Extrusion method and extrusion tooling for inner hole edges of metal parts

Abstract

This application relates to a method and tooling for extruding the inner hole edge of a metal part. The extrusion method includes: applying a first extrusion force to the edge between the inner hole wall and the chamfer surface of the earring structure using a first extrusion tooling to form a first extrusion layer between the inner hole wall and the chamfer surface; applying a second extrusion force to the edge between the first extrusion layer and the chamfer surface using a second extrusion tooling to form a second extrusion layer between the first extrusion layer and the chamfer surface; the extrusion surfaces of both the second extrusion tooling and the first extrusion tooling are conical surfaces, the taper of the extrusion surface of the second extrusion tooling is greater than the taper of the extrusion surface of the first extrusion tooling, and the taper of the extrusion surface of the second extrusion tooling is less than the angle between the chamfer surface and the axis of the earring structure. In this application, the inner hole edge of the earring structure is successively extruded by multiple extrusion toolings with different tapers to extrude the edge into a compressive stress layer with a continuous curved surface in appearance, improving the fatigue performance of the earring assembly.

Description

Technical Field

[0001] The present application relates to the technical field of metal part extrusion, and particularly relates to an extrusion method and an extrusion tooling for the inner hole edge of a metal part. Background Art

[0002] A hydraulic actuator is generally connected to an aircraft control surface through an earring assembly. The earring assembly includes an earring and a bearing assembled in the earring in a way of rolling and flanging. The earring assembly is used to directly bear the dynamic load output by the hydraulic actuator.

[0003] Under dynamic load, there is fretting fatigue wear between the earring and the bearing, which will cause cracks or even fractures in the earring. And as a single connection point structure between the hydraulic actuator and the aircraft control surface, the quality problem of the earring assembly will lead to the failure of the aircraft control surface.

[0004] In the prior art, for the perforated fasteners or perforated connectors that bear dynamic loads, most of them adopt the extrusion method of squeezing a mandrel with higher hardness through the connection hole, which can force the hole wall material to undergo elastoplastic deformation and improve the local stress distribution state of the hole edge under the action of external loads. However, in the prior art, for the case of fretting fatigue wear between the earring and the bearing, no method is given on how to extrude and strengthen the inner hole edge of the earring to eliminate the fretting fatigue wear between the earring and the bearing under dynamic load and improve the fatigue performance of the earring assembly.

[0005] Therefore, it is necessary to provide a new technical solution to improve one or more problems existing in the above solution.

[0006] It should be noted that the information disclosed in the above background art section is only used to strengthen the understanding of the background of the present application, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] The purpose of the embodiments of the present application is to provide an extrusion method and an extrusion tooling for the inner hole edge of a metal part to improve the fatigue performance of the earring assembly.

[0008] According to the first aspect of the present application, there is provided an extrusion method for the inner hole edge of a metal part. The metal part is an earring structure, and chamfered surfaces are provided at both ends of the earring structure. The method includes:

[0009] Applying a first extrusion force to the edge between the inner hole wall and the chamfered surface of the earring structure by using the extrusion surface of the first extrusion tooling to extrude and form a first extrusion layer between the inner hole wall and the chamfered surface;

[0010] Apply a second extrusion force to the edge between the first extrusion layer and the chamfer surface by means of the extrusion surface of the second extrusion tooling, so as to extrude and form a second extrusion layer between the first extrusion layer and the chamfer surface; wherein, the extrusion surfaces of both the second extrusion tooling and the first extrusion tooling are conical surfaces, the taper of the extrusion surface of the second extrusion tooling is greater than the taper of the extrusion surface of the first extrusion tooling, and the taper of the extrusion surface of the second extrusion tooling is less than the angle between the chamfer surface and the axial direction of the earring structure.

[0011] In an exemplary embodiment of the present application, before applying the first extrusion force to the edge between the inner hole wall of the earring structure and the chamfer surface by means of the extrusion surface of the first extrusion tooling, it further includes:

[0012] Determine the extrusion deformation amount according to the inner diameter of the earring structure, determine the first extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the first extrusion tooling, and determine the second extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the second extrusion tooling; wherein, the extrusion deformation amount is the deformation amount of the edge in the radial direction of the earring structure.

[0013] In an exemplary embodiment of the present application, the calculation formulas for both the first extrusion force and the second extrusion force are:

[0014] (1)

[0015] Wherein, when calculating the first extrusion force, represents the first extrusion force, represents the taper of the extrusion surface of the first extrusion tooling, and when calculating the second extrusion force, represents the second extrusion force, represents the taper of the extrusion surface of the second extrusion tooling; represents the extrusion allowance coefficient, The value of is 1.2 - 1.8, represents the extrusion deformation amount, represents the elastic modulus of the earring structure.

[0016] In an exemplary embodiment of the present application, the extrusion deformation amount is:

[0017] (2)

[0018] Wherein, represents the inner diameter of the earring structure, represents the extrusion deformation amount, represents the deformation coefficient, The value of is 0.5% - 2.0%.

[0019] In an exemplary embodiment of the present application, the difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the first extrusion tooling is 10-20°.

[0020] In an exemplary embodiment of the present application, after applying a second extrusion force to the edge between the first extrusion layer and the chamfered surface by using the extrusion surface of the second extrusion tooling, it further includes:

[0021] Applying a third extrusion force to the edge between the second extrusion layer and the chamfered surface by using the extrusion surface of the third extrusion tooling to extrude and form a third extrusion layer between the second extrusion layer and the chamfered surface;

[0022] Wherein, the extrusion surface of the third extrusion tooling is a conical surface, the taper of the extrusion surface of the third extrusion tooling is greater than the taper of the extrusion surface of the second extrusion tooling, and the taper of the extrusion surface of the third extrusion tooling is less than the angle between the chamfered surface and the axis of the earring structure.

