A terahertz non-destructive testing device capable of modulating acoustic excitation

Abstract

The application discloses a kind of modulated acoustic excitation's terahertz nondestructive testing device, by terahertz time-domain spectroscopy module, modulated acoustic excitation generation module, two-dimensional moving platform and computer composition;Terahertz time-domain spectroscopy module is by terahertz host computer, sensor and terahertz probe composition, for generating and detecting terahertz signal;Two-dimensional moving platform carries terahertz probe, and the full coverage two-dimensional scanning of sample to be measured is carried out;Modulated acoustic excitation generation module is used to adjust acoustic excitation field frequency, so that the defect region in the sample to be measured produces resonance phenomenon;Computer is used to control two-dimensional moving platform, while storing, displaying, processing and analyzing the terahertz time-domain spectroscopy data imported by sensor.The application is aimed at composite material, uses modulated acoustic excitation device as excitation source to stimulate sample, and uses terahertz nondestructive testing imaging technology to detect the vibration signal under the resonance frequency corresponding to defect, realizes the detection of small defect inside composite material structure.

Description

Technical Field

[0001] This invention belongs to the field of terahertz nondestructive testing, specifically relating to a modulated acoustic excitation terahertz nondestructive testing device, which is particularly suitable for the detection and identification of minute defects inside composite materials. Background Technology

[0002] In the existing field of composite material defect detection based on acoustic excitation, most methods use electronic speckle and laser speckle techniques to capture the vibration generated by the material after acoustic excitation. However, this method is limited by the physical characteristics of laser speckle and electronic speckle [Yu Changsong. Research on vibration detection based on electronic speckle shear interference technology [J]. Journal of Changchun University of Technology (Natural Science Edition), 2011, 34(03):10-12+18]. It cannot penetrate the composite material and directly detect the resonance at the defect location. It can only use the time averaging method or stroboscopic method to measure the light intensity change of speckle interference fringes formed by surface displacement and deformation caused by internal defects in the material. As a result, the edge of the defect identified in the end is relatively blurry, and it is impossible to achieve more accurate identification based on the resonance frequency at the defect location of the composite material.

[0003] Terahertz waves, situated between the far-infrared and submillimeter waves, lie in a frequency band between macroscopic electronics and microscopic optoelectronics. They occupy a unique position in the electromagnetic spectrum, characterized by low radiated energy, high signal-to-noise ratio, and wide bandwidth. This makes them applicable to the detection and analysis of most non-metallic materials, and they are currently widely used in the detection of aerospace composite materials, industrial coating materials, ceramic matrix composites, and many other non-metallic materials. Terahertz waves can measure detailed vibration details at various locations during an object's vibration process, including the central vibration frequency, second harmonic, and frequency distortion. The scattering effect of terahertz waves at the edges of composite material defects affects the intensity distribution of terahertz waves. By analyzing terahertz echoes at different depths, the energy field distribution inside the material can be obtained, thus revealing the shape, size, and spatial location of defects such as debonding, weak bonding, and delamination. Compared to traditional terahertz detection, combining terahertz waves with acoustic excitation allows for comparison of terahertz time-domain spectral data before and after acoustic excitation, highlighting data from defect areas, particularly suitable for minute defects. These advantages make terahertz waves a promising area for defect detection and vibration sensing. Summary of the Invention

[0004] To address the problem of defect detection in composite material samples, this invention provides a modulated acoustic excitation terahertz nondestructive testing device. For composite materials, a modulated acoustic excitation device is used as the excitation source. Based on the continuously changing acoustic excitation source, the sample is excited, and terahertz nondestructive testing imaging technology is used to detect the vibration signal at the resonant frequency corresponding to the defects in the composite material, thereby realizing terahertz nondestructive testing of minute defects in the internal structure of composite materials.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A modulated acoustically excited terahertz nondestructive testing device comprises a terahertz time-domain spectroscopy module, a modulated acoustic excitation generation module, a two-dimensional moving platform, and a computer. The terahertz time-domain spectroscopy module consists of a terahertz host, a sensor, and a terahertz probe, and is used to generate and detect terahertz signals. The two-dimensional moving platform carries the terahertz probe and performs a full-coverage two-dimensional scan of the sample under test. The modulated acoustic excitation generation module is used to adjust the frequency of the acoustic excitation field to induce resonance in the defective region of the sample under test. The computer is used to control the two-dimensional moving platform and simultaneously store, display, process, and analyze the terahertz time-domain spectral data transmitted from the sensor.

