A kind of squirrel cage structure thin-walled hollow shaft shot peening clamp and processing method

Abstract

The application discloses a kind of squirrel cage structure thin-walled hollow shaft shot peening clamps and processing methods, clamp includes with automatic centering branch angle and annular clamping mechanism's clamp base, and the split type protection clamp made of wear-resistant nylon PA66, by long center column auxiliary positioning, triple structure is realized in non-shot peening area comprehensive protection, still be equipped with size matching shot peening test piece clamp.There is also a kind of processing method, using three-position multi-angle shot peening path carries out shot peening processing.The application greatly improves clamping efficiency and protection reliability, avoids thin-walled rib deformation, so that the fatigue strength of part is significantly improved, and is suitable for the shot peening strengthening of aero-engine output shaft.

Description

Technical Field

[0001] This invention belongs to the field of shot peening technology, and specifically relates to a shot peening fixture for a squirrel-cage structure thin-walled hollow shaft. It also relates to a method for shot peening a squirrel-cage structure thin-walled hollow shaft. Background Technology

[0002] As a core transmission component, the output shaft of an aero-engine is typically made of high-strength structural steel. Its squirrel-cage elastic support structure is a key functional area for vibration suppression and load transfer in the rotor system. However, the thin-walled ribs evenly distributed along the circumference and their root fillets are the fatigue weak points of the entire shaft system. Under the long-term action of high engine speed, alternating torque, and complex vibration loads, fatigue cracks are prone to initiation and rapid propagation on the surface and near the surface of the ribs, ultimately leading to shaft fracture failure and seriously threatening flight safety. Shot peening is a widely used surface strengthening process in industry. By continuously impacting the surface of the part with high-speed shot, plastic deformation is caused, forming a strain-hardened layer of a certain thickness and introducing a high-amplitude residual compressive stress field. This can effectively counteract the alternating tensile stress during service, inhibit the initiation and propagation of fatigue cracks, and thus significantly improve the fatigue life of the part.

[0003] Because the squirrel cage structure is composed of multiple slender ribs connected to inner and outer rings, with narrow rib spacing, small root corner radii, and complex three-dimensional curved surfaces, traditional shot peening processes struggle to achieve 100% uniform coverage of all surfaces, especially at the root corners of the ribs. Areas not effectively strengthened can still become the origin of fatigue cracks. Existing processes often use a single parameter for overall shot peening, failing to differentiate strengthening based on the stress distribution characteristics of different parts of the squirrel cage. This results in uneven distribution of residual compressive stress amplitude and depth on the rib surface, insufficient strengthening at the root corners where stress concentration is severe, while areas with lower stress levels may experience surface damage due to over-peening. Simultaneously, the shot peening process inevitably increases the surface roughness of the parts, forming numerous micro-pits. These pits themselves generate new stress concentration effects, offsetting to some extent the fatigue gain brought by residual compressive stress, which is particularly detrimental to squirrel cage ribs under high-cycle fatigue conditions.

[0004] For shot peening of hollow shaft squirrel cage structures, the complex structure of the parts makes shot peening protection difficult. Therefore, specialized shot peening tape is often used to protect non-peened areas. However, this method is inefficient, costly, and prone to protection failure at the boundaries during shot peening. Therefore, it is necessary to develop a shot peening protection fixture and its process for hollow shaft squirrel cage structures to achieve high-efficiency, low-cost shot peening processing with effective protection for the hollow shaft with a squirrel cage structure. Patent application CN116276684A discloses a shot peening fixture and method for hollow shaft parts with a large length-to-diameter ratio. The part is vertically placed at the center of a turntable. The small end of the part is clamped and fixed by a protective fixture. An auxiliary support frame supports the upper end of the part. The shot peening fixture is equipped with two spray guns: a direct spray gun located on the side of the fixture and an inner diameter spear gun located on top of the fixture. The direct spray gun on the side is mainly responsible for shot peening the outer surface of the part, while the nozzle of the inner diameter spear gun on top extends into the hollow cavity of the part and is mainly responsible for shot peening the inner surface of the part. The direct spray gun and the inner diameter spear gun move to the bottom of the part simultaneously and shot peening the part from bottom to top at the same speed. By using two spray guns to shot peen the inner and outer surfaces of the part simultaneously, the problems of high process difficulty, difficulty in cleaning the accumulated shot in the inner cavity, and easy part tipping accidents are effectively solved for hollow shaft parts with a large length-to-diameter ratio. This patent is designed for ordinary long hollow shafts (such as low-pressure turbine shafts) with a wall thickness of approximately 20mm that require shot peening of both the inner and outer surfaces. However, the protective fixture in this patent only has the function of clamping parts and preventing shot leakage; it does not include any shielding or protective components for non-shot-peened areas. If used for shot peening of squirrel-cage structure shafts, the shot would directly impact the non-shot-peened outer surface of the shaft and the entire inner cavity, causing dimensional deviations, surface roughness deterioration, and direct scrapping of the parts. Summary of the Invention

[0005] This invention addresses the challenges of shot peening hollow shaft squirrel cage structures in existing technologies. Due to the complexity of the parts, shot peening protection is difficult. Therefore, special shot peening tape is often used to protect non-shot peening areas. However, this method is inefficient, costly, and prone to protection failure at the boundaries during shot peening. This invention proposes a shot peening fixture and processing method for thin-walled hollow shafts with squirrel cage structures.

