Anisotropic material damage assessment method based on ultrasonic array bottom surface reflection method

Abstract

The damage evaluation method of anisotropic materials based on the bottom surface reflection method of ultrasonic array belongs to the field of material detection and evaluation. The method includes the following steps: collecting the A-scan signal of anisotropic material sample based on the bottom surface reflection method of ultrasonic array; performing continuous wavelet transform on the corresponding signals of different array element combinations and reading the corresponding sound of the highest approximate coefficient, calculating the longitudinal wave sound velocity under different incident angles, and reading the highest amplitude from the signal; changing the rotation angle in the contact surface between the ultrasonic array and the sample, obtaining the distribution curve of the longitudinal wave sound velocity and the highest amplitude with the rotation angle; repeating the above steps for the sample at different damage degrees, and establishing the relationship between the longitudinal wave sound velocity, the highest amplitude and the damage degree at 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 anisotropic materials with the incident angle and rotation angle. The test process is simple and repeatable, and multi-parameter evaluation of the damage degree can be realized.

Description

Technical Field

[0001] 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 Art

[0002] Anisotropic materials have important applications in many high-end equipment fields. For example, directionally solidified nickel-based high-temperature alloys are widely used in aircraft engines, and carbon fiber reinforced resin-based composites (CFRP) are widely used in the aerospace field. Due to the harsh service environment, damage is inevitable. Therefore, if the damage of materials or components can be effectively non-destructively evaluated, it is possible to warn in advance of the serious harm caused by the late damage, which is of great significance to ensuring the load-bearing performance and service reliability of high-end equipment.

[0003] Ultrasonic nondestructive testing and evaluation technology has the advantages of high flexibility, high speed and non-destructiveness, and its effectiveness has been proven in many aspects. However, how to simply, reliably and efficiently obtain ultrasonic features is a key issue in the damage evaluation process. The ultrasonic array back-wall reflection method (BRM) is a new signal acquisition method developed in recent years based on phased array ultrasound. Based on the positional relationship between the transmitting array element and the receiving array element, ultrasonic signals with different incident angles can be accurately and conveniently obtained. However, the acoustic properties of anisotropic materials are more complex in three-dimensional space distribution. After damage occurs, the three-dimensional space distribution varies depending on the form and degree of damage. The existing ultrasonic evaluation method mainly extracts the feature quantity corresponding to a single angle or direction, which is difficult to fully reflect the damage characteristics, has low sensitivity, and the effect is not ideal. Therefore, conducting research on anisotropic material damage evaluation based on ultrasonic array back-wall reflection method is of great significance to ensure the load-bearing performance and service reliability of high-end equipment. Summary of the invention

[0004] The purpose of the present invention is to provide an anisotropic material damage evaluation method based on ultrasonic array bottom surface reflection method, by collecting ultrasonic array bottom surface reflection method signals for anisotropic materials with different damage degrees and performing continuous wavelet transform, changing the rotation angle in the contact surface between the ultrasonic array and the anisotropic material sample, establishing the correlation between the longitudinal wave sound velocity, the maximum amplitude and the damage degree under different incident angles and rotation angles, and obtaining 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. The method has a simple test process, high test result accuracy and good repeatability, and the extraction of characteristic values ​​can realize multi-parameter evaluation of different damage degrees, and has good application prospects for aging damage and early mechanical damage of isotropic and anisotropic materials.

[0005] The technical solution adopted by the present invention is: an anisotropic material damage evaluation method based on the ultrasonic array bottom surface reflection method, firstly, the anisotropic material is processed into a plate-like sample of equal thickness, and the bottom surface echo A-scan signal of the anisotropic material sample at different damage degrees is collected by the bottom surface reflection method based on the ultrasonic array; the received signal is subjected to continuous wavelet transform and the sound corresponding to the highest approximate coefficient is read, the longitudinal wave sound velocity at different incident angles is calculated, and the highest amplitude is read from the A-scan signal; the rotation angle within the contact surface between the ultrasonic array and the anisotropic material sample is changed to obtain the distribution curve of the longitudinal wave sound velocity and the highest amplitude with the rotation angle; for anisotropic material samples with different damage degrees, the relationship between the longitudinal wave sound velocity, the highest amplitude and the damage degree at different incident angles and rotation angles is obtained, and the relationship between the characteristic value and the damage degree is established. The specific calculation steps are as follows:

[0006] (1) Ultrasonic array bottom reflection method signal acquisition

[0007] The anisotropic material is processed into a plate-like sample of equal thickness. One element of the ultrasonic array is used as the transmitting element, and the others are used as the receiving elements to independently receive the A-scan signal of the echo from the bottom surface of the sample.

