CN102507739A - Ultrasonic guided wave defect imaging method for impact damages of carbon fiber composite material - Google Patents

Abstract

The invention relates to an ultrasonic guided wave defect imaging method for impact damage of carbon fiber composite materials. Based on the ellipse positioning method, an ellipse positioning imaging algorithm that comprehensively utilizes the time and amplitude full-wave information of the defect reflection echo signal is proposed. The algorithm uses the ultrasonic transducer array to obtain the reflection echo information of the defect on different paths, and applies the complex wavelet transform to accurately extract the arrival time and amplitude information of the signal. imaging. The CT algorithm directly adopts the amplitude of the original signal. Due to the influence of the sampling interval and the signal-to-noise ratio of the signal itself, the accuracy of the final imaging result is low. Therefore, this paper introduces an improved imaging algorithm based on the complex wavelet transform envelope. The algorithm only uses 6 transducers to realize the imaging of defects, and the application of complex wavelet transform improves the detection accuracy, and realizes the accurate quantitative detection of impact damage defects of composite boards.

Description

The supersonic guide-wave defective formation method of carbon fibre composite impact injury

One, technical field

The present invention relates to a kind of supersonic guide-wave defective formation method of carbon fibre composite impact injury.

Two, background technology

One of subject matter that influences at present the carbon fiber enhancement resin base composite material development is damage problem.Carbon fibre composite often is present in the structural member with plate hull shape formula; Be easy to receive loading perpendicular to the plate face; Because the congenital deficiency of compound substance interlayer intensity; So when receiving the loading of vertical panel face, be prone to the damage of various ways such as MATRIX CRACKING, interlayer layering and fibre breakage, make compound substance loss of weight usefulness be difficult to be not fully exerted.This paper adopts the supersonic guide-wave method that the hole defect in the composite plate is detected to the hole defect in the carbon fibre-epoxy resin composite plate commonly used in the aircraft industry.Continuous development along with the supersonic guide-wave technology; Guided wave detects main research work to be developed to quantitative test from qualitative analysis day by day; Through identification to defect type, geometric configuration and physical dimension; Realization is to the quantitative nondestructive evaluation of measurand, and judges the influence degree to measurand that exists of defective with this.Precise quantification to defective is the main target of supersonic guide-wave Non-Destructive Testing research.

When the defective with strong edge reflection effect is carried out ultrasound detection, have the obvious defects reflected signal and produce, time and amplitude characteristic that the defect reflection echo arrives comprise defective information.Therefore, can be through defect reflection echoed signal characteristic be analyzed, information such as the counter position of releasing the contained defective of test specimen, size and dimension.

Three, summary of the invention

The objective of the invention is: the supersonic guide-wave defective formation method that proposes a kind of carbon fibre composite impact injury.

Detection principle of the present invention is: signal is sent by stimulus sensor; After the defective edge reflection, arrive the travel-time of receiving sensor; In conjunction with Propagation of guided waves speed, calculate signal total propagation distance on the path, thereby it is oval to obtain the defective locations place.Owing to oval at any 1 o'clock to the distance of two focuses be constant, so defective one is positioned on stimulus sensor and residing two ellipses of position as focus of receiving sensor.Superpose after adopting two groups of above diverse locations to measure gained defective place elliptical path information, all oval common intersection are the position of defective.Because the defect reflection signal has the certain hour width; So the comprehensive utilization flaw echo amplitude and the all-wave information in travel-time; All points in the imaging region are superposeed after signal amplitude is given gray-scale value according to receiving; Make that the gray-scale value of defect area is bigger than non-defect area, can obtain the defective imaging behind the threshold filter.

It is characterized in that: the comprehensive utilization flaw echo amplitude and the all-wave information in travel-time; All points in the imaging region are superposeed after signal amplitude is given gray-scale value according to receiving; Make that the gray-scale value of defect area is bigger than non-defect area, can obtain the defective imaging behind the threshold filter.This algorithm only uses 6 transducers just can realize the imaging to defective, and uses multiple wavelet transformation and improved accuracy of detection, has realized that the accurate quantification of composite plate impact injury defective detects.

The invention has the advantages that: use less transducer array element number just can realize the imaging to defective, use time of arrival and amplitude information that multiple wavelet transformation accurately extracts signal, the input signal as imaging algorithm has improved accuracy of detection.

