Method and device for evaluating early damage of plate based on non-specular reflection

Abstract

The invention discloses a method and a device for evaluating early damage of a plate based on non-specular reflection. The method comprises the following steps: firstly, acquiring an incidence inclination angle theta of ultrasonic waves on the surface of the plate; then, randomly selecting one detection point on the plate, and setting the position of the ultrasonic transducer at the detection point according to the inclination angle theta; and then, according to an ultrasonic signal transmitted in the ultrasonic transducer, obtaining a linear ultrasonic coefficient so as to evaluate the early damage of the plate.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrasonic non-destructive testing, and relates to a method and device for evaluating early damage of a plate based on non-specular reflection. Background Art

[0002] In practical applications, due to complex service environments (vibration, temperature, corrosion, alternating load, force, etc.), the corresponding plates are prone to fatigue damage. Once fatigue damage occurs, it will greatly reduce the mechanical properties of the material structure. If not detected in time, with the accumulation of damage, structural fracture failure will occur in a short time, leading to serious accidents and even causing significant casualties and property damage. Therefore, effective characterization of early damage of plates is of great significance.

[0003] Existing ultrasonic non-destructive testing methods mainly use linear parameters (wave time history, sound velocity, attenuation) or non-linear parameters to characterize early damage of plates. However, traditional linear parameters are insensitive to early damage of plates, such as sound velocity and attenuation. The non-linear signals induced by material property damage are extremely weak, and coupled with other signal interferences such as noise, the non-linear parameters are extremely unstable and have poor robustness, making it difficult to apply in practical engineering. To address the above problems, a method and device for evaluating early damage of plates based on non-specular reflection are proposed. Summary of the Invention

[0004] To overcome the above problems, a method and device for evaluating early damage of plates based on non-specular reflection are developed. First, the incident angle θ of ultrasonic waves on the plate surface is obtained; then, a detection point is arbitrarily selected on the plate, and the position of the ultrasonic transducer at the detection point is set according to the angle θ; next, based on the ultrasonic wave signal transmitted in the ultrasonic transducer, a linear ultrasonic coefficient is obtained to evaluate the early damage of the plate. The method effectively quantitatively characterizes the damage degree of the plate, correlates the coupling law between the early damage degree of the plate and the S0 mode, and uses the linear ultrasonic coefficient to effectively quantitatively characterize the early damage of the plate, improving the sensitivity, accuracy and rapidity of early damage detection of the plate, thus completing the present invention.

[0005] Specifically, the object of the present invention is to provide the following aspects:

[0006] In the first aspect, a method for evaluating early damage of a plate based on non-specular reflection is provided, and the method includes:

[0007] Step 1, obtaining the incident angle θ of ultrasonic waves on the plate surface;

[0008] Step 2, arbitrarily selecting a detection point on the plate and setting the position of the ultrasonic transducer at the detection point according to the angle θ;

[0009] Step 3: Obtain the linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate the early damage of the plate.

[0010] In a second aspect, a device for evaluating the early damage of a plate based on non-specular reflection is provided. The device includes:

[0011] An acquisition unit for acquiring the incident angle θ of ultrasonic waves on the surface of the plate;

[0012] A position unit for arbitrarily selecting a detection point on the plate and setting the position of the ultrasonic transducer at the detection point according to the angle θ;

[0013] An evaluation unit for obtaining the linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate the early damage of the plate.

[0014] In a third aspect, an application of the device described in the second aspect in the evaluation of the early damage of a plate based on non-specular reflection is provided.

[0015] The beneficial effects of the present invention include:

[0016] (1) The method for evaluating the early damage of a plate based on non-specular reflection provided by the present invention can effectively and quantitatively detect the early damage of the plate, and realize the efficient, reliable, real-time and convenient health evaluation of the plate.

[0017] (2) The method for evaluating the early damage of a plate based on non-specular reflection provided by the present invention correlates the degree of early damage of the plate with the coupling law of the S0 mode, and uses the linear ultrasonic coefficient to effectively and quantitatively characterize the early damage of the plate, improving the sensitivity, accuracy and rapidity of the detection of the early damage of the plate. Description of the Drawings

[0018] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The accompanying drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0019] In the drawings:

[0020] Figure 1 A schematic structural diagram of a device for evaluating the early damage of a plate based on non-specular reflection according to a preferred embodiment of the present invention is shown;

[0021] Figure 2 A top view of the 6061 aluminum plate in Examples 1 to 9 is shown;

[0022] Figure 3 Show the waveform diagrams of specular reflection ultrasonic signals in Embodiment 1 to Embodiment 9;

[0023] Figure 4 Show the comparison diagrams of linear ultrasonic coefficients obtained in Embodiment 1 to Embodiment 9.

