CN109507297B - Method for determining defect depth of composite material detected by ultrasonic-acoustic emission - Google Patents

Method for determining defect depth of composite material detected by ultrasonic-acoustic emission Download PDF

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CN109507297B
CN109507297B CN201811511277.5A CN201811511277A CN109507297B CN 109507297 B CN109507297 B CN 109507297B CN 201811511277 A CN201811511277 A CN 201811511277A CN 109507297 B CN109507297 B CN 109507297B
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defect
acoustic emission
depth
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CN109507297A (en
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刘松平
刘菲菲
傅天航
李乐刚
杨玉森
李治应
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AVIC Composite Corp Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/30—Arrangements for calibrating or comparing, e.g. with standard objects
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0231—Composite or layered materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/0289—Internal structure, e.g. defects, grain size, texture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
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    • G01N2291/102—Number of transducers one emitter, one receiver

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Abstract

The invention belongs to a nondestructive detection technology, and relates to a method for determining the defect depth of composite material ultrasonic-acoustic emission detection in the fields of aviation, aerospace, weapons, ships, metallurgy, steel, traffic, buildings and the like. The method comprises the steps of firstly preparing a thickness calibration test block, then obtaining a test block thickness reference signal and checking the defect depth, and finally determining the depth of the detected defect. According to the invention, by utilizing the time domain relation between the propagation behavior of the sound wave and the defect in the detected material or structure and adopting the time domain pulse characteristic of the improved ultrasonic-acoustic emission signal, the longitudinal resolution of the ultrasonic-acoustic emission is improved, and the depth of the detected defect can be more accurately determined; the method is easy to realize, very quick, easy to operate and master and has better engineering detection application applicability; the method is more favorable for quality control of detection results, thereby being more favorable for popularization and application of the ultrasonic-acoustic emission method and playing a role in engineering.

Description

Method for determining defect depth of composite material detected by ultrasonic-acoustic emission
Technical Field
The invention belongs to a nondestructive detection technology, and relates to a method for determining the defect depth of composite material ultrasonic-acoustic emission detection in the fields of aviation, aerospace, weapons, ships, metallurgy, steel, traffic, buildings and the like.
Background
Because the ultrasonic-acoustic emission signal source comes from the inside of the detected part or structure, the ultrasonic-acoustic emission signal source is insensitive to the orientation of the defect and has stronger penetrating power, the ultrasonic-acoustic emission signal source has a plurality of unique applications in the fields of aerospace, weapons, electronics, ships, metallurgy, petrochemical petroleum, traffic, buildings and the like, and one important application is the defect detection of composite materials and metal material structures.
The ultrasonic-acoustic emission detection method adopted at present has the following remarkable defects: the transducer is used for receiving acoustic emission signals from the defects, the horizontal distance from the detected defects to the receiving transducer can be roughly determined, but the depth of the detected defects is difficult to determine, and the depth of the detected defects, such as layered defects, cannot be determined at the position of the layer depth of the composite material structure due to the poor time-domain pulse characteristic and the poor resolution rate of the traditional ultrasonic-acoustic emission detection signals, so that the requirement for accurately determining the depth of the detected defects in the fields of composite material detection and the like is difficult to meet, the detection application of an ultrasonic-acoustic emission method is further limited, the depth of the detected defects is determined by adopting the traditional ultrasonic thickness measurement principle, the sound velocity measurement is required to be performed by using a test block with known thickness, and the deviation caused by the sound velocity measurement is easy to bring in. As an improved method, the time domain relation between the propagation behavior of the sound wave and the defect in the detected material or structure is utilized, the time domain pulse characteristic of the ultrasonic-acoustic emission signal is improved, the longitudinal resolution of the ultrasonic-acoustic emission is improved, meanwhile, the deviation caused by sound velocity measurement is reduced, and the detected defect is accurately fixed in depth.
Disclosure of Invention
The invention aims to provide a method for determining the depth of a defect detected by ultrasonic-acoustic emission of a composite material, which is constructed by utilizing the propagation behavior of a high-resolution pulse ultrasonic-acoustic emission signal in the thickness direction of the detected material or structure.
