Nano- and Micromechanicsmrl.illinois.edu/sites/default/files/pdfs/Nano- and...Microindenter Tips...

Nano- and Micromechanics

Kathy Walsh, Ph.D.

Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign

How does stuff respond when you poke it, squeeze it, or stretch it?

Sample

The Right Tool for the Job

• Sensitive enough to measure the sample

– Appropriate force resolution

• Spatial resolution on an interesting scale

– Lateral resolution: 10s of nm, 100s of µm, mm

– Displacement: nm, µm, mm

Choose the Right Technique for Your Sample

Small-Scale Mechanical Testing

• Nanoscale – AFM

– Nanoindenter

• Microscale – Nanoindenter

– Microindenter

• Milliscale – Rheometer (twisting)

– DMA (stretching, compressing)

Nanoindenter

Small-scale Mechanical Testing

Why Measure Nano- or Micromechanical Properties?

• Mechanical properties help define materials

– Optimize applications

– Flexibility, biomechanical compatibility

– Crack formation, wear resistance

• Local composition variations in samples

– Spatially-resolved mechanical testing

• Samples may be inherently small

– Thin films, MEMS devices, nanopillars

What Mechanical Properties Do People Measure?

• Quasistatic

– Elastic modulus

– Hardness

• Dynamic

– Time-dependent (viscoelastic) properties

– Storage modulus, loss modulus, tan delta

What Mechanical Properties Do People Measure?

• Quasistatic

– Stress vs. strain curves

– Load (force) vs. displacement curves

• Dynamic

– Properties as a function of time or frequency

– Creep or stress relaxation

Displacement

How do People Measure Mechanical Properties?

• Quasistatic

– AFM force curves

– Nanoindentation, microindentation

– Stress vs. strain curves

• Dynamic

– AFM dynamic measurements

– nanoDMA, Modulus Mapping

– Dynamic Mechanical Analysis

oscale m

icroscale m

illiscale

How do People Measure Mechanical Properties?

• Quasistatic

– Nanoindentation, microindentation

• Elastic (Young’s) modulus

– Related to sample stiffness

• Hardness

– Related to amount of plastic deformation

Micro- vs. Nanoindentation

• (Instrumented) microindentation is sometimes more useful

– Indents to greater depths

– Cares less about • Surface roughness

• Surface forces (adhesion)

Micro- vs. Nanoindentation

Nanoindenter

Microindenter

Optical microscope (indent positioning)

Instrumented Indentation

• Different names, same technique

– Nanoindentation

• Indentation depths shallower than a few µm

• Microindentation if deeper (some instruments)

– Instrumented Indentation

– Depth-Sensing Indentation

Record applied load and indent depth

Poke a sample and record its response

Nanoindenter Basic Parts

Tip Transducer

Nanoindenter Basic Parts

Tip Transducer

Stiff frame

Nanopositioning

Why Does the Instrument Frame Stiffness Matter?

It’s Basically About the Tip and Sample

Tip Transducer

Stiff frame

Nanopositioning

Nanoindenter Tips

• Tips are made of diamond or sapphire

– Tip characteristics are well-known

– Tip compliance is negligible

• Variety of shapes for different applications

– Induce different deformation mechanisms

– Berkovich, Vickers, cube corner

– Flat punch, conospherical (bending, soft materials)

Nanoindenter Tips

• Nanoindentation

– Up to a few µm deep

– Up to several mN

• Most popular tip shape for nanoindentation:

– Berkovich 3-sided pyramid

Nanoindentation residual imprint Berkovich tip on aluminum foil (atomic force microscopy image)

Microindenter Tips

• Microindentation

– Many µm deep

– Up to several N

• Most popular tip shape for microindentation:

– Vickers 4-sided pyramid

– Soft materials: sphere

Microindentation residual imprints Vickers tip on steel (bright field and dark field optical microscopy images)

Contact Area

• Contact area between tip and sample

– Very, very important (crucial calibration)

– How much of your tip is applying force on how much of your sample?

