Non-contact high-voltage excitation air coupling ultrasonic detection system

Abstract

The invention relates to the technical field of ultrasonic detection, in particular to a non-contact high-voltage excitation air coupling ultrasonic detection system which comprises a waveform generator, an excitation high-voltage waveform amplifying circuit and an ultrasonic transducer. The transmitting end of the ultrasonic transducer is used for transmitting an echo signal to a detected target, and the receiving end is used for receiving the echo signal to realize ultrasonic detection; the excitation high-voltage waveform amplification circuit comprises a two-stage amplification circuit and a differential amplification circuit which are connected in series, the two-stage amplification circuit comprises a first amplifier and a second amplifier, the in-phase input end of the first amplifier is connected with a resistor R1 and a resistor R4 respectively, the inverted input end of the first amplifier is connected with a resistor R2 and a resistor R3 respectively, and the output end of the first amplifier is connected with the other ends of a resistor R5 and a resistor R4 respectively; the non-inverting input end of the second amplifier is connected with the other end of the resistor R5 and the resistor R6, the inverting input end of the second amplifier is grounded, and the output end of the second amplifier is connected with the other end of the resistor R6 and the resistor R7.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic testing technology, specifically to a non-contact high-voltage excitation air-coupled ultrasonic testing system. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Honeycomb sandwich composites have important applications in many fields due to their excellent impact resistance, superior specific strength, and good light transmission characteristics. However, due to the complex molding process and harsh operating conditions, these materials are prone to defects such as debonding, voids, and fiber breakage during manufacturing and use. These defects can lead to deterioration of the structural load-bearing capacity or even failure. To ensure structural reliability, ultrasonic non-destructive testing is one of the important methods for early detection and assessment of internal defects in honeycomb sandwich composites.

[0004] Air-coupled ultrasonic testing uses air as the coupling medium, eliminating the need for direct contact with the object being tested. This makes it particularly suitable for special applications such as high-temperature environments and in-situ testing. Currently, this technology is widely used for non-destructive testing of thin-walled composite honeycomb sandwich structures.

[0005] However, for thick-walled honeycomb sandwich composite structures, due to the thickness of the sandwich layer, ultrasonic waves attenuate significantly during propagation, making it difficult for energy to effectively penetrate the structure, resulting in a significant reduction in detection accuracy and reliability.

[0006] The reason for this is that conventional air-coupled ultrasonic systems have limitations in penetration capability, the excitation voltage is usually 400 V, and the signal energy is weak, which makes it difficult to meet the detection requirements of internal defects in thick-walled structures.

[0007] In addition, existing ultrasonic testing systems mostly use single-frequency continuous waveforms or narrow-band pulse signals for testing, which limits the flexibility of testing and makes it difficult to meet the defect detection requirements of thick-walled honeycomb sandwich composite structures. Summary of the Invention

[0008] To address the technical problems described in the background section, this invention provides a non-contact high-voltage excitation air-coupled ultrasonic testing system. The system can transmit excitation signals such as square wave pulses, sharp pulses, sinusoidal signals, and custom waveforms. By optimizing the bandwidth of the excitation waveform and utilizing linear frequency modulation and pulse compression processing, the signal-to-noise ratio of the received signal is improved, thereby enhancing the sensitivity of defect detection. Increasing the excitation voltage to 800 V enhances the initial acoustic energy, significantly improving the penetration capability and detection accuracy for internal defects in thick-walled honeycomb sandwich composite materials.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a non-contact high-voltage excitation air-coupled ultrasonic testing system, including a waveform generator, an excitation high-voltage waveform amplification circuit, and an ultrasonic transducer. The waveform generator generates an arbitrary waveform, which is amplified by the excitation high-voltage waveform amplification circuit, emitted to the target by the transmitting end of the ultrasonic transducer, and received by the receiving end to realize ultrasonic testing. The excitation high-voltage waveform amplifier circuit includes a series two-stage amplifier circuit and a differential amplifier circuit. The two-stage amplifier circuit includes a first amplifier and a second amplifier. The non-inverting input terminal of the first amplifier is connected to resistors R1 and R4, respectively, and the inverting input terminal is connected to resistors R2 and R3, respectively. The output terminal is connected to the other end of resistors R5 and R4, respectively. The non-inverting input terminal of the second amplifier is connected to the other end of resistor R5 and resistor R6, the inverting input terminal is grounded, and the output terminal is connected to the other end of resistor R6 and resistor R7, respectively.