[0024] Explanation of the reference numerals in the drawings:

[0025] 1 - Plate;

[0026] 2 - Transmitting transducer;

[0027] 3 - Receiving transducer. Detailed implementation manners

[0028] The following will refer to the appended Figures 1 to 4 Describe the specific embodiments of the present invention in more detail. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0029] It should be noted that in the description of the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. The specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. As mentioned throughout the specification and claims, "comprising" or "including" is an open-ended term and should be interpreted as "including but not limited to". The subsequent description in the specification is the preferred implementation manner for implementing the present invention, but the description is for the purpose of the general principles of the specification and is not used to limit the scope of the present invention. The protection scope of the present invention shall be defined by the appended claims.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front", "rear", etc. is the orientation or positional relationship based on the working state of the present invention, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0031] For the convenience of understanding the embodiments of the present invention, the following will further explain and illustrate with specific embodiments in conjunction with the accompanying drawings, and the accompanying drawings do not limit the embodiments of the present invention.

[0032] On the one hand, a method for evaluating early damage of a plate based on non-specular reflection is provided. The method includes:

[0033] Step 1: Obtain the incident angle θ of ultrasonic waves on the surface of the plate 1.

[0034] Step 2: Arbitrarily select a detection point on the plate 1, and set the position of the ultrasonic transducer at the detection point according to the incident angle θ.

[0035] Step 3: Obtain the linear ultrasonic coefficient based on the ultrasonic wave signal transmitted in the ultrasonic transducer to evaluate the early damage of the plate 1.

[0036] The method for evaluating early damage of a plate based on non-specular reflection is described in detail below.

[0037] Step 1: Obtain the incident angle θ of ultrasonic waves on the surface of the plate 1.

[0038] In Step 1, the incident angle θ of ultrasonic waves on the surface of the plate 1 is obtained by including the following steps: Immerse the plate 1 in a liquid, and the ultrasonic waves are transmitted in the liquid to the surface of the plate 1. Obtain the incident angle θ of ultrasonic waves on the surface of the plate 1 based on the longitudinal wave sound velocity of the liquid and the phase velocity of the S0 Lamb wave in the plate 1. Specifically, the incident angle θ, the longitudinal wave sound velocity of the liquid, and the phase velocity of the S0 Lamb wave in the plate 1 have the following relationship:

[0039]

[0040] In the formula: C w is the longitudinal wave sound velocity of the liquid, and C S0 is the phase velocity of the S0 Lamb wave in the plate 1.

[0041] In Step 1, the liquid is water, ethanol, or hydraulic oil, and the hydraulic oil is any one of kerosene, gasoline, and lubricating oil; the liquid is preferably water which is cheap and easily available.

[0042] In Step 1, the plate 1 is an isotropic material.

[0043] Step 2: Arbitrarily select a detection point on the plate 1, and set the position of the ultrasonic transducer at the detection point according to the incident angle θ.

[0044] In Step 2, the ultrasonic transducer is immersed in the liquid. The ultrasonic transducer includes a transmitting transducer 2 and a receiving transducer 3, and the transmitting transducer 2 and the receiving transducer 3 are arranged on the same side of the plate 1.

[0045] In the present invention, the same side is understood as follows: the transmitting transducer 2 and the receiving transducer 3 are arranged on the same side of any one of the upper edge, lower edge, left edge, and right edge of the plate 1. Preferably, the transmitting transducer 2 and the receiving transducer 3 are arranged on the upper edge of the plate 1.

[0046] In step 1, the plate 1 is immersed in a liquid, and the liquid serves as a couplant. The ultrasonic transducers arranged in step 2 are also immersed in the liquid and do not contact the plate 1. By adjusting the angle of the ultrasonic transducer, the direction of the sound beam emitted by the ultrasonic transducer can be conveniently changed, facilitating the realization of focused sound beam detection and meeting the requirements of high sensitivity and high resolution. However, using air instead of liquid as the couplant will cause an increase in interface reflection attenuation, and the propagation attenuation of ultrasonic waves in air is severe.

