Laser shock peening method for in-situ non-detachable structure

Abstract

The invention relates to the technical field of laser shock peening, and particularly discloses a laser shock peening method for an in-situ non-detachable structure, and the method comprises the following steps: inspection before laser shock, equipment preparation and detection of an area to be peened; carrying out unfolding installation and function debugging on the laser strengthening equipment; laser pulse energy, pulse width, spot size and strengthening strength are tested, so that laser parameters are stable and meet preset requirements; a laser path is generated according to the to-be-strengthened area, and arrangement of an absorption layer and a restraint layer, energy setting, laser shock processing and quality inspection are completed in sequence; and finishing final quality inspection and arrangement and resetting of the equipment and the site. According to the method, the strengthening effect equivalent to that of vertical incidence can still be obtained under the complex space condition, the spot size and path planning are optimized, the amplitude, depth and distribution of residual compressive stress are more uniform, and therefore the anti-fatigue capacity and long-term service reliability of the structure are improved.

Description

Technical Field

[0001] This invention relates to a laser shock strengthening method, specifically a laser shock strengthening method for in-situ non-removable structures, and belongs to the field of laser shock strengthening technology. Background Technology

[0002] Laser shock peening is a processing technique that uses high-energy laser pulses to generate high-density plasma on the material surface, forming a strong shock wave that acts on the metal surface. This shock wave can induce plastic deformation of the surface material under extremely high strain rates, instilling high levels of residual stress within a certain depth range, thereby improving the structure's fatigue resistance, wear resistance, and stress corrosion resistance. However, when performing laser shock peening on complex structures for fatigue resistance, there are often many in-situ areas that are either non-removable or difficult to access after assembly. The laser beam's incident direction is restricted, leading to insufficient strengthening depth or uneven distribution of residual stress, thus affecting the fatigue resistance effect of laser shock peening. Currently, there is no adaptive laser shock peening process for non-removable structures, therefore, there is room for improvement. Summary of the Invention

[0003] To address the problems in the prior art, this invention provides a laser shock strengthening method for in-situ non-removable structures.

[0004] The objective of this invention can be achieved through the following technical solutions: A laser shock strengthening method for in-situ non-removable structures, the method comprising the following steps: Step 1: Inspection before laser shock, equipment preparation, and detection of the area to be strengthened; Step Two: Deployment, installation, and functional debugging of the laser enhancement equipment; Step 3: Test the laser pulse energy, pulse width, spot size, and enhancement intensity to stabilize the laser parameters and ensure they meet the preset requirements; Step 4: Generate a laser path based on the area to be strengthened, and sequentially complete the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection; Step 5: Complete the final quality inspection and tidy up and reset the equipment and site to ensure that the reinforcement operation is completed safely and meets the requirements.

[0005] Optionally, the pre-laser shock inspection, equipment preparation, and area inspection in step one specifically include checking and verifying the required specialized process equipment and confirming the model of the end processing head, conducting an exposure inspection of the area to be strengthened, verifying the absence of obstruction using a beam positioning mold, ensuring that the area has been inspected for flaws and its surface cleanliness, and arranging laser protection and water protection for non-strengthened areas to create a safe processing environment for subsequent strengthening operations.

[0006] Optionally, the deployment, installation, and functional debugging of the laser enhancement equipment in step two specifically includes completing the layout and connection of the laser cabin, accessory cabin, robot, external optical path, water path, air path, and electrical system; using the beam positioning mold and path positioning mold to debug the robot's posture; and simultaneously calibrating the external optical path and laser to ensure that the entire system operates stably, parameters are adjustable, and the predetermined laser incident direction is achieved.

[0007] Optionally, the specific parameters of the laser in step three are: single pulse energy of 3.2J to 4.6J, pulse width of 20ns to 25ns, spot overlap rate of 50%, spot shape of rectangle or circle, black tape or black paint as absorption layer, and flowing water layer as constraint layer.

[0008] Optionally, step three also includes the calculation of laser power density, specifically: laser power density = single pulse energy / (spot area * pulse width), preferably the laser power density with the largest peak value of surface residual stress.

[0009] Optionally, the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection in step four are as follows: After generating offline and online laser beam movement paths for the areas to be strengthened (Area 1 to Area 3), the following steps are performed sequentially according to the planned paths: applying black tape (forming an absorption layer), arranging a water constraint layer (forming a constraint layer), setting the pulse energy, and laser shock processing. The resulting shock spots are then inspected and their quality verified point by point. The sub-paths and each area are strengthened to ensure no missed areas or ablation during processing, and that the strengthened coverage is complete.