[0010] Furthermore, both the first amplifier and the second amplifier are AD8065.

[0011] Furthermore, the other end of resistor R1 is connected to the signal input terminal VinA.

[0012] Furthermore, the other end of resistor R2 is connected to the signal feedback terminal VinB.

[0013] Furthermore, resistor R3 is grounded.

[0014] Furthermore, the other end of resistor R7 is connected to the output terminal Vout.

[0015] Furthermore, the waveform generator includes an FPGA, a D / A converter, and a small-signal amplifier circuit. The FPGA is communicatively connected to the RAM and the digital synthesizer. The RAM stores the excitation waveform in advance. The digital synthesizer uses the FPGA to adjust the phase, frequency, and amplitude of the output waveform based on the excitation waveform. After the output waveform is output through the D / A converter and the small-signal amplifier circuit, it is transmitted to the excitation high-voltage waveform amplifier circuit.

[0016] Furthermore, the differential amplifier circuit includes a non-inverting amplifier circuit and an inverting amplifier circuit, and the power amplifier in both amplifier circuits is a PA94.

[0017] Furthermore, in the non-inverting amplifier circuit, the power amplifier is powered by positive and negative power supplies. The non-inverting input terminal is connected to Vin, and the inverting input terminal is connected to resistors R1 and R2 respectively. The other end of resistor R1 is grounded. The output terminal VoutA is connected to the other end of resistor R2 and resistor R3 respectively. The other end of resistor R3 is grounded.

[0018] Furthermore, in the inverting amplifier circuit, the power amplifier is powered by positive and negative power supplies. The non-inverting input is grounded, and the inverting input is connected to resistors R4 and R5 respectively. The other end of resistor R4 is connected to Vin. The output VoutB is connected to the other end of resistor R5 and resistor R6 respectively. The other end of resistor R6 is grounded.

[0019] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects: The PA94 high-voltage power amplifier employs a two-stage amplification circuit combined with a dual-supply differential amplification circuit design. It can operate stably under high-voltage conditions of ±450V dual power supply or up to 900V single power supply, achieving a ±800V high-voltage waveform output. Its high linearity effectively suppresses output waveform distortion, simplifies high-impedance matching circuit design, and can directly drive high-impedance piezoelectric transducers. By increasing the excitation voltage to 800V, this power amplifier enhances the initial acoustic energy output, thereby significantly improving the penetration capability and detection accuracy of internal defects in thick-walled honeycomb sandwich composite materials. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram of the ultrasonic testing system provided by the present invention; Figure 2 This is a schematic diagram of the ultrasonic testing system provided by the present invention; Figure 3 This is a schematic diagram of the circuit architecture of the ultrasonic testing system provided by the present invention; Figure 4 This is a schematic diagram illustrating the principle of arbitrary waveform signal generation provided by the present invention; Figure 5 This is a schematic diagram of the two-stage amplifier circuit structure provided by the present invention; Figure 6 This is a schematic diagram of the non-inverting amplifier circuit provided by the present invention; Figure 7 This is a schematic diagram of the inverting amplifier circuit provided by the present invention.

[0022] In the diagram: 1. Transmitter, 2. Receiver, 3. Honeycomb sandwich composite material, 4. Defect, 5. High voltage excitation circuit, 6. Ultrasonic acquisition circuit. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] like Figure 1 As shown, a non-contact high-voltage excitation air-coupled ultrasonic testing system uses air as the coupling medium, and its core hardware includes: A high-voltage arbitrary waveform signal generator is used to drive an ultrasonic transducer and enhance the initial acoustic energy. An ultrasonic transducer, including a transmitting transducer and a receiving transducer, is used for transmitting and receiving ultrasonic signals. High-speed signal acquisition card, used for accurate acquisition of echo signals; Mechanical scanning device and motion controller are used to realize the automatic positioning and scanning of the probe in the area to be measured; The host computer control terminal is used for data processing, imaging, and interface interaction.

