NanoTest impact module

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Impact
NanoTest impact module

• for
• Impact testing
• Contact fatigue testing
• Erosive wear testing
• Fracture toughness
• Adhesion testing
• Dynamic hardness

The only commercial nano-impact tester available
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Bringing nanomechanical measurements into the
real-world
Importance of Nano-impact testing
Quasi-static tests are very useful Nanoindentatio
n mechanical properties (hardness,
modulus, creep) Nanoscratch tribological
properties (abrasive and sliding wear)
The need for dynamic testing Materials often
fail by fatigue not overload so optimisation
based on nanoindentation/scratch can be
insufficient for applications where materials are
exposed in service and/or in processing to
fatigue wear or erosive wear (impact wear)
Dynamic nanomechanical tests (nano-impact and
contact fatigue) have been developed by Micro
Materials to address this problem
The solution
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Impact
Nano-impact testing - simulating fatigue wear and
failure
2 different methods
Sample oscillation

• Accurately controlled impacts
• Known energy to failure
• Wear mechanisms

• High frequency oscillation
• High cycle fatigue

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Impact by sample oscillation Operating principles
Impact testing - simulating fatigue wear and
failure
Test parameters
Key features

• Applied Load
• Oscillation frequency
• Oscillation Amplitude
• Sample scanning
• Probe geometry
• Impact Angle

• High frequency oscillation
• High cycle fatigue
• Time-to-failure
• Adhesion failure
• Fracture Behaviour

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Impact by sample oscillation
Impact Testing of a brittle TiN coating on Si

• 100 mN applied load is
• on throughout test
• 80 Hz oscillation frequency
• Oscillation on 30 s after start
• Oscillation off 30 s before end
• Film failure after 250 s

• For bulk materials wear rates are determined
  from changes in probe depth
• For coatings, time-to-failure is related to the
  bonding strength to the substrate

SEM of test stopped just after
transition Impact-induced coating damage - ring
cracks spread outwards until failure
CRAFT Project BRST-CT97-5196 Impact
characterisation of single and duplex surface
engineered steels
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Contact fatigue testing of thick ceramic glazes
Collaboration with Ito Tecnologia Cerámica,
Castellon, Spain
80 Hz oscillation frequency 1 N applied load

...clear differences in time-to-failure and
overall depth changes...
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Contact fatigue testing of thick ceramic glazes
Effect of microstructure on impact performance
Glaze coating B
Glaze coating C
small needle-like crystals aid impact resistance
larger rounded crystals do not help impact
resistance
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Contact fatigue of ceramic coatings comparison
to other testing techniques

• Hardness and Youngs modulus did not vary
• Scratch testing frustrated by high surface
  roughness
• Correlation with fracture toughness data
• Impact resistant samples had high fracture
  toughness

• Time-to-failure
• Change in Probe Depth

measures of resistance to brittle fracture
Micro-impact testing a new technique for
investigating fracture toughness BD Beake (MML),
Maria Jesus Ibanez Garcia (ITC Spain) and JF
Smith (MML), Thin Solid Films 398-399 (2001)
438-443.
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Pendulum impulse Operating principles

• Unique points
• Quantification of adhesion energy
• Determination of total energy delivered
• to contact point
• Dynamic hardness measurement

Static Force Impact Angle Acceleration
distance Impact Frequency Test probe geometry
Experimental variables include
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Impact by sample oscillation
Impact-induced fatigue failure of Polymeric
Coating on soft Al substrate
Fatigue-induced surface damage Contact changes
from impact (essentially non-energy absorbing) to
contact fatigue (energy absorbing) on film failure

• Time-to-failure
• Rapid high-cycle fatigue tests

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Ceramics and glasses brittle behaviour
Fracture and fatigue wear by Nano-impact testing
Unimplanted SiO2
1 x 1016 N cm-2 implanted SiO2
1 impact every 4 s in these tests
Damage regimes in the impact test 1 before
impact 2 plastic deformation 3 slow crack
growth (fatigue) 4 abrupt failure and material
removal 5 further slow crack growth

• Fatigue resistance from
• time-to-failure
• Ion-implantation
• improves toughness

BD Beake (MML), J Lu, Q Xue, J E and T Xu, (all
Lanzhou Institute of Chemical Physics) Proc FMC8
2003
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Impact
Nano-impact testing reveals fatigue differences
on coatings of the same hardness
DLC coating on tool steel
Carbon coating on tool steel
Coating failure
Multiple coating failures

• depth vs. time impact plot for multilayered
  carbon coating at 1mN
• long time to failure

• depth vs. time impact plot for multilayered DLC
  coating at 1mN
• note short time-to-failure

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Impact failure of 550 nm DLC film on Silicon
Coating debonding - adhesion failure Abrupt depth
change at failure gt film thickness
CVD Coating Deposition RF Power

• Nano-impact shows how deposition conditions
• influence coating performance
• Time-to-failure
• Failure mechanism

Coating fracture cohesive failure Depth change
at failure less than film thickness
BD Beake et al, Diamond and Related Materials,
11, 1606, 2002
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Impact failure of 100 nm DLC films on Silicon
1 initial contact 2 plastic deformation 3
fatigue (slow crack growth) 4 fast crack
propagation and material removal 5 further slow
crack growth

• Scratch test showed little difference in
  critical load
• Impact test shows clear difference in behaviour

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Fatigue and Fracture Wear of ta-C films
80 nm on Si
80 nm on Si
60 nm on Si
5 nm on Si
Damage mechanism in the impact test before
impact - plastic deformation - slow crack growth
(fatigue) - abrupt failure and material removal -
further slow crack growth

• time-to-first-failure to rank impact resistance
• some plastic deformation of the substrate does
  occur (depth at failure)

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Fatigue and Fracture Wear of ta-C films
Procedure developed for analysing fracture
behaviour

• Sort initial time to failure in individual tests
  into ascending order
• Plot time to failure vs. probability of the
  sample failing in that time
• Use time for failure probability of 0.5 to rank
  impact resistance

Probability of fracture within 300 s 0.9
A key advantage of nano-scale impact is
the possibility of repeat testing at different
locations
Probability of fracture 0.5 at 75 s
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Nano-impact mapping of biomaterials
Grids of impacts to determine differences in
toughness/ductility

• Nano-scale ductility of crab shell varies
  across the shell
• Finer mesh sizes can be used to investigate
  this behaviour at much smaller scale

• Initial results suggest test can be used to
  identify osteopaenia (2-5 times greater risk of
  osteoporosis in later life)

Collaboration in progress with Universities of
Limerick and Lancaster
Collaboration in progress with University of
Maryland