[0010] Optionally, step five includes a final quality inspection after reinforcement, confirming the impact spot coverage and processing technology of all reinforced areas, safely shutting down and transferring the equipment according to preset requirements, cleaning and removing protective measures at the site, and reviewing and registering all tools and process equipment to ensure that the reinforcement operation is safely completed, the regional quality meets the technical standards, and the equipment and work site are restored to a usable state.

[0011] The beneficial effects of this invention are: 1. Overcome the spatial limitation problem of in-situ non-removable structures and achieve accurate laser accessibility determination.

[0012] This invention, by introducing laser reachability analysis and optimized incident direction design, enables the laser beam to precisely determine the direction range in which it can directly enter the area to be strengthened without dismantling the surrounding frame, skin, or reinforcement components. This method effectively solves the technical bottleneck of traditional processes being unable to strengthen deep cavity structures such as concave corners and frame beam joints.

[0013] 2. It achieves good uniformity of strengthening effect and significantly improves the fatigue performance of the structure.

[0014] This invention can still achieve a strengthening effect comparable to that of vertical incidence under complex spatial conditions. By optimizing the spot size and path planning, the amplitude, depth and distribution of residual compressive stress are made more uniform, thereby improving the fatigue resistance and long-term service reliability of the structure. Attached Figure Description

[0015] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 This is a process flow diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of the area to be strengthened on the workpiece in an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the incident direction of the laser beam in the region to be strengthened in an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1-3 As shown, a laser shock peening method for in-situ non-removable structures includes the following steps: Step 1: Inspection before laser shock, equipment preparation, and detection of the area to be strengthened; Step Two: Deployment, installation, and functional debugging of the laser enhancement equipment; Step 3: Test the laser pulse energy, pulse width, spot size, and enhancement intensity to stabilize the laser parameters and ensure they meet the preset requirements; Step 4: Generate a laser path based on the area to be strengthened, and sequentially complete the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection; Step 5: Complete the final quality inspection and tidy up and reset the equipment and site to ensure that the reinforcement operation is completed safely and meets the requirements.

[0021] Specifically, the pre-laser shock inspection, equipment preparation, and area inspection in step one include checking and verifying the required specialized process equipment and confirming the model of the end processing head, conducting an exposure inspection of the area to be strengthened, verifying the absence of obstruction using a beam positioning mold, ensuring that the area has been inspected for flaws and its surface cleanliness, and arranging laser protection and water protection for non-strengthened areas to create a safe processing environment for subsequent strengthening operations. Specifically, the deployment, installation, and functional debugging of the laser enhancement equipment in step two includes completing the layout and connection of the laser cabin, accessory cabin, robot, external optical path, water path, air path, and electrical system; using beam positioning molds and path positioning molds to debug the robot's posture; and calibrating the external optical path and laser to ensure that the entire system operates stably, parameters are adjustable, and the predetermined laser incident direction is achieved.

[0022] Specifically, the laser parameters in step three are as follows: single pulse energy of 3.2J to 4.6J, pulse width of 20ns to 25ns, spot overlap rate of 50%, and the spot is rectangular or circular. Black tape or black paint is used as the absorption layer, and the flowing water layer is used as the constraint layer. Step three also includes the calculation of laser power density, specifically: laser power density = single pulse energy / (spot area * pulse width). Preferably, the laser power density is the laser power density with the highest peak value of surface residual stress.

[0023] Specifically, the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection in step four are as follows: After generating offline and online laser beam movement paths for the areas to be strengthened (Area 1 to Area 3), the following steps are performed sequentially according to the planned paths: applying black tape (forming an absorption layer), arranging a water constraint layer (forming a constraint layer), setting the pulse energy, and laser shock processing. The resulting shock spots are then inspected and their quality verified point by point. The sub-paths and each area are strengthened to ensure no missed areas or ablation during processing, and that the strengthened coverage is complete.

[0024] Specifically, step five includes a final quality inspection after reinforcement, confirming the impact spot coverage and processing technology of all reinforced areas, safely shutting down and transferring the equipment according to preset requirements, cleaning and removing protective measures at the site, and reviewing and registering all tools and process equipment to ensure that the reinforcement operation is safely completed, the regional quality meets the technical standards, and the equipment and work site are restored to a usable state.

[0025] To better illustrate the methods in this application, the present invention will be described in detail below with reference to specific embodiments.

