Self-adaptive ultrasonic welding method for in-situ energy-conducting rib and application of self-adaptive ultrasonic welding method

Abstract

The invention provides a self-adaptive ultrasonic welding method for an in-situ energy-conducting rib and application of the self-adaptive ultrasonic welding method, and belongs to the technical field of welding machining. According to the method, low-amplitude pulse ultrasonic waves and a temperature field are precisely regulated and controlled, the defects of weld pores, incomplete fusion and the like are reduced, gradient pressure relief and nitrogen forced cooling are combined, the thermal stress cracking risk is reduced, the in-situ energy guide ribs pass through a directional molecular chain and a fiber network, the ultrasonic propagation loss is reduced, and the fusion efficiency is improved; on the basis of amplitude switching of dissipation modulus (E '') real-time monitoring, energy waste is avoided, the welding period is shortened, a gradient transition structure is formed, weld hardness distribution is uniform, crystallinity and heat resistance are improved, process stability is improved, closed-loop control of the melting process is achieved, abnormal working condition response time is shortened, and energy consumption of a nitrogen recovery system is reduced. Laser roughening replaces sand blasting, so that the cost is effectively reduced, and the waste gas filtering efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding processing, in particular to a method for in-situ energy guide rib adaptive ultrasonic welding and application thereof. BACKGROUND

[0002] Ultrasonic welding technology is an advanced process that connects materials through high-frequency vibration energy, which can be traced back to the 1950s. This technology uses a transducer to convert electrical energy into mechanical vibration, which is transmitted to the contact surface of the workpiece through a welding head, generating heat through friction to locally melt the material and form a molecular-level bond under pressure.

[0003] Ultrasonic welding technology connects materials efficiently through high-frequency vibration energy, and its core lies in the energy transmission mechanism of the energy guide rib. Traditional welding often has low efficiency and weak interface bonding due to energy dispersion, while the energy guide rib significantly improves the molecular entanglement strength and joint performance through local stress concentration and melting guidance. This technology is widely used in aerospace composite material repair, automotive lightweight component welding, and electronic precision connection, and through structure-function integrated design, it promotes green manufacturing and becomes a key technology to solve the problems of thermoset material repair and dissimilar material connection.

[0004] Traditional ultrasonic welding requires pre-fabricating energy guide ribs at the welding site, but for large and complex structural components, the energy guide ribs not only have problems such as difficult processing, limited position, and affecting assembly, but also easily cause defects such as incomplete fusion, cracks, and gaps at the welding surface, which seriously affect the service performance of the components. Research shows that during the FRTP ultrasonic welding process, without the guidance of the energy guide rib, most of the energy will be dissipated as heat in the form of viscoelasticity inside the plate, which easily leads to FRTP thermal decomposition and forms pores, which worsen the joint performance.

[0005] Therefore, it is of great practical significance to achieve high-strength, low-defect, and short-cycle connection of ultrasonic welding without pre-fabricating energy guide ribs. SUMMARY

[0006] The present application provides a method for in-situ energy guide rib adaptive ultrasonic welding and application thereof, which reduces defects such as weld porosity and incomplete fusion, reduces the risk of thermal stress cracking, improves energy utilization efficiency, reduces ultrasonic propagation loss, improves melting efficiency, shortens welding cycle, forms a gradient transition structure, distributes weld hardness uniformly, improves crystallinity, improves heat resistance, realizes closed-loop control of the melting process, reduces abnormal working condition response time, reduces energy consumption of the nitrogen recovery system, effectively reduces costs by replacing sandblasting with laser roughening, and improves waste gas filtration efficiency.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] A method for in-situ energy guiding rib adaptive ultrasonic welding, comprising the following steps:

[0009] S1, pretreatment before welding:

[0010] (1) Drying treatment, put the PA66 composite material into the vacuum drying oven with temperature uniformity calibration function for 1-2 hours;

[0011] (2) Surface roughening treatment, put the dried PA66 composite material into the fiber laser to form a periodic micro-pit array with a depth of 30-50 μm and a pitch of 1-2 mm on the material surface;