The technical solution of the present invention is that, the detection system for realizing the method mainly comprises a transmitting transducer, an ultrasonic transmitting unit, a receiving transducer, an acoustic emission receiving unit, a signal processing unit, a scanning unit and a display unit, wherein:
the transmitting transducer generates exciting ultrasonic wave P1This exciting ultrasonic wave P1The acoustic emission stress wave is formed inside the detected composite material structure through the transmission of the coupling medium to the detected composite material structure,
the receiving transducer receives the transmitted acoustic wave E from the internal defect of the composite structure being inspected1，
The ultrasonic transmitting unit generates an ultrasonic excitation signal, and the excitation transmitting transducer generates an excitation ultrasonic wave P1，
The acoustic emission receiving unit preprocesses the acoustic emission signals from the receiving transducer,
the signal processing unit carries out digital processing on the acoustic emission signal of the receiving transducer after being preprocessed by the acoustic emission receiving unit, and is used for ultrasonic-acoustic emission defect judgment, quantitative positioning analysis and detection result imaging,
the scanning unit is used for controlling the transmitting transducer and the receiving transducer to scan the structure of the detected composite material, the display unit is used for reconstructing the acoustic emission signal and the position signal of each scanning detection position to form an acoustic emission display signal and/or an image signal, and displaying, recording, storing and analyzing the ultrasonic-acoustic emission detection result,
1) preparation of thickness calibration test block
Preparing a thickness calibration test block with the thickness of H by adopting a composite material with the same material and forming process as the detected composite material, wherein the thickness calibration test block is in the shape of an equal-thickness flat plate, and 4 defects F with the same size are prefabricated at different depth positions in the thickness calibration test block1、F2、F3、F4The size of which is selected according to the detection requirements of the structure of the composite material to be detected, defect F1、F2、F3、F4The central points are separated from each other by L in the plane direction of the thickness calibration test block1Defect F1、F2、F3、F4The minimum distance from the center point of the thickness calibration test block to the edge near the edge of the thickness calibration test block is not less than L1Wherein, in the step (A),
defect F1、F2The depths from the surface of the thickness calibration test block are all H1，
Defect F3And F4The depth distance H in the thickness direction of the thickness calibration test block1Wherein the defect F3And defect F1、F2The depth distance H in the thickness direction of the thickness calibration test block1Defect F4The depth from the surface of the thickness calibration test block is H1；
Thickness H of thickness calibration test block is 3H1；
2) Acquisition of thickness reference signal
Will transmit energyDefect F in moving device and receiving transducer to thickness calibration test block3Moving the position of the acoustic emission unit, and observing the acoustic emission signal displayed on the screen of the display unit so that the acoustic emission signal comes from F3Is maximum, the recording and marking now coming from the defect F3Time horizontal scale T of display screen of acoustic emission signal in display unit3And recording and marking the time measurement recording start point T in the display unit at that time0；
Then, the transmitting transducer and the receiving transducer are moved to the defect F in the thickness calibration test block4Moving the position of the acoustic emission device, and observing the acoustic emission signal displayed on the screen of the display unit to make the acoustic emission signal come from the defect F4Is maximum, recording and marking now from F4Time horizontal scale T of display screen of acoustic emission signal in display unit4；
3) Defect depth verification
Respectively moving the transmitting transducer and the receiving transducer to the defect F in the thickness calibration test block1And F2Respectively observing the acoustic emission signals displayed on the screen of the display unit to make the acoustic emission signals come from the defect F1And F2Is maximum, respectively recorded and marked at that time from the defect F1And F2Time horizontal scale T of display screen of acoustic emission signal in display unit1And T2Changing T to T1And T ═ T2Respectively substituting the formula (1) to calculate to obtain the defect F1Depth h of1And defect F2Depth h of2Wherein, in the step (A),
defect F1Depth h of1＝h(t＝T1) And defect F2Depth h of2＝h(t＝T2)，
Figure BDA0001900844740000031
Where t is the time level scale corresponding to the acoustic emission signal from the defect, corresponding to the time displayed and recorded in the display unit,
when h is generated1And h2Satisfying formula (2), the defect depth check meets the requirement, otherwise, the transmitting transducer and the receiving transducer are moved again to the defect F in the thickness calibration test block1And F2Top, from defect F displayed by display unit screen1And F2Respectively calculating the defects F according to the formula (1)1Depth h of1And defect F2Depth h of2Until the requirement of formula (2) is satisfied.
hi∈(H1-Δh,H1+Δh) (2)
Here, i is 1,2, and Δ h is a depth positioning deviation of the set defect in the thickness direction, and is determined by the structure and process of the composite material to be detected and the detection requirement.