[0026] This embodiment relates to a method for post-flight laser shock reinforcement of the lower right side ear plate of an aircraft fuselage structure. The area to be reinforced is the R region at the root of the right lower right side ear plate of the aircraft fuselage structure after flight. Figure 2 As shown, it comprises three areas: Area 1 is the rounded corner above the flash corner, with a reinforced area covering a rounded corner of 10mm + 3mm + 0mm in length; Area 2 is the rounded corner at the flash corner, with a reinforced area covering a rounded corner of 5mm + 3mm + 0mm in length; Area 3 is the rounded corner below the flash corner, with a reinforced area covering a rounded corner of 5mm + 3mm + 0mm in length. The main steps include: Step 1: Inspection before laser shock, equipment preparation, and detection of the area to be strengthened.

[0027] Before the reinforcement operation, verify the model of the end-effector to be used, and inventory and record the models and quantities of specialized process equipment, general process equipment, and auxiliary materials. Inspect the R-zone at the root of the right lower ear plate of the aircraft frame 1 after flight to confirm that the shielding panel has been cut. Use the inspection mold for the area to be reinforced to verify that the area is fully exposed. Install the beam positioning mold on the surface of the area to be reinforced, ensuring that there are no obstructions that would affect the transmission of the laser beam. Check the aircraft quality records. After the area to be reinforced is inspected, check its surface condition to ensure that the surface is clean, dry, and free of rust, damage, oil stains, and coating deposits. Set up a protective curtain within a diameter of about 2mm around the area to be reinforced. Cover the non-reinforced areas with a laser protective film and then a waterproof film. Shield the water splash area, set up wastewater buckets and waterproof films, and lay waterproof mats on the ground. After completing environmental protection, the laser chamber and accessory chamber are deployed in sequence, the robot is installed, the external optical path is set up, and the water, gas and electrical systems are connected. Then the power is turned on to ensure that the power supply, circulating water and circulating gas are all operating normally, ensuring the stability of the foundation of the laser shock peening equipment and the safety of the working environment.

[0028] Step 2: Deployment, installation, and functional debugging of the laser enhancement equipment.

[0029] After completing environmental protection, the laser chamber and accessory chamber were deployed sequentially, the robot was installed, the external optical path was established, and the water, gas, and electrical systems were connected. Power was then turned on to ensure the power supply, circulating water system, and circulating gas system were all functioning correctly. The robot was debugged using beam positioning and path positioning molds, and its posture was adjusted according to the incident direction of each laser beam. Then, the external optical path and laser equipment were debugged sequentially to ensure that the laser output direction, energy, and optical path status all met the requirements for enhanced operations, achieving precise configuration of the laser system under complex in-situ conditions.

[0030] Step 3: Test the pulse energy, pulse width, spot size, and enhancement intensity to ensure that the laser parameters are stable and meet the requirements.

[0031] During the parameter testing phase, two sets of pulse energies, 4J and 5.2J, were tested, and all results were verified. The maximum and minimum values ​​of the 4J pulse energy test results were controlled within the range of 4J ± 0.2J, and the maximum and minimum values ​​of the 5.2J pulse energy test results were controlled within the range of 5.2J ± 0.2J. Subsequently, 25ns laser pulse width and Φ3mm impact spot size tests were conducted. The test data were specially inspected, and the average pulse width should meet the process requirement of 25ns ± 2ns, and the impact spot size should be within the range of Φ3mm ± 0.1mm. Finally, laser shock intensity testing was conducted according to the specified AlmenC specimen strengthening process parameters (pulse energy 4J±0.2J, vertical incident impact spot size Φ2mm±0.1mm, overlap rate 50%, single impact, water constraint layer, black tape absorption layer, laser pulse width 25ns±2ns, pulse frequency 1Hz). Subsequently, a special inspection was carried out on the arc height deformation value of the strengthened AlmenC specimen, and its arc height should meet the process judgment standard of 0.35mm~0.43mm.

[0032] Step 4: Generate laser paths based on the region, and sequentially complete the arrangement of the absorption layer, constraint layer (water layer), energy setting, laser shock processing, and quality inspection.

