CN114778676A - Anisotropic material damage evaluation method based on ultrasonic array bottom reflection method - Google Patents

Abstract

Anisotropic material damage evaluation method based on ultrasonic array bottom surface reflection method belongs to the field of material detection and evaluation. The method includes the following steps: collecting the scanning signal of the anisotropic material sample A based on the ultrasonic array bottom surface reflection method; performing continuous wavelet transformation on the corresponding signals of different array element combinations and reading the corresponding sound with the highest approximate coefficient, calculating the difference under different incident angles. Longitudinal wave sound velocity, and read the highest amplitude from the signal; change the rotation angle in the contact surface between the ultrasonic array and the sample to obtain the longitudinal wave sound velocity and the distribution curve of the highest amplitude with the rotation angle; repeat the above steps for the sample with different damage degrees , to establish the relationship between the longitudinal wave sound velocity, the highest amplitude and the damage degree under different incident angles and rotation angles. The method can obtain the three-dimensional distribution of the longitudinal wave sound velocity and the highest amplitude of the anisotropic material with the incident angle and rotation angle.

Description

Anisotropic material damage evaluation method based on ultrasonic array bottom reflection method

technical field

The invention relates to an anisotropic material damage evaluation method based on an ultrasonic array bottom surface reflection method, and belongs to the field of high-end equipment detection.

Background technique

Anisotropic materials have important applications in many high-end equipment fields. For example, directionally solidified nickel-based superalloys are widely used in aero-engines, and carbon fiber reinforced resin matrix composites (Carbon Fiber Reinforced Plastics, CFRP) are widely used in aerospace fields. Corresponding to the harsh service environment, damage is inevitable. Therefore, if an effective non-destructive evaluation of the damage of materials or components can be carried out, the serious harm caused by the damage in the later stage can be warned in advance, which is of great significance to ensure the bearing performance and service reliability of high-end equipment.

Ultrasound-based NDT evaluation technology has the advantages of high flexibility, fast speed and non-destructiveness, and its effectiveness has been proved in many aspects. However, how to obtain ultrasonic features simply, reliably and efficiently is a key issue in the process of damage assessment. The back-wall reflection method (BRM) of the ultrasonic array is a new type of signal acquisition method developed based on phased array ultrasound in recent years. Incidence angle of the ultrasonic signal. However, the acoustic properties of anisotropic materials are relatively complex in three-dimensional space distribution. After damage occurs, the three-dimensional space distribution varies with the form and degree of damage. The existing ultrasonic evaluation methods mainly extract the feature quantity corresponding to a single angle or direction, which is difficult to fully reflect the damage characteristics, and the sensitivity is low, and the effect is not ideal. Therefore, the research on damage evaluation of anisotropic materials based on the ultrasonic array bottom reflection method is of great significance to ensure the bearing performance and service reliability of high-end equipment.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for evaluating the damage of anisotropic materials based on the ultrasonic array bottom reflection method. The in-plane rotation angle of the contact surface of the anisotropic material sample was used to establish the correlation between the longitudinal wave sound velocity, the highest amplitude and the damage degree under different incident angles and rotation angles, and the longitudinal wave sound velocity and the highest amplitude of the anisotropic material were obtained as a function of the incident angle, Three-dimensional distribution of rotation angles. The method has simple testing process, high accuracy and good repeatability of test results. The extraction of eigenvalues can realize multi-parameter evaluation of different damage degrees. It has good application to aging damage and early mechanical damage of isotropic and anisotropic materials. prospect.

The technical scheme adopted in the present invention is as follows: an anisotropic material damage evaluation method based on the ultrasonic array bottom reflection method, firstly, the anisotropic material is processed into an equal-thickness plate sample, and the anisotropic material is collected by the ultrasonic array based bottom reflection method. The material sample echoes the A-scan signal on the bottom surface of different damage degrees; when the received signal is subjected to continuous wavelet transform and the sound corresponding to the highest approximation coefficient is read, the longitudinal wave sound velocity at different incident angles is calculated and read from the A-scan signal. The highest amplitude; change the in-plane rotation angle of the contact surface between the ultrasonic array and the anisotropic material sample to obtain the longitudinal wave sound velocity and the distribution curve of the highest amplitude with the rotation angle; for the anisotropic material samples with different damage degrees, obtain different incident angles , the relationship between the longitudinal wave sound velocity, the highest amplitude and the damage degree under the rotation angle, and establish the relationship between the eigenvalue and the damage degree. The specific calculation steps are as follows:

(1) Signal acquisition of ultrasonic array bottom reflection method

The anisotropic material was processed into an equal-thickness plate-like sample. One array element of the ultrasonic array is used as the transmitting array element, and the other is used as the receiving array element to independently receive the A-scan signal of the bottom surface echo of the sample.

