Method for reconstructing crack profiles based on composite-mode total focusing method

Patent metadata

Field	Value
Publication number	US-12007362-B2
Application number	US-202117549908-A
Country	US
Kind code	B2
Filing date	Dec 14, 2021
Priority date	Jul 20, 2020
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

A method for reconstructing the crack profiles based on the composite-mode total focusing method (CTFM), including: selecting the parameters for phased array ultrasonic testing; acquiring the A-scan signal matrix; establishing the coordinate system and grid division of the region of interest (ROI); determining the wave modes; solving the positions of the refracted points; reconstructing the image by CTFM; and realizing the quantification, positioning, and orientation of cracks. The A-scan signal matrix including 21 views is acquired. Based on Fermat's principle, the refracted points at the interface between wedge and sample for the 21 views are calculated, to obtain the corresponding amplitude for each view in the ROI. For each reconstruction point, the strongest response is selected from the 21 views. The profiles of the cracks with different orientation angles are reconstructed by CTFM.

First claim

What is claimed is:

1. A method for reconstructing crack profiles based on a composite-mode total focusing method, wherein
a detection system comprising an ultrasonic phased array device, a phased array probe, and an angle wedge is adopted to acquire A-scan signal matrix;
based on Fermat's principle, refracted points of ultrasonic waves at an interface between a wedge and a sample are calculated to obtain a corresponding amplitude for each view in a region of interest;
for each reconstructed point, a view having a strongest response is selected from 21 views;
the crack profiles corresponding to different orientation angles are reconstructed by delay-and-sum beamforming; and
the method comprises the following steps:
(a) selection of parameters for detection, comprising:
selecting parameters for detection according to a material, a shape, and a size of a to-be-measured sample, where the parameters comprise: a frequency of an ultrasonic phased array probe, the number of array elements, and a wedge angle;
(b) acquisition of an A-scan signal matrix, comprising:
acquiring the A-scan signal matrix comprising different views at one time by using a full matrix capture function of the ultrasonic phased array device, based on selected parameters for ultrasonic testing, and saving the A-scan signal matrix in a txt format, in which, for an ultrasonic phased array probe having n elements, the number of the A-scan signals in matrix is n 2 ;
(c) establishment of a coordinate system and grid division of the region of interest, comprising:
establishing the coordinate system by defining the interface between the wedge and the sample as an x-axis, defining a projection point from a center position of a first element of the phased array probe to the x-axis as a coordinate origin, defining a direction of a leading edge of the wedge as a positive direction of the x-axis, and defining a depth direction of the sample as a positive direction of a y-axis; and dividing the region of interest into M×N rectangular grids, wherein grid nodes are image reconstruction points;
(d) determination of wave modes, comprising:
classifying the wave modes as three types according to different propagation paths of ultrasonic beams, where the three types of wave modes comprise:
a direct mode, where the ultrasonic beam is emitted by one element, interacts with a crack, and is directly received by array element;
a half-skip mode, where the ultrasonic beam is emitted by one element and reflected by a bottom of the to-be-measured sample, interacts with the crack, and is received by array element; and
a full-skip mode, where the ultrasonic beam is emitted by one element and reflected by the bottom of the to-be-measured sample, interacts with the crack, is reflected by the bottom of the sample, and is received by array element; and
mode conversion occurs at the interface between the wedge and the sample, the bottom of the sample, and the crack surface, so the three types of wave modes are divided into 21 views, which contain 3 views in direct mode (LL, TT, and LT, where L for longitudinal wave and T for transverse wave), 8 views in half-skip mode (TLT, LLT, TTT, LTT, LLL, TLL, TTL, and LTL), and 10 views in full-skip mode (LLLL, TTTT, LLLT, LLTT, LLTL, LTLT, TLTT, TLTL, LTTT, and LTTL);
(e) solving positions of refracted points, comprising:
defining abscissas of the refracted points at the interface between the wedge and the sample for the emitted and received signals in view p as x pi and x pj , respectively; establishing equation (1) according to the Fermat's principle:

∂

t
pi

∂

x
pi

=

∂

t
pj

∂

x
pj

=
0

,

(
1
)

wherein 1≤p≤21, t pi is travel time of an ultrasonic beam excited from i-th element and to the reconstruction point, and t pj is travel time of the ultrasonic beam from the reconstruction point to j-th element, where 1≤i≤n and 1≤j≤n; and
calculating t pi and t pj according to ray paths of the ultrasonic beams and the wave modes;
(f) image reconstruction by the composite-mode total focusing method, comprising:
for each reconstruction point (a, b) in the region of interest, where 1≤a≤M, 1≤b≤N, selecting a strongest response from the 21 views for the signal A ij transmitted by the i-th element and received by the j-th element as a corresponding reconstruction amplitude I ij (a, b):

I
ij

⁡

(

a
,
b

)

=

max

1
≤
p
≤
21

⁢

(

A
ij

⁡

(

t
p

⁡

(

a
,
b

)

)

)

,

Assignees

• Univ Dalian Tech

Inventors

• Jin Shijie
• Lin Li
• Liu Chenfei
• Luo Zhongbing

Classifications

• G01N2291/023

  Solids · CPC title

• G01N29/4472

  Mathematical theories or simulation · CPC title

• G01N29/043

  in the interior, e.g. by shear waves · CPC title

• G01N2291/044

  Internal reflections (echoes), e.g. on walls or defects · CPC title

• G01N29/348

  with frequency characteristics, e.g. single frequency signals, chirp signals (measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00) · CPC title