[0033] Five rows of laser beams are arranged on the rounded corner surfaces of regions one, two, and three. Based on the characteristics of each region, offline laser beam movement paths are generated for regions one through three respectively. One offline laser beam movement path is generated for the first two rows of laser beams in each region, and another is generated for the third through fifth rows, for a total of six offline laser beam movement paths. Figure 3 As shown, the incident angle between the laser beams of the first and second rows and the normal to the flash edge is 0°±3°, and the incident angle between the laser beams of the third, fourth, and fifth rows and the normal to the curved surface of the rounded corner's central axis is 0°±3°. These are then converted into six online moving paths using a path positioning mold. During the strengthening process, the pulse energy is monitored in real time. The pulse energy of the first to third rows should be maintained at 4J±0.2J, and the pulse energy of the fourth to fifth rows should be maintained at 5.2J±0.2J. Simultaneously, the condition of the black tape in the absorption layer is monitored to ensure there is no damage. The laser beam moving paths of the third to fifth rows in region two are verified. After confirming that the spot coverage area matches the detection mold for the area to be strengthened, it is divided into six sub-paths, and strengthening is carried out sequentially. Subsequently, the processing head window was inspected, the covered area was cleaned, black tape was applied, and a water constraint layer was applied (55KPa~60KPa, nozzle distance 40mm~60mm). The pulse energy was set according to the spot position to complete the strengthening process. After each sub-path was completed, the impact spot was inspected to ensure there were no leaks or ablation. The same process was followed to strengthen each row of spots in regions one through three. This achieved a highly uniform and repeatable laser shock strengthening effect for in-situ, non-removable structures.

[0034] Step 5: Complete the final quality inspection and tidy up and reset the equipment and site to ensure that the reinforcement operation is completed safely and meets the requirements.

[0035] All reinforced areas were inspected, and the impact marks were visually checked to confirm that there were no leaks or ablation and that the reinforced areas were completely covered by the impact marks. The mobile reinforcement equipment was then moved according to the subsequent aircraft repair procedures. On-site debris was cleared and the ground was cleaned. Finally, the models and quantities of special process equipment, general process equipment and auxiliary materials were counted and verified to ensure consistency with the records.

[0036] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A laser shock peening method for in-situ non-removable structures, characterized in that, The method includes the following steps: Step 1: Inspection before laser shock, equipment preparation, and detection of the area to be strengthened; Step Two: Deployment, installation, and functional debugging of the laser enhancement equipment; Step 3: Test the laser pulse energy, pulse width, spot size, and enhancement intensity to stabilize the laser parameters and ensure they meet the preset requirements; Step 4: Generate a laser path based on the area to be strengthened, and sequentially complete the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection; Step 5: Complete the final quality inspection and tidy up and reset the equipment and site.

2. The laser shock peening method for in-situ non-removable structures according to claim 1, characterized in that, The pre-laser shock inspection, equipment preparation, and area to be strengthened inspection in step one specifically include checking and verifying the required special process equipment and confirming the model of the end processing head, conducting an exposure inspection of the area to be strengthened, verifying the absence of obstruction using a beam positioning mold, ensuring that the area has been inspected for flaws and its surface cleanliness, and arranging laser protection and water protection for non-strengthened areas.

3. The laser shock peening method for in-situ non-removable structures according to claim 1, characterized in that, The second step, which involves the deployment, installation, and functional debugging of the laser enhancement equipment, specifically includes the arrangement and connection of the laser cabin, accessory cabin, robot, external optical path, water path, air path, and electrical system; the debugging of the robot's posture using beam positioning molds and path positioning molds; and the calibration of the external optical path and laser.

4. The laser shock peening method for in-situ non-removable structures according to claim 1, characterized in that, In step three, the single pulse energy is 3.2J to 4.6J, the pulse width is 20ns to 25ns, the spot overlap rate is 50%, the spot is rectangular or circular, black tape or black paint is used as the absorption layer, and the flowing water layer is used as the constraint layer.

5. The laser shock strengthening method for in-situ non-removable structures according to claim 4, characterized in that, Step three also includes the calculation of laser power density, specifically: laser power density = single pulse energy / (spot area * pulse width).

6. The laser shock strengthening method for in-situ non-removable structures according to claim 1, characterized in that, The specific details of step four, including the arrangement of the absorption layer and constraint layer, energy setting, laser shock processing, and quality inspection, are as follows: After generating the offline and online laser beam movement paths for the area to be strengthened, the black tape is pasted, the water constraint layer is arranged, the pulse energy is set, and the laser shock processing is carried out in sequence according to the planned path. The resulting shock spots are then checked and their quality verified point by point.

7. The laser shock peening method for in-situ non-removable structures according to claim 1, characterized in that, Step five includes the final quality inspection after reinforcement, confirming the impact spot coverage and processing technology of all reinforced areas, safely shutting down and relocating the equipment according to preset requirements, and cleaning and removing protective measures at the site.

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