Anisotropic material damage assessment method based on phased array-critical refraction longitudinal wave

Abstract

The anisotropic material damage evaluation method based on phased array-critical refracted longitudinal waves belongs to the field of nondestructive testing and evaluation of materials. The method includes the following steps: exciting critical refracted longitudinal waves in a certain direction on the surface of the sample, establishing a relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude, and obtaining the optimal excitation sound velocity; using the calculated phased array ultrasonic delay law, exciting critical refracted longitudinal waves along different directions of the sample and measuring the amplitude; performing continuous wavelet transform on the critical refracted longitudinal waves, and calculating the critical refracted longitudinal wave sound velocity in different directions; obtaining the relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude in a certain direction of the sample under different damage degrees, as well as the critical refracted longitudinal wave amplitude and sound velocity change curve; establishing the corresponding relationship between the highest amplitude and the optimal excitation sound velocity, the critical refracted longitudinal wave amplitude and sound velocity in a certain direction and the damage degree. This method solves the evaluation problem caused by the change of material acoustic properties with direction and damage state, and significantly improves the evaluation sensitivity and efficiency.

Description

Technical Field

[0001] The anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave belongs to the field of high-end equipment detection. Background Art

[0002] Anisotropic materials such as carbon fiber reinforced plastic (CFRP) and directionally solidified nickel-based high-temperature alloys are widely used in aerospace, automotive, navigation, sports and other fields. Affected by factors such as temperature, humidity, chemical media and stress in the service environment, components are prone to aging, fatigue, etc., forming defects and damage such as cracks and holes, causing their mechanical and physical properties to decline to varying degrees. Therefore, it is of great significance to carry out non-destructive evaluation of anisotropic material damage.

[0003] In our previous research - Critical refracted longitudinal wave multi-material detection system based on single-angle wedge and its sound velocity measurement method (CN112903820A), the method of exciting and receiving critical refracted longitudinal waves was recorded. Critical refracted longitudinal waves are sound waves that are incident at the first critical angle and propagate on the surface or near the surface of the material. They have many advantages such as being sensitive to stress and being less affected by surface conditions. They are widely used in the detection of residual stress, surface defects and damage of materials. However, for anisotropic materials, their sound velocity changes with direction, and further changes with time during the evolution of damage, which brings challenges to damage assessment based on critical refracted longitudinal waves. Existing critical refracted longitudinal wave methods adapt to the above-mentioned sound velocity changes by designing multi-angle or variable-angle wedges. The accuracy and reliability of damage assessment are difficult to guarantee, and the efficiency is low. The present invention evaluates anisotropic material damage through a phased array-critical refraction longitudinal wave method, effectively solving the evaluation problem caused by the acoustic properties of anisotropic materials changing with direction and damage degree, significantly improving the evaluation sensitivity and efficiency, and reducing the evaluation cost. The present invention can be widely used in the detection and evaluation of surface / near-surface damage of isotropic and anisotropic materials. Summary of the invention

[0004] The present invention proposes an anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave. Through the phased array-critical refraction longitudinal wave method, it can flexibly adapt to the measurement difficulties of variable acoustic characteristics caused by different directions and different damage degrees of anisotropic materials, effectively extract characteristic parameters reflecting the degree of damage, and has wide adaptability.

[0005] The technical solution adopted by the present invention is: based on the phased array-critical refracted longitudinal wave method, the maximum amplitude and optimal excitation sound velocity corresponding to the critical refracted longitudinal wave in a certain direction of the anisotropic material are determined, the amplitude and sound velocity of the critical refracted longitudinal wave in different directions are calculated, and the corresponding relationship between the above-mentioned acoustic characteristic quantity and the degree of damage is established.

