TY - GEN
T1 - Ultrasonic assessment of material degradation by thermal fatigue
AU - Pitkänen, Jorma
AU - Kauppinen, Pentti
AU - Jeskanen, Harri
PY - 2004
Y1 - 2004
N2 - Near surface areas can contain many types of defects,
material changes and degradation. Materials subjected to
thermal fatigue or annealing have been evaluated with a
special ultrasonic probe optimised for surface
measurements, and with a 0 longitudinal wave probe.
Combining measured data from a large area and calculating
depths of interest in the sound path (RF-signal)
information provides improved estimation of degradation
levels. The technique is using a combination of three
factors: (1) back-scattered ultrasonic signals and
induced leaky Rayleigh wave information), and (2) simple
statistical data analysis in combination with (3) an
optimised ultrasonic transducer. The back-scattered
ultrasonic signal is a measure of the effect of
geometrical reflectors such as micro-pores, inclusions,
precipitates, segregation, micro-cracks and cracks as
well as of back-scattering from phase boundaries during
fatigue damaging and increase of degradation inside the
material. The leaky Rayleigh wave component is sensitive
to surface properties, and especially to cracks. Deep
cracks will totally cancel the leaky Rayleigh wave
signal.
AB - Near surface areas can contain many types of defects,
material changes and degradation. Materials subjected to
thermal fatigue or annealing have been evaluated with a
special ultrasonic probe optimised for surface
measurements, and with a 0 longitudinal wave probe.
Combining measured data from a large area and calculating
depths of interest in the sound path (RF-signal)
information provides improved estimation of degradation
levels. The technique is using a combination of three
factors: (1) back-scattered ultrasonic signals and
induced leaky Rayleigh wave information), and (2) simple
statistical data analysis in combination with (3) an
optimised ultrasonic transducer. The back-scattered
ultrasonic signal is a measure of the effect of
geometrical reflectors such as micro-pores, inclusions,
precipitates, segregation, micro-cracks and cracks as
well as of back-scattering from phase boundaries during
fatigue damaging and increase of degradation inside the
material. The leaky Rayleigh wave component is sensitive
to surface properties, and especially to cracks. Deep
cracks will totally cancel the leaky Rayleigh wave
signal.
M3 - Conference article in proceedings
SN - 951-38-6293-3
T3 - VTT Symposium
SP - 681
EP - 686
BT - BALTICA VI - Life management and maintenance for power plants. Vol. 2
PB - VTT Technical Research Centre of Finland
CY - Espoo
T2 - BALTICA VI - Life Management and Maintenance for Power Plants
Y2 - 8 June 2004 through 10 June 2004
ER -