[0047] In step 2, the transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point, and the angles between the transmitting transducer 2 and the receiving transducer 3 and the vertical plane of the detection point are both θ.

[0048] Furthermore, there are no strict requirements for the heights of the transmitting transducer 2 and the receiving transducer 3. On the one hand, they do not contact the plate 1, and on the other hand, they are immersed in the liquid.

[0049] Step 3: Obtain the linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate the early damage of the plate 1.

[0050] According to the embodiment, step 3 includes the following steps:

[0051] Step 3-1: The transmitting transducer 2 excites ultrasonic waves in the liquid. The ultrasonic waves are reflected by the detection point and then received by the receiving transducer 3, obtaining the amplitude of the excitation ultrasonic signal of the transmitting transducer 2 and the amplitude of the specular reflection ultrasonic signal on the receiving transducer 3.

[0052] Step 3-2: Based on the amplitude of the excitation ultrasonic signal of the transmitting transducer 2 and the amplitude of the specular reflection ultrasonic signal on the receiving transducer 3, obtain the linear ultrasonic coefficient to evaluate the early damage of the plate 1.

[0053] In step 3-1, the ultrasonic waves are ultrasonic waves with a finite time width. The transverse dimension of the ultrasonic waves with a finite time width perpendicular to the propagation direction is the length d of the transmitting transducer 2 in actual excitation.

[0054] In step 3-1, the amplitude of the excitation ultrasonic signal is the maximum value of the ultrasonic signal excited by the transmitting transducer 2 in the liquid, and the amplitude of the specular reflection ultrasonic signal is the maximum value of the specular reflection ultrasonic signal received by the receiving transducer 3 carrying the specular reflection point on the plate 1.

[0055] In step 3-2, the linear ultrasonic coefficient is the ratio between the amplitude of the specularly reflected ultrasonic signal and the amplitude of the exciting ultrasonic signal, and is specifically expressed as:

[0056]

[0057] In the formula: W is the linear ultrasonic coefficient, and A i is the amplitude of the exciting ultrasonic signal; A r is the amplitude of the specularly reflected ultrasonic signal.

[0058] In step 3-2, the linear ultrasonic coefficient is compared with the intact linear ultrasonic coefficient in the sheet 1 (the intact linear ultrasonic coefficient means that there is no damage of any form on the surface and inside of the sheet) to quantitatively evaluate the early damage of the sheet 1.

[0059] According to the present invention, by simultaneously adjusting the position of the detection point and the relative positions of the ultrasonic transducers (i.e., the transmitting transducer 2 and the receiving transducer 3), repeating step 3 can evaluate the damage at different detection points of the sheet 1. More specifically, randomly select another detection point on the sheet 1, and at this time, adjust the transmitting transducer 2 and the receiving transducer 3 to be symmetrically distributed on both sides of the vertical plane of the detection point, and the angles with the vertical plane of the detection point are both θ, and repeat step 3 to evaluate the damage of the detection points at different positions of the sheet 1. By replacing the sheet 1 with different degrees of damage, the degree of damage of the corresponding sheet 1 can be quantitatively evaluated.

[0060] In step 3, the center frequency of the exciting transmitting transducer 2 is the same as the sampling frequency of the receiving transducer 3. According to the finite element simulation results, the specularly reflected ultrasonic signal will show a trend of first increasing and then decreasing as the sampling frequency increases. According to the preferred embodiment, the frequencies of both the transmitting transducer 2 and the receiving transducer 3 are selected to be 2 MHz, and the number of cycles of the transmitting transducer 2 is 10.

[0061] On the other hand, a device for evaluating the early damage of a sheet based on non-specular reflection is provided, as Figure 1 shown, the device includes:

[0062] An acquisition unit for acquiring the incident angle θ of the ultrasonic wave on the surface of the sheet 1;

[0063] A position unit for randomly selecting a detection point on the sheet 1 and setting the position of the ultrasonic transducer at the detection point according to the angle θ;

[0064] An evaluation unit for obtaining the linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate the early damage of the sheet 1.

[0065] According to the present invention, in the position unit, the ultrasonic transducer includes a transmitting transducer 2 and a receiving transducer 3, and the transmitting transducer 2 and the receiving transducer 3 are arranged on the same side of the plate 1.