4) Determining depth of detected defects
And moving the transmitting transducer and the receiving transducer to the position above the detected defect of the detected composite material structure to maximize the acoustic emission signal from the detected defect, acquiring a time horizontal scale t corresponding to the maximum acoustic emission signal on a display unit screen, and determining the detected defect depth h of the detected composite material structure according to the formula (1).
According to the method for determining the defect depth detected by ultrasonic-acoustic emission of the composite material, time horizontal scales on a display unit are manually read or automatically read.
The method for determining the depth of the detected defect of the composite material by ultrasonic-acoustic emission selects delta h between 0.12 and 0.60mm for the laminated structure of the composite material, and is used for meeting the requirements of different detected composite material structures on the depth positioning of the detected defect.
The method for determining the defect depth of the composite material detected by ultrasonic-acoustic emission is used for calibrating the defect depth H in a test block by the thickness of a laminated structure of the composite material1In that
Figure BDA0001900844740000032
And selecting the defect distance and the depth distance of the surface of the thickness calibration test block to be not less than 2 paving layers, wherein N is the paving layer number of the composite material structure.
According to the method for determining the defect depth of the composite material detected by ultrasonic-acoustic emission, the size of the defect in the thickness calibration test block is selected according to the detection requirement of the structure of the detected composite material and is selected from 3mm-20mm, and the shape of the defect is circular or rectangular.
The method for determining the defect depth of the composite material detected by ultrasonic-acoustic emission comprises the steps of selecting a separate ultrasonic-acoustic emission transducer and an integrated ultrasonic-acoustic emission transducer for a transmitting transducer and a receiving transducer, and selecting a contact or non-contact coupling mode.
The method for determining the depth of the detected defect of the ultrasonic-acoustic emission of the composite material is suitable for determining the depth of the detected defect in other ultrasonic methods for detecting the defect based on the acoustic wave propagation behavior.
The invention has the advantages and beneficial effects that,
1) the method has the advantages and beneficial effects that the time domain relation between the propagation behavior of the sound wave and the defects in the detected material or structure is utilized, and the improved time domain pulse characteristic of the ultrasonic-acoustic emission signal is adopted, so that the longitudinal resolution of the ultrasonic-acoustic emission is improved, and the depth of the detected defects can be more favorably and accurately determined;
2) by utilizing the method, the depth of the detected defect can be accurately determined without additional sound velocity measurement, the measurement deviation caused by the sound velocity measurement is overcome, the depth of the detected defect is further accurately determined, the depth of the ultrasonic-acoustic emission detected defect is accurately positioned, and the accuracy of determining the depth of the detected defect is obviously improved;
3) the defect depth checking method based on the thickness reference test block is easy to implement, very quick, easy to operate and master and has better engineering detection application applicability;
4) the method for verifying the defect depth based on the thickness reference test block is more beneficial to the quantity value transmission of the determined detected defect depth data and the quality control of the detection result, thereby being more beneficial to the popularization and application of the ultrasonic-acoustic emission method and playing a role in engineering.
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FIG. 1 is a schematic diagram of the basic structure and principle of the detection system of the present invention
FIG. 2 is a schematic diagram of a thickness reference block and defect distribution in the present invention
Detailed Description
The detection system for realizing the method mainly comprises a transmitting transducer 1, an ultrasonic transmitting unit 2, a receiving transducer 3, an acoustic emission receiving unit 4, a signal processing unit 5, a scanning unit 6 and a display unit 7, and is shown in figure 1, wherein:
the transmitting transducer 1 generates an excitation ultrasonic wave P1This exciting ultrasonic wave P1The acoustic emission stress wave is formed inside the detected composite material structure 8 by propagating to the detected composite material structure 8 through the coupling medium,
the receiving transducer 3 receives the transmitted acoustic wave E from the internal defect 8A of the composite structure 8 being inspected1，
The ultrasonic transmitting unit 2 generates an ultrasonic excitation signal, and the excitation transmitting transducer 1 generates an excitation ultrasonic wave P1，
The acoustic emission receiving unit 4 pre-processes the acoustic emission signals from the receiving transducer 3,
the signal processing unit 5 carries out digital processing on the acoustic emission signal of the receiving transducer 3 which is preprocessed by the acoustic emission receiving unit 4, and is used for ultrasonic-acoustic emission defect judgment, quantitative positioning analysis and detection result imaging,