[0006] A shot peening fixture for a thin-walled hollow shaft with a cage structure includes a fixture base and a protective fixture. The fixture base includes a base body and an annular clamping mechanism. Multiple evenly distributed support brackets along the circumferential direction are fixedly connected to the lower part of the base body. The annular clamping mechanism is connected to and fixedly installed above the base body. The annular clamping mechanism includes two symmetrically arranged semi-circular pressure rings. One end of each semi-circular pressure ring is hinged, and the hinge is fixedly connected to the two semi-circular pressure rings by screws. The other ends of the two semi-circular pressure rings are bolted together. The protective fixture includes a base cylinder, a positioning sleeve, a first knurled screw, a protective sleeve, a plug, a second knurled screw, a sleeve, and a cover. The bottom cylinder has an axially arranged long mandrel that is clearance-fitted with the inner wall of the hollow shaft for auxiliary axial and radial positioning. The positioning sleeve is coaxially embedded inside the bottom cylinder and fits against the inner wall of the inner cavity of the bottom cylinder. The protective sleeve is coaxially sleeved on the outside of the part of the workpiece to be protected, with one end of the protective sleeve abutting against the outer side of the positioning sleeve, and the protective sleeve is pressed and fixed to the positioning sleeve by the first knurled screw. The plug is located above the long mandrel and fits against the inner cavity of the lower part of the cage structure. The cover is interference-fitted with the inner wall of the upper end of the hollow shaft to protect the upper inner cavity. The sleeve is sleeved on the outside of the upper end of the hollow shaft and fastened by the second knurled screw. The cover is detachably fitted onto the top opening of the sleeve. The bracket is used to cooperate with the T-slot of the shot peening equipment workbench to achieve automatic centering. The base body is pressed and fixed to the shot peening equipment workbench by a universal pressure plate. The protective clamp is radially centered by the semi-circular pressure ring and axially tightened by the wing nut.

[0007] Furthermore, the protective clamp has a split structure, and the entire protective clamp is made of wear-resistant nylon PA66 material.

[0008] Furthermore, one end of each of the two semicircular pressure rings extends outward to form a connecting lug. One of the connecting lugs is hinged to a hinge bolt by a pin, and the other connecting lug has an opening groove that matches the hinge bolt. A wing nut is threaded onto the hinge bolt. When the hinge bolt is engaged in the opening groove, tightening the wing nut can lock the two semicircular pressure rings together, so that the two semicircular pressure rings enclose a circular clamping cavity for holding the workpiece to be shot peened.

[0009] Furthermore, it also includes a shot peening test piece fixture, which is detachably connected to the fixture base and is used to install shot peening test pieces to simulate the shot peening strengthening process of the hollow shaft squirrel cage portion.

[0010] Furthermore, the shot peening specimen fixture includes a positioning shaft, a third knurled screw, a mounting plate, a specimen mounting block, a Phillips head screw, and an internal hexagon head screw. The positioning shaft is vertically fixed to the lower end face of the mounting plate and inserted into the fixture base. The mounting plate is fixed to the end of the positioning shaft by the third knurled screw. The specimen mounting block is fastened to the mounting plate by the internal hexagon head screw in a split structure. The shot peening Almen A specimen is detachably fixed in the mounting groove of the specimen mounting block by the Phillips head screw. The height and rotation radius of the specimen clamping are consistent with the height and outer diameter of the cage portion. Shot peening of the specimen can simulate shot peening of the part to verify shot peening strengthening.

[0011] Furthermore, the first knurled screw is radially inserted through the protective sleeve and abuts against the outer wall of the positioning sleeve; the second knurled screw is radially inserted through the side wall of the sleeve and abuts against the outer wall of the bottom cylinder, for fixing the sleeve above the hollow shaft.

[0012] A shot peening method for a thin-walled hollow shaft with a squirrel cage structure, using the aforementioned shot peening fixture, includes the following steps: S1. Fixture base installation: Insert the three support corners of the fixture base into the T-slots of the shot peening equipment worktable to achieve automatic centering. Use a universal pressure plate to press the body of the fixture base to complete the fixation of the fixture base on the worktable. S2. Connect and fix the lower cylinder of the protective clamp to the clamp base. Slide the hollow shaft to be processed into the long mandrel of the lower cylinder. Use the positioning sleeve to achieve radial centering and axial support of the hollow shaft. Use the protective sleeve and the first knurled screw to press and fix the hollow shaft. Put the plug into the upper end of the hollow shaft and make it fit tightly against the inner cavity of the lower part of the cage structure. Insert the cover into the inner wall of the upper end of the hollow shaft to achieve a tight fit. Then put the sleeve on the outer side of the upper end of the hollow shaft and tighten it with the second knurled screw. S3. Use small-diameter shot to perform shot peening on the hollow shaft squirrel cage structure with low shot peening intensity. Adjust the spray gun to four preset positions and angles, mark the XYZ coordinate directions, and then perform full-coverage shot peening on the squirrel cage structure in sequence. Specifically, shot peening at the first preset position and the second preset position: The spray gun is first moved to the first preset position. At this time, the spray gun is facing the radial direction of the cage structure and is kept horizontal in the ZX plane. It is also deflected 15° counterclockwise in the XY plane with the X direction as the starting point. Shot peening is performed on the inner and outer surfaces and sides of the ribs from the top to the bottom of the cage structure. The spray gun is then adjusted to the second preset position. At this time, the spray gun is deflected 15° clockwise in the XY plane with the X direction as the starting point. Shot peening is then performed from the bottom to the top on the other side and inner and outer surfaces of the ribs. Third preset position shot peening: The spray gun moves to the third preset position. At this time, the spray gun deflects 45° counterclockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface of the rat cage ribs along the direction with the rat cage structure axis as the 45° angle. The shot peening time is 12s. Fourth preset position shot peening: The spray gun moves to the fourth preset position. At this time, the spray gun deflects 45° clockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface under the rat cage ribs along the direction with the rat cage structure axis as the 45° angle. The shot peening time is 12s. S4. After shot peening, loosen the second knurled screw and remove the sleeve and cover in sequence, loosen the first knurled screw and remove the protective sleeve, and take the machined hollow shaft out from the long mandrel of the lower cylinder.

