CN110688800A

CN110688800A - Ultrasonic nondestructive testing method based on ART algorithm

Info

Publication number: CN110688800A
Application number: CN201910933569.6A
Authority: CN
Inventors: 李彩林; 张奥申
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2020-01-14

Abstract

The invention provides an ultrasonic nondestructive testing method based on an ART algorithm, which comprises the steps of creating an aluminum plate with defects in finite element software, combining a python language to realize automatic model submission and solving operation, then utilizing the ART algorithm to carry out programming to carry out image reconstruction, and finally judging the information of the defects according to the obtained images. The method comprises the following steps: (1) creating a model; (2) setting parameters including Young modulus, density, Poisson ratio and the like of the model; (3) automatically submitting and solving a finite element simulation analysis task; (4) extracting waveform data after the task solution is completed; (5) compiling an image reconstruction algorithm, namely an ART algorithm; (6) and (4) combining the waveform data with an ART algorithm to reconstruct an image.

Description

Ultrasonic nondestructive testing method based on ART algorithm

Technical Field

The invention belongs to an ultrasonic nondestructive testing technology, and relates to an ultrasonic nondestructive testing method based on an ART algorithm.

Background

In the fields of materials, machinery, chemical engineering and the like, aluminum plates are easy to generate defects such as cracks, corrosion and the like in production, processing, transportation and use. Modern industries have very strict requirements on product quality, and small defects can cause serious threats to the environment and economy. Therefore, nondestructive testing is added to the production system of many countries as a key technical link for controlling the product quality. With the improvement of detection technology, the requirements of modern industry on nondestructive detection are no longer simple to determine whether a defect exists, and also determine information such as the position, the size and the like of the defect, so that a new technology is required to be combined with the defect to complete the detection. The ultrasonic lamb wave tomography technology is a novel nondestructive testing technology developed by combining ultrasonic lamb waves with tomography technology, can provide a large amount of visual information, and can vividly describe the defect outline, thereby further evaluating the quality and performance of a workpiece.

At present, a method from finite element software numerical simulation to defect imaging is mostly adopted for defect imaging, but when the finite element software is used for numerical simulation, the multiple-effect rate is low, the time consumption is long, the repetitive work is more, and the like, and when the defect imaging is carried out, the reconstructed image speed is low, the quality is poor, and the problems cause low detection efficiency and poor effect. By adopting the method provided by the invention, finite element analysis solving can be rapidly realized, and required data is provided for image reconstruction.

Lamb wave detection adopts a 'line scanning' mode to detect a test piece, and the efficiency is higher compared with a 'point scanning' mode of body wave detection. Meanwhile, attenuation of lamb waves is reduced when the lamb waves propagate in the plate-shaped structure, and the propagation distance is long. When one-shot multi-shot detection is carried out by adopting multiple probes, the received lamb wave signals carry the overall information of the test piece between the probes, and the travel time information of the lamb wave signals is imaged by utilizing an ART algorithm, so that the information such as the position, the size and the like of the defect can be obtained.

Disclosure of Invention

In order to solve the defects of low solving speed efficiency and poor image reconstruction quality of finite element simulation analysis, the invention aims to improve the solving speed and the image reconstruction quality of the finite element simulation analysis. In order to achieve the above object, the present invention provides an ultrasonic nondestructive testing method based on ART algorithm, which comprises the following steps:

1. establishing a model, and determining the model as a three-dimensional entity stretching model;

2. setting model parameters including Young modulus, density, Poisson ratio and the like of the model;

3. automatically submitting and solving a finite element simulation analysis task by using a python language script file;

4. and extracting waveform data after the task solving is completed, and storing the waveform data into an excel table.

5. And writing an image reconstruction algorithm.

In step 3, a finite element simulation analysis task is automatically submitted and solved by using a python script file, and the method comprises the following steps:

(1) determining the number of tasks submitted each time according to the number of the tasks, the running speed of the tasks and the size of a memory occupied by each task;

(2) the method comprises the following steps of writing a py script file for automatically submitting tasks in a python language, wherein the py script file controls the number of tasks running each time;

(3) the script file is associated and runs in finite element software, and the py file realizes automatic submission, solving and analysis of tasks.

The en-route reconstruction algorithm in step 5 is an ART algorithm comprising the steps of:

(4) and assigning an initial estimation value to the unknown reconstruction image vector:

(5) calculating the estimated projection value of the ith equation, namely the ith ray:

(6) calculating an error value, i.e. the correction artifact:

(7) calculating a correction value for the jth grid:

(8) and correcting the jth grid value:

(9) substituting the corrected value into the next equation, recycling the steps from 2 to 5, and designing all rays passing through the image in sequence, namely finishing one iteration;

(10) and taking the iteration value as a new initial value, and circulating the steps 2 to 5 again until the requirement is met.

The invention at least comprises the following beneficial effects or advantages:

in the finite element simulation analysis, the finite element simulation analysis is combined with a computer programming language python, and the task solving analysis is automatically submitted, so that the time is saved, and the simulation speed and efficiency are improved.