[0066] Further, the plate 1 and the ultrasonic transducer are both immersed in a liquid. The inclination angle θ of the ultrasonic wave incident on the surface of the plate 1 when the ultrasonic wave is transmitted in the liquid is predetermined. An inspection point is arbitrarily selected on the plate 1. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the inspection point, and the angles between the transmitting transducer 2 and the receiving transducer 3 and the vertical plane of the inspection point are both θ.

[0067] In another aspect, there is provided an application of the device described in the second aspect in the evaluation of early damage of a plate based on non-specular reflection.

[0068] Embodiment

[0069] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation to the protection scope of the present invention.

[0070] Example 1

[0071] As Figure 1 shown in the device, a intact 6061 aluminum plate (6061 aluminum plate at the time of factory) is used as the plate 1 to be tested, and its damage is evaluated. The top view size of the 6061 aluminum plate is as Figure 2 shown. In the figure, the length of L 11 is 50 mm, the length of L 41 is the same as that of L 4 , both are 50 mm. The area shown as L 11 ×L 41 is the area to be detected. The length of L 1 is 150 mm, the length of L 2 is 250 mm, the length of L 3 is 336.6 mm. There are a total of 4 arcs shown in the figure, namely the upper, lower, left and right arcs. The radius R of the arcs is 50 mm. The widths L 5 on both sides of the 6061 aluminum plate are both 100 mm. The thickness H of the 6061 aluminum plate is 2.64 mm. The density of the 6061 aluminum plate is 2700 kg / m 3 , the Young's modulus is 70 GPa, and the Poisson's ratio is 0.33. The liquid used is water, with a density of 1000 kg / m 3 , a sound speed of 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. The inclination angle θ is calculated based on the phase velocity of the S0 Lamb wave in the plate 1 and the longitudinal wave sound speed of the liquid:

[0072]

[0073] Where: C w is the longitudinal wave sound velocity of the liquid, with a value of 1500 m / s; C s0 is the phase velocity of the S0 Lamb wave in the plate 1, with a value of 2951 m / s, and the calculated θ is 30.6°;

[0074] Adjust Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in are both 30.6° with the vertical plane of the detection point. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the mirror reflection point F is c, where c is 40 mm.

[0075] The frequencies of both the transmitting transducer 2 and the receiving transducer 3 are 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. The ultrasonic waves are reflected by the detection point F and then received by the receiving transducer 3. The amplitudes of the excitation ultrasonic wave signal of the transmitting transducer 2 and the mirror reflection ultrasonic wave signal on the transducer 3 are 1 and 0.0167 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic wave signal; A r is the amplitude of the mirror reflection ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0167.

[0076] In Examples 2 to 9, eight intact (at the time of factory) 6061 aluminum plates (with the same size as the 6061 aluminum plate used in Example 1) are subjected to fatigue tensile tests with different numbers of cycles, thereby introducing early fatigue damage to different degrees. All fatigue tests are carried out under the room temperature conditions in the laboratory. The fatigue tensile equipment used is a 100 kN servo-hydraulic test system (MTS 809.10). Under the stress control mode, continuous fatigue tensile tests are carried out with a sinusoidal wave cycle at a frequency of 20 Hz. 80% of the yield force is used as the fatigue stress reference. The maximum load and the minimum load of the fatigue tensile are 13.2 kN and 1.32 kN respectively, and the stress ratio is 0.1.

[0077] Example 2

[0078] A single intact 6061 aluminum plate is subjected to a fatigue tensile test of 30,000 times (N = 30000), and the damage evaluation is carried out on it using the device shown in Figure 1 . The liquid used is water, with a density of 1000 kg / m 3 , a sound velocity of 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. The inclination angle θ is calculated based on the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid:

[0079]

[0080] Where: C w is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in the plate 1, and its value is 2951 m / s, and the calculated θ is 30.6°;

[0081] Adjust Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0082] The frequencies of the transmitting transducer 2 and the receiving transducer 3 are both 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. The ultrasonic waves are reflected by the detection point F and received by the receiving transducer 3, obtaining the excitation ultrasonic wave signal of the transmitting transducer 2 and the specular reflection ultrasonic wave signal on the receiving transducer 3. The amplitudes of the excitation ultrasonic wave signal of the transmitting transducer 2 and the specular reflection ultrasonic wave signal on the receiving transducer 3 are 1 and 0.0191 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic wave signal; A r is the amplitude of the specular reflection ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0191.