[0007] Furthermore, the terahertz host consists of a laser source, a time delay line, a beam splitter, and a reflector, used to generate pump light and probe light; the terahertz probe consists of a photoconductive detection antenna, a photoconductive transmitting antenna, and a terahertz beam splitter, which illuminates the sample surface with terahertz light and collects the sample terahertz echo signal, transmitting it to the sensor through the photoconductive detection antenna; the sensor acquires the raw terahertz spectrum data and transmits the raw data to a computer.

[0008] Preferably, the laser source is a femtosecond laser.

[0009] Preferably, the femtosecond laser pulse emitted by the femtosecond laser is split into pump light and probe light by a beam splitter. The pump light is incident on the photoconductive transmitting antenna via a signal delay line and the beam splitter. Under the action of an applied bias voltage, the photoconductive transmitting antenna generates terahertz time-domain pulses. The probe light is incident on the photoconductive detecting antenna via a reflector. A terahertz signal is generated in the photoconductive transmitting antenna, which then illuminates the sample under test via a terahertz beam splitter. The terahertz echo from the sample is transmitted to the photoconductive detecting antenna via the terahertz beam splitter, and then to the sensor. The sensor receives the raw terahertz time-domain spectrum data from the photoconductive detecting antenna, converts it into a voltage signal, amplifies it, and then converts the amplified voltage signal into a digital signal for input into a computer.

[0010] Furthermore, the modulated acoustic excitation generation module consists of a signal generator, a power amplifier, and a speaker; the signal generator is used to generate waveform signals of arbitrary frequency (which can be sine waves, triangle waves, or square waves, etc.); the power amplifier is used to receive the frequency signal from the signal generator, amplify the power of the signal, and output it to the speaker; the speaker is used to receive the voltage signal from the power amplifier and generate an acoustic excitation field.

[0011] Furthermore, the expression for the sine wave generated by the signal generator is:

[0012] F(t) = Asin(2πft + θ)

[0013] In the formula, A is the amplitude of the sinusoidal signal, f is the frequency of the sinusoidal signal, and θ is the initial phase;

[0014] The sinusoidal signal F(t) is input into the power amplifier, where β is the power amplifier gain. After amplification, the signal becomes G(t):

[0015] G(t)=βAsin(2πft+θ)

[0016] The amplified sine wave signal is transmitted to the loudspeaker, which is placed on both sides of the sample as a sound source to make the generated sound excitation field more uniform.

[0017] Preferably, the two-dimensional moving platform includes a motor and a guide rail. The initial position, moving speed, scanning step size and scanning range of the guide rail are set by a computer. The motor drives the guide rail to move, realizing movement in two-dimensional space. The terahertz probe is fixed on the guide rail. The sample to be tested is scanned point by point in two dimensions. The terahertz echo signal of the sample to be tested is collected and transmitted to the terahertz probe, and the terahertz probe transmits the signal to the sensor.

[0018] The present invention has the following beneficial effects:

[0019] This invention provides a modulated acoustically excited terahertz nondestructive testing (NDT) device, applicable to the field of terahertz NDT. It analyzes defective samples using time-of-flight characteristics to determine the defect resonant frequency, and performs correlation analysis by applying acoustic excitation to the sample at this frequency. Compared to terahertz testing of composite material samples under normal conditions, applying acoustic excitation to the sample causes minute out-of-plane displacements in the material defect area. Terahertz waves can penetrate the material surface to detect subtle mechanical vibrations within the object, and the stronger the vibration, the higher the energy field generated. By analyzing the terahertz echoes, the shape, size, and spatial location of defects such as debonding, weak bonding, and delamination within the object can be determined, improving the ability of terahertz NDT to identify minute defects. Attached Figure Description