[0006] Anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave, based on phased array-critical refraction longitudinal wave method, determines the highest amplitude and optimal excitation sound velocity corresponding to the critical refraction longitudinal wave in a certain direction of the anisotropic material, calculates the amplitude and sound velocity of the critical refraction longitudinal wave in different directions, and establishes the corresponding relationship between the above acoustic characteristic quantity and the degree of damage. The specific steps are as follows:

[0007] (1) Surface treatment of anisotropic material samples

[0008] The surface of the anisotropic material sample is ground and polished to obtain a flat and smooth surface.

[0009] (2) Estimating the sound velocity range of anisotropic materials and exciting critical refracted longitudinal waves

[0010] Estimate the sound velocity range of anisotropic materials, calculate and optimize the phased array ultrasonic delay law in a certain direction of the sample, read the arrival time of the received signal and calculate the longitudinal wave sound velocity, and excite and receive the critical refracted longitudinal wave. In the sound velocity range, step at a certain sound velocity to preliminarily establish the relationship curve between different excitation sound velocities and the critical refracted longitudinal wave amplitude, select the sound velocity range corresponding to the higher amplitude, reduce the sound velocity step, re-excite, and finally establish the relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude, where the excitation sound velocity corresponding to the highest amplitude is the optimal excitation sound velocity.

[0011] (3) Exciting critical refracted longitudinal waves in different directions

[0012] Based on the optimal excitation sound velocity in a certain direction described in step (2), critical refracted longitudinal waves in different directions of the anisotropic material are excited, and the amplitude of the critical refracted longitudinal wave is read.

[0013] (4) Wavelet transform processing of critically refracted longitudinal waves

[0014] Perform continuous wavelet transform on the critical refracted longitudinal wave in step (3), read the highest approximate coefficient of the wavelet transformed signal of different array elements and the corresponding sound time, and perform polynomial fitting to obtain the slope k of the straight line to calculate the sound velocity v of the critical refracted longitudinal wave in different directions. The calculation method is as follows:

[0015]

[0016] Where: v w is the wedge sound velocity, θ w is the wedge inclination angle, and P is the array element spacing.

[0017] (5) Obtaining the acoustic characteristics of critical refracted longitudinal waves under different damage levels

[0018] Repeat steps (2) to (4) for anisotropic material samples with different damage degrees to establish the relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude at different damage degrees, as well as the critical refracted longitudinal wave amplitude and sound velocity change curve in different directions.

[0019] (6) Extraction of damage assessment parameters

[0020] The maximum amplitude, the optimal excitation sound velocity, and the critical refracted longitudinal wave amplitude and sound velocity corresponding to a certain direction in step (2) are extracted from the curve in step (5), and the relationship between the change of the four acoustic parameters and the damage parameters is established to evaluate the degree of damage of the anisotropic material.

[0021] In step (2), the sound velocity range corresponding to the higher amplitude is selected to narrow the sound velocity step and re-excite, and finally a relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude is established.

[0022] The damage parameter is time, quality or the number of micro defects.

[0023] The beneficial effects of the present invention are as follows: the anisotropic material damage evaluation method based on phased array-critical refracted longitudinal wave: estimates the sound velocity range of the anisotropic material, calculates and optimizes the phased array ultrasonic delay law on one side of the sample, reads the arrival time of the received signal and calculates the longitudinal wave sound velocity, excites and receives the critical refracted longitudinal wave, establishes a relationship curve between different excitation sound velocities and critical refracted longitudinal wave amplitudes, and obtains the highest amplitude and the corresponding optimal excitation sound velocity; calculates the phased array ultrasonic delay law with the optimal excitation sound velocity, excites the critical refracted longitudinal wave along different directions of the sample and measures the amplitude; performs continuous wavelet transformation on the critical refracted longitudinal wave, and calculates the critical refracted longitudinal wave sound velocity in different directions; obtains the relationship curve between the excitation sound velocity in the characteristic direction of the flat sample and the critical refracted longitudinal wave amplitude under different damage degrees, as well as the critical refracted longitudinal wave amplitude and sound velocity change curve in different directions; establishes the corresponding relationship between the highest amplitude and the optimal excitation sound velocity, the critical refracted longitudinal wave amplitude and sound velocity in a certain direction and the damage degree. The present invention evaluates anisotropic material damage through phased array-critical refracted longitudinal waves, effectively solving the evaluation problem caused by changes in material acoustic properties with direction and damage degree, significantly improving detection sensitivity and efficiency, and reducing detection costs. It can be widely used in the detection and evaluation of surface / near-surface defects and damage of isotropic and anisotropic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a CFRP one-way plate specimen.