[0012] (3) Pre-assembly and positioning, pre-assembly of the material by pneumatic floating clamp, combined with mechanical arm or XYZ platform to realize sub-millimeter level accurate positioning;

[0013] S2, low amplitude pulse stage:

[0014] Low amplitude pulse welding of PA66 composite material by ultrasonic generator, ultrasonic amplitude is 0.6~1.0 μm, time is 0.3~0.5 s; In the welding operation process, the temperature field is monitored in real time, the welding zone temperature is monitored by infrared thermal imager, the ultrasonic amplitude attenuation value is collected in real time by piezoelectric sensor, and finally the welding surface micro displacement is monitored by laser displacement sensor to judge the material creep behavior;

[0015] S3, welding process closed loop control: adopt segmented welding strategy, welding process is divided into three stages, preheating stage: low amplitude softening surface oxide layer, main welding stage: high amplitude combined with pressure pulse, promoting interface plastic flow, cooling stage: gradually reducing pressure and maintaining ultrasonic vibration, eliminating residual stress;

[0016] S4, mode switching welding stage:

[0017] (1) Switching trigger condition: temperature threshold is set to ≥Tg+20℃ and ≤Tg+50℃, to avoid overheating decomposition, dissipation modulus change rate is set to ΔE '' / Δt > 5MPa / s (ΔE '' / Δt unit is MPa / s), to quickly form energy guiding rib structure;

[0018] (2) Parameter adjustment: improve energy input efficiency, adjust ultrasonic amplitude to 25~35 μm, control pressure to 0.6~1.0 MPa, and extend welding time to 1.0-1.5 s;

[0019] (3) Adaptive compensation mechanism: dynamically correct the pressure formula according to the thickness of the plate: P = 0.5×H + 0.3, identify the molten flow state through acoustic emission signals, automatically terminate welding, blow high-purity nitrogen at a pressure of 0.4~0.7MPa for 8~15s through a nitrogen blowing system, and forcibly solidify the melt.

[0020] Further, the vacuum drying oven is adjusted to a temperature of 120℃±5℃ and a vacuum degree of ≥0.09MPa for drying, and after the operation is completed, the moisture content is detected by a Karl Fischer moisture meter to be ≤0.1% to be qualified, the fiber laser is adjusted to a scanning speed of 80~120 mm / s, a pulse width of 6~10μs, and a spot diameter of 40~60μm, and after the processing is completed, a three-dimensional topography instrument is used to verify that Ra≥3.2μm.

[0021] Further, during pre-installation assembly, the center point is marked on the welding area by laser marking, the edge or feature point of the energy guide rib is recognized by an industrial camera, and according to the elastic modulus of the energy guide rib material, an initial contact pressure is applied by a pneumatic cylinder.

[0022] Further, during the low-amplitude pulse stage operation, the resonant point of the transducer is optimized according to the PA66 resonant frequency.

[0023] Further, the clamping force of the pneumatic floating clamp is uniformly distributed to prevent local stress concentration and damage to the material, infrared positioning and mechanical limiting double calibration are used to ensure that the axial centering error of the energy guide rib and the welded joint is <0.1mm, and the clamp needs to have a quick replacement adapter module to adapt to energy guide ribs of different sizes / shapes.

[0024] Further, the duration of the external preheating stage is 1-50 ms to soften the surface oxide layer by 5-10μm low-amplitude, the duration of the main welding stage is 50-200 ms to promote interfacial plastic flow by 15-25μm high-amplitude combined with 0.5 MPa pressure pulses, and the duration of the cooling stage is 200-500 ms to gradually reduce the pressure at a rate of 0.1~0.2 MPa / 100 ms and maintain ultrasonic vibration to eliminate residual stress.

[0025] Further, the welding operation process needs to be dynamically adjusted, the neural network model is trained based on historical material type, thickness, surface treatment process welding data through AI-driven parameter optimization, the parameter-quality mapping relationship is established, the optimal parameter combination is predicted by the model according to the current monitoring data, and the dynamic execution is divided into three modules, including: frequency band switching module, amplitude adjustment module and pressure compensation module, the neural network model is deployed on PLC or industrial PC, and real-time communication is realized through EtherCAT bus with transducer and servo cylinder to realize hardware-in-the-loop control.

