I am performing nanoindentation simulation on Ni-Al FGM using LAMMPS with MEAM potential. Pure Ni and Al substrate gives smooth indentation morphology, but the FGM structure consistently shows severe surface tearing, rough mesh morphology during indentation. Force displacement graph is okay for all structures on current condition, But penetration snap at higher displacement shows teared mesh surface which is very abnormal.
Current setup:
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Units: metal
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Boundary: p p f / p p s
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Potential: MEAM (NiAlTi.meam)
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Substrate thickness: ~40 Å
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Bottom fixed layer: 10 Å
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Thermostat layer: 10–20 Å
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Indenter radius: 20 Å
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Indentation depth: 20 Å
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Indentation speed: 0.1 Å/ps
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Timestep: 0.001 ps
I already tried:
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Langevin thermostat
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NPT relaxation
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longer minimization
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OVITO smoothing
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reducing thermal noise
However, FGM still develops:
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jagged penetration surface
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mesh tearing
Pure Ni and Al under same conditions behaves normally.
Current indentation command:
fix 8 mobile indent 100 sphere ${xmid} ${ymid} v_z 20 units box
Some snap of dump file from OVITO:
Any suggestions regarding stable indentation setup or validated Ni-Al potentials would be highly appreciated.