[0026] This system can complete ultrasonic transmission and echo reception under high-voltage excitation without the need for a coupling agent, and is suitable for non-destructive testing of honeycomb sandwich structures in high temperature and complex morphology.

[0027] The principle of ultrasonic testing is mainly based on the fact that the difference in sound wave transmittance between the presence and absence of defects inside the material being tested causes a change in the received signal, thus enabling the detection of internal defects. In air-coupled ultrasonic testing of honeycomb sandwich composite structures, the transmission method involves placing air-coupled ultrasonic transducers, one transmitting and one receiving, on both sides of the object being tested. Ultrasonic waves enter the honeycomb sandwich structure of the composite material through the air, and the echo signal is received by the receiving transducer on the other side. The health status of the object's interior is then determined based on the received signal.

[0028] The above-mentioned non-contact high-pressure air-coupled ultrasonic transmission detection principle, such as Figure 2 As shown, the high-voltage excitation circuit 5 generates a signal, which is transmitted through the transmitter 1. The signal passing through the honeycomb sandwich composite material 3 is acquired by the receiver 2, and the signal is read by the ultrasonic acquisition circuit 6. The condition of defect 4 is obtained through subsequent signal processing.

[0029] This solution increases the voltage of the excitation circuit to achieve arbitrary waveforms to excite the ultrasonic transducer, thereby enabling the detection of internal defects in thick-walled honeycomb sandwich composite structures.

[0030] The structure of the high-voltage excitation circuit for air-coupled ultrasonic testing of arbitrary waveforms is as follows: Figure 3As shown, the arbitrary waveform generator uses an FPGA as the main control chip and a digital synthesizer (DDS) to generate arbitrary waveforms, which are then output by a small-signal amplifier circuit via a D / A converter. The excitation high-voltage waveform amplifier circuit receives the signal from the arbitrary waveform generator, amplifies the small signal through a two-stage amplifier, and finally achieves a high-voltage excitation of up to 800 V for the arbitrary waveform through a differential amplifier circuit, which is then emitted using an air-coupled ultrasonic transducer.

[0031] Direct Digital Synthesizer (DDS) is a frequency synthesis technology with high bandwidth, extremely short frequency transitions, and high frequency resolution. It allows for high-precision phase, frequency, and amplitude control of the output waveform through an FPGA development platform. In air-coupled ultrasonic testing of thick-walled honeycomb sandwich composite structures, arbitrary waveform generators can meet the requirements of different working scenarios for ultrasonic signals, enabling precise control of the time-domain waveform, spectral characteristics, and phase of the ultrasonic excitation signal. Arbitrary waveform generators can output wide-bandwidth excitation waveforms, and combined with frequency modulation technology, can improve the amplitude of the air-coupled ultrasonic received signal in composite materials and enhance the signal-to-noise ratio (SNR) of the air-coupled ultrasonic testing signal. Arbitrary waveform excitation provides a new technical approach for achieving more demanding air-coupled ultrasonic testing of thick-walled honeycomb sandwich composite structures.

[0032] By using FPGA-based DDS design, the process of generating arbitrary waveforms can be performed, such as... Figure 4 As shown, the DDS mainly consists of a phase accumulator, a phase modulator, a waveform data table, and a D / A converter. The specific process includes: RAM is used to store excitation waveforms. The Block RAM inside the FPGA is used to store custom waveforms, and the waveform data is written to the PC host computer. Input control commands into the DDS module, and for parameterizable signals (such as modulation and amplitude modulation signals), implement real-time algorithm calculation in the FPGA; The obtained phase control word and frequency control word are input into the synchronization register. The phase accumulator register and the synchronization register are used as sampling addresses to query the custom waveform data table. The data obtained from the query is converted into the corresponding voltage by a multi-channel, high-precision digital-to-analog converter (DAC). The digital waveform values ​​can be converted into the required synthetic frequency analog data. The generated analog signal is passed through a low-pass filter to attenuate and filter out redundant sampled components.