(2) Calculation of sound reading time and longitudinal wave sound velocity based on wavelet transform

Perform continuous wavelet transform on the A-scan signal collected in step (1), and when reading the sound corresponding to the highest approximation coefficient of different array element signals, calculate the ultrasonic incident according to the size and position relationship of the ultrasonic array transmitting array element and other array elements. horn:

θ _ij =arctan((2d)/|x _i -x _j |) (1)

Among them, θ _ij is the ultrasonic incident angle, x _i , x _j are the positions of the transmitting array element and the receiving array element, respectively, d is the thickness of the plate sample, and the longitudinal wave sound velocity at each angle is calculated as follows:

Among them, t _ij is the acoustic time corresponding to the highest approximation coefficient of different array element signals. Read the highest amplitude from the A-scan signal, and establish the curve of the longitudinal wave sound velocity and the highest amplitude with the incident angle.

(3) Signal acquisition under different rotation angles of the ultrasonic array

Change the in-plane rotation angle between the ultrasonic array and the anisotropic material sample to ensure good coupling during rotation. Repeat steps (1) and (2), collect A-scan signals at different rotation angles, calculate the variation curves of the longitudinal wave sound speed and the highest amplitude with the incident angle under different rotation angles, and obtain the longitudinal wave sound speed and the highest amplitude of the anisotropic material. The three-dimensional distribution of the angle of incidence and the angle of rotation.

(4) Signal acquisition of different damage degrees

For anisotropic material samples with different damage degrees, repeat steps (1) to (3) to obtain the distribution of longitudinal wave sound velocity and maximum amplitude with incident angle and rotation angle, and establish the variation trend of the distribution with damage parameters .

(5) Ultrasound eigenvalue extraction and damage degree evaluation

The distribution characteristics of the results obtained in step (4) are analyzed, and the longitudinal wave sound velocity and the highest amplitude at a specific incident angle and rotation angle are extracted as ultrasonic characteristic values, and the relationship between them and damage parameters is established to evaluate the damage degree of anisotropic materials.

The damages are aging damage and early mechanical damage.

The beneficial effects of the present invention are: through this method for evaluating damage of anisotropic materials based on the ultrasonic array bottom surface reflection method, the longitudinal wave sound velocity and the highest amplitude under different incident angles and rotation angles are obtained, and the ultrasonic characteristic value is selected to establish its correlation with the damage degree. The correlation of parameters is used to evaluate the damage degree of anisotropic materials. Ultrasonic nondestructive testing technology has the advantages of non-destructive, suitable for large-scale component testing and low cost, and the method has simple testing process, high accuracy and repeatability of test results, and extraction of eigenvalues can realize multi-parameter evaluation of different damage degrees. The aging damage and early mechanical damage of isotropic and anisotropic materials have good application prospects.

Description of drawings

FIG. 1 is a schematic diagram of a bottom echo ultrasonic array signal acquisition system.

Figure 2 is the A-scan signal received by the No. 1 element of the ultrasonic array when the CFRP one-way plate sample is aged for 0 h.

Figure 3 shows the longitudinal wave sound velocity distribution curves of CFRP unidirectional boards (aging 0h and 120h) under different angles between the fiber direction and the ultrasonic array: (a) 0°; (b) 45°; (c) 90°.

Figure 4 is the distribution of the highest amplitudes under different angles between the fiber direction of the CFRP unidirectional board (aging 0h and 120h) and the ultrasonic array: (a) 0°; (b) 45°; (c) 90°.

Figure 5 is a three-dimensional distribution diagram of (a) longitudinal wave sound velocity and (b) the highest amplitude with incident angle and rotation angle of CFRP one-way plate (aging 0h).

Figure 6 is a three-dimensional distribution diagram of (a) longitudinal wave sound velocity and (b) the highest amplitude with the incident angle and rotation angle of the CFRP one-way plate (aging for 120h).

Figure 7 is a graph of the change of longitudinal wave sound velocity when the incident angle of the CFRP one-way board is 90° at different aging times.

Figure 8 is a graph showing the change of the highest amplitude of the received signal of the No. 1 array element at different aging times of the CFRP unidirectional board.

Detailed ways

(1) Signal acquisition of ultrasonic array bottom reflection method

The anisotropic material sample used is CFRP unidirectional board, and the prepreg is prepared by autoclave molding. The schematic diagram of the ultrasonic array bottom echo signal acquisition system used is shown in Figure 1. Through the MultiX++ phased array ultrasonic testing system, the 5L64-NW1 linear array probe is controlled to excite and receive ultrasonic signals, and the echo A-scan signals of the bottom surface of the CFRP unidirectional plate sample are collected. Figure 2 shows the A-scan signal transmitted and received by the No. 1 array element when the rotation angle of the ultrasonic array and the fiber direction on the surface of the CFRP sample is 0° under the aging condition of 0 h.

(2) Calculation of sound reading time and longitudinal wave sound velocity based on wavelet transform

Select the wavelet basis "mexh" wavelet as the basis function, perform continuous wavelet transformation on the A-scan signal of the sample bottom surface echo collected in step (1), and read the sound corresponding to the highest approximate coefficient of the different array element signals after wavelet transformation. Time. It is known that the distance p between the centers of adjacent array elements of the ultrasonic array probe is 1 mm, and the thickness d of the sample is 5.55 mm. Taking the signal received by the No. 5 array element as an example, the ultrasonic incident angle is calculated according to formula (1). The corresponding ultrasonic longitudinal wave sound velocity at this incident angle is calculated according to the formula (2).