[0020] Figure 1 This is a diagram of a modulated acoustically excited terahertz nondestructive testing device according to an embodiment of the present invention;

[0021] In the picture:

[0022] 1-Femtosecond laser; 2-Beam splitter 1; 3-Beam splitter 2; 4-Delay line; 5-Reflector; 6-Photoconductive detection antenna; 7-Photoconductive transmitting antenna; 8-Terahertz beam splitter; 9-Sensor; 10-Sample under test; 11-Metal plate; 12-Two-dimensional moving platform; 13-Computer; 14-Signal generator; 15-Power amplifier; 16-Speaker. Detailed Implementation

[0023] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments:

[0024] A modulated acoustically excited terahertz nondestructive testing device comprises a terahertz time-domain spectroscopy module, a modulated acoustic excitation generation module, a two-dimensional moving platform, and a computer. The terahertz time-domain spectroscopy module consists of a terahertz host, a sensor, and a terahertz probe, and is used to generate and detect terahertz signals. The two-dimensional moving platform carries the terahertz probe and performs a full-coverage two-dimensional scan of the sample under test. The modulated acoustic excitation generation module is used to adjust the frequency of the acoustic excitation field to induce resonance in the defective region of the sample under test. The computer is used to control the two-dimensional moving platform and simultaneously store, display, process, and analyze the terahertz time-domain spectral data transmitted from the sensor.

[0025] Furthermore, the terahertz host consists of a laser source, a time delay line, a beam splitter, and a reflector, used to generate pump light and probe light; the terahertz probe consists of a photoconductive detection antenna, a photoconductive transmitting antenna, and a terahertz beam splitter, which illuminates the sample surface with terahertz light and collects the sample terahertz echo signal, transmitting it to the sensor through the photoconductive detection antenna; the sensor acquires the raw terahertz spectrum data and transmits the raw data to a computer.

[0026] Preferably, the laser source is a femtosecond laser.

[0027] Preferably, the femtosecond laser pulse emitted by the femtosecond laser is split into pump light and probe light by a beam splitter. The pump light is incident on the photoconductive transmitting antenna via a signal delay line and the beam splitter. Under the action of an applied bias voltage, the photoconductive transmitting antenna generates terahertz time-domain pulses. The probe light is incident on the photoconductive detecting antenna via a reflector. A terahertz signal is generated in the photoconductive transmitting antenna, which then illuminates the sample under test via a terahertz beam splitter. The terahertz echo from the sample is transmitted to the photoconductive detecting antenna via the terahertz beam splitter, and then to the sensor. The sensor receives the raw terahertz time-domain spectrum data from the photoconductive detecting antenna, converts it into a voltage signal, amplifies it, and then converts the amplified voltage signal into a digital signal for input into a computer.

[0028] Furthermore, the modulated acoustic excitation generation module consists of a signal generator, a power amplifier, and a speaker; the signal generator is used to generate waveform signals of arbitrary frequency (which can be sine waves, triangle waves, or square waves, etc.); the power amplifier is used to receive the frequency signal from the signal generator, amplify the power of the signal, and output it to the speaker; the speaker is used to receive the voltage signal from the power amplifier and generate an acoustic excitation field.

[0029] Furthermore, the expression for the sine wave generated by the signal generator is:

[0030] F(t) = Asin(2πft + θ)

[0031] In the formula, A is the amplitude of the sinusoidal signal, f is the frequency of the sinusoidal signal, and θ is the initial phase;

[0032] The sinusoidal signal F(t) is input into the power amplifier, where β is the power amplifier gain. After amplification, the signal becomes G(t):

[0033] G(t)=βAsin(2πft+θ)

[0034] The amplified sine wave signal is transmitted to the loudspeaker, which is placed on both sides of the sample as a sound source to make the generated sound excitation field more uniform.