[0013] Furthermore, in step S3, the shot peening parameters for the first, second, third, and fourth preset positions of the spray gun are all set as follows: shot peening gas source pressure 0.25±0.02MPa, shot flow rate 8±0.5Kg / min, part rotation speed 10r / min, spray distance 150±10mm, and shot peening coverage ≥100%.

[0014] Furthermore, in step S3, cast steel shot ASR70 is used as the shot peening medium.

[0015] Furthermore, before shot peening the cage structure, the positioning shaft of the shot peening test piece fixture is installed into the fixture base and tightened. The shot peening Almen A test piece is fixed in the mounting groove of the test piece mounting block. The mounting plate is inserted into the positioning shaft and the third knurled screw is tightened. The test piece is shot peened using the same shot peening process parameters as in step S3. After the shot peening intensity and coverage of the test piece meet the requirements, the hollow shaft parts are then shot peened.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention includes a clamp base and a protective clamp. The clamp base includes a base body and a ring clamping mechanism. Multiple support angles evenly distributed along the circumference are fixedly connected to the lower part of the base body. The clamp base of this invention achieves automatic centering by engaging with the T-slot of the shot peening equipment's worktable through the evenly distributed circumferential support angles. Combined with a quick-locking structure using a semi-circular pressure ring and a wing nut, the connection and fixation of the protective clamp to the base can be completed within minutes. The split design of the protective clamp eliminates the need for complex tape application during clamping, reducing the clamping time for a single part by more than 80% compared to traditional methods. Furthermore, each component of the protective clamp can be independently disassembled and replaced; only severely worn parts need to be replaced for continued use, significantly reducing the maintenance and consumable costs of the clamp.

[0017] 2. This invention uses a split-type protective clamp to replace the traditional shot peening tape. Through the tight fit between the plug and the inner cavity of the lower part of the cage, the interference fit between the cover and the inner wall of the upper end of the shaft, and the complete wrapping of the sleeve on the outer side of the upper end of the shaft, three-dimensional protection of the non-shot peening area of ​​the hollow shaft is achieved, which completely solves the problems of easy failure of tape protection and uneven shot peening at the boundary.

[0018] 3. This invention addresses the thin-walled and slightly rounded characteristics of the ribs in a squirrel cage structure by optimizing the shot peening process parameters. While ensuring sufficient residual compressive stress layer depth, it effectively avoids rib deformation and surface defects such as edge flanging and burrs. Through multi-angle shot peening at three preset positions, 100% coverage of the squirrel cage rib structure and its upper and lower hollow surfaces is achieved. After shot peening, the edges of the squirrel cage ribs are free of flanging and burrs, and the changes in dimensions of the squirrel cage, such as outer and inner diameters, are controlled within 0.02 mm. The fatigue strength performance of the sample is improved by 13.4%, fully meeting the design and usage requirements of aero-engines. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a top view of the structure of the clamp base of the present invention; Figure 3 This is a side view of the structure of the clamp base of the present invention; Figure 4 This is a schematic diagram of the structure of the protective clamp of the present invention; Figure 5 This is a schematic diagram of the structure of the test piece clamp of the present invention; Figure 6 This is a schematic diagram of the shot peening process of the present invention; Figure 7 This is a schematic diagram of positions ①-1 and ①-2 of the spray gun of the present invention; Figure 8 This is a schematic diagram of a mouse cage structure; In the above figure, 1. support corner, 2. base body, 3. semi-circular pressure ring, 4. hinge, 5. screw, 6. hinge bolt, 7. wing nut, 8. pin, 9. bottom cylinder, 10. positioning sleeve, 11. first knurled screw, 12. protective sleeve, 13. plug, 14. second knurled screw, 15. sleeve, 16. cover, 17. positioning shaft, 18. third knurled screw, 19. mounting plate, 20. test piece mounting block, 21. cross-head pan head screw, 22. socket head cap screw, 23. mouse cage structure. Detailed Implementation