the scanning unit 6 is used for controlling the transmitting transducer 1 and the receiving transducer 3 to scan the detected composite material structure 8, the display unit 7 is used for reconstructing the acoustic emission signal and the position signal of each scanning detection position to form an acoustic emission display signal and/or an image signal, and displaying, recording, storing and analyzing the ultrasonic-acoustic emission detection result,
1) preparation of thickness calibration test block
Preparing a thickness calibration test block with the thickness of H by adopting a composite material with the same forming process and material as the detected composite material, wherein the thickness calibration test block is in the shape of an equal-thickness flat plate and is not arranged in the thickness calibration test blockThe same depth position is prefabricated with 4 defects F with the same size1、F2、F3、F4The size of which is selected according to the inspection requirements of the composite structure 8 to be inspected, defect F1、F2、F3、F4The central points are separated from each other by L in the plane direction of the thickness calibration test block1Defect F1、F2、F3、F4The minimum distance from the center point of the thickness calibration test block to the edge near the edge of the thickness calibration test block is not less than L1See, for example, fig. 2, wherein,
defect F1、F2The depths from the surface of the thickness calibration test block are all H1As shown in reference to figure 2, in this embodiment,
defect F3And F4The depth distance H in the thickness direction of the thickness calibration test block1Wherein the defect F3And defect F1、F2The depth distance H in the thickness direction of the thickness calibration test block1Defect F4The depth from the surface of the thickness calibration test block is H1See, fig. 2;
thickness H of thickness calibration test block is 3H1；
2) Acquisition of thickness reference signal
Moving the transmitting transducer 1 and the receiving transducer 3 to the defect F in the thickness calibration test block3Moving the position of the acoustic emission signal to observe the acoustic emission signal displayed on the screen of the display unit 7 so that the acoustic emission signal comes from F3Is maximum, the recording and marking now coming from the defect F3Time horizontal scale T of the display screen of the acoustic emission signal in the display unit 73And records and marks the time measurement recording start point T in the display unit 7 at that time0；
Then, the transmitting transducer 1 and the receiving transducer 3 are moved to the defect F in the thickness calibration test block4Moving its position, observing the acoustic emission signal displayed on the screen of the display unit 7, so that the acoustic emission signal comes from the defect F4Is maximum, recording and marking now from F4Time horizontal scale T of the display screen of the acoustic emission signal in the display unit 74；
3) Defect depth verification
Respectively moving the transmitting transducer 1 and the receiving transducer 3 to the defect F in the thickness calibration test block1And F2Respectively observing the acoustic emission signals displayed on the screen of the display unit 7 so that the acoustic emission signals come from the defect F1And F2Is maximum, respectively recorded and marked at that time from the defect F1And F2Time horizontal scale T of the display screen of the acoustic emission signal in the display unit 71And T2Changing T to T1And T ═ T2Respectively substituting the formula (1) to calculate to obtain the defect F1Depth h of1And defect F2Depth h of2Wherein, in the step (A),
defect F1Depth h of1＝h(t＝T1) And defect F2Depth h of2＝h(t＝T2)，
Figure BDA0001900844740000051
Where t is the time level scale corresponding to the acoustic emission signal from the defect, corresponding to the time displayed and recorded in the display unit 7,
when h is generated1And h2Satisfying formula (2), the defect depth check meets the requirement, otherwise, the transmitting transducer 1 and the receiving transducer 3 are moved again to the defect F in the thickness calibration test block1And F2Upper, from defect F, displayed on screen by display unit 71And F2Respectively calculating the defects F according to the formula (1)1Depth h of1And defect F2Depth h of2Until the requirement of formula (2) is satisfied.
hi∈(H1-Δh,H1+Δh) (2)
Here, i is 1,2, and Δ h is a depth positioning deviation of the set defect in the thickness direction, and is determined by the structure and process of the composite material to be detected and the detection requirement.
4) Determining depth of detected defects
And moving the transmitting transducer 1 and the receiving transducer 3 to the position above the detected defect of the detected composite material structure 8 to maximize the acoustic emission signal from the detected defect, acquiring a time horizontal scale t corresponding to the maximum acoustic emission signal on a screen of the display unit 7, and determining the depth h of the detected defect of the detected composite material structure 8 according to the formula (1).
The time level scale on the display unit 7 is either manually read or automatically read.
For the composite laminated structure, the delta h is selected between 0.12 mm and 0.60mm, and is used for the requirements of different detected composite structures on the depth positioning of the detected defects.
