Aluminum alloy welding pore defect online detection device

Abstract

The invention discloses an online detection device for aluminum alloy welding pore defects, and relates to the technical field of welding seam detection. The device comprises a platform, a conveyor belt support and a detection frame. The device realizes straight or deflection movement of the welding seam through the first and second conveyor belts which are independently controlled, and adapts to various welding seam forms. The detection frame integrates a photoacoustic excitation assembly (high-frequency pulse laser, 1064nm) and an eddy current induction assembly (10kHz-1MHz electromagnetic field) to form a composite signal of a sound wave and an eddy current field, and pore defect characteristics are amplified by utilizing a coupling effect, so that the detection resolution is improved. The signal acquisition assembly comprises a piezoelectric sensor array and an eddy current probe, and is matched with a band-pass filter, a signal amplifier and a feature extractor to output defect waveforms or give an alarm in real time. A polishing motor and a polishing disc remove a weld joint oxide layer, and detection stability is ensured. The device realizes non-contact, efficient and accurate detection, and is suitable for a modern aluminum alloy welding production line.

Description

Technical Field

[0001] The present invention relates to the technical field of weld detection, in particular to an online detection device for aluminum alloy welding porosity defects. Background Art

[0002] Prior art detection of porosity defects in aluminum alloy welds primarily relies on a single method. For example, ultrasonic testing uses a probe to emit sound waves and receive echoes to determine defects. However, this requires direct contact with the weld surface, making it susceptible to interference from factors such as surface oxide layers and unevenness, leading to signal attenuation or distortion. Furthermore, resolution of tiny pores is insufficient. Furthermore, existing equipment often utilizes a fixed transmission mechanism, making it difficult to adapt to complex weld trajectories. Manual oxide layer removal is often required before testing, resulting in low efficiency. These shortcomings include low detection accuracy, contact limitations, poor adaptability, and inefficient surface pretreatment. Summary of the Invention

[0003] In order to overcome the defects of the above-mentioned prior art, the present invention provides the following technical solutions: an online detection device for porosity defects in aluminum alloy welding, comprising a platform, a conveyor belt bracket is fixedly installed on the platform, and a first conveyor belt and a second conveyor belt are symmetrically arranged on the conveyor belt bracket for rotation, and the first conveyor belt and the second conveyor belt are used to drive the aluminum alloy weldment to move; wherein the rotation speeds of the first conveyor belt and the second conveyor belt are independently controlled; a detection frame is overhead arranged above the platform, and the distance between the detection frame and the weld can be adjusted; wherein a photoacoustic excitation component and an eddy current sensing component are arranged inside the detection frame, and the photoacoustic excitation component and the eddy current sensing component are used to form a composite signal; a signal acquisition component is also arranged inside the detection frame, and the signal acquisition component includes a piezoelectric sensor array for capturing acoustic wave signals and an eddy current probe for detecting impedance changes.

[0004] Preferably, the detection frame is fixedly mounted on the detection frame mounting plate, on which two parallel guide slides are fixedly mounted, the two guide slides are slidably mounted on the adjustment bracket, on which an electric cylinder is fixedly mounted, the telescopic rod end of the electric cylinder is fixedly fitted with the detection frame mounting plate, and the adjustment bracket is fixedly mounted on the platform.

[0005] Preferably, an extension frame is fixedly mounted on the adjustment bracket, two parallel grinding motor slides are fixedly mounted on the extension frame, a grinding motor is slidably mounted on the two grinding motor slides, a grinding disc seat is fixedly mounted on the output shaft of the grinding motor, and a grinding disc is fixedly mounted on the grinding disc seat in a manner that is easy to disassemble.

[0006] Preferably, the photoacoustic excitation component is used to emit a beam of high-frequency pulsed laser to irradiate the weld surface. The laser energy is absorbed by the weld surface, the local temperature rises instantaneously, resulting in a thermal expansion effect, and exciting an ultrasonic signal. If there are pores inside the weld, the sound waves will be reflected and scattered at the pore boundaries, forming an echo feature, which can be captured by the piezoelectric sensor array.

[0007] Preferably, the eddy current induction component is used to generate a high-frequency alternating electromagnetic field which is applied to the weld area by the annular eddy current coil, and the change of the eddy current impedance inside the weld is detected by the eddy current probe.

[0008] Preferably, the photoacoustic excitation component and the eddy current induction component can also form a composite signal; the composite signal is the interaction between the sound wave and the eddy current field at the pore defect.

