CN115558777A - Aircraft engine fan blade treatment method - Google Patents
Aircraft engine fan blade treatment method Download PDFInfo
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- CN115558777A CN115558777A CN202211308084.6A CN202211308084A CN115558777A CN 115558777 A CN115558777 A CN 115558777A CN 202211308084 A CN202211308084 A CN 202211308084A CN 115558777 A CN115558777 A CN 115558777A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D10/00—Modifying the physical properties by methods other than heat treatment or deformation
- C21D10/005—Modifying the physical properties by methods other than heat treatment or deformation by laser shock processing
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Abstract
The invention relates to the field of maintenance of aero-engines, in particular to a method for processing an aero-engine fan blade, which can generate high residual compressive stress in a region of the blade within a depth range of more than 1.5mm, has very low surface roughness, obviously improves the fatigue damage resistance of the blade and ensures the surface integrity of the blade, and comprises the following steps: a. determining laser energy density, laser spot overlapping rate and spot shape; b. determining the motion track of a mechanical arm for controlling the laser beam, so that the light spot of the incident laser beam covers the whole strengthening area according to the required overlapping rate, and the incident angle of the laser beam is vertical incidence or oblique incidence; c. adhering a protective layer to the strengthening area, clamping the blade on a clamp, and applying a restraint layer; d. controlling the light spot to move according to a set track, and performing laser shock peening treatment; e. and after the strengthening is finished, whether the surface of the blade has the defects of leakage strengthening, burning and the like is checked. If there is no defect, it is qualified, if there is defect, it needs to be reworked.
Description
Technical Field
The invention relates to the field of maintenance of aero-engines, in particular to a method for processing fan blades of an aero-engine.
Background
The aeroengine has the characteristics of high rotating speed, high maneuverability and high acceleration, the blade is used as one of core parts of the aeroengine, the main failure mode is fatigue failure, the blade bears various loads such as stretching, bending and vibration in the working process, and the working condition is extremely severe. In the running process of severe environment, foreign matters such as birds, sand, hail, metal debris and the like can be sucked into the engine inevitably, and the fan blades of the engine can be damaged firstly when the foreign matters are sucked into the engine. The damage of foreign objects on the blades is mainly expressed as pits, gaps, cracks, tearing, local deformation, material loss and the like, and particularly, the damage of the foreign objects is easily generated after the fan blades at the air inlet end are impacted by foreign objects (such as sand and stones) sucked by strong airflow.
As the blade is usually made of titanium alloy material, the fatigue life of the blade is greatly reduced due to the notch/crack sensitivity of the titanium alloy, the elastic stress concentration, residual stress and possible microcracks caused by foreign object damage can greatly reduce the fatigue strength of the blade under the vibration load condition, so that the blade of the engine is subjected to fatigue fracture failure in advance, fracture fragments generate secondary damage to a subsequent runner of the engine, the service life of the engine is shortened due to the crack expansion of the blade in a light case, and the death of the engine due to the fracture of the blade in a heavy case, thereby seriously threatening the flight safety.
At present, residual stress is formed on the surface of the blade through shot blasting to improve the fatigue performance of the blade, residual compressive stress can be generated only in the range of about 100 mu m on the surface by the existing shot blasting strengthening technology, the expansion of fatigue cracks of the blade cannot be effectively inhibited, and the improvement of the surface integrity of the blade is restricted due to poor surface roughness of the blade after shot blasting.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for processing a fan blade of an aeroengine, which can generate high residual compressive stress in a region of the blade within the depth range of more than 1.5mm, has very low surface roughness, obviously improves the fatigue damage resistance of the blade and ensures the surface integrity of the blade.
The technical scheme adopted by the invention is as follows: the aircraft engine fan blade processing method comprises the following steps:
a. firstly, determining laser energy density, laser spot lap joint rate and spot shape according to the thickness of a blade to be strengthened and a blade area to be strengthened;
b. determining the motion track of a mechanical arm for controlling a laser beam according to the shape and the angle of an area to be strengthened of the blade, so that the light spot of the incident laser beam covers the whole strengthening area according to the required overlapping ratio, and the incident angle of the laser beam is vertical incidence or oblique incidence;
c. adhering a protective layer to a strengthening area of the blade to be strengthened, clamping the blade on a clamp, and applying a restraint layer to the strengthening area;
d. setting laser shock peening process parameters, controlling light spots to move according to a set track, and performing laser shock peening treatment;
e. and after the strengthening is finished, checking whether the surface of the blade has defects such as leakage strengthening, burn and the like. If the defect is not present, the product is qualified, and if the defect is present, the product needs to be reworked.