[0008] (2) Reading the sound time and calculating the longitudinal wave speed based on wavelet transform

[0009] Perform continuous wavelet transform on the A-scan signal collected in step (1), read the acoustic time corresponding to the highest approximate coefficient of different array element signals, and calculate the ultrasonic incident angle according to the size and position relationship between the ultrasonic array transmitting element and other elements:

[0010] θ ij =arctan((2d) / |x i -x j |) (1)

[0011] 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 speed at each angle is calculated as follows:

[0012]

[0013] where t ij is the acoustic time corresponding to the highest approximate coefficient of different array element signals. The highest amplitude is read from the A-scan signal, and the curve of longitudinal wave speed and highest amplitude changing with the incident angle is established.

[0014] (3) Signal acquisition at different rotation angles of the ultrasonic array

[0015] Change the rotation angle of the ultrasonic array and the anisotropic material sample contact surface to ensure good coupling during the rotation process. Repeat steps (1) and (2), collect A-scan signals at different rotation angles, calculate the change curves of longitudinal wave sound velocity and maximum amplitude with incident angle at different rotation angles, and obtain the three-dimensional distribution of longitudinal wave sound velocity and maximum amplitude of anisotropic materials with incident angle and rotation angle.

[0016] (4) Signal acquisition at different damage levels

[0017] For anisotropic material samples with different damage degrees, repeat steps (1) to (3) to obtain the distribution of longitudinal wave speed and maximum amplitude with incident angle and rotation angle, and establish the variation trend of the distribution with damage parameters.

[0018] (5) Ultrasonic feature value extraction and damage degree assessment

[0019] Analyze the distribution characteristics of the results obtained in step (4), extract the longitudinal wave sound velocity and the maximum amplitude at specific incident angles and rotation angles as ultrasonic characteristic values, and establish their correlation with damage parameters to evaluate the degree of damage of anisotropic materials.

[0020] The damage is aging damage and early mechanical damage.

[0021] The beneficial effects of the present invention are: through this anisotropic material damage evaluation method based on the ultrasonic array bottom surface reflection method, the longitudinal wave sound velocity and the maximum amplitude under different incident angles and rotation angles are obtained, the ultrasonic characteristic value is selected and the correlation relationship between it and the damage degree parameter is established to evaluate the damage degree of the anisotropic material. Ultrasonic non-destructive testing technology has the advantages of being non-destructive, suitable for large-scale component testing and low cost, and the method has a simple testing process, high accuracy and repeatability of the test results, and the extraction of characteristic values ​​can realize multi-parameter evaluation of different damage degrees, which has good application prospects for aging damage and early mechanical damage of isotropic and anisotropic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the bottom surface echo ultrasonic array signal acquisition system.

[0023] Figure 2 It is the A-scan signal received by the No. 1 element of the ultrasonic array after aging of the CFRP unidirectional plate sample for 0h.

[0024] Figure 3 The longitudinal wave sound velocity distribution curves of CFRP unidirectional plate (aged for 0h and 120h) under different angles between the fiber direction and the ultrasonic array: (a) 0°; (b) 45°; (c) 90°.

[0025] Figure 4The maximum amplitude distribution diagram of CFRP unidirectional plate (aged for 0h and 120h) under different angles between the fiber direction and the ultrasonic array: (a) 0°; (b) 45°; (c) 90°.

[0026] Figure 5 Three-dimensional distribution diagram of (a) longitudinal wave velocity and (b) maximum amplitude of CFRP unidirectional plate (aged 0h) with incident angle and rotation angle.

[0027] Figure 6 Three-dimensional distribution diagram of (a) longitudinal wave velocity and (b) maximum amplitude with incident angle and rotation angle of CFRP unidirectional plate (aged for 120 h).

[0028] Figure 7 This is a graph showing the change in longitudinal wave sound velocity at an incident angle of 90° for CFRP one-way plates at different aging times.

[0029] Figure 8 This is the change diagram of the maximum amplitude of the received signal of array element No. 1 at different aging times of the CFRP one-way plate. DETAILED DESCRIPTION

[0030] (1) Ultrasonic array bottom reflection method signal acquisition

[0031] The anisotropic material sample used is a CFRP unidirectional plate, and the prepreg is prepared by autoclave molding. The schematic diagram of the ultrasonic array bottom surface echo signal acquisition system used is as follows Figure 1 As shown. Through the MultiX++ phased array ultrasonic testing system, the 5L64-NW1 linear array probe is controlled to excite and receive ultrasonic signals, and the A-scan signal of the bottom echo of the CFRP one-way plate sample is collected. Figure 2 It is the A-scan signal emitted and received by array element 1 when the rotation angle between the ultrasonic array and the fiber direction of the CFRP specimen surface is 0° under the aging condition of 0h.

[0032] (2) Reading the sound time and calculating the longitudinal wave speed based on wavelet transform

[0033] The wavelet basis "mexh" is selected as the basis function, and the A-scan signal of the sample bottom echo collected in step (1) is subjected to continuous wavelet transform, and the acoustic time corresponding to the highest approximate coefficient of the different array element signals after wavelet transform is read. It is known that the center spacing p of adjacent array elements of the ultrasonic array probe is 1mm, and the sample thickness d is 5.55mm. Taking the received signal of array element No. 5 as an example, the ultrasonic incident angle is calculated according to formula (1). The corresponding ultrasonic longitudinal wave speed at this incident angle is calculated according to formula (2).