[0025] Figure 2 It is a schematic diagram of the phased array-critical refraction longitudinal wave detection system.

[0026] Figure 3 It is a curve diagram showing the relationship between the excitation sound velocity at 0° and the critical refracted longitudinal wave amplitude of a CFRP one-way plate.

[0027] Figure 4 It is a curve of the change of the critical refraction longitudinal wave amplitude in the CFRP one-way plate from 0° to 25°.

[0028] Figure 5 It is a curve of the change of critical refracted longitudinal wave sound velocity in the CFRP one-way plate from 0° to 25°.

[0029] Figure 6 This is the maximum amplitude change diagram of CFRP one-way plate at different wet-heat aging times.

[0030] Figure 7 This is the optimal excitation sound velocity change diagram of CFRP one-way plate at different wet-heat aging times.

[0031] Figure 8 This is a graph showing the change in the critical refraction longitudinal wave amplitude at 0° for CFRP one-way plates at different wet-heat aging times.

[0032] Fig. 9 This is the change diagram of the critical refracted longitudinal wave sound velocity at 0° for CFRP one-way plates with different wet-heat aging times. DETAILED DESCRIPTION

[0033] (1) Preparation of CFRP one-way plate specimens

[0034] The hot-pressed cured CFRP unidirectional plate was used as the test object for anisotropic material damage evaluation. The processed specimen was a 100 mm × 80 mm, 5.5 mm wide flat plate. The surface of the specimen was polished. Figure 1 After polishing, the sample was placed in a 70℃ constant temperature oven for engineering dry treatment.

[0035] (2) Estimating the sound velocity range and exciting critical refracted longitudinal waves

[0036] The sound velocity range of the CFRP unidirectional plate specimen in the 0° direction in step (1) is estimated to be 8000m / s to 12000m / s, and the sound velocity step is initially set to 100m / s. Figure 2 According to the "Multi-material detection system of critical refracted longitudinal waves based on single-angle wedge and its sound velocity measurement method", in step (1), the phased array ultrasonic delay law is optimized in the 0° direction of the sample, the arrival time of the received signal is read and the longitudinal wave sound velocity is calculated to excite the critical refracted longitudinal wave. The relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude is established, and the step is reduced to 25m / s in the range of 9000-1000m / s with higher amplitude, and the excitation sound velocity and critical refracted longitudinal wave amplitude curve is established, such as Figure 3 In the curve at 0h, the sound velocity corresponding to the highest amplitude is 9425m / s, which is the optimal excitation sound velocity.

[0037] (3) Exciting critical refracted longitudinal waves in different directions

[0038] The critical refracted longitudinal wave in the 0° to 25° direction in the CFRP one-way plate is excited with the optimal excitation sound velocity of 9425 m / s in step (2), and the A scan and B scan signals are recorded in the computer, and the amplitude of the critical refracted longitudinal wave is read, such as Figure 4 The curve at 0h.

[0039] (4) Wavelet transform processing of critically refracted longitudinal waves

[0040] The critical refracted longitudinal wave A-scan signal in step (3) is subjected to continuous wavelet transform with "mexh" as the basis function, and the acoustic time corresponding to the highest approximate coefficient of the signal element 20 to 32 after the wavelet transform is read, and a polynomial fitting is performed to obtain the slope k and substitute it into formula (1) to calculate the critical refracted longitudinal wave sound velocity, v w is 2730m / s, θ w is 30°, P is 0.6mm. Taking the 0° direction as an example, the slope is 49.48, and the critical refracted longitudinal wave sound velocity is 9342m / s. Calculate the sound velocity in the 0°~25° direction, as follows: Figure 5 The curve at 0h.