[0009] Preferably, the signal acquisition component also includes a bandpass filter, a signal amplifier and a feature extractor; wherein the bandpass filter is used to separate specific frequency bands of sound waves and eddy current signals; wherein the signal amplifier is used to amplify weak composite signals to a measurable range; wherein the feature extractor directly extracts defect features through hardware circuits, and the defect features include peak offset and waveform distortion.

[0010] Preferably, the output result of the signal acquisition component is presented in the form of a waveform or an audible and visual alarm.

[0011] Compared with the prior art, the present invention has the following advantages: (1) The present invention uses the composite signal formed by the photoacoustic excitation component and the eddy current induction component to significantly amplify the signal characteristics of the porosity defect inside the weld by utilizing the coupling effect of the sound wave and the eddy current field. The sound wave is reflected and scattered at the pore boundary to form an echo, while the eddy current impedance produces an abnormality due to the changes in conductivity and magnetic permeability caused by the pore. The interaction between the two makes the defect signal more obvious, and the detection resolution is improved to ΔZ / Z0≈0.1%-5%. Compared with the traditional single detection method, this composite detection method can more accurately identify tiny porosity defects, avoid missed detection, and improve the reliability of aluminum alloy weldment quality control; (2) The photoacoustic excitation component of the present invention uses a high-frequency pulsed laser (wavelength 1064nm, pulse width 10ns) to induce ultrasonic waves, without the need for the traditional ultrasonic probe to directly contact the weld surface, thus avoiding the signal distortion problem caused by surface unevenness or oxide layer interference in contact detection. At the same time, the laser irradiation area is focused on the weld area with a diameter of 1-2mm, and combined with the high-frequency electromagnetic field (10kHz-1MHz) of the eddy current induction component, non-contact rapid scanning is achieved, which greatly improves the detection efficiency and adapts to the needs of modern assembly line production; (3) The present invention can flexibly adjust the weld movement trajectory through independent speed control of the first conveyor belt and the second conveyor belt. When the speeds of the two conveyor belts are the same, the weld moves straight; when there is a speed difference, the weld deflects in the direction of lower speed. This design enables the device to adapt to the different detection requirements of straight welds and curved welds. Combined with the electric cylinder to adjust the distance between the detection frame and the weld, it further enhances the adaptability to complex weld shapes and improves the versatility of detection; (4) The grinding motor of the present invention drives the grinding disc to rotate, which can effectively remove the oxide layer on the weld surface before detection. If the oxide layer exists, it will interfere with the laser energy absorption and eddy current field distribution, resulting in signal distortion. By keeping the grinding disc in stable contact with the weld under gravity and motor drive, the surface is kept clean and consistent, thereby improving the signal quality of photoacoustic excitation and eddy current induction, reducing the interference of environmental factors on the detection results, and enhancing the stability of the detection process; (5) The signal acquisition component of the present invention integrates a bandpass filter, a signal amplifier, and a feature extractor, which can process the composite signal in real time, directly extract defect features such as peak offset and waveform distortion, and output the results in the form of a waveform graph or sound and light alarm. This design avoids the disadvantage of traditional detection requiring complex data analysis in the later stage, allowing operators to quickly and intuitively determine the presence and severity of weld porosity defects, greatly improving the decision-making efficiency of the production site. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0013] Figure 2 It is a structural schematic diagram of the detection frame of the present invention.

[0014] In the figure: 101- platform; 102- conveyor belt bracket; 103- first conveyor belt; 104- second conveyor belt; 105- adjustment bracket; 106- extension frame; 107- grinding motor slide rod; 108- grinding motor; 109- grinding disc seat; 110- grinding disc; 111- electric cylinder; 112- guide slide rod; 113- detection frame mounting plate; 114- detection frame. DETAILED DESCRIPTION

[0015] The following is combined with Figure 1 and Figure 2 , and further illustrate the technical solution of the present invention through specific implementation methods.

[0016] The present invention provides an online detection device for porosity defects in aluminum alloy welding, comprising a platform 101, on which a conveyor belt bracket 102 is fixedly mounted, and on which a first conveyor belt 103 and a second conveyor belt 104 are symmetrically rotatably arranged, wherein the first conveyor belt 103 and the second conveyor belt 104 are used to drive the aluminum alloy weldment to move; wherein the rotation speeds of the first conveyor belt 103 and the second conveyor belt 104 are independently controlled; when the rotation speeds of the first conveyor belt 103 and the second conveyor belt 104 are the same, the weld moves straightly; when there is a rotation speed difference between the first conveyor belt 103 and the second conveyor belt 104, the weld will deflect toward the direction of lower rotation speed (the first conveyor belt 103 and the second conveyor belt 104 have the same rotation speed). A detection frame 114 is installed overhead above the platform 101, and the distance between the detection frame 114 and the weld can be adjusted; the detection frame 114 is internally provided with a photoacoustic excitation component and an eddy current sensing component, which are used to form a composite signal; the detection frame 114 is also internally provided with a signal acquisition component, which includes a piezoelectric sensor array for capturing acoustic wave signals and an eddy current probe for detecting impedance changes.