[0020] To clearly illustrate the technical features of the present invention, the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0022] Furthermore, in the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In this invention, unless otherwise expressly specified and limited, the "on" or "below" of the second feature can mean that the first feature is in direct contact with the second feature, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0025] Example 1 like Figure 1As shown, a shot peening fixture for a thin-walled hollow shaft with a cage structure includes a fixture base and a protective fixture. The fixture base includes a base body 2 and an annular clamping mechanism. Multiple support brackets 1 evenly distributed along the circumferential direction are fixedly connected to the lower part of the base body 2. The annular clamping mechanism is connected to and fixedly installed above the base body 2. The annular clamping mechanism includes two symmetrically arranged semi-circular pressure rings 3. One end of each semi-circular pressure ring 3 is hinged by a hinge 4, and the hinge 4 is fixedly connected to the two semi-circular pressure rings 3 by screws 5. The other ends of the two semi-circular pressure rings 3 are connected by bolts. The protective fixture includes a base cylinder 9, a positioning sleeve 10, a first knurled screw 11, a protective sleeve 12, a plug 13, a second knurled screw 14, a sleeve 15, and a cover 16. The cylinder 9 is provided with a long core column along the axial direction, which is clearance-fitted with the inner wall of the hollow shaft to assist in axial and radial positioning; the positioning sleeve 10 is coaxially embedded in the inside of the bottom cylinder 9 and fits against the inner wall of the inner cavity of the bottom cylinder 9; the protective sleeve 12 is coaxially sleeved on the outside of the part of the workpiece to be protected, one end of the protective sleeve 12 abuts against the outer side of the positioning sleeve 10, and the protective sleeve 12 is pressed and fixed to the positioning sleeve 10 by the first knurled screw 11; the plug 13 is provided above the long core column, and the plug 13 fits against the inner cavity of the lower part of the cage structure; the cover 16 is interference-fitted with the inner wall of the upper end of the hollow shaft to protect the upper inner cavity; the sleeve 15 is sleeved on the outside of the upper end of the hollow shaft and is fastened by the second knurled screw 14; the cover 16 is detachably covered at the top opening of the sleeve 15. The support angle 1 is used to cooperate with the T-slot of the shot peening equipment workbench to achieve automatic centering. The base body 2 is pressed and fixed to the shot peening equipment workbench by a universal pressure plate. The protective clamp is radially centered by the semi-circular pressure ring 3 and axially tightened by the wing nut 7.

[0026] In this embodiment, as Figure 7 As shown, the rib wall thickness of the cage structure 23 is 2mm, and the edge rounding Rmax ≤ 0.5mm. After shot peening, the rib edges are free of burrs and have no flanging. The fixture base is used to achieve rapid positioning and fixation with the shot peening equipment worktable, and to drive the protective fixture and parts to rotate coaxially. The fixture base is made of 45# steel with heat treatment to ensure sufficient rigidity and wear resistance.

[0027] Specifically, the fixture base includes a disc-shaped base body 2 (diameter and thickness). Three evenly distributed support brackets 1 along the circumference are fixedly connected to the lower surface of the base body 2 to support the body. The dimensions of the support brackets 1 are adapted to the standard T-slot of the shot peening equipment's worktable. The fixture base is placed flat in the T-slot, and a universal pressure plate is used to press the base body 2 to fix the fixture base. After the three support brackets 1 on the fixture base are embedded in the T-slot, the fixture base can automatically center itself with a centering accuracy ≤0.05mm, ensuring the consistency of the subsequent rotation axis with the main shaft of the equipment's worktable. The protective fixture is centered by a semi-circular pressure ring 3 and tightened by a wing nut 7, which allows the part to rotate coaxially with the worktable and facilitates quick installation and removal of the part by the protective sleeve 12.

[0028] like Figure 2 and Figure 3 As shown, an annular clamping mechanism is fixedly installed at the center of the upper surface of the base body 2. The annular clamping mechanism includes two symmetrically arranged semi-circular pressure rings 3, each with a size φC = 80mm. The upper ends of the two semi-circular pressure rings 3 are hinged together by hinges 4, and both ends of the hinges 4 are fixedly connected to the two semi-circular pressure rings 3 by screws 5. The other ends of the two semi-circular pressure rings 3 extend outward to form connecting ears. One connecting ear is hinged to a hinge bolt 6 by a pin 8, and the other connecting ear has an opening groove adapted to the hinge bolt 6. A wing nut 7 is threaded onto the hinge bolt 6. When the hinge bolt 6 is engaged in the opening groove, tightening the wing nut 7 can lock the two semi-circular pressure rings 3, so that the two semi-circular pressure rings 3 enclose a circular clamping cavity for holding the workpiece to be shot peened. The protective clamp is radially centered by the semi-circular pressure rings 3 and axially fastened by the wing nut 7.

[0029] like Figure 4 As shown, the protective fixture is injection molded from wear-resistant nylon PA66 material with a Shore hardness of D75. This provides sufficient rigidity to withstand shot peening impact while preventing scratches on the part surface during clamping. The protective fixture has a modular structure, allowing for flexible replacement of any component that wears or breaks during shot peening, thus avoiding the need for complete scrapping.

