 1.0eV/Å for all the simulation.

	[[Image:Indenter_K_Modulus.png \| 500px \| center \| Fig.4 The Effective Modulus of the Indenter in Terms of the Indent Depth.]]		[[Image:Indenter_K_Modulus.png \| thumb \| 500px \| center \| Fig.4 The Effective Modulus of the Indenter in Terms of the Indent Depth.]]

	=== Fix the bottom ===		=== Fix the bottom ===