Material Flaw Sizing by Ultrasonic Multipath Detection

Abstract

Sizing of material flaw is addressed in the multipath scene, and a method is developed to detect an isolated sized flaw and estimate its height based on imaging theory of different path profiles. A signal model based on the multipath higher order reflections of the flaw is built to detect the sized flaw. Multipaths are predicted and identified on the basis of the direct reflection path, which is relatively easy to be identified using the conventional flaw detection techniques. Direct reflection path and combined path are applied to detect the flaw from the top, and multipath w is to detect its bottom of the flaw. Ultrasonic imaging is formed and synthesized by all the identified multipaths, which shows the size of the material flaw. Simulations and experimentations demonstrate that the flaw sizing can be calculated utilizing the time-of-arrivals of the multipath signals.

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Material Flaw Sizing By Ultrasonic Multipath Detection
Xizhong Shen
1,a
, Pan Li
1
1
Electrical and Automatic School, Shanghai Institute of Technology, Shanghai, China, 201418,
China
ashen_sh@yahoo.cn
Keywords: multipath, sizing, flaw, ultrasonic imaging.
Abstract. Sizing of material flaw is addressed in the multipath scene, and a method is developed to
detect an isolated sized flaw and estimate its height based on imaging theory of different path profiles.
A signal model based on the multipath higher order reflections of the flaw is built to detect the sized
flaw. Multipaths are predicted and identified on the basis of the direct reflection path, which is
relatively easy to be identified using the conventional flaw detection techniques. Direct reflection
path and combined path are applied to detect the flaw from the top, and multipath ‘w’ is to detect its
bottom of the flaw. Ultrasonic imaging is formed and synthesized by all the identified multipaths,
which shows the size of the material flaw. Simulations and experimentations demonstrate that the
flaw sizing can be calculated utilizing the time-of-arrivals of the multipath signals.
Introduction
Sizing of material flaws is an important problem in ultrasonic nondestructive evaluation (NDE) [1].
One of the direct methods of flaw sizing is B-scan imaging from two different profiles, and transducer
arrays are practical since no scanning is required.
In this paper, we propose a method of sizing an isolated flaw using pitch-catch measurements with
a line transducer array. Different from [2], we analyze the multipahs and get combined multipath,
and then show that the fusion of physical and virtual sensor data makes possible sizing of the flaw.
Multipath Signal Model and scenarios
Consider an ultrasonic pitch-catch measurement system as illustrated in Fig.1a. We model the
measured ultrasound signal [2] at the receiving transducer,
(
)
r t
, as follows,
(
)
(
)
i i
i
r t s t
τα
= −
∑
, (1)
(a) DRP (b) MP-1 (c) MP-2 (d) MP-W
Fig.1. Direct reflection and multipath scenarios in a pitch-catch measurement.
where  is the ultrasonic pulse-echo wavelet, 

and 

are -th path reflectivity and delay time
respectively. Fig.1 illustrates some first and second-order multipath scenarios [2].
Multipath delays and identification
Multipath Delays. Consider a region of interest, which is a two-dimensional cross-section under
the linear array, and a receiving mode backprojection beamforming algorithm is utilized to construct
the image of the cross-section in interior material [3]. A sized flaw is assumed to be circle-like
Advanced Materials Research Online: 2013-06-27
ISSN: 1662-8985, Vols. 712-715, pp 1067-1070
doi:10.4028/www.scientific.net/AMR.712-715.1067
© 2013 Trans Tech Publications Ltd, All Rights Reserved
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