[0030] Specifically, the protective clamp includes a base cylinder 9, a positioning sleeve 10, a first knurled screw 11, a protective sleeve 12, a plug 13, a second knurled screw 14, a sleeve 15, and a cover 16. The base cylinder 9 has a diameter of φC=80mm at one end. A long mandrel is integrally formed along the axial direction of the base cylinder 9, which has a clearance fit with the inner wall of the hollow shaft, used to assist in axial and radial positioning. A flange is provided at the lower end of the base cylinder 9, which is adapted to the annular clamping mechanism of the clamp base. Radial centering and axial fastening are achieved through a semi-circular pressure ring 3. The positioning sleeve 10 is coaxially embedded inside the base cylinder 9 and fits against the inner wall of the internal cavity of the base cylinder 9. The protective sleeve 12 is coaxially sleeved on the outside of the part of the workpiece to be protected. One end of the protective sleeve 12 abuts against the outer surface of the positioning sleeve 10, and the protective sleeve 12 passes radially through the first knurled screw 11 and presses against the outer wall of the positioning sleeve 10, thereby achieving clamping and fixing. The plug 13 is positioned above the long core column and fits snugly against the inner cavity of the lower part of the cage structure 23 to prevent projectile impact and entry, thus protecting the inner cavity of the shaft. The cover 16 is press-fitted against the inner wall of the upper end of the hollow shaft to protect the upper inner cavity. The sleeve 15 is fitted onto the outer side of the upper end of the hollow shaft. Two second knurled screws 14 are provided on the outer side of the sleeve 15, and the second knurled screws 14 are radially inserted through the side wall of the sleeve 15 and press against the outer wall of the bottom cylinder 9 to fix the sleeve 15 above the hollow shaft. The cover 16 is detachably fitted onto the top opening of the sleeve 15, forming multiple layers of inner cavity protection.

[0031] This implementation achieves stable positioning of the thin-walled hollow shaft during shot peening through the cooperation of the long core column of the bottom cylinder 9 and the positioning sleeve 10; the combination of the split protective sleeve 12, plug 13, cover 16 and sleeve 15 effectively prevents shot from entering the non-shot peening area; and the quick clamping structure of the semi-circular pressure ring 3 and the wing nut 7 enables the coaxial rotation of the parts and the worktable and quick assembly and disassembly, significantly improving the efficiency of shot peening and the reliability of protection.

[0032] Example 2 like Figure 6 As shown, this embodiment provides a shot peening method for a thin-walled hollow shaft with a squirrel cage structure using the fixture described in Embodiment 1. The part to be processed in this embodiment is an aero-engine output shaft with a total length of approximately φ217mm, an inner diameter of φ36mm, and an outer diameter of φ40mm for the non-shot-peened portion. The squirrel cage structure 23 is located in the middle of the shaft, with a length of approximately 36mm, and 10 ribs are evenly distributed circumferentially. The rib wall thickness is 2mm, and the edge rounding Rmax=0.5mm. Only the surface of the ribs of the squirrel cage structure 23 needs to be shot-peened for strengthening; all other areas need to be strictly protected, including the following steps: S1. Fixture base installation: Insert the three support corners 1 of the fixture base into the T-slots of the shot peening equipment worktable, use the automatic centering function of the support corners 1 and the T-slots to complete the positioning, and then use 4 universal pressure plates to press the body of the fixture base to complete the fixation of the fixture base on the worktable. S2. Protective Fixture and Workpiece Clamping: Connect and fix the base cylinder 9 of the protective fixture to the fixture base. Insert the hollow shaft to be processed into the long mandrel of the base cylinder 9, with a clearance fit between the long mandrel and the inner wall of the hollow shaft to achieve auxiliary axial and radial positioning. The locating sleeve 10 achieves radial centering and axial support for the hollow shaft. Place the protective sleeve 12 on the outside of the part of the workpiece to be protected, so that one end of the protective sleeve 12 abuts against the outer surface of the locating sleeve 10, and tighten the first knurled screw 11 to press the locating sleeve 10, thereby fixing the hollow shaft. Insert the plug 13 from the upper end of the hollow shaft, ensuring it fits tightly against the inner cavity of the lower part of the cage structure to prevent projectiles from entering the shaft cavity from below. Insert the cover 16 into the inner wall of the upper end of the hollow shaft, achieving an interference fit to protect the upper inner cavity. Finally, place the sleeve 15 on the outer side of the upper end of the hollow shaft, and tighten the second knurled screw 14 to press it against the outer wall of the base cylinder 9, completing the overall clamping. S3. Shot Peening: Small-diameter shot is used to perform shot peening on the hollow shaft squirrel cage structure with low shot peening intensity. In this embodiment, the shot peening coverage is ≥100%, and the shot peening medium is cast steel shot ASR70. The spray gun is adjusted to four preset positions and angles: the first preset position and the second preset position (corresponding to...) Figure 6 The shot peening guns at positions ①-1 and ①-2 respectively peened the inner and outer surfaces and sides of the ribs of the rat cage structure; the third preset position (such as...) Figure 6 Shot peening is performed on the upper hollowed-out surface of the rib at position ② of the spray gun; the fourth preset position (such as...) Figure 6 (③) Shot peening the lower hollow surface of the ribs using the spray gun in the middle position.

[0033] Specifically, shot peening at position ①: shot peening gas pressure 0.25MPa, shot flow rate 8Kg / min, part rotation speed 10r / min, spray distance 150mm. The shot peening gun first moves to position ①-1, at which point the shot peening gun is kept horizontal on the ZX plane and deflected counterclockwise by 15° on the XY plane with the X direction as the starting point. Shot peening is performed on the inner and outer surfaces of the ribs and one side from the top to the bottom of the cage. The shot peening gun is then adjusted to position ①-2, at which point the shot peening gun is deflected clockwise by 15° on the XY plane with the X direction as the starting point. Shot peening is performed on the inner and outer surfaces of the ribs and the other side from bottom to top.