[0083] Example 3

[0084] A fatigue tensile test of 50,000 times (N = 50000) is carried out on a intact 6061 aluminum plate, and the damage evaluation is carried out on it using the device shown in Figure 1 . The liquid used is water, with a density of 1000 kg / m 3 , a sound velocity of 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. According to the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid, the inclination angle θ is calculated:

[0085]

[0086] Where: C w is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in the plate 1, and its value is 2951 m / s, and the calculated θ is 30.6°;

[0087] AdjustFigure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in the figure and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0088] The frequencies of both the transmitting transducer 2 and the receiving transducer 3 are 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. After the ultrasonic waves are reflected by the detection point F, they are received by the receiving transducer 3. The amplitudes of the excitation ultrasonic wave signal of the transmitting transducer 2 and the specular reflection ultrasonic wave signal on the transducer 3 are 1 and 0.0227 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic wave signal; A r is the amplitude of the specular reflection ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0227.

[0089] Example 4

[0090] A sound - intact aluminum plate of model 6061 is subjected to 70,000 (N = 70000) fatigue tensile tests, and the device shown in Figure 1 is used to evaluate its damage. The liquid used is water, with a density of 1000 kg / m 3 , a sound - velocity of 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. According to the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal - wave sound - velocity of the liquid, the inclination angle θ is calculated as follows:

[0091]

[0092] In the formula: C w is the longitudinal - wave sound - velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in the plate 1, and its value is 2951 m / s. The calculated θ is 30.6°;

[0093] Adjust Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in the figure and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0094] The frequencies of the transmitting transducer 2 and the receiving transducer 3 are both 2 MHz, the number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. After being reflected by the detection point F, the ultrasonic waves are received by the receiving transducer 3. The amplitudes of the exciting ultrasonic wave signal of the transmitting transducer 2 and the mirror-reflected ultrasonic wave signal on the transducer 3 are 1 and 0.0285 respectively. According to W = A r / A i (where W is the linear ultrasonic coefficient, A i is the amplitude of the exciting ultrasonic wave signal; A r is the amplitude of the mirror-reflected ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0285.

[0095] Example 5

[0096] A fatigue tensile test of 90,000 times (N = 90000) is carried out on a intact aluminum plate of model 6061, and the damage evaluation is carried out using the device as Figure 1 shown. The liquid used is water, with a density of 1000 kg / m 3 , and the sound velocity is 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. According to the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid, the inclination angle θ is calculated as follows:

[0097]

[0098] In the formula: C w is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in the plate 1, and its value is 2951 m / s. The calculated θ is 30.6°;

[0099] Adjust the Figure 1 vertical plane angles between the transmitting transducer 2 and the receiving transducer 3 shown in and the detection point to be both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the mirror reflection point F is c, where c is 40 mm.

[0100] The frequencies of the transmitting transducer 2 and the receiving transducer 3 are both 2 MHz, the number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. After being reflected by the detection point F, the ultrasonic waves are received by the receiving transducer 3. The amplitudes of the exciting ultrasonic wave signal of the transmitting transducer 2 and the mirror-reflected ultrasonic wave signal on the transducer 3 are 1 and 0.0335 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, and A i is the amplitude of the exciting ultrasonic wave signal; A rFor the amplitude of the specularly reflected ultrasonic signal), the linear ultrasonic coefficient W is obtained as 0.0335.

[0101] Example 6

[0102] A sound aluminum plate of type 6061 is subjected to 110,000 (N = 110000) fatigue tensile tests, and the damage evaluation is carried out using the device shown as Figure 1 The liquid used is water with a density of 1000 kg / m 3 , a sound velocity of 1500 m / s. The ultrasonic wave is transmitted in the liquid to the surface of the plate 1. According to the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid, the inclination angle θ is calculated as follows:

[0103]

[0104] In the formula: C w is the longitudinal wave sound velocity of the liquid, with a value of 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in the plate 1, with a value of 2951 m / s. The calculated θ is 30.6°.