Further, in the step a, the thickness of the blade ranges from 0.2mm to 15mm.
Further, in step a, the laser energy density is in the range of 3GW/cm 2 ～10GW/cm 2 。
Further, in step a, the shape of the light spot is a circular light spot or a square light spot.
Further, in the step a, when the laser spot is round, the lapping rate of the laser spot is 30-80%; when square light spots are formed, the lapping rate of the laser light spots is 5% -80%, and a single-sided or double-sided laser shock strengthening process can be adopted if necessary, so that the deformation of the blade caused by laser shock strengthening is reduced.
Further, in the step b, the light spot coverage is realized in a mode that the light beam is not moved and the part moves, or the light beam is moved and the part does not move.
Further, in the step b, the mechanical arm is a 6-degree-of-freedom mechanical arm or a five-axis machine tool.
Furthermore, in the step c, the laser shock peening pretreatment operation comprises: (1) attaching a black adhesive tape or an aluminum foil adhesive tape to the reinforced area or spraying black paint to the reinforced area to serve as a protective layer; (2) the back surface is attached with a wave guide layer; (3) and loading water or transparent glass as a constraint layer, wherein if the constraint layer is purified ultrapure water, the thickness range of the water film is 0.5-3 mm.
Furthermore, in the step d, both sides of the blade are strengthened, so that the deformation caused by residual stress is reduced; wherein, if a circular light spot is adopted, the lamination is selected for multiple times of strengthening.
Furthermore, in the step e, whether the strengthened area is completely covered by the faculae after the laser shock strengthening, whether the strengthened area has leakage strengthening and whether the surface of the blade has burn are checked; the reworking comprises the following steps: and performing secondary strengthening on the area which is not completely covered by the light spot and the leakage strengthening area, and polishing, finishing or finishing the burn area to remove the defects.
The invention has the beneficial effects that: through the mode of laser shock peening, can produce high residual compressive stress in the region that the blade exceeds 1.5mm degree of depth within range, the surface has very low surface roughness simultaneously, shows the anti fatigue failure ability that promotes the blade, guarantees blade surface integrality. The invention can effectively solve the failure problem caused by the fatigue damage of the blade due to the severe service environment, greatly prolong the service life of the blade of the aeroengine and improve the use reliability of the blade in the severe environment.
Drawings
FIG. 1 is a schematic diagram of laser shock peening technology.
Fig. 2 is a schematic diagram of circular spot overlapping.
Fig. 3 is a schematic diagram of square spot overlapping.
FIG. 4 is a schematic diagram of an embodiment of laser shock peening of a blade.
Reference numerals are as follows: the ultrasonic wave absorption layer comprises an absorption layer 1, a constraint layer 2, a plasma explosion layer 3, a laser beam 4, a shock wave 5, a metal part 6, a circular light spot lap joint 7, a square light spot lap joint 8, a laser beam 9, an engine blade 10, a protective layer 11, a constraint layer 12, an ultrasonic coupling agent 13 and a wave absorption layer 14.
Detailed Description
The aircraft engine fan blade processing method as shown in fig. 1 to 4 comprises the following steps: a. firstly, selecting proper laser energy density, laser spot lap joint rate and spot shape according to the thickness of the blade to be strengthened and the area to be strengthened, wherein the spot shape can be a circular spot or a square spot; b. according to the shape and the angle of the area to be strengthened of the blade, a computer is used for programming to control the movement of the mechanical arm, so that the laser beam 9 is vertically incident or is incident at a certain angle, and the light spot covers the whole strengthening area according to the required overlapping ratio; c. pasting a protective layer 11 on a strengthening area of the blade to be strengthened, wherein the protective layer 11 can be a black adhesive tape or an aluminum foil adhesive tape, then clamping the blade on a special clamp, and applying a restraint layer 12 on the strengthening area, wherein the restraint layer 12 is usually water or transparent glass; d. setting laser shock peening process parameters, controlling light spots to move according to a set track, and performing laser shock peening treatment; e. and after the strengthening is finished, whether the surface of the blade has the defects of leakage strengthening, burning and the like is checked. If the defect is not present, the product is qualified, and if the defect is present, the product needs to be reworked.