[0017] The detection frame 114 is fixedly mounted on the detection frame mounting plate 113. Two parallel guide slides 112 are fixedly mounted on the detection frame mounting plate 113. The two guide slides 112 are slidably mounted on the adjustment bracket 105. The adjustment bracket 105 is fixedly mounted with an electric cylinder 111. The end of the telescopic rod of the electric cylinder 111 is fixedly engaged with the detection frame mounting plate 113. The adjustment bracket 105 is fixedly mounted on the platform 101. The adjustment bracket 105 is fixedly mounted with an extension frame 106. The extension frame 106 is fixedly mounted with two parallel grinding motor slides 107. The grinding motor 108 is slidably mounted on the two grinding motor slides 107. The output shaft of the grinding motor 108 is fixedly mounted with a grinding disc seat 109. The grinding disc 110 is fixedly mounted on the grinding disc seat 109 in a manner that is easy to disassemble. Before testing, the grinding motor 108 is started, and the output shaft of the grinding motor 108 drives the grinding disc 110 to rotate. The grinding disc 110 is used to remove the oxide layer (if any) on the surface of the weld. The grinding disc 110 maintains contact with the weld under the grinding motor 108 and its own gravity.

[0018] The photoacoustic excitation assembly emits a high-frequency pulsed laser beam (e.g., an Nd:YAG laser with a wavelength of 1064 nm and a pulse width of approximately 10 ns) onto the weld surface. The laser energy is absorbed by the weld surface, causing a transient increase in local temperature and thermal expansion, which in turn stimulates an ultrasonic signal. If pores are present within the weld, the acoustic wave will reflect and scatter at the pore boundaries, generating an echo signature that can be captured by the piezoelectric sensor array. Laser power: approximately 100 mJ / pulse, frequency adjustable (10-100 Hz); irradiation area: approximately 1-2 mm in diameter, ensuring focus on the weld. By inducing acoustic waves with the laser, the limitation of traditional ultrasonic probes requiring contact with the surface is avoided.

[0019] The eddy current sensing component generates a high-frequency alternating electromagnetic field (frequency range 10kHz-1MHz) applied to the weld area by a toroidal eddy current coil. The eddy current probe then detects changes in the eddy current impedance within the weld. Aluminum alloy, as a conductive material, generates induced eddy currents. The presence of pores can cause local changes in electrical and magnetic conductivity, leading to abnormal eddy current field impedance. The coil diameter is approximately 5mm, placed close to the weld surface (with a spacing of 0.1-0.5mm). The current intensity is adjustable from 1-5A to ensure sensitivity.

[0020] The photoacoustic excitation and eddy current sensing components can also generate a composite signal; this composite signal is the interaction between the acoustic wave and the eddy current field at the pore defect. (The acoustic wave vibration causes microscopic displacements in the local material, changing the eddy current distribution. Simultaneously, the eddy current field disturbance modulates the propagation characteristics of the acoustic wave. The Lorentz force induced by the eddy current acts on the material, changing the local stress distribution and affecting the speed of sound. The eddy current generates microscopic Joule heating at the defect, altering the temperature and density of the local acoustic propagation medium. As a result, the eddy current field disturbance is more concentrated, and the modulation of the acoustic wave by electromagnetic forces or thermal effects may be more pronounced.) The result is a composite signal consisting of the acoustic wave frequency component (kHz range) and the eddy current impedance change (electrical signal). The acoustic wave frequency is 20-500kHz (depending on the laser pulse and material properties). The eddy current impedance change is ΔZ / Z0 ≈ 0.1%-5% (related to the pore size). The coupling effect of the two physical fields is exploited to amplify the defect signal, significantly improving detection resolution.

[0021] The signal acquisition component also includes a bandpass filter, a signal amplifier and a feature extractor; the bandpass filter is used to separate specific frequency bands of sound waves and eddy current signals; the signal amplifier is used to amplify weak composite signals to a measurable range; and the feature extractor directly extracts defect features through hardware circuits, and the defect features include peak offset and waveform distortion.