[0033] For air-coupled ultrasonic testing systems, the most common excitation voltage supported is 400 V. Further increases in excitation voltage are mainly limited by the dielectric strength and mechanical deformation limits of the air-coupled ultrasonic transducer, and further increases in voltage will lead to increased hardware design complexity.

[0034] However, for thick-walled honeycomb sandwich composite structures, due to their multiple composite structures, ultrasonic energy is reflected and scattered multiple times, resulting in significant energy loss and insufficient penetration depth, necessitating an increase in excitation voltage.

[0035] This solution achieves comprehensive optimization of the excitation signal linearity, output matching circuit, and excitation voltage by further increasing the voltage, selecting a suitable high-voltage power amplifier, and improving the circuit design. Increasing the excitation voltage compensates for the high attenuation characteristics in air, increases the initial acoustic energy, and ensures the signal can be detected after penetrating the material. Increasing the excitation voltage of the emitted ultrasonic waves increases the transmitted energy and overcomes acoustic impedance mismatch. An 800V excitation can generate higher amplitude ultrasonic waves, overcoming the high acoustic impedance difference at the air-material interface, resulting in more energy penetrating into the honeycomb sandwich composite structure, increasing the penetration depth, and making it more effective for low-density honeycomb and thick sandwich structures, while also adapting to defect detection in more complex structures.

[0036] This solution uses the AD8065 as a low-noise amplifier. Its high bandwidth ensures distortion-free amplification of ultrasonic pulses, making it suitable for high-frequency ultrasound. It features high speed, low noise, and strong driving capability, and can be used as an ultrasonic excitation preamplifier circuit.

[0037] This solution utilizes the Apex PA94 as a high-voltage operational amplifier, which features high-voltage and high-current drive capabilities, enabling operation under dual-supply ±450V and single-supply up to 900V. Its application in ultrasonic testing is advantageous; a single-chip design can achieve outputs exceeding ±400V, while a dual-chip differential circuit design can achieve high-voltage waveform excitation of ±800V. Its high linearity ensures distortion-free output waveforms; it reduces the complexity of high-impedance matching circuits and can directly drive high-impedance piezoelectric transducers. With its ultra-high voltage and high reliability, the PA94 can serve as a core component of high-power ultrasonic transmission systems, particularly suitable for aerospace thick-walled composite material testing.

[0038] Figure 3 The block diagram for high-voltage excitation in air-coupled ultrasonic testing is shown. By using the DDS algorithm of FPGA, the analog voltage output of the D / A converter is realized. The small signal is amplified and then amplified by two stages of amplification circuit so that the output waveform reaches a certain voltage. Finally, the arbitrary output waveform is amplified to 800 V through a differential amplifier circuit.

[0039] The structure of a two-stage amplifier circuit is as follows: Figure 5As shown, it includes a first amplifier and a second amplifier, both of which are AD8065. The non-inverting input of the first amplifier is connected to resistors R1 and R4, the inverting input is connected to resistors R2 and R3, and the output is connected to the other ends of resistors R5 and R4. The other end of resistor R1 is connected to the signal input VinA, the other end of resistor R2 is connected to the signal feedback VinB, and resistor R3 is grounded. The non-inverting input of the second amplifier is connected to the other end of resistor R5 and resistor R6 respectively, the inverting input is grounded, and the output is connected to the other end of resistor R6 and resistor R7 respectively. The other end of resistor R7 is connected to the output Vout.

[0040] Differential amplifier circuits include, for example Figure 6 The non-inverting amplifier circuit shown and as follows Figure 7 The inverting amplifier circuit shown contains two PA94 power amplifiers.

[0041] like Figure 6 As shown, the non-inverting input of the non-inverting amplifier circuit is connected to Vin, the inverting input is connected to ground through resistor R1 and to feedback resistor R2 respectively, and the output VoutA is connected to the other end of resistor R2 and to ground through resistor R3.