– Depends on depth indented into sample

– Depends on roughness

Vickers indent on steel (AFM image)

Contact Area

• To ensure well-defined contact area between tip and sample…

• make your sample as smooth as possible

– Polishing

– But beware of work hardening

smooth rough

The 5% Rule

• Contact area between tip and sample

• Sample roughness should be ≤ 5% of indent depth…

• … indent 20x deeper than surface roughness

• Can get tricky for thin samples because of the 10% rule

This indent is not deep enough to get good data

The 10% Rule

• The substrate effect

• Indent depth should be ≤ 10% of sample thickness

• Indent too deep, start measuring the substrate

feels like foam feels stiffer

sample

indent here

substrate

The 5% and 10% Rules

• 5% rule and 10% rule are just rules of thumb… the actual values are sample-dependent

– Compliant sample on stiff substrate: can probably go deeper than 10%

– Stiff sample on compliant substrate: probably see substrate effect at depths shallower than 10%

Performing an Indent Th

is is actually a n

-instru

can hold to do a creep/stress relaxation test

Example Nanoindentation Data (Quartz)

Load P (few µN to few mN)

Displacement h (few tens of nm to few µm)

“Load—displacement curve”

loading curve

unloading curve

(optional) hold segment

to measure creep

unloading curve

fit for analysis

Getting “the Answer”

Reduced modulus Hardness

(Actually, , but just look up “fundamental equation of nanoindentation.”)

Contact area: area of tip in contact with sample at a given depth

Why Does Contact Area Matter, Again?

Reduced modulus

Hardness

Elastic from Reduced Modulus

Elastic (Young’s) modulus

Already known (diamond tips)

Poisson’s ratio of the sample

Measure using nanoindentation

Many people just quote this value

(Quasi)static vs. Dynamic Testing

• Many materials are somewhat viscoelastic

– Time-dependent mechanical behavior

• Creep or stress relaxation

– Hold a constant load or displacement for a long time

– Beware of drift

• Dynamic testing

relaxation

creep and stress relaxation tests on nitrile glove

(Quasi)static vs. Dynamic Testing

Nanomechanical Properties as a Function of Depth

hardness

(reduced) modulus

indentation depth (tens of nm to few µm typical)

5% rule

surface effects and calibrations matter more for shallower indents

Nanomechanical Properties as a Function of Depth

hardness

(reduced) modulus

indentation depth (tens of nm to few µm typical)

10% rule

may start to measure substrate properties

Nanoindentation Gives Nanomechanical Properties as a Function of Depth and Location

hardness

(reduced) modulus

These indents were done at different places on the sample as well as at different depths

Nanoindenters Are (Usually) Not Made for Soft Materials

• Nanoindenters are usually made for the “engineering materials” community

– Metals, composites, non-porous materials

• Using a traditional nanoindenter to study soft, compliant, porous, or sticky materials

– Usually doesn’t go deep enough

– Usually doesn’t have awesome enough force resolution

Measurements are Harder on Soft Materials

~MPa comfortable modulus for nanoindentation (try AFM-based techniques for more compliant samples)

Practical Concerns for Biomaterials

• Fixative changes mechanical properties!

– Fixative makes things stiffer

– If that’s the only way you can study your sample…

• Do a comparative study (no absolute numbers)

• Make control samples with just the fixative

• May need a heating cell/stage to stay at biorelevant temperatures

• May need to work in fluid

Practical Considerations for Biomaterials

Keeping the “Hydro” in Hydrogel

• Keep wet samples wet

– Drying and rewetting can change properties

– Samples may dry out during measurements

• Don’t get fluid (or vapors) into the instrument

• Petri dishes, closed fluid cells, special tips

Keeping the “Hydro” in Hydrogel

standard

fluid-compatible

the tip is at the end

Sample Preparation

• Know what your surface looks like first

– Look at it under an optical microscope

– Check sample roughness

• Mounting the sample

– Can’t measure mechanical properties of something that’s floating

– Compliant glue affects results

Sample Preparation

Sample Mounting

• Glue (usually superglue)