[0022] The output results of the signal acquisition component are presented in the form of waveforms or sound and light alarms.

[0023] The piezoelectric sensor array consists of 4-6 ultra-thin piezoelectric ceramic discs (approximately 0.2mm thick), each approximately 3mm in diameter. The discs are coated with a sound-absorbing layer to reduce ambient noise interference. They are symmetrically distributed on both sides of the weld, approximately 5-10mm from the center, and secured with flexible, adjustable spacing brackets to accommodate various weld widths. The eddy current probe is a toroidal coil (5mm diameter, 2mm thickness) wound with highly conductive copper wire and embedded in an insulating ceramic substrate. The coil is coated with a high-temperature-resistant coating (such as alumina ceramic) to withstand transient temperatures of 1000°C and maintain a 0.1-0.5mm gap from the weld surface. Adjustment is achieved by controlling the extension and retraction of the telescopic rod of the electric cylinder 111.

Claims

1. An online detection device for aluminum alloy welding porosity defects, characterized by: The invention comprises a platform (101), a conveyor belt bracket (102) is fixedly mounted on the platform (101), a first conveyor belt (103) and a second conveyor belt (104) are symmetrically arranged on the conveyor belt bracket (102), and the first conveyor belt (103) and the second conveyor belt (104) are used to drive the aluminum alloy weldment to move; wherein the rotation speeds of the first conveyor belt (103) and the second conveyor belt (104) are independently controlled; A detection frame (114) is overheadly provided above the platform (101), and the distance between the detection frame (114) and the weld can be adjusted; The detection frame (114) is provided with a photoacoustic excitation component and an eddy current sensing component, which are used to form a composite signal; the detection frame (114) is also provided with a signal acquisition component, which includes a piezoelectric sensor array for capturing acoustic wave signals and an eddy current probe for detecting impedance changes.

2. The online detection device for aluminum alloy welding porosity defects according to claim 1, characterized in that: The detection frame (114) is fixedly mounted on the detection frame mounting plate (113), two parallel guide slides (112) are fixedly mounted on the detection frame mounting plate (113), the two guide slides (112) are slidably mounted on the adjustment bracket (105), an electric cylinder (111) is fixedly mounted on the adjustment bracket (105), the telescopic rod end of the electric cylinder (111) is fixedly matched with the detection frame mounting plate (113), and the adjustment bracket (105) is fixedly mounted on the platform (101).

3. The online detection device for aluminum alloy welding porosity defects according to claim 2, characterized in that: An extension frame (106) is fixedly mounted on the adjustment bracket (105), two parallel grinding motor slide bars (107) are fixedly mounted on the extension frame (106), a grinding motor (108) is slidably mounted on the two grinding motor slide bars (107), a grinding disc seat (109) is fixedly mounted on the output shaft of the grinding motor (108), and a grinding disc (110) is fixedly mounted on the grinding disc seat (109) in a manner that is easy to disassemble.

4. The online detection device for aluminum alloy welding porosity defects according to claim 3, characterized in that: The photoacoustic excitation component is used to emit a beam of high-frequency pulsed laser to irradiate the weld surface. The laser energy is absorbed by the weld surface, causing the local temperature to rise instantaneously, resulting in a thermal expansion effect and exciting an ultrasonic signal. If there are pores inside the weld, the sound waves will be reflected and scattered at the pore boundaries, forming an echo feature that can be captured by the piezoelectric sensor array.

5. The online detection device for aluminum alloy welding porosity defects according to claim 4, characterized in that: The eddy current sensing component is used to generate a high-frequency alternating electromagnetic field which is applied to the weld area by the annular eddy current coil, and the changes in the eddy current impedance inside the weld are detected by the eddy current probe.

6. The online detection device for aluminum alloy welding porosity defects according to claim 5, characterized in that: The photoacoustic excitation component and the eddy current induction component can also form a composite signal; the composite signal is the interaction between the sound wave and the eddy current field at the pore defect.

7. The online detection device for aluminum alloy welding porosity defects according to claim 6, characterized in that: The signal acquisition component also includes a bandpass filter, a signal amplifier and a feature extractor; the bandpass filter is used to separate specific frequency bands of sound waves and eddy current signals; the signal amplifier is used to amplify weak composite signals to a measurable range; and the feature extractor directly extracts defect features through hardware circuits, and the defect features include peak offset and waveform distortion.

8. The online detection device for aluminum alloy welding porosity defects according to claim 7, characterized in that: The output results of the signal acquisition component are presented in the form of waveforms or sound and light alarms.

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