[0034] Shot peening at position ②: Shot peening gas pressure 0.25MPa, shot flow rate 8Kg / min, part rotation speed 10r / min, spray distance 150mm. The spray gun moves to position ②. At this time, the spray gun deflects 45° counterclockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface of the squirrel cage ribs along the direction with the axis of the squirrel cage structure as the 45° angle. The shot peening time is 12s.

[0035] Shot peening at position ③: Shot peening gas pressure 0.25MPa, shot flow rate 8Kg / min, part rotation speed 10r / min, spray distance 150mm. The spray gun moves to position ③. At this time, the spray gun deflects 45° clockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface under the squirrel cage ribs along the direction with the axis of the squirrel cage structure as the 45° angle. The shot peening time is 12s.

[0036] During shot peening, the spray gun moves up and down along the axial direction of the hollow shaft to ensure full coverage. After shot peening, the edges of the ribs of the squirrel cage structure are free of burrs and flanges, and the changes in the dimensions of the squirrel cage, such as the outer diameter and inner diameter, are controlled within 0.02 mm. The fatigue strength of the sample is improved by 13.4%. Among them, the spray gun positions ①, ②, and ③ represent three different positions and angles of shot peening.

[0037] S4. After shot peening, loosen the second knurled screw 14 in sequence and remove the sleeve 15 and cover 16. Loosen the first knurled screw 11 and remove the protective sleeve 12. Take the machined hollow shaft out from the long mandrel of the lower cylinder.

[0038] In this embodiment, before shot peening the cage structure, the positioning shaft 17 of the shot peening test piece fixture is installed into the fixture base and tightened. The shot peening Almen A test piece is fixed in the mounting groove of the test piece mounting block 20. The mounting plate 19 is inserted into the positioning shaft 17 and the third knurled screw 18 is tightened. The test piece is shot peened using the same shot peening process parameters as in step S3. After the shot peening intensity and coverage of the test piece meet the requirements, the hollow shaft parts are then shot peened.

[0039] After shot peening in this embodiment, the fatigue strength of the simulated specimen of the rat cage structure is significantly improved, and there are no shot residues or impact marks in the non-shot peening areas. The clamping efficiency is several times higher than that of the traditional tape protection method.

[0040] Example 3 like Figure 1As shown, a shot peening fixture for a thin-walled hollow shaft with a cage structure includes a fixture base and a protective fixture. The fixture base includes a base body 2 and an annular clamping mechanism. Multiple support brackets 1 evenly distributed along the circumferential direction are fixedly connected to the lower part of the base body 2. The annular clamping mechanism is connected to and fixedly installed above the base body 2. The annular clamping mechanism includes two symmetrically arranged semi-circular pressure rings 3. One end of each semi-circular pressure ring 3 is hinged by a hinge 4, and the hinge 4 is fixedly connected to the two semi-circular pressure rings 3 by screws 5. The other ends of the two semi-circular pressure rings 3 are connected by bolts. The protective fixture includes a base cylinder 9, a positioning sleeve 10, a first knurled screw 11, a protective sleeve 12, a plug 13, a second knurled screw 14, a sleeve 15, and a cover 16. The cylinder 9 is provided with a long core column along the axial direction, which is clearance-fitted with the inner wall of the hollow shaft to assist in axial and radial positioning. The positioning sleeve 10 is coaxially embedded in the inside of the bottom cylinder 9 and fits against the inner wall of the inner cavity of the bottom cylinder 9. The protective sleeve 12 is coaxially sleeved on the outside of the part of the workpiece to be protected. One end of the protective sleeve 12 abuts against the outer side of the positioning sleeve 10, and the protective sleeve 12 is pressed and fixed to the positioning sleeve 10 by the first knurled screw 11. The plug 13 is provided above the long core column and fits against the inner cavity of the lower part of the cage structure. The cover 16 is interference-fitted with the inner wall of the upper end of the hollow shaft to protect the upper inner cavity. The sleeve 15 is sleeved on the outside of the upper end of the hollow shaft and is fastened by the second knurled screw 14. The cover 16 is detachably covered by the top opening of the sleeve 15. The support angle 1 is used to cooperate with the T-slot of the shot peening equipment workbench to achieve automatic centering. The base body 2 is pressed and fixed to the shot peening equipment workbench by a universal pressure plate. The protective clamp is radially centered by the semi-circular pressure ring 3 and axially tightened by the wing nut 7.

[0041] This embodiment, based on Embodiment 2, further includes the installation and verification steps of the shot peening test piece fixture, in order to accurately verify the shot peening process parameters before formal processing and ensure the machining quality of the hollow shaft parts. like Figure 5 As shown, the shot peening fixture also includes a shot peening test piece fixture, which is used to mount the Almen A test piece to simulate the shot peening environment of the hollow shaft squirrel cage section and verify the accuracy of the shot peening process parameters. The test piece fixture is made of 45# steel with a quenching and tempering treatment, and its split design facilitates the replacement of worn parts.