For the distribution of the highest ultrasonic amplitude at different incident angles, the highest amplitude of the primary back surface echo of the A-scan signal received by array elements 1 to 11 is used as a benchmark for comparison. By this method, the acoustic velocity of longitudinal waves and the highest amplitude vary with the incident angle. The change curves of , are shown in Figure 3(a) and Figure 4(a).

(3) Signal acquisition under different rotation angles of the ultrasonic array

Based on the acquisition system shown in Figure 1, ensure that the ultrasonic array probe is fixed, and make the ultrasonic array and the CFRP one-way plate sample contact surface within a specific angle of rotation, repeat steps (1) and (2), and calculate the longitudinal wave sound velocity at different rotation angles. Figure 5 and Figure 6 show the three-dimensional distribution of the longitudinal wave sound velocity and the highest amplitude with the incident angle and rotation angle of the CFRP one-way plate sample (aging 0h and 120h).

(4) Signal acquisition of different damage degrees

The CFRP one-way plate sample in step (1) was subjected to humid heat aging in a constant temperature water bath at 70°C, and the aging time was 0h and 120h respectively. Steps (1) to (3) are repeated to obtain the distribution of the longitudinal wave sound speed and the highest amplitude with the incident angle and different rotation angles.

(5) Ultrasound eigenvalue extraction and damage degree evaluation

From the distribution curve in step (4), extract the acoustic velocity of longitudinal waves at an incident angle of 90° and the highest amplitude of the signal received by the No. 1 array element, and establish the variation relationship of different acoustic parameters with aging time, as shown in Figures 7 and 8, the longitudinal wave As the speed of sound decreases, the maximum amplitude decreases, that is, the attenuation increases. The results show that the acoustic parameters of the CFRP one-way plate specimens change with the extension of time at 70 ℃ wet heat aging, and the multi-parameter characterization of the damage degree of the CFRP one-way plate samples by wet heat aging is realized.

Claims (2)

1. The damage evaluation method for anisotropic materials based on the ultrasonic array bottom surface reflection method, which is characterized in that: based on the ultrasonic array bottom surface reflection method, the three-dimensional distribution of the longitudinal wave sound speed and the highest amplitude of the anisotropic material with the incident angle and the rotation angle are obtained, and established. The relationship between the eigenvalue and the degree of damage; the specific calculation steps are as follows: (1) Signal acquisition of ultrasonic array bottom reflection method The anisotropic material is processed into an equal-thickness plate sample; one array element of the ultrasonic array is used as the transmitting array element, and the other array elements are used as the receiving array elements to independently receive the echo A-scan signal from the bottom surface of the sample; (2) Calculation of sound reading time and longitudinal wave sound velocity based on wavelet transform Perform continuous wavelet transform on the A-scan signal collected in step (1), and when reading the sound corresponding to the highest approximation coefficient of different array element signals, calculate the ultrasonic incident according to the size and position relationship of the ultrasonic array transmitting array element and other array elements. horn: θ _ij =arctan((2d)/|x _i -x _j |) (1) Among them, θ _ij is the ultrasonic incident angle, x _j , x _j are the positions of the transmitting array element and the receiving array element, respectively, d is the thickness of the plate sample, and the longitudinal wave sound velocity at each angle is calculated as follows:

Among them, t _ij is the sound time corresponding to the highest approximate coefficient of different array element signals; read the highest amplitude from the A-scan signal, and establish the change curve of longitudinal wave sound speed and highest amplitude with incident angle; (3) Signal acquisition under different rotation angles of the ultrasonic array Change the in-plane rotation angle of the contact surface between the ultrasonic array and the anisotropic material sample to ensure good coupling during the rotation; repeat steps (1) and (2), collect A-scan signals at different rotation angles, and calculate the longitudinal sound velocity at different rotation angles , the curve of the maximum amplitude with the incident angle, and obtain the three-dimensional distribution of the longitudinal wave sound velocity and the maximum amplitude of the anisotropic material with the incident angle and rotation angle; (4) Signal acquisition of different damage degrees For anisotropic material samples with different damage degrees, repeat steps (1) to (3) to obtain the distribution of longitudinal wave sound velocity and maximum amplitude with incident angle and rotation angle, and establish the variation trend of the distribution with damage parameters ; (5) Ultrasound eigenvalue extraction and damage degree evaluation The distribution characteristics of the results obtained in step (4) are analyzed, and the longitudinal wave sound velocity and the highest amplitude at a specific incident angle and rotation angle are extracted as ultrasonic characteristic values, and the relationship between them and damage parameters is established to evaluate the damage degree of anisotropic materials. 2 . The damage evaluation method for anisotropic materials based on the ultrasonic array bottom surface reflection method according to claim 1 , wherein the damage is aging damage and early mechanical damage. 3 .

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