For composite laminated structures, the depth of defect H in the thickness calibration test block1In that
Figure BDA0001900844740000061
And selecting the defect distance and the depth distance of the surface of the thickness calibration test block to be not less than 2 paving layers, wherein N is the paving layer number of the composite material structure.
The size of the defect in the thickness calibration test block is selected according to the detection requirement of the detected composite material structure 8 and is selected from 3mm-20mm, and the shape of the defect is circular or rectangular.
The transmitting transducer 1 and the receiving transducer 3 select a separating ultrasonic-acoustic emission transducer and an integrated ultrasonic-acoustic emission transducer, and select a contact or non-contact coupling mode.
The method is suitable for determining the depth of the detected defect in other ultrasonic methods for detecting the defect based on the propagation behavior of the sound wave.
Examples
The method for determining the defect depth of the composite material by ultrasonic-acoustic emission selects a high-resolution A-U ultrasonic-acoustic emission transducer produced by Zhonghong composite material company Limited, utilizes MUT-1 and CUS-21J produced by Zhonghong composite material company Limited as ultrasonic-acoustic emission detector units, prepares two thickness reference test blocks and a defect F by a carbon fiber composite material laminated structure respectively1、F2、F3、F4The diameters of the two parts are respectively 3mm and 9mmThe product has the same specification as that of the product,
h3 mm, corresponding to a number of plies of 24, the nominal thickness of the individual plies being about 0.125mm, H1The thickness of 6 layers is equal to the thickness of the layer,
h20 mm, corresponding to a respective number of plies of 160, and a nominal thickness of the individual plies of about 0.125mm, H1The thickness of 40 layers of the ply is equal to the thickness of the ply,
according to the defect detection verification method and the steps, the carbon fiber composite material structures of 5mm, 10mm, 40mm and 50mm are subjected to series of actual detection application, the detected defects are deeply determined, and the actual detection application effect shows that the depth of the detected defects can be very conveniently and quickly determined.

Claims (7)

1. A method for determining the defect depth of composite material ultrasonic-acoustic emission detection mainly comprises a transmitting transducer (1), an ultrasonic transmitting unit (2), a receiving transducer (3), an acoustic emission receiving unit (4), a signal processing unit (5), a scanning unit (6) and a display unit (7), wherein:
the transmitting transducer (1) generates an excitation ultrasonic wave (P)1) This excites the ultrasonic wave (P)1) Propagating into the detected composite material structure (8) through the coupling medium, forming acoustic emission stress waves inside the detected composite material structure (8),
the receiving transducer (3) receives a transmitted acoustic wave (E) from an internal defect (8A) of the composite structure (8) being inspected1)，
The ultrasonic transmitting unit (2) generates an ultrasonic excitation signal, and the excitation transmitting transducer (1) generates an excitation ultrasonic wave (P)1)，
The acoustic emission receiving unit (4) preprocesses the acoustic emission signals from the receiving transducer (3),
the signal processing unit (5) carries out digital processing on the acoustic emission signal of the receiving transducer (3) which is preprocessed by the acoustic emission receiving unit (4) and is used for ultrasonic-acoustic emission defect judgment, quantitative positioning analysis and detection result imaging,
the scanning unit (6) is used for controlling the transmitting transducer (1) and the receiving transducer (3) to scan the detected composite material structure (8), the display unit (7) is used for reconstructing the acoustic emission signal and the position signal of each scanning detection position to form an acoustic emission display signal and an image signal, and displaying, recording, storing and analyzing the ultrasonic-acoustic emission detection result,
1) preparation of thickness calibration test block
Preparing a thickness calibration test block with the thickness of H by adopting a composite material with the same material and forming process as the detected composite material, wherein the thickness calibration test block is in the shape of an equal-thickness flat plate, and 4 defects F with the same size are prefabricated at different depth positions in the thickness calibration test block1、F2、F3、F4The size of which is selected according to the inspection requirements of the composite structure (8) to be inspected, a defect F1、F2、F3、F4The central points are separated from each other by L in the plane direction of the thickness calibration test block1Defect F1、F2、F3、F4The minimum distance from the center point of the thickness calibration test block to the edge near the edge of the thickness calibration test block is not less than L1Wherein, in the step (A),
defect F1、F2The depths from the surface of the thickness calibration test block are all H1，
Defect F3And F4The depth distance H in the thickness direction of the thickness calibration test block1Wherein the defect F3And defect F1、F2The depth distance H in the thickness direction of the thickness calibration test block1Defect F4The depth from the surface of the thickness calibration test block is H1；