[0034]

[0035]

[0036] For the distribution of the highest amplitude of ultrasound at different incident angles, the highest amplitude of the bottom echo of the A-scan signal received by array elements 1 to 11 is used as a benchmark for comparison. This method obtains the curves of the longitudinal wave speed and the highest amplitude changing with the incident angle, as shown in the figure. Figure 3 (a) and Figure 4 (a) shown.

[0037] (3) Signal acquisition at different rotation angles of the ultrasonic array

[0038] based on Figure 1 The acquisition system shown in the figure ensures that the ultrasonic array probe is fixed, so that the ultrasonic array and the CFRP one-way plate sample contact surface rotate at a specific angle, repeat steps (1) and (2), calculate the longitudinal wave sound velocity and maximum amplitude with the incident angle at different rotation angles, and obtain the three-dimensional distribution of the longitudinal wave sound velocity and maximum amplitude with the incident angle and rotation angle of the CFRP one-way plate sample (aged for 0h and 120h) as shown in the figure. Figure 5 and Figure 6 shown.

[0039] (4) Signal acquisition at different damage levels

[0040] The CFRP one-way plate sample in step (1) was subjected to 70°C constant temperature water bath wet heat aging, and the aging time was 0 h and 120 h respectively. Steps (1) to (3) were repeated to obtain the distribution of longitudinal wave speed and maximum amplitude with incident angle and different rotation angles.

[0041] (5) Ultrasonic feature value extraction and damage degree assessment

[0042] Extract the longitudinal wave speed at an incident angle of 90° and the maximum amplitude of the received signal of array element 1 from the distribution curve in step (4), and establish the relationship between the variation of different acoustic parameters and aging time, such as Figure 7 and 8 As shown in the figure, the longitudinal wave speed decreases and the maximum amplitude decreases, that is, the attenuation increases. This shows that the acoustic parameters of the CFRP one-way plate sample change with the extension of time after 70℃ hygrothermal aging, and the multi-parameter characterization of the degree of damage of the CFRP one-way plate sample during hygrothermal aging is achieved.

Claims

1. Anisotropic material damage evaluation method based on ultrasonic array bottom surface reflection method, characterized by: Based on the ultrasonic array bottom reflection method, the three-dimensional distribution of the longitudinal wave velocity and the maximum amplitude of the anisotropic material with the incident angle and the rotation angle is obtained, and the relationship between the characteristic value and the damage degree is established; the specific calculation steps are as follows: (1) Ultrasonic array bottom reflection method signal acquisition The anisotropic material is processed into a plate-shaped sample of equal thickness; a certain array element of the ultrasonic array is used as a transmitting array element, and the others are used as receiving array elements to independently receive the A-scan signal of the echo of the bottom surface of the sample; (2) Reading the sound time and calculating the longitudinal wave speed based on wavelet transform Perform continuous wavelet transform on the A-scan signal collected in step (1), read the acoustic time corresponding to the highest approximate coefficient of different array element signals, and calculate the ultrasonic incident angle according to the size and position relationship between the ultrasonic array transmitting element and other elements: 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 speed at each angle is calculated as follows: where t ij is the acoustic time corresponding to the highest approximate coefficient of different array element signals; read the highest amplitude from the A-scan signal, and establish the curve of longitudinal wave speed and highest amplitude changing with the incident angle; (3) Signal acquisition at different rotation angles of the ultrasonic array The ultrasonic array bottom surface echo signal acquisition system used controls the linear array probe to excite and receive ultrasonic signals through the phased array ultrasonic detection system, and acquires the bottom surface echo A-scan signal of the CFRP one-way plate sample; based on the acquisition system, the rotation angle of the ultrasonic array and the anisotropic material sample contact surface is changed to ensure that the ultrasonic array probe is fixed, so that the rotation angle of the ultrasonic array and the CFRP one-way plate sample contact surface is a specific angle; ensure good coupling during the rotation process; repeat steps (1) and (2), acquire A-scan signals at different rotation angles, calculate the change curves of the longitudinal wave sound velocity and the maximum amplitude with the incident angle at different rotation angles, 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 the rotation angle; (4) Signal acquisition at different damage levels For anisotropic material samples with different damage degrees, repeat steps (1) to (3) to obtain the distribution of longitudinal wave speed and maximum amplitude with incident angle and rotation angle, and establish the variation trend of the distribution with damage parameters; (5) Ultrasonic feature value extraction and damage degree assessment Analyze the distribution characteristics of the results obtained in step (4), extract the longitudinal wave sound velocity and the maximum amplitude at specific incident angles and rotation angles as ultrasonic characteristic values, and establish their correlation with damage parameters to evaluate the degree of damage of anisotropic materials.

2. The anisotropic material damage evaluation method based on ultrasonic array bottom surface reflection method according to claim 1 is characterized in that: The damage is aging damage and early mechanical damage.

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