As a further optimization of the steps, the processing quality of the blade is further improved. For step a, the blade 10 is a thin-walled part, generally having a thickness of 0.2mm to 15mm. Setting the laser energy density to be 3GW/cm according to different thicknesses 2 ～10GW/cm 2 For the lap ratio: if the light spot is a circular light spot, 30-80% is selected, and if the light spot is a square light spot, 5-80% is selected. If necessary, the single-sided or double-sided laser shock strengthening process can be adopted, and the deformation of the thin-walled part caused by laser shock strengthening can be reduced. For step b, the light spot coverage can be realized by adopting a mode that the light beam does not move the part or the light beam moves the part. The laser shock peening motion mechanical arm needs to adopt a mechanical arm with 6 degrees of freedom or a five-axis machine tool. For step c, the laser shock peening pretreatment operation is preferably performed mainly by: (1) attaching black adhesive tape, aluminum foil adhesive tape or spraying black paint on the reinforced area, wherein the adhesive tape absorbs laserAnd the function of protecting the leaves from laser burn during strengthening. (2) The back is attached with a wave guide layer which is made of a paste material with acoustic impedance close to that of the part and aims to conduct back shock waves. (3) And loading the constraint layer 12, wherein the constraint layer is required to be added on the surface of the part to obtain a good strengthening effect, the constraint layer is purified ultrapure water, and the thickness of a water film is 0.5-3 mm. In step d, both sides of the blade are reinforced to reduce deformation due to residual stress. If a circular spot is used, consideration is given to whether the absorbing layer can withstand multiple spot irradiations without being damaged, and multiple layers are required to be reinforced when necessary. In step e, checking whether the strengthened area is completely covered by the light spot after the laser shock strengthening, whether the strengthened area has the defects of missing strengthening, whether the surface of the blade has burn, and the like. And the reworking refers to secondary strengthening of the area which is not completely covered by the light spots and the leakage strengthening area, and polishing, finishing or finishing the burn area to remove defects.
Examples
Example 1
Compared with the traditional shot blasting process, the method proves the related technical advantages of the application.
The laser shock peening research is carried out on 6 fan blades, notches are artificially prefabricated, and the process that the blades are damaged by foreign objects in severe environment is simulated. The surface residual stress of the blade is measured by an X-ray stress testing instrument, the vibration fatigue performance of the blade under the bending frequency of the blade is measured by an SAI60F-H560BAC type vibration fatigue testing machine, the vibration fatigue limit of the blade is measured by adopting a step-by-step loading method, and the test result is shown in table 1.
The test of laser shock peening of 6 fan blades shows that the original surface of the blade has residual compressive stress of-432.4 MPa to-483.5 MPa after shot blasting treatment; the surface of the laser shock-strengthened blade has a residual compressive stress of-817.1 MPa to-886.3 MPa, and the notch vibration fatigue limit of the blade can be averagely improved by 63.15 percent compared with that of the traditional shot blasting technology, so that the fatigue life of the blade under the condition of foreign object damage is greatly improved, the probability of fatigue damage of the blade is reduced, and the use reliability of the blade in severe environment is improved.
TABLE 1 peening and laser shock peening of blade surface residual stress and fatigue limit
Example 2
The wall thickness of a reinforced area of a secondary fan blade of a certain turbofan engine is 0.8 mm-3 mm. The implementation steps for improving the fatigue performance of the blade in the embodiment are as follows: 1. firstly, selecting process parameters according to the thickness and the area of the blade to be strengthened as follows: the laser single pulse energy is 10J, the laser pulse width is 20ns, the spot diameter is 4mm, the spot shape is a circular spot, the laser spot overlapping rate is 50%, and double-sided reinforcement is adopted. 2. According to the analysis of the service conditions of the blades, when the engine blades operate, the air inlet edges are easily damaged by foreign objects to form gaps, so that the fatigue strength of the blades is greatly reduced, and the flight safety is threatened. Therefore, in the embodiment, the range of 30mm from the front edge of the air inlet edge is selected as the laser shock strengthening area, and the motion path of the mechanical arm is programmed by computer software, so that the full coverage of the strengthening area is realized. 3. Laser shock peening pretreatment comprising: (1) and sticking a black adhesive tape on the area needing to be strengthened as a protective layer, wherein the protective layer is used for absorbing laser and protecting the blade from being burnt by the laser. (2) And uniformly coating a layer of ultrasonic coupling agent on the back of the reinforced area, and attaching a guided wave material, wherein the ultrasonic coupling agent and the guided wave material aim at guiding away the shock wave transmitted to the back. (3) And clamping the blade in a special blade laser shock peening clamp. (4) And applying a uniform ultrapure water film as a restraint layer on the strengthening area, wherein the restraint layer is used for reflecting shock waves generated by plasma explosion and enabling the shock waves to propagate to one side of the part as far as possible. 4. After the pretreatment is ready, the blades are strengthened, and the strengthening process needs to be carried out for multiple times in a layering mode. One side is strengthened first, and the other side is strengthened. 5. And after the strengthening is finished, whether the surface of the blade has the defects of leakage strengthening, burning and the like is checked. If the defect is not present, the product is qualified, and if the defect is present, the product needs to be reworked.
