TITLE:
Frequency Dependence of the b-Value Used for Acoustic Emission Analysis of Glass Fiber Reinforced Plastics
AUTHORS:
Do Yun Jung, Yoshihiro Mizutani, Akira Todoroki, Yoshiro Suzuki
KEYWORDS:
Structure Health Monitoring, b-Value Analysis, Acoustic Emission Testing, Fi-ber Reinforced Plastics, Frequency Dependence of Attenuation
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.7 No.3,
July
6,
2017
ABSTRACT: Acoustic Emission Testing (AT)
is one of the major non-destructive testing methods used for severity
evaluation of structures. Amplitude distributions of AE signals are
characterized by b-value and the value is mainly used for the
severity evaluation of concrete structures until now. The value is assumed to
be independent with propagation distance between acoustic emission sources to
AE sensors. We evaluate the influence of the wide frequency band encountered in
the fracture behavior of glass fiber reinforced plastic (GFRP) on the b-value
analysis. In tensile tests, the b-value was determined from an
acoustic emission (AE) source generated near a centered hole in a specimen of
GFRP. At 15 mm from the hole, the b-value analysis indicated a
decreasing trend with increasing tensile stress. At a propagation length of 45
mm, farthest from the hole, asmall number of AE signals were received. The attenuation is more rapid
for high-frequency AE signals. Thus, the amplitude distribution bandwidth is
wide and the b-value changes. This change in b-value
for GFRPs is investigated by analyzing the spectral components of the AE
signals. For a single-frequency AE source, the b-value is unchanged
with propagation length. In contrast, multiple-frequency AE sources produce changes in b-value
proportional to the fraction of each spectral component in the received signal.
This is due to the frequency dependence of the attenuation with propagation
length.From these results, the b-value analysis cannot be applied to
considering frequency dependence of AE attenuation.