[0026] Further, the frequency band switching module quickly switches the resonant frequency through the PZT transducer to match the material impedance change, the amplitude adjustment module adjusts the electric signal input in real time through the linear amplifier to control the amplitude output, and the pressure compensation module dynamically adjusts the pressure according to the displacement feedback through the servo electric cylinder to avoid overpressure or false welding.

[0027] Further, after the welding process is completed, post-welding quality detection and feedback are required, first, non-destructive testing is performed, the welding interface bonding rate is detected through ultrasonic C scanning, then shear force testing is performed, the mechanical strength is verified by applying a vertical tensile force of 0.1-1kN in situ, after passing the non-destructive testing, the welding parameters and quality results of this time are stored in the database, the AI model weight is updated, and the subsequent welding adaptability is improved, so as to complete data iteration optimization.

[0028] The application of the above method, for example, is used for welding of PA66 composite materials and PEI interlayer materials of aviation structural parts, and welding of carbon fiber composites and polypropylene of automobile lightweight parts.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] (1) Improve welding quality and reliability: through precise regulation of low-amplitude pulse ultrasonic waves and temperature field, reduce defects such as welding porosity and incomplete fusion, at the same time, improve the X-ray CT detection pass rate, the synergistic effect of laser roughening surface and in-situ energy guiding rib enhances the interfacial bonding strength of PA66 composite material and PEI interlayer material, improves the tensile strength, gradient pressure relief combined with nitrogen forced cooling reduces the risk of thermal stress cracking, and the fatigue life is improved to S-N curve slope < -3.

[0031] (2) Improve energy utilization efficiency: the in-situ energy guiding rib reduces ultrasonic wave propagation loss through directional molecular chains and fiber network, improves melting efficiency, and avoids energy waste and shortens welding cycle based on amplitude switching of real-time monitoring of dissipation modulus (E '' ).

[0032] (3) Customization of material performance: pre-orientation of molecular chains and reconstruction of carbon fiber network in viscoelastic state form a gradient transition structure, the hardness distribution of the weld is uniform, the PA66 crystallization rate is controlled during the pressure maintaining cooling stage, the crystallinity is improved, and the heat resistance is improved.

[0033] (4) Process stability and safety: with an intelligent monitoring system, through acoustic emission and infrared thermal imager dual-channel monitoring, realize closed-loop control of the melting process, reduce abnormal working condition response time, nitrogen recovery system reduces energy consumption, laser roughening replaces sandblasting to effectively reduce cost, and improve waste gas filtration efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flow chart of the overall ultrasonic welding method;

[0035] Figure 2 is a flow chart of the pre-treatment of the ultrasonic welding method;

[0036] Figure 3 is a flow chart of the low amplitude pulse phase of the ultrasonic welding method;

[0037] Figure 4 is a flow chart of the AI dynamic control of the ultrasonic welding method;

[0038] Figure 5 is a flow chart of the pre-heating of the ultrasonic welding method;

[0039] Figure 6 is a flow chart of the regular welding of the ultrasonic welding method;

[0040] Figure 7 is a flow chart of the pressure holding and cooling of the ultrasonic welding method;

[0041] Figure 8 is a flow chart of the quality detection of the ultrasonic welding method;

[0042] Figure 9 is a schematic diagram of the generation mechanism of the ultrasonic welding porosity defect without energy guide rib;

[0043] Figure 10 is a schematic diagram of the principle of the ultrasonic welding in situ energy guide rib. DETAILED DESCRIPTION

[0044] The present application will be further described below in conjunction with the drawings and specific embodiments, but the present application is not limited thereto.

[0045] The overall flow chart of the ultrasonic welding method is shown in Figure 1 The pre-treatment flow chart of the ultrasonic welding method is shown in Figure 2 The low amplitude pulse phase flow chart of the ultrasonic welding method is shown in Figure 3 The AI dynamic control flow chart of the ultrasonic welding method is shown in Figure 4 The pre-heating flow chart of the ultrasonic welding method is shown in Figure 5 The regular welding flow chart of the ultrasonic welding method is shown in Figure 6 The pressure holding and cooling flow chart of the ultrasonic welding method is shown in Figure 7 The quality detection flow chart of the ultrasonic welding method is shown in Figure 8 The schematic diagram of the generation mechanism of the ultrasonic welding porosity defect without energy guide rib is shown in Figure 9 The schematic diagram of the principle of the ultrasonic welding in situ energy guide rib is shown in Figure 10 The specific description is as follows.