The simulation model adopts double span pitch, the scanning time is short, and the efficiency is high.

The reconstructed image obtained by the ART algorithm is clear and reliable, so that the reliability and accuracy of the defect detection method are improved.

Description of the drawings:

the invention is described in further detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a flow chart of a method for rapidly implementing ultrasonic nondestructive testing from numerical simulation to defect tomography.

Fig. 2 is a schematic diagram of ART algorithm set-up equations.

The specific implementation mode is as follows:

in order to make the present application more clearly understood by those skilled in the art to which the present application pertains, the following detailed description of the technical solution of the present application with reference to the accompanying drawings includes the following steps.

(1) Creating a model, determining the length, the width, the stretching height, the radius of the circular defect in the center of the model and the cutting and stretching depth of the model, and determining the scanning mode of the model.

(2) Parameter settings including young's modulus, density, poisson's ratio of the model; determining the time length of an analysis step, the type of grid division and the size of a grid; the magnitude of the applied load and the center frequency of the excited lamb wave are determined.

(3) And automatically submitting and solving, writing the py script file by using a pyhton language, and automatically submitting the job solving by finite element simulation analysis.

(4) Extracting data, and extracting waveform data obtained by analysis and solution into an excel table.

(5) Writing an image reconstruction algorithm, namely an ART algorithm, and realizing algorithm writing by using a python language.

(6) And image reconstruction, namely combining data obtained by finite element simulation analysis and solution with an algorithm to realize image reconstruction.

In step 1, the model is a square aluminum plate, and the sensors are arranged in a double span pitch. The structure is that the sensors are uniformly distributed on each side of a detected area, wherein one sensor on one side transmits lamb wave signals to penetrate through the detected area, and the sensors on the other three sides receive the transmitted lamb wave signals.

In step 2, the grid type and the unit size are determined according to the model size and the waveform propagation speed, and the applied load is in the Z-axis direction. And selecting five-period Hanning window sinusoidal signals as ultrasonic excitation signals to simulate ultrasonic lamb waves. The expression is as follows:

in formula 1

，

The central frequency of the ultrasonic excitation signal is represented, signal interference of other frequencies is avoided under the frequency, the signal identification degree is improved, and the energy is concentrated, so that the energy loss of lamb waves in the propagation process can be greatly reduced, the propagation distance of the lamb waves is improved, and the characteristic signal extraction is facilitated.

In step 5, the ART algorithm is one of iterative algorithms, and the process of the ART algorithm is mainly to solve a linear equation set, the principle of which is shown in fig. 2, and there are 16 unknowns in total, and each ray can establish an equation, and 16 equations in total can be established. The value of each pixel can be found by solving the unknowns in the system of linear equations. The matrix of the system of equations is:

wherein,

，

Is a matrix of coefficients.

The preferred embodiments of the present invention are provided to help illustrate the present invention and are not exhaustive and do not limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The examples were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention.

Claims

1. An ultrasonic nondestructive testing method based on ART algorithm is characterized by comprising the following steps:

(1) creating a model, and determining the model as a three-dimensional entity stretching model;

(2) model parameter settings including Young's modulus, density, Poisson's ratio, etc. of the model;

(3) automatically submitting and solving a finite element simulation analysis task by using a python language script file;

(4) extracting waveform data after the task solution is completed, and storing the waveform data into an excel table.

(5) Writing an image reconstruction algorithm, and determining the algorithm to be an ART algorithm.

2. The method of claim 1, wherein the model creation comprises a scanning mode in which the sensors are arranged in a double cross-hole pitch structure and are uniformly arranged in the peripheral direction of the simulation model.

3. The method for rapidly realizing the ultrasonic nondestructive testing from numerical simulation to defect imaging according to claim 1, wherein the parameter setting comprises the following steps:

(1) determining that lamb waves are simulated by using Hanning window sinusoidal signals, and selecting Hanning window sinusoidal signals with five periods as ultrasonic excitation signals to simulate ultrasonic lamb waves. The expression is as follows:

in formula 1

，

Representing the center frequency of the ultrasonic excitation signal.

(2) Determining the size of the unit cell of the model grid, wherein the expression is as follows:

the size of the grid cell is represented,

representing the minimum wavelength.

Representing the propagation velocity of the lamb wave.

(3) Determining an analysis step length based on a maximum distance between the sensor emitting the signal and the sensor receiving the signal.

(4) And determining the application mode of the excitation signal to be lamb wave vertical incidence, namely the Z-axis direction.

4. The ART algorithm-based ultrasonic nondestructive testing method as claimed in claim 1, wherein said automatic submission of finite element simulation analysis solving task is compiling all information of model in python language and saving it as file of.

5. The ART algorithm-based ultrasonic nondestructive testing method as claimed in claim 1, wherein the image reconstruction algorithm is an ART algorithm, and image reconstruction of the algorithm is realized by python language.