[0042] like Figure 7 As shown, the non-inverting input of the inverting amplifier circuit is grounded, the inverting input is connected to the input Vin and the feedback resistor R5 through the connecting resistor R4, and the output VoutB is connected to the other end of the resistor R5 and the output signal is connected to ground through R6.

[0043] By using outputs VoutA and VoutB as output terminals and selecting appropriate feedback resistors R2 and R5, the amplification factor can reach 100 times and the voltage of the output excitation waveform can reach ±800V.

[0044] This scheme uses an 800 V excitation voltage to excite the air-coupled ultrasonic probe, which can be used to detect internal defects in thick-walled honeycomb sandwich composite materials, thus improving penetration capability.

[0045] For air-coupled ultrasonic testing of honeycomb sandwich composite materials, it is possible to transmit excitation signals such as square wave pulses, sharp pulses, sine signals and custom waveforms. The output excitation waveform has wide bandwidth characteristics. Combined with frequency modulation technology and pulse compression technology, the signal-to-noise ratio of the received signal is improved.

[0046] The high-voltage waveform amplifier circuit uses a highly integrated power amplifier, which reduces the design complexity of matching the circuit output impedance with the ultrasonic transducer impedance and reduces the loss of ultrasonic transducer conversion power.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-contact high-voltage excitation air-coupled ultrasonic testing system, characterized in that, It includes a waveform generator, an excitation high-voltage waveform amplifier circuit, and an ultrasonic transducer. The waveform generator generates arbitrary waveforms, which are amplified by the excitation high-voltage waveform amplifier circuit. The waveforms are then emitted to the target by the transmitting end of the ultrasonic transducer, and the echo signals are received by the receiving end to achieve ultrasonic detection. The excitation high-voltage waveform amplifier circuit includes a series two-stage amplifier circuit and a differential amplifier circuit. The two-stage amplifier circuit includes a first amplifier and a second amplifier. The non-inverting input terminal of the first amplifier is connected to resistors R1 and R4, respectively, and the inverting input terminal is connected to resistors R2 and R3, respectively. The output terminal is connected to the other end of resistors R5 and R4, respectively. The non-inverting input terminal of the second amplifier is connected to the other end of resistor R5 and resistor R6, the inverting input terminal is grounded, and the output terminal is connected to the other end of resistor R6 and resistor R7, respectively.

2. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, Both the first amplifier and the second amplifier are AD8065.

3. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The other end of the resistor R1 is connected to the signal input terminal VinA.

4. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The other end of the resistor R2 is connected to the signal feedback terminal VinB.

5. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The resistor R3 is grounded.

6. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The other end of the resistor R7 is connected to the output terminal Vout.

7. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The waveform generator includes an FPGA, a D / A converter, and a small-signal amplifier circuit. The FPGA is communicatively connected to a RAM and a digital synthesizer. The RAM stores the excitation waveform in advance. The digital synthesizer uses the FPGA to adjust the phase, frequency, and amplitude of the output waveform based on the excitation waveform. After the output waveform is output through the D / A converter and the small-signal amplifier circuit, it is transmitted to the excitation high-voltage waveform amplifier circuit.

8. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 1, characterized in that, The differential amplifier circuit includes a non-inverting amplifier circuit and an inverting amplifier circuit, and the power amplifiers in both amplifier circuits are PA94.

9. The non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 8, characterized in that, In the non-inverting amplifier circuit, the power amplifier is powered by positive and negative power supplies. The non-inverting input terminal is connected to Vin, and the inverting input terminal is connected to resistors R1 and R2 respectively. The other end of resistor R1 is grounded. The output terminal VoutA is connected to the other end of resistor R2 and resistor R3 respectively. The other end of resistor R3 is grounded.

10. A non-contact high-voltage excitation air-coupled ultrasonic testing system as described in claim 8, characterized in that, In the inverting amplifier circuit, the power amplifier is powered by positive and negative power supplies. The non-inverting input is grounded, and the inverting input is connected to resistors R4 and R5 respectively. The other end of resistor R4 is connected to Vin. The output VoutB is connected to the other end of resistor R5 and resistor R6 respectively. The other end of resistor R6 is grounded.

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