Ultrasound Multipath Signature of Material Flaw Depth with Single Mono/bi-Static Measurement

Abstract

Ultrasonic signature of flaw is studied in the multipath scene, and a method is developed to localize the flaw by only single mono/bi-static measurement. A signal model based on the concept of multipath is built to construct flaw position, of which multipath scenarios are reviewed for signature of flaw depth. Multipath scenarios may be identified by direct path, which is relatively easy to be detected. Algebraic solution is proposed to solve the multipath equations to obtain the position of the flaw depth. Experiments show that the solution of the flaw depth is valid.

Full text

Ultrasound Multipath Signature Of Material Flaw Depth
With Single mono/bi-static measurement
Shen Xizhong
1
, Yuan Kui
1
1Electrical Information Group, School of Electrical and Electronical Engineering, Shanghai Institute
of Technology, Shanghai, China
shen_sh@yahoo.cn
Keywords: ultrasound, signal model, flaw, multipath, signature
Abstract. Ultrasonic signature of flaw is studied in the multipath scene, and a method is developed to
localize the flaw by only single mono/bi-static measurement. A signal model based on the concept of
multipath is built to construct flaw position, of which multipath scenarios are reviewed for signature
of flaw depth. Multipath scenarios may be identified by direct path, which is relatively easy to be
detected. Algebraic solution is proposed to solve the multipath equations to obtain the position of the
flaw depth. Experiments show that the solution of the flaw depth is valid.
Introduction
Ultrasound is a crucial technology that finds widespread applications in industrial and medical areas.
Ultrasound nondestructive testing (NDT) provides reliable, efficient structure evaluation and
structural health monitoring in civil engineering and aerospace, automotive, and other transportation
sectors [1][2].
We consider the signature of flaw depth in a material by NDT. Our focus is the exploitation of
multipath scenarios that yield extended virtual array apertures to enhance imaging capability beyond
the limitation of traditional multisensor approaches[3]. The key concept examined here is the
utilization of reflections of ultrasonic signals that occur when they encounter different media and
interior discontinuities. The waveforms observed at the physical as well as virtual sensors result in
rich phases of measuring data set for fusion processing with different aspect angles. The exploitation
of multipath scenarios is found to able to address unique issues observed in ultrasonic imaging.
Ultrasonic images usually only have a narrow spread angle of view because of the narrow
beamwidth of ultrasound transducers. Utilization of physical and virtual sensors significantly extends
the array aperture for image enhancement. Thus, multipath scenarios extend the spread angle of view
for improved visibility and array design flexibility. Ultrasonic signals experience difficulty in
penetrating a flaw, thus the aspect angle of the observation is limited unless access to other sides is
available. The significant extension of the aperture makes it possible to yield flaw observation from
multiple aspect angles. We analytically demonstrate that data fusion of physical and virtual sensor
data significant can be utilized to sign the depth of the flaw.
We utilize the multipath scenarios and get the signature of the flaw depth in the material only by
single mono/bi-static measuring. A new solution is developed to localize the flaw by single
mono/bi-static measurement. A new signal model based on the concept of multipath is built to
construct flaw position. Algebraic solution is proposed to solve the multipath equations to obtain the
position of the flaw. Experiments show that the signature is obtained.
Signal Model
Consider a mono/bi-static system. A received echo,
(
)
r t
, is the summation of the reflection of each
path [3], i.e.,
(
)
(
)
(
)
i i i
i i
r t t s tr
β τ
= = −
∑∑
(1)
where
(
)
(
)
ii i
t s tr
β τ
= −
,
i
β
is
i
-th path reflectivity,
i
τ
is
i
-th path delay time.
Advanced Materials Research Online: 2012-02-27
ISSN: 1662-8985, Vols. 468-471, pp 1199-1202
doi:10.4028/www.scientific.net/AMR.468-471.1199
© 2012 Trans Tech Publications Ltd, All Rights Reserved
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