Nanoindentation Scratch test Tribometers References

Description

Niveau: Supérieur
Nanoindentation. Scratch test. Tribometers References. Experimental approaches to contact mechanics. Jarmila Savkova Centre des Materiaux, MINES ParisTech. 22nd June 2010 Jarmila Savkova — Experimental approaches to contact mechanics. 1/53

• file can scratch


• relative hardness


• scratch test


• prescribed load


• hard indenter


• diamond tips


• instrumented indentation


• hardness

Sujets

• Scratch test
• Hardness

Informations

• Publié par: chaeh
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Nanoindentation. Scratch test. Tribometers References.
Experimental approaches to contact mechanics.
Jarmila Savkova
Centre des Mat´eriaux, MINES ParisTech.
nd22 June 2010
Jarmila Savkova — Experimental approaches to contact mechanics. 1/53Nanoindentation. Scratch test. Tribometers References.
Outline
1 Nanoindentation.
Hardness
Instrumented indentation
Indenter tips
Data analysis
Dynamic testing
Factors affecting nanoindentation
2 Scratch test.
3 Tribometers
4 References.
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Hardness
Hardness is resistance to penetration of a hard indenter
Barba (1640) - ”..hardness is such a property of precious stones that those which
file can scratch are not so classed.”
Martens (1912) - Hardness is the resistance of a body against the penetration of
another (harder) one
Hardness can’t be measured if there is no remaining impression, i.e. when only
elastic deformation takes place. Hardness is a measure of a material’s resistance
to surface penetration by an indenter with a force applied to it.
Hardness
Brinell, 10 mm indenter ball, 3000 kg Load F surface
area of indentation A
Microhardness
Vickers microindentation : size of pyramid comparable
to microstructural features. You can use to assess
relative hardness of various phases or
microconstituents.
Nanoindentation
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Micro vs Nanoindentation
Microindentation
A prescribed load appled to an indenter in contact
with a specimen and the load is then removed and the
area of the residual impression is measured. The load
divided by the by the area is called the hardness.
Nanoindentation
A prescribed load is appled to an indenter in contact
with a specimen. As the load is applied, the depth of
penetration is measured. The area of contact at full
load is determined by the depth of the impression and
the known angle or radius of the indenter. The
hardness is found by dividing the load by the area of
contact. Shape of the unloading curve provides a
measure of elastic modulus.
Jarmila Savkova — Experimental approaches to contact mechanics. 4/53Nanoindentation. Scratch test. Tribometers References.
Instrumented indentation
Most important method for measurement of mechanical surface properties :
Load and depth sensing indentation = instrumented indentation
Continuous recording of force and depth during indentation of surface with diamond
tips
Standartized DIN EN ISO 14577 1-3
Metallic materials - Instrumented indentation test for hardness and materials
parameters
Macro-range : 2N ¡ F ¡ 30000N
Mi : F ¡ 2 N
Nano-range : depth h ¡ 200 nm
Indenter as Pyramid : Vickers (4 edges), Berkovich(3 edges) - standardized
Indenter as Sphere or cone with spherical cap (not standartized)
Sharp :Sperical :
Immediately elastic AND plasticElastic, THEN plastic deformation
Can facet diamod into pyramids, not conesDifficult to machine diamond
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Indenter tips
(a) Vickers (b) Berkovich (c) Knoop (d) Conical (e) Rockwell (f) Spherical
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Indenter tips[2]
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Berkovich tip
Advantage
Sharp and well-defined tip
geometry
Well-defined plastic deformation
into the surface
Good for measuring modulus and
hardness values
Disadvantage
Elastic-plastic transition is not
clear
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Spherical tip
Advantage
Extended elastic-plastic
deformation
Load displacement results can be
converted to indentation
stress-strain curve
Useful in determination of yield
point
Disadvantage
Tip geometry is not very sharp
and the spherical surface is not
always perfect
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Data analysis
P : applied load
h : indenter displacement
h r : plastic deformation after load removal
h e : surface displacement at the contact perimeter
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