Diapositiva 1

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ACOUSTIC EMISSION AND STRUCTURAL TRANSITIONS
Lluís Mañosa Departament dEstructura i
Constituents de la Matèria Facultat de
Física lluis_at_ecm.ub.es
Erell Bonnot Francisco José Pérez-Reche Antoni
Planes Eduard Vives
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Acoustic Emission (AE)
? Transient elastic waves resulting from
localized internal microdisplacements
taking place in a solid (American Society for
Testing and Materials, ASTM) .
? Technique to measure these elastic waves.
First EA measurements J. Kaiser (1950)
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AE Fundamentals
Equation of motion
(Einstein notation)
along the n direction
for a point force
The solution is the Green funcion
Uniqueness theorem Reciprocity theorem
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Displacement field for body forces f throughout
V and to boundary conditions on S
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Discontinuities across an internal surface
? much smaller than x
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Usual assumption
No body forces
SEISMIC MOMENT
which yields
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DETECTION OF AE WAVES
Detectability
Typically Dislocation propagating 10?m at
3000m/s 100?m at 300m/s Crack area
(propagating at 1000 m/s) 10 ?m2 Phase
change 10 ?m3
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TRANSDUCERS
Optical (laser), Electromagnetic, Piezoelectric

Acoustic coupling
Displacement
Conical broad band
Damped piezoelectric
Piezoelectric
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Transducer calibration
Breaking pencil lead (0.3mm thick)
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TYPES OF AE SIGNALS
Burst
Continuous
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AE Detection
Ring-down counting Count rate
Distributions amplitude, duration,
RESSONANT
RMS Power and energy
Frequency spectrum
Source characterization
BROAD BAND
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SELECTED EXPERIMENTAL RESULTS
1. Broad band detection
2. Ressonant detection
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Application to martensitic transformations
Ll. Mañosa, et al Appl. Phys. Lett. 54, 2574
(1989) Ll. Mañosa, et al. Acta Metall. Mater. 38
1635 (1990)
Kinematics
Radiation pattern (spatial information)
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RADIATION PATTERN
Longitudinal waves
Shear waves
perpendicular to
and
KINEMATICS
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Thermoelastic martensitic transformation
Only longitudinal waves
Cubic single crystal (Cu-Zn-Al) with faces
parallel to (111), (-102) and (2-31)
planes Trained ? activated martensite variant
(011)lt0-1 1gt
Shear mechanism ? (0,1,1)
n(0,-1,1) Volume mechanism ? (0,1,1)
n(0,1,1)
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Predicted radiation pattern
EXPERIMENT Simultaneous detection on four
directions.
Predominant mechanism shear
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KINEMATICS
Model Fault with unidirectional propagation
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? depends on the measurement direction ?
DOPPLER EFFECT
EXPERIMENT Simultaneous detection at opposite
faces
Source location (depth, z)
Fault length
Fault velocity
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Broad-band detection 1.- Low sensitivity, 2.-
Complex experimental set-up 3.- Difficult
interpretation
Most studies use ressonant detection
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AE as a sensitive probe
Bell sounds ? Something happens!!
Monitoring large structures oil plants, rock
mines, tunnels, underground caverns, etc
Detection of phase transitions
Martensitic transition in Cu-Zn-Al
A.Planes et al, Phys. Stat. Sol (a) 66, 717 (1981)
Heat flow
Acoustic emission (count rate)
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NUCLEATION
Extreme sensitivity to small transforming
volumes!!
Martensitic transformation In Fe-30Ni. J.
Galligan, T. Garosshen, Nature 274, 674 (1978)
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MARTENSITIC TRANSFORMATION IN Cu-BASED
SHAPE-MEMORY ALLOYS
Step like experiments ?T0.2K ?t4hours
Cu-Al-Ni
Cu-Zn-Al
ATHERMAL
ISOTHERMAL
Perez-Reche et al, PRL 87, 195701 (2001)
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EXPERIMENTS REVEALING THE ATHERMAL CHARACTER OF A
PHASE TRANSITION
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Driving rate dependence (cooling)
Perez-Reche et al, PRL 87, 195701 (2001)
Cu-Zn-Al
Cu-Al-Ni
? (Hz)
?/T (K-1)
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STATISTICAL ANALYSIS OF AE SIGNALS
Source location
Creep deformation of ice (J. Weiss, D. Marsan,
Science 299, 80 (2003))
Experiment 5 piezoelectric transucers frozen on
an ice crystal subjected to uniaxial load.
1.- Clustering of dislocation avalanches 2.-
Migration of dislocation avalanches
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STATISTICAL ANALYSIS OF AE SIGNALS
Fracture by H precipitation in Nb G. Cannelli et
al. PRL 70, 3923 (1993)
AE from paper fracture L.I Salminen et al. PRL
89,185503 (2002)
Dislocation motion in ice. MC Miguel et al.
Nature 410, 667 (2001).
AE from volcanic rocks P.Diodati et al. PRL 67,
2239 (1991)
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PHASE TRANSISIONS
Martensitic transition in Cu-based shape memory
alloys
E. Vives et al PRL 72, 1694 (1994)
Ll.Carrillo et al PRL 81, 1889 1694 (1998)
Magnetostructural transition in giant
magnetocaloric Gd-Si-Ge Pérez-Reche et al. PRB
submitted.
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TYPICAL AE DETECTION SYSTEM
Electric signal
Piezoelectric transducer (PZT)
Acoustic source
Peltier element
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DETECTION OF A.E. EXPERIMENTAL SET-UP
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RESULTS ON THE MARTENSITIC TRANSITION IN Cu-BASED
ALLOYS
1. Reproducibility of the transition (mesoscale)
training.
Cu-Zn-Al
Correlation function
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Cu-Al-Mn
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Cu-Al-Mn
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REPRODUCIBILITY (microscale
C. Picornell et al. Thermochim. Acta 113, 171
(1987)
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2. Effect of driving rate
F.J. Pérez-Reche et al. PRL 93, 195701 (2004)
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SUMMARY
AE very sensitive and powerful technique for
fast motion
Microscopic information spatial and temporal
Adequate to follow nucleation and kinetics of
phase (structural) transitions
Particularly suitable to study avalanche-mediated
processes
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Selected references