Four, description of drawings

The oval location of a pair of probe of Fig. 1 synoptic diagram

The oval positioning and imaging schematic diagram of Fig. 2

Fig. 3 transducer array CT detection system schematic diagram

Supersonic guide-wave propagation characteristic figure in the carbon fiber reinforced epoxy resin-based composite plate of Fig. 4

Fig. 5 transducer arrays imaging experiment typical case AB path receives signal

The CT arithmetic result of Fig. 6 AB path one-channel signal

All array element combination experiment signal stack result of Fig. 7

The defect image that obtains behind Fig. 8 threshold filter

Five, embodiment

Following specific embodiments of the invention is elaborated:

As shown in Figure 5, the position coordinates of establishing transmitting transducer A and receiving transducer B is respectively (x ₁, y ₁) and (x ₂, y ₂), the coordinate of defect center point F is (x ₀, y ₀), the path is then arranged With

The time T that two paths of signals arrives ₁And T ₂Be respectively:

T ₁＝L _AB/c _p (1)

T ₂＝L _AFB/c _p (2)

$L_{\mathrm{AB}}=\sqrt{{(x_1-x_2)}^2+{(y_1-y_2)}^2}---\left(3\right)$

$L_{\mathrm{AFB}}=\sqrt{{(x_1-x_0)}^2+{(y_1-y_0)}^2}+\sqrt{{(x_0-x_2)}^2+{(y_0-y_2)}^2}---\left(4\right)$

Wherein, c _pBe S0 pattern Propagation of guided waves speed.

T ₂Constantly signal is the reflected signal that contains defect information.Because the position of transducer A and B is known, so can remove T through time window ₁Constantly garbage signal, i.e. path

Signal.

(x y) to 2 of A, B apart from sum does any point X in the surveyed area

$L_{\mathrm{AXB}}=\sqrt{{(x_1-x)}^2+{(y_1-y)}^2}+\sqrt{{(x-x_2)}^2+{(y-y_2)}^2}---\left(5\right)$

As shown in Figure 6, imaging region any point X corresponding gray is taken as

G _i(x，y)＝W′(L _AXB/c _p)，(i＝1，2，...，N) (6)

Wherein, N is the sum of different transducer combinations, and W (t) is for removing the multiple wavelet transformation envelope envelope value behind the signal of path .

As shown in Figure 7, with all N organize result that different transducer combinations obtain superpose can obtain all data stacking images as a result G (x, y), (x y) can represent as follows G

$G(x,y)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{G}_i(x,y)---\left(7\right)$

As shown in Figure 8, to all data stacking images in the formula (7) as a result G (x, y) adopt threshold filter after, can obtain defect image.

Claims (4)

1. An ultrasonic guided wave defect imaging method for impact damage of carbon fiber composite materials. Based on the ellipse positioning method, an ellipse positioning imaging algorithm that comprehensively utilizes the time and amplitude full-wave information of the defect reflection echo signal is proposed. The algorithm uses the ultrasonic transducer array to obtain the reflection echo information of the defect on different paths, and applies the complex wavelet transform to accurately extract the arrival time and amplitude information of the signal. imaging. The tomography algorithm directly adopts the amplitude of the original signal. Due to the influence of the sampling interval and the signal-to-noise ratio of the signal itself, the accuracy of the final imaging result is low. Therefore, an improved imaging algorithm based on the complex wavelet transform envelope is introduced. The algorithm only uses 6 transducers to realize the imaging of defects, and the application of complex wavelet transform improves the detection accuracy, and realizes the accurate quantitative detection of impact damage defects of composite boards. 2. The ellipse method positioning imaging algorithm according to claim 1, characterized in that: the full-wave information of the defect echo amplitude and propagation time is comprehensively utilized, and all points in the imaging area are assigned gray values according to the received signal amplitude and then superimposed, The gray value of the defect area is larger than that of the non-defect area. 3. The ultrasonic guided wave transducer array technology according to claim 1, characterized in that: use an irregular ultrasonic transducer array, adopt a 1MHz low-frequency band narrow-band modulated sinusoidal signal, and apply a symmetrical mode and an antisymmetrical mode in the excitation area of the test piece Mode guided wave excitation conditions. 4. The method for extracting defect signals in carbon fiber reinforced epoxy resin-based composite panels according to claim 1, characterized in that: after applying the stationary wavelet adaptive filtering method to suppress the interference of other mode guided waves, complex wavelet transform is used to accurately extract signals The imaging of defects can be realized after obtaining the arrival time and amplitude information.

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