According to the embodiment, the reliability of the aero-engine fan blade in severe environment is effectively improved, the problem of failure of the blade caused by fatigue damage is solved, the technical advantages are obvious, and the market popularization prospect is wide.
Claims (10)
1. The aircraft engine fan blade processing method is characterized by comprising the following steps:
a. firstly, determining laser energy density, laser spot lap joint rate and spot shape according to the thickness of a blade to be strengthened and a blade area to be strengthened;
b. determining the motion track of a mechanical arm for controlling a laser beam according to the shape and the angle of an area to be strengthened of the blade, so that the light spot of the incident laser beam covers the whole strengthening area according to the required overlapping ratio, and the incident angle of the laser beam is vertical incidence or oblique incidence;
c. adhering a protective layer to a strengthening area of the blade to be strengthened, clamping the blade on a clamp, and applying a restraint layer to the strengthening area;
d. setting laser shock peening process parameters, controlling light spots to move according to a set track, and performing laser shock peening treatment;
e. and after the strengthening is finished, whether the surface of the blade has the defects of leakage strengthening, burning and the like is checked. If the defect is not present, the product is qualified, and if the defect is present, the product needs to be reworked.
2. The aircraft engine fan blade treatment method of claim 1, wherein: in the step a, the thickness range of the blade is 0.2 mm-15 mm.
3. The aircraft engine fan blade treatment method of claim 2, wherein: in the step a, the laser energy density range is 3GW/cm 2 ～10GW/cm 2 。
4. The aircraft engine fan blade treatment method of claim 3, wherein: in the step a, the shape of the light spot is a circular light spot or a square light spot.
5. The aircraft engine fan blade treatment method of claim 4, wherein: in the step a, when the laser spot is round, the lapping rate of the laser spot is 30-80 percent; when square light spots are formed, the lapping rate of the laser light spots is 5% -80%, and a single-sided or double-sided laser shock strengthening process can be adopted if necessary, so that the deformation of the blade caused by laser shock strengthening is reduced.
6. An aircraft engine fan blade treatment method according to claim 1, 2, 3, 4 or 5, wherein: in the step b, the light spot coverage is realized in a mode that the light beam is not moved and the part moves, or the light beam is moved and the part does not move.
7. The aircraft engine fan blade treatment method of claim 1, 2, 3, 4 or 5, wherein: in the step b, the mechanical arm is a mechanical arm with 6 degrees of freedom or a five-axis machine tool.
8. An aircraft engine fan blade treatment method according to claim 1, 2, 3, 4 or 5, wherein: in the step c, the laser shock peening pretreatment operation comprises the following steps: (1) attaching a black adhesive tape or an aluminum foil adhesive tape to the reinforced area or spraying black paint to the reinforced area to serve as a protective layer; (2) the back surface is attached with a wave guide layer; (3) and loading water or transparent glass as a constraint layer, wherein if the constraint layer is purified ultrapure water, the thickness range of the water film is 0.5-3 mm.
9. The aircraft engine fan blade treatment method of claim 1, 2, 3, 4 or 5, wherein: in the step d, reinforcing both sides of the blade to reduce deformation caused by residual stress; wherein, if a circular light spot is adopted, the lamination is selected for multiple times of strengthening.
10. The aircraft engine fan blade treatment method of claim 1, 2, 3, 4 or 5, wherein: in the step e, whether the strengthened area is completely covered by the light spot after the laser shock strengthening, whether the strengthened area has the leakage strengthening, and whether the surface of the blade has the burn is checked; the reworking comprises the following steps: and performing secondary strengthening on the area which is not completely covered by the light spot and the leakage strengthening area, and polishing, finishing or finishing the burn area to remove the defects.
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| CN202211308084.6A CN115558777A (en) | 2022-10-25 | 2022-10-25 | Aircraft engine fan blade treatment method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115992337A (en) * | 2023-03-23 | 2023-04-21 | 国营川西机器厂 | Reinforced repair method for blade tip of high-temperature alloy compressor blade and repair powder |
| CN116038505A (en) * | 2023-04-03 | 2023-05-02 | 国营川西机器厂 | Fan rotor blade polishing method based on grading |
-
2022
- 2022-10-25 CN CN202211308084.6A patent/CN115558777A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115992337A (en) * | 2023-03-23 | 2023-04-21 | 国营川西机器厂 | Reinforced repair method for blade tip of high-temperature alloy compressor blade and repair powder |
| CN116038505A (en) * | 2023-04-03 | 2023-05-02 | 国营川西机器厂 | Fan rotor blade polishing method based on grading |
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