[0042] The shot peening test piece fixture includes a positioning shaft 17, a third knurled screw 18, a mounting plate 19, a test piece mounting block 20, a cross-head pan screw 21, and an internal hexagon head screw 22. The positioning shaft 17 is vertically fixed to the lower end face of the mounting plate 19 and is inserted into the fixture base. The mounting plate 19 is fixed to the end of the positioning shaft 17 by the third knurled screw 18. The test piece mounting block 20 is fastened to the mounting plate 19 by the internal hexagon head screw 22, forming a separate structure. The shot peening Almen A test piece is detachably fixed in the mounting groove of the test piece mounting block 20 by the cross-head pan screw 21. The height and rotation radius of the test piece clamping are consistent with the height and outer diameter of the cage portion, allowing the shot peening of the test piece to realistically simulate the shot peening state of the part.

[0043] Installation of the shot peening test piece fixture before test peening: Before shot peening the test piece, first install the positioning shaft 17 into the fixture base and tighten it with the third knurled screw 18. Before using the test piece fixture, first tighten the test piece mounting block 20 to the mounting plate 19 as a whole with the hexagon socket head cap screw 22. The split structure is designed so that the test piece mounting block 20 will wear during the shot peening process, making it easy to remove for repair or replacement. You can first install the shot peening Almen A test piece into the test piece mounting block 20 and tighten it with the cross-head pan head screw 21, then insert the mounting plate 19 into the positioning shaft 17 and tighten the third knurled screw 18 to perform shot peening. Alternatively, you can first insert the mounting plate 19 into the positioning shaft 17, then tighten the third knurled screw 18, and then install the shot peening Almen A test piece into the test piece mounting block 20 and tighten it with the cross-head pan head screw 21.

[0044] Before shot peening the cage structure, the test piece was shot peened using the same shot peening process parameters as in step S3 of Example 2 (shot peening intensity 0.10–0.15 mm, coverage ≥100%, cast steel shot ASR70, three-position shot peening). After shot peening, the test piece was removed and its arc height and coverage were measured. Once the test results met the process requirements, the test piece fixture was replaced with a protective fixture and workpiece, and the shot peening of the hollow shaft parts was formally carried out.

[0045] Since the test piece mounting block 20 and the mounting plate 19 are separate structures, when the test piece mounting block 20 is worn after multiple shot peenings, it can be removed separately for repair or replacement without replacing the entire mounting plate 19, which significantly reduces the cost of use.

[0046] This embodiment enables rapid and accurate verification of shot peening process parameters, avoiding the scrapping of hollow shaft parts due to improper parameter settings. It is especially suitable for process debugging and batch sampling inspection scenarios before mass production.

[0047] Obviously, the embodiments described above are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A shot peening fixture for a thin-walled hollow shaft with a cage-like structure, comprising a fixture base and a protective fixture, characterized in that, The clamp base includes a base body and an annular clamping mechanism. Multiple evenly distributed support brackets are fixedly connected to the lower part of the base body. The annular clamping mechanism is connected to and fixedly installed above the base body. The annular clamping mechanism includes two symmetrically arranged semi-circular pressure rings. One end of each semi-circular pressure ring is hinged, and the hinge is fixedly connected to the two semi-circular pressure rings by screws. The other ends of the two semi-circular pressure rings are connected by bolts. The protective clamp includes a base cylinder, a positioning sleeve, a first knurled screw, a protective sleeve, a plug, a second knurled screw, a sleeve, and a cover. The base cylinder is axially positioned to meet the inner wall of the hollow shaft. A long mandrel with clearance fit is used to assist in axial and radial positioning. The positioning sleeve is coaxially embedded inside the bottom cylinder and fits against the inner wall of the inner cavity of the bottom cylinder. The protective sleeve is coaxially sleeved on the outside of the part of the workpiece to be protected. One end of the protective sleeve abuts against the outer side of the positioning sleeve, and the protective sleeve is pressed and fixed to the positioning sleeve by the first knurled screw. The plug is located above the long mandrel and fits against the inner cavity of the lower part of the cage structure. The cover is interference-fitted with the inner wall of the upper end of the hollow shaft to protect the upper inner cavity. The sleeve is sleeved on the outside of the upper end of the hollow shaft and fastened by the second knurled screw. The cover is detachably fitted to the top opening of the sleeve. The bracket is used to cooperate with the T-slot of the shot peening equipment workbench to achieve automatic centering. The base body is pressed and fixed to the shot peening equipment workbench by a universal pressure plate. The protective clamp is radially centered by the semi-circular pressure ring and axially tightened by the wing nut.

2. The shot peening fixture for a thin-walled hollow shaft with a cage structure according to claim 1, characterized in that, The protective clamp is a split structure, and the entire protective clamp is made of wear-resistant nylon PA66 material.

3. The shot peening fixture for a thin-walled hollow shaft with a cage structure according to claim 1, characterized in that, One end of each of the two semicircular pressure rings extends outward to form a connecting lug. One of the connecting lugs is hinged to a hinge bolt by a pin, and the other connecting lug has an opening groove that matches the hinge bolt. A wing nut is threaded onto the hinge bolt. When the hinge bolt is engaged in the opening groove, tightening the wing nut can lock the two semicircular pressure rings together, so that the two semicircular pressure rings enclose a circular clamping cavity for holding the workpiece to be shot peened.