[0035] Preferably, the two-dimensional moving platform includes a motor and a guide rail. The initial position, moving speed, scanning step size and scanning range of the guide rail are set by a computer. The motor drives the guide rail to move, realizing movement in two-dimensional space. The terahertz probe is fixed on the guide rail. The sample to be tested is scanned point by point in two dimensions. The terahertz echo signal of the sample to be tested is collected and transmitted back to the terahertz probe. The terahertz probe then transmits the signal to the sensor.

[0036] Example

[0037] like Figure 1 As shown, this embodiment is a modulated acoustically excited terahertz nondestructive testing device, including: a femtosecond laser 1, a first beam splitter 2, a second beam splitter 3, a delay line 4, a reflector 5, a photoconductive detection antenna 6, a photoconductive transmitting antenna 7, a terahertz beam splitter 8, a sensor 9, a sample to be tested 10, a metal plate 11, a two-dimensional moving platform 12, a computer 13, a signal generator 14, a power amplifier 15, and a speaker 16.

[0038] The femtosecond laser 1, beam splitter 2, beam splitter 3, delay line 4, and reflector 5 constitute the terahertz host; the photoconductive detection antenna 6, photoconductive transmitting antenna 7, and terahertz beam splitter 8 constitute the terahertz probe, which is mounted on the two-dimensional moving platform 12 to form a two-dimensional scanning module; the signal generator 14, power amplifier 15, and speaker 16 constitute the sound excitation generation module.

[0039] The femtosecond laser pulse emitted from femtosecond laser 1 is split into pump light and probe light by beam splitter 2. The pump light is incident on photoconductive transmitting antenna 7 via signal delay line 4 and beam splitter 3. Under the action of an applied bias voltage, photoconductive transmitting antenna 7 generates terahertz time-domain pulses. The probe light is incident on photoconductive detecting antenna 6 via mirror 5. A terahertz signal is generated in the photoconductive antenna 7, and then irradiates the sample 10 under test through the terahertz beam splitter 8. The terahertz echo of the sample 10 under test is transmitted to the photoconductive detection antenna 6 through the terahertz beam splitter 8, and then to the sensor 9. The sensor 9 receives the raw terahertz time-domain spectrum data of the photoconductive detection antenna 6, converts it into a voltage signal and amplifies it, and then converts the amplified voltage signal into a digital signal and sends it to the computer 13. The signal generator 14 generates a waveform signal of arbitrary frequency (which can be a sine wave, a triangular wave, or a square wave, etc.). The power amplifier 15 receives the frequency signal from the signal generator, amplifies the power of the signal, and outputs it to the speaker 16. The speaker 16 receives the voltage signal from the power amplifier 15 and generates a sound wave field.

[0040] Since the terahertz probe can only acquire terahertz time-domain spectral data from one point at a time, the terahertz probe is mounted on a two-dimensional moving platform 12, and the terahertz probe is moved by a guide rail to achieve two-dimensional point-by-point scanning and complete the acquisition of terahertz signals.

[0041] The expression for the sine wave generated by the signal generator 14 is:

[0042] F(t) = Asin(2πft + θ) (1)

[0043] Where A is the amplitude of the sinusoidal signal, f is the frequency of the sinusoidal signal, and θ is the initial phase.

[0044] The sinusoidal signal F(t) is fed into power amplifier 15, where β is the power amplifier gain. After amplification, the signal becomes G(t):

[0045] G(t)=βAsin(2πft+θ) (2)

[0046] The amplified sine wave signal is transmitted to the loudspeaker 16, which is placed on both sides of the sample as a sound source to make the generated sound excitation field more uniform.

[0047] The two-dimensional moving platform 12 is composed of electronic components such as motors and guide rails. The initial position, moving speed, scanning step size and scanning range of the guide rail are set by the computer 13. The motor drives the guide rail to move, realizing movement in two-dimensional space. At the same time, a terahertz probe can be fixedly installed on the guide rail to perform two-dimensional point-by-point scanning of the sample 10 to be tested, collect the terahertz echo signal of the sample 10 to be tested and transmit it back to the terahertz probe, and the terahertz probe transmits the signal to the sensor 9.