• ? J.A. Hudson, The Excitation and propagation of
  elastic waves,
• Cambridge Univ. Press (1980).
• ? K. Aki, P.G. Richards, Quantitative Seismology,
  W.H. Freeman and Company (1980).
• ? C.B. Scruby, Quantitative Acoustic emission
  techniques, in Research Techniques
• in Nondestructive Testing, Vol III, Ed. By R.S.
  Sharpe, Academic Press, 1985.
• ? Acoustic emission Beyond the Millennium, Ed.
  T. Kishi, M. Ohtsu, S. Yuyama,
• Elsevier (2000).
• C.B. Scruby, J. Phys. E Sci. Instrum. 20, 946
  (1987).
• Nondestructive testing techniques, Ed. D.E. Bray
  and D. McBride,
• John Wiley and Sons, INC (1992).

THANKS for the attention
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MICROSCOPIC MEASUREMENTS OF AVALANCHES
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Vives et al., PRL, 72, 1694 (1994) Carrillo et
al. PRL, 81, 1889 (1998)
Structural transition (martensitic) BCC ? close
packed stress- or T- driven Acoustic emission
pulse detection counting

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MULTIMAT. Kick-off Meeting. Introductory Courses.
Leipzig, October 26-30 2004.
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Uniqueness theorem The displacement u through
the volume V with surface S is uniquely Determined
after a time t0 by the initial values of
displacment and particle velocity at t0,
throughout V and by values at all times t?t0 of
(i) the body forces f and the heat supplied
throughout V (ii) the tractions T over any part
S1 of S and (iii) the displacement over the
remainder S2 of S, with S1S2S