[0041]

[0042] (5) Obtaining the critical refraction longitudinal wave acoustic characteristics under different aging damage states

[0043] The CFRP one-way plate sample in step (1) was heated in a water bath at 70°C. The above steps (2) to (4) were repeated for the sample aged for 120 hours, and the relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude under aging conditions of 0 hours and 120 hours was established, as shown in Fig. Figure 3 , the critical refraction longitudinal wave amplitude and sound velocity change curve in the direction of 0°~25°, such as Figure 4 and 5 .

[0044] (6) Extracting aging evaluation parameters

[0045] Extract the acoustic parameters such as the highest amplitude, optimal excitation sound velocity, and critical refracted longitudinal wave sound velocity and amplitude in the 0° direction from the curve in step (5), and establish the relationship between different acoustic parameters and aging time, such as Figures 6 to 9 , evaluate the degree of damage of CFRP one-way plate subjected to wet-heat aging.

Claims

1. Anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave, Features: This method determines the maximum amplitude and optimal excitation sound velocity of the critical refracted longitudinal wave corresponding to a certain direction of the anisotropic material, calculates the amplitude and sound velocity of the critical refracted longitudinal wave in different directions, and establishes the corresponding relationship between the above acoustic characteristic quantities and the degree of damage; The specific steps are as follows: (1) Surface treatment of anisotropic material samples The surface of the anisotropic material sample is ground and polished to obtain a flat and smooth surface; (2) Estimating the sound velocity range of anisotropic materials and exciting critical refracted longitudinal waves Estimate the sound velocity range of anisotropic materials, calculate and optimize the phased array ultrasonic delay law in a certain direction of the sample, read the arrival time of the received signal and calculate the longitudinal wave sound velocity, excite and receive the critical refracted longitudinal wave; within the sound velocity range, step at a certain sound velocity and preliminarily establish the relationship curve between different excitation sound velocities and critical refracted longitudinal wave amplitudes, where the excitation sound velocity corresponding to the highest amplitude is the optimal excitation sound velocity; (3) Exciting critical refracted longitudinal waves in different directions Based on the optimal excitation sound velocity in a certain direction in step (2), the critical refracted longitudinal waves of the anisotropic material are excited in different directions, and the amplitude of the critical refracted longitudinal waves is read; (4) Wavelet transform processing of critically refracted longitudinal waves Perform continuous wavelet transform on the critical refracted longitudinal wave in step (3), read the highest approximate coefficient of the wavelet transformed signal of different array elements and the corresponding sound time, and perform polynomial fitting to obtain the slope k of the straight line to calculate the sound velocity v of the critical refracted longitudinal wave in different directions. The calculation method is as follows: Where: v w is the wedge sound velocity, θ w is the wedge inclination angle, P is the array element spacing; (5) Obtaining the acoustic characteristics of critical refracted longitudinal waves under different damage levels Repeat steps (2) to (4) for anisotropic material samples with different damage degrees to establish relationship curves between excitation sound velocity and critical refracted longitudinal wave amplitude at different damage degrees, as well as curves of critical refracted longitudinal wave amplitude and sound velocity variation in different directions; (6) Extraction of damage assessment parameters The maximum amplitude, the optimal excitation sound velocity, and the critical refracted longitudinal wave amplitude and sound velocity corresponding to a certain direction in step (2) are extracted from the curve in step (5), and the relationship between the change of the four acoustic parameters and the damage parameters is established to evaluate the degree of damage of the anisotropic material.

2. The anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave according to claim 1, Features: In step (2), the sound velocity range corresponding to the higher amplitude is selected to narrow the sound velocity step and re-excite, and finally a relationship curve between the excitation sound velocity and the critical refracted longitudinal wave amplitude is established.

3. The anisotropic material damage evaluation method based on phased array-critical refraction longitudinal wave according to claim 1, Features: The damage parameter is time, quality or the number of micro defects.

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