4. The shot peening fixture for a thin-walled hollow shaft with a cage structure according to claim 1, characterized in that, It also includes a shot peening test piece fixture, which is detachably connected to the fixture base and is used to install shot peening test pieces to simulate the shot peening strengthening process of the hollow shaft squirrel cage.

5. The shot peening fixture for a thin-walled hollow shaft with a cage structure according to claim 4, characterized in that, The shot peening test piece fixture includes a positioning shaft, a third knurled screw, a mounting plate, a test piece mounting block, a Phillips head screw, and an internal hexagon head screw. The positioning shaft is vertically fixed to the lower end face of the mounting plate and inserted into the fixture base. The mounting plate is fixed to the end of the positioning shaft by the third knurled screw. The test piece mounting block is fastened to the mounting plate by the internal hexagon head screw in a split structure. The shot peening Almen A test piece is detachably fixed in the mounting groove of the test piece mounting block by the Phillips head screw. The height and rotation radius of the test piece clamping are consistent with the height and outer diameter of the cage portion. Shot peening of the test piece can simulate shot peening of the part to verify shot peening strengthening.

6. The shot peening fixture for a thin-walled hollow shaft with a cage structure according to claim 1, characterized in that, The first knurled screw passes radially through the protective sleeve and abuts against the outer wall of the positioning sleeve; the second knurled screw passes radially through the side wall of the sleeve and abuts against the outer wall of the bottom cylinder, for fixing the sleeve above the hollow shaft.

7. A shot peening method for a thin-walled hollow shaft of a rat cage structure, characterized in that, The shot peening fixture for a thin-walled hollow shaft with a cage structure as described in any one of claims 1 to 6 includes the following steps: S1. Fixture base installation: Insert the three support corners of the fixture base into the T-slots of the shot peening equipment worktable to achieve automatic centering. Use a universal pressure plate to press the body of the fixture base to complete the fixation of the fixture base on the worktable. S2. Connect and fix the lower cylinder of the protective clamp to the clamp base. Slide the hollow shaft to be processed into the long mandrel of the lower cylinder. Use the positioning sleeve to achieve radial centering and axial support of the hollow shaft. Use the protective sleeve and the first knurled screw to press and fix the hollow shaft. Put the plug into the upper end of the hollow shaft and make it fit tightly against the inner cavity of the lower part of the cage structure. Insert the cover into the inner wall of the upper end of the hollow shaft to achieve a tight fit. Then put the sleeve on the outer side of the upper end of the hollow shaft and tighten it with the second knurled screw. S3. Use small-diameter shot to perform shot peening on the hollow shaft squirrel cage structure with low shot peening intensity. Adjust the spray gun to four preset positions and angles, mark the XYZ coordinate directions, and then perform full-coverage shot peening on the squirrel cage structure in sequence. Specifically, shot peening at the first preset position and the second preset position: The spray gun is first moved to the first preset position. At this time, the spray gun is facing the radial direction of the cage structure and is kept horizontal in the ZX plane. It is also deflected 15° counterclockwise in the XY plane with the X direction as the starting point. Shot peening is performed on the inner and outer surfaces and sides of the ribs from the top to the bottom of the cage structure. The spray gun is then adjusted to the second preset position. At this time, the spray gun is deflected 15° clockwise in the XY plane with the X direction as the starting point. Shot peening is then performed from the bottom to the top on the other side and inner and outer surfaces of the ribs. Third preset position shot peening: The spray gun moves to the third preset position. At this time, the spray gun deflects 45° counterclockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface of the rat cage ribs along the direction with the rat cage structure axis as the 45° angle. The shot peening time is 12s. Fourth preset position shot peening: The spray gun moves to the fourth preset position. At this time, the spray gun deflects 45° clockwise on the ZX surface with the X direction as the starting point, and performs fixed-point shot peening on the hollow surface under the rat cage ribs along the direction with the rat cage structure axis as the 45° angle. The shot peening time is 12s. S4. After shot peening, loosen the second knurled screw and remove the sleeve and cover in sequence, loosen the first knurled screw and remove the protective sleeve, and take the machined hollow shaft out from the long mandrel of the lower cylinder.

8. The shot peening method for a thin-walled hollow shaft with a rat cage structure according to claim 7, characterized in that, In step S3, the shot peening parameters for the first, second, third, and fourth preset positions of the spray gun are all set as follows: shot peening gas source pressure 0.25±0.02MPa, shot flow rate 8±0.5Kg / min, part rotation speed 10r / min, spray distance 150±10mm, and shot peening coverage ≥100%.

9. The shot peening method for a thin-walled hollow shaft with a rat cage structure according to claim 7, characterized in that, In step S3, ASR70 cast steel shot is used as the shot peening medium.

10. The shot peening method for a thin-walled hollow shaft with a rat cage structure according to claim 7, characterized in that, Before shot peening the cage structure, install the positioning shaft of the shot peening test piece fixture into the fixture base and tighten it. Fix the shot peening Almen A test piece in the mounting groove of the test piece mounting block. Insert the mounting plate into the positioning shaft and tighten the third knurled screw. Use the same shot peening process parameters as in step S3 to shot peen the test piece. After checking that the shot peening intensity and coverage of the test piece meet the requirements, then perform shot peening processing on the hollow shaft parts.

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