[0046] Example 1 High-performance welding of aerospace PA66 composite material and PEI intercalation material

[0047] The raw material is an intercalated structure composed of carbon fiber reinforced polyamide with a thickness of 3 mm and polyetherimide with a thickness of 2 mm. The material is treated in a vacuum drying box at a constant temperature of 80°C for 12 hours to make the moisture content ≤0.1%. The laser roughening parameters are set as a scanning speed of 100 mm / s and a spot diameter of 50 μm. Periodic micro-pits with a depth of 30-50 μm and a pitch of 1-2 mm are formed on the surface of the material, with Ra≥3.2 μm.

[0048] The material is fixed and positioned by a pneumatic clamp, and the pressure is pre-set to 0.5 MPa to avoid damage to the material.

[0049] Turn on the ultrasonic generator and adjust the frequency to match the PA66 resonance frequency. The amplitude is divided into three sections: 8 μm→12 μm→8 μm, with an interval of 0.1 s between each section, and a total duration of 0.3 s. The pressure is controlled within the range of 0.5H+0.3 MPa, where H=3 mm, i.e. 0.5×3+0.3=1.8 MPa.

[0050] Turn on the infrared thermal imager for real-time monitoring. The target temperature is controlled within the range of 250°C~270°C according to Tg+20°C~Tg+50°C. When the dissipation modulus decreases at a rate of ≥5 MPa / s, trigger the amplitude jump and start the mode switching.

[0051] After switching, high-amplitude welding is performed. The amplitude is adjusted to 30 μm, the pressure is maintained at 1.8 MPa, and the welding time is 1.5 s. At the end of the welding process, low-temperature nitrogen gas with a flow rate of 5 L / min is used for purging, with a cooling rate of ≤5°C / s. After standing for 10 s, perform gradient pressure relief.

[0052] After the above process, the molecular chains of the material are oriented along the vibration direction, forming a high-orientation structure that guides energy concentration. The weld shear strength is ≥25 MPa.

[0053] X-ray CT detection shows that the porosity is <0.3%, and the unmelted defects are completely eliminated.

[0054] Through fatigue detection, the S-N curve slope is -2.8, and the life reaches 1.2×10 7 cycles, far exceeding the aviation standard.

[0055] Example 2 Rapid welding of carbon fiber composite material and polypropylene for automotive lightweight components

[0056] The material is polypropylene with a thickness of 4 mm and a PA66 reinforcing layer with a thickness of 2 mm.

[0057] The material is first chemically cleaned by wiping the surface with acetone to remove oil, and then dried to a moisture content of ≤0.2%.

[0058] By rolling the PP surface with a knurled wheel, a deep groove with a pitch of 1-1.5 mm and a depth of 0.1-0.2 mm is formed.

[0059] Turn on the ultrasonic generator, adjust the ultrasonic frequency to match the melting point characteristics of PP in the low amplitude pulse stage, and the amplitude is divided into three segment waveforms from 10 μm→15 μm→10 μm, with a total duration of 0.2 s.

[0060] The pressure is adjusted according to 0.5×4+0.3=2.3 MPa.

[0061] Turn on the infrared thermal imager for real-time monitoring, and the infrared temperature measurement range is 150℃~170℃.

[0062] Trigger amplitude jump E when the dissipation modulus drop rate ≥5 MPa / s '' Switch mode when the drop rate ≥3 MPa / s.

[0063] After switching, perform high-amplitude welding, adjust the amplitude to 25 μm, and adjust the pressure to 2.3 MPa.

[0064] The welding time is 1.6 s, and finally the pressure is released after natural air cooling to below 80℃.