[0105] Adjust Figure 1 The vertical plane angles between the transmitting transducer 2 and the receiving transducer 3 shown in are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0106] The frequencies of both the transmitting transducer 2 and the receiving transducer 3 are 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. The ultrasonic waves are reflected by the detection point F and received by the receiving transducer 3. The amplitudes of the excitation ultrasonic signal of the transmitting transducer 2 and the specularly reflected ultrasonic signal on the transducer 3 are obtained as 1 and 0.0391 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic signal; A r is the amplitude of the specularly reflected ultrasonic signal), the linear ultrasonic coefficient W is obtained as 0.0391.

[0107] Example 7

[0108] A sound aluminum plate of type 6061 is subjected to 130,000 (N = 130000) fatigue tensile tests, and the damage evaluation is carried out using the device shown as Figure 1 The liquid used is water with a density of 1000 kg / m 3, the sound velocity is 1500 m / s. The ultrasonic wave is transmitted to the surface of plate 1 in the liquid. The inclination angle θ is calculated based on the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid:

[0109]

[0110] In the formula: C w is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in plate 1, and its value is 2951 m / s. The calculated θ is 30.6°;

[0111] Adjust Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0112] The frequencies of the transmitting transducer 2 and the receiving transducer 3 are both 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. The ultrasonic waves are reflected by the detection point F and then received by the receiving transducer 3. The amplitudes of the excitation ultrasonic wave signal of the transmitting transducer 2 and the specular reflection ultrasonic wave signal on the transducer 3 are 1 and 0.0429 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic wave signal; A r is the amplitude of the specular reflection ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0429.

[0113] Example 8

[0114] A fatigue tensile test of 150,000 times (N = 150000) is carried out on a complete 6061 aluminum plate, and the device shown in Figure 1 is used to evaluate its damage. The liquid used is water, with a density of 1000 kg / m 3 , the sound velocity is 1500 m / s. The ultrasonic wave is transmitted to the surface of plate 1 in the liquid. The inclination angle θ is calculated based on the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid:

[0115]

[0116] In the formula: C w is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C S0 is the phase velocity of the S0 Lamb wave in plate 1, and its value is 2951 m / s. The calculated θ is 30.6°;

[0117] Adjustment Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in Figure 1 and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0118] The frequencies of both the transmitting transducer 2 and the receiving transducer 3 are 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. After the ultrasonic waves are reflected by the detection point F, they are received by the receiving transducer 3. The amplitudes of the excitation ultrasonic wave signal of the transmitting transducer 2 and the specular reflection ultrasonic wave signal on the transducer 3 are 1 and 0.0464 respectively. According to W = A r / A i (W is the linear ultrasonic coefficient, A i is the amplitude of the excitation ultrasonic wave signal; A r is the amplitude of the specular reflection ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0464.

[0119] Example 9

[0120] A sound aluminum plate of model 6061 is subjected to 170,000 (N = 170000) fatigue tensile tests, and the device shown in Figure 1 is used to evaluate its damage. The liquid used is water with a density of 1000 kg / m Figure 1 and a sound velocity of 1500 m / s. The ultrasonic waves are transmitted in the liquid to the surface of the plate 1. According to the phase velocity of the S0 Lamb wave in the intact plate 1 and the longitudinal wave sound velocity of the liquid, the inclination angle θ is calculated as follows: 3 In the formula: C

[0121]

[0122] is the longitudinal wave sound velocity of the liquid, and its value is 1500 m / s; C w is the phase velocity of the S0 Lamb wave in the plate 1, and its value is 2951 m / s. The calculated θ is 30.6°; S0

[0123] Adjustment Figure 1 The included angles between the transmitting transducer 2 and the receiving transducer 3 shown in Figure 1 and the vertical plane of the detection point are both 30.6°. The transmitting transducer 2 and the receiving transducer 3 are symmetrically distributed on both sides of the vertical plane of the detection point. The distance from the midpoint of the excitation surface of the transmitting transducer 2 to the specular reflection point F is c, where c is 40 mm.

[0124] The frequencies of the transmitting transducer 2 and the receiving transducer 3 are both 2 MHz. The number of cycles of the transmitting transducer 2 is 10. The transmitting transducer 2 excites ultrasonic waves in water. After being reflected by the detection point F, the ultrasonic waves are received by the receiving transducer 3. The amplitudes of the exciting ultrasonic wave signal of the transmitting transducer 2 and the mirror-reflected ultrasonic wave signal on the transducer 3 are 1 and 0.0470 respectively. According to W = A r / A i (where W is the linear ultrasonic coefficient, A i is the amplitude of the exciting ultrasonic wave signal; A r is the amplitude of the mirror-reflected ultrasonic wave signal), the linear ultrasonic coefficient W is obtained as 0.0470.