[0048] The computer 13 can control the initial position, moving speed, scanning step size and scanning range of the two-dimensional moving platform 12 through the host computer software, detect the sample 10 to be tested, acquire the terahertz time-domain spectral data of the sensor 9, and process, analyze, display and store the data.

Claims

1. A modulated acoustically excited terahertz nondestructive testing device, characterized in that, The system comprises a terahertz time-domain spectroscopy module, a modulated acoustic excitation generation module, a two-dimensional moving platform, and a computer. The terahertz time-domain spectroscopy module consists of a terahertz host, a sensor, and a terahertz probe, used to generate and detect terahertz signals. The two-dimensional moving platform carries the terahertz probe and performs a full-coverage two-dimensional scan of the sample under test. The modulated acoustic excitation generation module adjusts the frequency of the acoustic excitation field to induce resonance in defective areas of the sample. The computer controls the two-dimensional moving platform and simultaneously stores, displays, processes, and analyzes the terahertz time-domain spectral data transmitted from the sensor. The modulated acoustic excitation generation module consists of a signal generator, a power amplifier, and a speaker. The signal generator generates waveform signals of arbitrary frequencies. The power amplifier receives the frequency signals from the signal generator, amplifies the signal power, and outputs it to the speaker. The speaker receives the voltage signals from the power amplifier and generates an acoustic excitation field.

2. The modulated acoustically excited terahertz nondestructive testing device as described in claim 1, characterized in that, The terahertz host consists of a laser source, a time delay line, a beam splitter, and a reflector, used to generate pump light and probe light; the terahertz probe consists of a photoconductive detection antenna, a photoconductive transmitting antenna, and a terahertz beam splitter, which illuminates the sample surface with terahertz light and collects the sample terahertz echo signal, transmitting it to the sensor through the photoconductive detection antenna; the sensor acquires the raw terahertz spectrum data and transmits the raw data to a computer.

3. The modulated acoustically excited terahertz nondestructive testing device as described in claim 2, characterized in that, The laser source is a femtosecond laser.

4. The modulated acoustically excited terahertz nondestructive testing device as described in claim 2, characterized in that, The femtosecond laser pulse emitted by the laser source is split into pump light and probe light by a beam splitter. The pump light is incident on the photoconductive transmitting antenna via a signal delay line and the beam splitter. Under the action of an applied bias voltage, the photoconductive transmitting antenna generates terahertz time-domain pulses. The probe light is incident on the photoconductive detecting antenna via a reflector. A terahertz signal is generated in the photoconductive transmitting antenna, which is then irradiated onto the sample under test by a terahertz beam splitter. The terahertz echo from the sample under test is transmitted to the photoconductive detecting antenna by the terahertz beam splitter, and then to the sensor. The sensor receives the raw terahertz time-domain spectrum data from the photoconductive detecting antenna, converts it into a voltage signal and amplifies it, and then converts the amplified voltage signal into a digital signal and sends it to the computer.

5. The modulated acoustically excited terahertz nondestructive testing device as described in claim 1, characterized in that, The expression for the sine wave generated by the signal generator is: F(t) = Asin(2πft + θ) In the formula, A is the amplitude of the sinusoidal signal, f is the frequency of the sinusoidal signal, and θ is the initial phase; The sinusoidal signal F(t) is input into the power amplifier, where β is the power amplifier gain. After amplification, the signal becomes G(t): G(t)=βAsin(2πft+θ) The amplified sine wave signal is transmitted to the loudspeaker, which is placed on both sides of the sample as a sound source.

6. The modulated acoustically excited terahertz nondestructive testing device as described in claim 1, characterized in that, The two-dimensional moving platform includes a motor and a guide rail. The initial position, moving speed, scanning step size and scanning range of the guide rail are set by a computer. The motor drives the guide rail to move, realizing movement in two-dimensional space. The terahertz probe is fixed on the guide rail. The sample to be tested is scanned point by point in two dimensions. The terahertz echo signal of the sample to be tested is collected and transmitted to the terahertz probe, and then the terahertz probe transmits the signal to the sensor.

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