Thickness H of thickness calibration test block is 3H1；
2) Acquisition of thickness reference signal
Moving the transmitting transducer (1) and the receiving transducer (3) to the defect F in the thickness calibration test block3Moving the position of the acoustic emission signal to observe the acoustic emission signal displayed on the screen of the display unit (7) from the direction F3Is maximum, the recording and marking now coming from the defect F3Time horizontal scale T of the display screen of the acoustic emission signal in the display unit (7)3And recording and markingThe time measurement in the display unit (7) at this time records the starting point T0；
Then, the transmitting transducer (1) and the receiving transducer (3) are moved to the defect F in the thickness calibration test block4Moving the position of the acoustic emission device, and observing the acoustic emission signal displayed on the screen of the display unit (7) to make the acoustic emission signal come from the defect F4Is maximum, recording and marking now from F4Time horizontal scale T of the display screen of the acoustic emission signal in the display unit (7)4；
3) Defect depth verification
Respectively moving the transmitting transducer (1) and the receiving transducer (3) to the defect F in the thickness calibration test block1And F2Respectively observing the acoustic emission signals displayed on the screen of the display unit (7) to make the acoustic emission signals come from the defect F1And F2Is maximum, respectively recorded and marked at that time from the defect F1And F2Time horizontal scale T of the display screen of the acoustic emission signal in the display unit (7)1And T2Changing T to T1And T ═ T2Respectively substituting the formula (1) to calculate to obtain the defect F1Depth h of1And defect F2Depth h of2Wherein, in the step (A),
defect F1Depth h of1＝h(t＝T1) And defect F2Depth h of2＝h(t＝T2)，
Figure FDA0002914993420000021
Where t is the time level scale corresponding to the acoustic emission signal from the defect, corresponding to the time displayed and recorded in the display unit (7),
when h is generated1And h2Satisfying formula (2), the defect depth check meets the requirement, otherwise, the transmitting transducer (1) and the receiving transducer (3) are moved again to the defect F in the thickness calibration test block1And F2Upper, from defect F displayed on screen by display unit (7)1And F2Is divided again according to the formula (1)Separately calculating the defect F1Depth h of1And defect F2Depth h of2Until the requirement of (2) is met;
hi∈(H1-Δh,H1+Δh) (2)
where i is 1,2, Δ h is the depth positioning deviation of the set defect in the thickness direction, and is determined by the structure and process of the composite material to be detected and the detection requirement;
4) determining depth of detected defects
And moving the transmitting transducer (1) and the receiving transducer (3) to the position above the detected defect of the detected composite material structure (8) to maximize the acoustic emission signal from the detected defect, acquiring a time horizontal scale t corresponding to the maximum acoustic emission signal on a screen of the display unit (7), and determining the detected defect depth h of the detected composite material structure (8) according to the formula (1).
2. A method for determining the depth of a defect detected by ultrasonic-acoustic emission of composite materials according to claim 1, characterized in that the time-level scale on the display unit (7) is manually or automatically read.
3. A method as claimed in claim 1, wherein Δ h is selected between 0.12 and 0.60mm for composite laminate structures, for locating the depth of a detected defect for different composite structures to be detected.
4. The method of claim 1, wherein the depth of the defect H in the test block is calibrated by thickness for a composite laminate structure1In that
Figure FDA0002914993420000031
And selecting the defect distance and the depth distance of the surface of the thickness calibration test block to be not less than 2 paving layers, wherein N is the paving layer number of the composite material structure.
5. A method for determining the depth of a defect in composite material detected by ultrasonic-acoustic emission according to claim 1, wherein the size of the defect in the thickness calibration block is selected according to the detection requirements of the structure (8) of the composite material to be detected, and is selected between 3mm and 20mm, and the shape of the defect is circular or rectangular.
6. The method for determining the defect depth of composite material ultrasonic-acoustic emission detection according to claim 1, wherein two separate ultrasonic-acoustic emission transducers are used to realize the functions of the transmitting transducer (1) and the receiving transducer (3), respectively, or an integrated ultrasonic-acoustic emission transducer is used to realize the functions of the transmitting transducer (1) and the receiving transducer (3) simultaneously, and the contact or non-contact coupling mode is selected.
7. The method of claim 1, wherein the depth of the detected defect is determined by an ultrasonic-acoustic emission method suitable for defect detection based on acoustic propagation behavior.
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