[0125] Figure 3 The waveform diagrams of the mirror-reflected ultrasonic wave signals in Embodiments 1 to 9 are shown. It can be clearly seen that Figure 1 the device can effectively avoid the interference of shear wave signals. Compared with the waveform of the mirror-reflected ultrasonic wave signal in Embodiment 1, the waveforms of the mirror-reflected ultrasonic wave signals of the 6061 aluminum plates with fatigue damage in Embodiments 2 to 9 have changed significantly. Moreover, the more severe the fatigue damage, the more obvious the change in the waveform of the mirror-reflected ultrasonic wave signal of the 6061 aluminum plate.

[0126] Figure 4 The comparison diagram of the linear ultrasonic coefficient W obtained in Embodiments 1 to 9 is shown. It can be clearly seen that the increase in the number of cyclic loadings will exacerbate the performance damage of the 6061 aluminum plate. The parameter W increases with the increase in the degree of early damage of the plate. The effectiveness of the method for evaluating the early damage of the plate based on non-mirror reflection of the present invention is verified.

[0127] The present invention has been described in detail above in combination with preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are only illustrative explanations of the present invention and do not constitute any limitation to the protection scope of the present invention. Without departing from the spirit and protection scope of the present invention, various improvements, equivalent replacements or modifications can be made to the technical content and its implementation manners of the present invention, and these all fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A plate early damage assessment method based on non-specular reflection, characterized in that: The method comprises: Step 1, obtaining the inclination angle θ of the ultrasonic wave incident on the surface of the plate (1); Step 2, randomly select a detection point on the plate (1), and set the position of the ultrasonic transducer at the detection point according to the inclination angle θ; Step 3, obtaining a linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate the early damage of the plate (1).

2. The method according to claim 1, characterized in that Preferably, in step 1, the inclination angle θ of the ultrasonic wave incident on the surface of the plate (1) is obtained by the following steps: the plate (1) to be tested is immersed in a liquid, the ultrasonic wave is transmitted to the surface of the plate 1 in the liquid, and the inclination angle θ is obtained based on the longitudinal wave sound velocity of the liquid and the phase velocity of the S0 Lamb wave in the plate (1).

3. The method according to claim 2, characterized in that In step 1, the inclination angle θ, the longitudinal sound velocity of the liquid and the phase velocity of the S0 Lamb wave in the plate (1) have the following relationship: Where: C w is the longitudinal sound velocity of the liquid, C S0 is the phase velocity of the S0 Lamb wave in the plate (1).

4. The method according to claim 1, characterized in that: In step 1, the liquid is water, ethanol or hydraulic oil.

5. The method according to claim 4, characterized in that The hydraulic oil is any one of kerosene, gasoline and lubricating oil.

6. The method according to claim 1, characterized in that In step 2, the ultrasonic transducer is immersed in a liquid.

7. The method according to claim 1, characterized in that The ultrasonic transducer comprises a transmitting transducer (2) and a receiving transducer (3), and the transmitting transducer (2) and the receiving transducer (3) are arranged on the same side of the plate (1).

8. The method according to claim 7, characterized in that The transmitting transducer (2) and the receiving transducer (3) are symmetrically distributed on both sides of the vertical plane of the detection point, and the included angles between the transmitting transducer (2) and the receiving transducer (3) and the vertical plane of the detection point are both θ.

9. A plate early damage assessment device based on non-specular reflection, characterized in that: The device comprises: An acquisition unit, used for acquiring an inclination angle θ of the ultrasonic wave incident on the surface of the plate (1); A position unit, which is used to select any detection point on the plate (1) and set the position of the ultrasonic transducer at the detection point according to the inclination angle θ; An evaluation unit is used to obtain a linear ultrasonic coefficient based on the ultrasonic signal transmitted in the ultrasonic transducer to evaluate early damage of the plate (1).

10. Use of the device according to claim 9 in early damage evaluation of plate materials based on non-specular reflection.

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