– Porous samples may get partially filled with glue

– Some glue is designed for biological use

• Alternative sample mounting strategies

– Cast gels directly onto substrate

• Glass slide, Petri dish

– Wrap or clamp samples

• Don’t stress the area you want to measure

Sample Mounting

How to Approach Your Data

• Oliver—Pharr model

– Elastoplastic materials

• But your samples may be…

– Sticky, compliant

– Poroelastic

– Viscoelastic

– Poroviscoelastic

– Thin films

Try continuous stiffness measurements

JKR model

Do dynamic testing, creep/relaxation tests

Most people start here

TA Instruments Q800 DMA clamps: dual cantilever, tension

Nano/micromechanical Testing Facilities

Asylum Cypher 5µm z range

30µm x 30µm scan size

Asylum MFP-3D-SA (x2) 15µm z range

90µm x 90µm scan size

Hysitron TI-950 TriboIndenter transducers: standard, nanoDMA,

high load (2.8N), AE, nanoECR

Nano/micromechanical Testing Facilities at MRL

DMA (milliscale) AFM (nanoscale)

Nanoindentation and Microindentation (nano/microscale)

Nano- and Micromechanicsmrl.illinois.edu/sites/default/files/pdfs/Nano- and...Microindenter Tips...

Documents

Transcript of Nano- and Micromechanicsmrl.illinois.edu/sites/default/files/pdfs/Nano- and...Microindenter Tips...

Microindentation characterization of polymers and …Microindentation of polymers Vickers hardness definition •Average pressure on the lateral surface of the residual indentation

Petri Nets –Motivation Discrete Event Systems• Timed Petri nets • Definition • Simulation 4 Petri Net –Definition • A Petri net is a bipartite, directed graph defined by

Standard Test Method for Microindentation Hardness of Materials1 · 2018-09-09 · Designation: E 384 – 05a Standard Test Method for Microindentation Hardness of Materials1 This

Petri Vasara

Introduction Petri

Fernanda Petri Coelho - Fernanda Petri ES… · Fernanda Petri Coelho, Utilização de DataWarehouse na geração de informações para a Área de Recursos Humanos . Fernanda Petri

Nanoindentation - Eötvös Loránd Universityszft.elte.hu/oktat/hkaroly/mikronano/Nano_indentation.pdf · Micro vs Nano Indentation • Microindentation A prescribed load applied

Petri-Nets and Other Models. Summary Petri-Net Models Definitions Modeling protocols using Petri-Nets Modeling Queueing Systems using Petri-Nets.

Coloured Petri Nets - HVLhome.hvl.no/ansatte/lmkr/acpn2010/ColouredPetriNets.pdf · 2010. 9. 15. · Advanced Course on Petri Nets 2010 - 2. Coloured Petri Nets (CPNs) Petri Nets

1 Petri Nets Ina Koch and Monika Heiner. 2 Petri Nets(1962) Carl Adam Petri.

Charpy Impact Energy and Microindentation Hardness of 60-NITINOL

Petri Dishes - flmedical.com · PIASTRE DI PETRI 60 mm 60 mm PETRI DISHES PIASTRE DI PETRI 150 mm 150 mm PETRI DISHES GAMMA DI PRODOTTI RANGE OF PRODUCTS Petri Dishes. FL Medical

Petri Vasara_Pöyry_Lähienergia_03112011

Redes Petri

Patrimonium Petri

Cuaderno Petri

Low-Load Vickers Microindentation Hardness Testing

Retele Petri

CHAPTER 6 QUANTITATIVE METHODS- MICROINDENTATION ...

Vickers Microindentation Hardness Profile of Brazed Joints ...