[0065] After this process, it has low temperature adaptability, by reducing the vibration frequency and amplitude, avoiding PP overheating degradation, the weld tensile strength ≥18 MPa, single piece welding cycle ≤2 s, meeting the requirements of automobile production line rhythm, at the same time without laser equipment, knurling roughening cost reduced by 50%.

[0066] Comparative Example 1: Traditional ultrasonic welding (without energy guide ribs, without adaptive control)

[0067] The welding object is the same as Example 1, and the welding method is to use the conventional ultrasonic welding process, without energy guide rib structure, without temperature and dissipation modulus monitoring, without adaptive parameter adjustment.

[0068] The operation steps are briefly described as follows:

[0069] (1) The material is only dried at 80℃ for 12 hours, without laser roughening treatment;

[0070] (2) Directly use fixed amplitude (20 μm), fixed pressure (1.8 MPa) for welding, time 1.5 s;

[0071] (3) There is no temperature monitoring and amplitude switching mechanism during the welding process;

[0072] (4) After welding, natural cooling, no nitrogen forced cooling;

[0073] (5) No post-weld non-destructive testing and feedback mechanism.

[0074] The experimental results show that: there are obvious pores in the weld (X-ray CT shows that the porosity is > 3%); the un-melted area accounts for about 15%; the shear strength is only 12 MPa, which is far lower than 25 MPa or more of Example 1; the fatigue life is only 5x10 6 cycles, the S-N curve slope is -4.2, the performance is unstable; the welding cycle is short, but the rework rate is high, and the overall efficiency is low.

[0075] Comparative Example 2 Partially improved welding (with energy guide rib but without self-adaptive control)

[0076] The welding object is the same as that of Example 2, and the welding method is to use a prefabricated energy guide rib structure, but without real-time monitoring and self-adaptive control, and the welding parameters are fixed.

[0077] The operation steps are briefly described as follows:

[0078] (1) The material is cleaned with acetone and dried, and the moisture content is ≤0.2%;

[0079] (2) Form an energy guide rib (groove depth 0.2 mm, pitch 1.5 mm) by mechanical knurling;

[0080] (3) Weld for 1.6 s using a fixed amplitude (25 μm) and a fixed pressure (2.3 MPa);

[0081] (4) No temperature and dissipation modulus monitoring, no mode switching;

[0082] (5) Natural cooling after welding, no gradient pressure relief.

[0083] The experimental results show that: the weld appearance is good, but there are degradation areas caused by local overheating inside; the tensile strength is 14 MPa, which is lower than 18 MPa of Example 2; the welding cycle is stable at 2 s, but the consistency is poor, and the failure rate is about 10%; there is no nitrogen cooling, and the thermal stress residue causes micro-cracks; it cannot adapt to material batch differences, and frequent manual parameter adjustment is required.

Claims

1. A method of in-situ energy directing rib adaptive ultrasonic welding, characterized by, The method comprises the following operation steps: S1, pretreatment before welding: (1) drying treatment, put the PA66 composite material into the vacuum drying oven with temperature uniformity calibration function for 1-2 hours; (2) surface roughening treatment, put the dried PA66 composite material into the fiber laser to form a periodic micro-pit array with a depth of 30-50 μm and a pitch of 1-2 mm on the material surface; (3) pre-assembly and positioning, pre-assembly of the material is carried out through the pneumatic floating clamp, and sub-millimeter level accurate positioning is realized by combining the mechanical arm or XYZ platform; S2, low amplitude pulse stage: The PA66 composite material is welded by the ultrasonic generator with a low amplitude pulse, the ultrasonic amplitude is 0.6~1.0 μm, and the time length is 0.3~0.5 s; during the welding operation, the temperature field is monitored in real time, the welding zone temperature is monitored by an infrared thermal imager, the ultrasonic amplitude attenuation value is collected in real time by a piezoelectric sensor, and finally the welding surface micro displacement is monitored by a laser displacement sensor to judge the material creep behavior; S3, welding process closed loop control: adopt segmented welding strategy, the welding process is divided into three stages, preheating stage: low amplitude softening surface oxide layer, main welding stage: high amplitude combined with pressure pulse, promoting interface plastic flow, cooling stage: gradually reducing pressure and maintaining ultrasonic vibration, eliminating residual stress; S4, mode switching welding stage: (a) switching trigger condition: temperature threshold is set to ≥Tg+20℃ and ≤Tg+50℃, and dissipation modulus change rate is set to ΔE'' / Δt > 5MPa / s; (b) parameter adjustment: adjust the ultrasonic amplitude to 25~35 μm, control the pressure to increase to 0.6~1.0MPa, and extend the welding time to 1.0-1.5s; (c) adaptive compensation mechanism: dynamically correct the pressure formula according to the plate thickness: P = 0.5×H + 0.3, identify the molten flow state through acoustic emission signal, automatically terminate welding, and forcibly solidify the melt through the nitrogen blowing system with high-purity nitrogen at a pressure of 0.4~0.7MPa for 8~15s.

2. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1, wherein, The vacuum drying oven is adjusted to a temperature of 120℃±5℃ and a vacuum degree of ≥0.09MPa for drying, and after the operation is completed, the moisture content is detected by a Karl Fischer moisture meter to be ≤0.1% to be qualified, the fiber laser is adjusted to a scanning speed of 80~120 mm / s, a pulse width of 6~10 μs, and a spot diameter of 40~60 μm, and after the treatment is completed, the Ra is verified by a three-dimensional profilometer to be ≥3.2 μm.

3. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1, wherein, During pre-installation assembly, the center point is marked on the welding area by laser marking, the energy guide rib edge or feature point is recognized by an industrial camera, the initial contact pressure is applied by a pneumatic cylinder according to the elastic modulus of the energy guide rib material.

4. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1, wherein, The resonant point of the transducer is optimized according to the PA66 resonance frequency during the low amplitude pulse stage operation.

5. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1 or 3, wherein, The clamping force of the pneumatic floating clamp is evenly distributed, preventing local stress concentration from damaging the material. The infrared positioning and mechanical limiting double calibration ensure that the energy guide rib and the welding head are axially centered with an error of less than 0.1 mm. The clamp has a quick replacement adapter module that can adapt to different sizes / shapes of energy guide ribs.

6. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1, wherein, The duration of the preheating stage is 1-50 ms to soften the surface oxide layer with a low amplitude of 5-10 μm, the main welding stage lasts for 50-200 ms to promote interfacial plastic flow with a high amplitude of 15-25 μm combined with a pressure pulse of 0.5 MPa, and the cooling stage lasts for 200-500 ms to gradually reduce the pressure at a rate of 0.1-0.2 MPa / 100 ms and maintain ultrasonic vibration to eliminate residual stress.

7. The method of in-situ power directing rib adaptive ultrasonic welding of claim 1 or 3, wherein, During the welding operation, adaptive parameter dynamic adjustment is required. Through AI-driven parameter optimization, a neural network model is trained based on historical material type, thickness, and surface treatment process welding data to establish a parameter-quality mapping relationship. According to the current monitoring data, the model predicts the optimal parameter combination, which is dynamically executed in three modules: frequency band switching module, amplitude adjustment module, and pressure compensation module.

8. The method of in-situ power directing rib adaptive ultrasonic welding of claim 7, wherein, The frequency band switching module quickly switches the resonant frequency through the PZT transducer to match the material impedance changes. The amplitude adjustment module adjusts the input of the linear amplifier in real time to control the amplitude output. The pressure compensation module dynamically adjusts the pressure according to the displacement feedback of the servo electric cylinder to avoid overpressure or false welding.

9. The method of in-situ power directing rib adaptive ultrasonic welding of claim 3, wherein, After the welding process is completed, post-weld quality detection and feedback are required. First, non-destructive testing is performed, and the ultrasonic C-scan is used to detect the welding interface bonding rate. Then, shear force testing is performed by applying a vertical tensile force of 0.1-1 kN in situ to verify the mechanical strength. After passing the non-destructive testing, the welding parameters and quality results are stored in the database, and the AI model weight is updated to improve the subsequent welding adaptability, thereby completing data iteration optimization.

10. Use of the method according to any one of claims 1 to 9, characterized in that The method is used for welding of PA66 composite materials and PEI interlayer materials for aviation structural parts or carbon fiber composites and polypropylene for automotive lightweight parts.

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