[0023] In an exemplary embodiment of the present application, the difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the first extrusion tooling is equal to the difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the third extrusion tooling.

[0024] In an exemplary embodiment of the present application, the difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the third extrusion tooling is 10-20°.

[0025] In an exemplary embodiment of the present application, the taper of the extrusion surface of the first extrusion tooling is 10°.

[0026] According to a second aspect of the present application, there is provided an extrusion tooling for the edge of the inner hole of a metal part, which is applied to the extrusion method for the edge of the inner hole of the metal part as described in any one of the above, the extrusion tooling is columnar, and one end of the extrusion tooling along its axis is provided with an extrusion part, and the outer peripheral surface of the extrusion part is a conical surface for extruding the edge of the inner hole of the metal part.

[0027] The technical solution provided by the present application may include the following beneficial effects:

[0028] In the embodiments of the present application, the edges inside the hole of the earring structure are sequentially extruded by a plurality of extrusion tools with different tapers, so as to extrude the edges between the chamfered surface and the inner hole wall to form a compressive stress layer composed of a first extrusion layer and a second extrusion layer, realizing the extrusion strengthening of the edges; and by designing the taper of the extrusion surface of the first extrusion tool to be smaller than the taper of the extrusion surface of the second extrusion tool, and the taper of the extrusion surface of the second extrusion tool to be smaller than the angle between the chamfered surface and the axis of the earring structure, the compressive stress layer is presented as a continuous curved surface in terms of morphology. Therefore, when a part similar to a bearing is assembled in the earring structure in the form of rolling flanging, the fretting fatigue wear existing at the edges under dynamic loads can be eliminated, and the compressive stress layer formed by extrusion at the edges can effectively reduce the stress level of the earring structure under dynamic loads, thereby improving the fatigue performance of the entire earring assembly.

[0029] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0031] Figure 1 A flowchart showing the steps of a method for extruding the edges of the inner hole of a metal part in an exemplary embodiment of the present application;

[0032] Figure 2 A schematic diagram showing an earring structure in an exemplary embodiment of the present application;

[0033] Figure 3 A schematic diagram showing an earring structure and a bearing in an exemplary embodiment of the present application;

[0034] Figure 4 Show Figure 3 An enlarged view of part A in;

[0035] Figure 5 A schematic diagram showing a bearing assembled in an earring structure in a rolling flanging manner in an exemplary embodiment of the present application;

[0036] Figure 6 A schematic diagram showing an extrusion tool applying an extrusion force to the edges of the inner hole of an earring structure in an exemplary embodiment of the present application;

[0037] Figure 7 A schematic diagram showing the first edge being extruded by the first extrusion tool in an exemplary embodiment of the present application;

[0038] Figure 8 Simplified schematic diagram showing the extrusion of the first edge using the extrusion surface of the first extrusion tooling in an exemplary embodiment of the present application;

[0039] Figure 9 Simplified schematic diagram showing the first extrusion layer in an exemplary embodiment of the present application;

[0040] Figure 10 Schematic diagram showing the extrusion of the second edge using the second extrusion tooling in an exemplary embodiment of the present application;

[0041] Figure 11 Simplified schematic diagram showing the extrusion of the second edge using the extrusion surface of the second extrusion tooling in an exemplary embodiment of the present application;

[0042] Figure 12 Simplified schematic diagram showing the first extrusion layer and the second extrusion layer in an exemplary embodiment of the present application;

[0043] Figure 13 Schematic diagram showing the extrusion of the third edge using the third extrusion tooling in an exemplary embodiment of the present application;

[0044] Figure 14 Simplified schematic diagram showing the extrusion of the third edge using the extrusion surface of the third extrusion tooling in an exemplary embodiment of the present application;

[0045] Figure 15 Simplified schematic diagram showing the first extrusion layer, the second extrusion layer, and the third extrusion layer in an exemplary embodiment of the present application;

[0046] Figure 16 Simplified schematic diagram showing the assembled structure of the bearing after roll forming and flanging and the earring structure after extrusion in an exemplary embodiment of the present application;

[0047] Figure 17 Schematic diagram showing the extrusion part of the extrusion tooling in an exemplary embodiment of the present application. Description of the Drawings:

[0049] 100. Earring structure; 110. Chamfered surface; 120. Inner hole wall; 131. First edge; 132. Second edge; 133. Third edge; 140. First extrusion layer; 150. Second extrusion layer; 160. Third extrusion layer; 200. Bearing; 210. Flanging part; 300. First extrusion tooling; 400. Second extrusion tooling; 500. Third extrusion tooling; 600. Extrusion part. Detailed Description

[0050] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0051] In addition, the accompanying drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus repeated descriptions thereof will be omitted.

[0052] In this example embodiment, a method for extruding the inner hole edge of a metal part is first provided. Referring to Figures 1 to 12 as shown, the metal part is an earring structure 100. Chamfered surfaces 110 are provided at both ends of the earring structure 100 along its axial direction. The chamfered surfaces 110 are annular surfaces and are located between the inner hole wall 120 of the earring structure 100 and the end face of the earring structure 100. The angle between the chamfered surface 110 and the axial direction of the earring structure 100 is an acute angle, so that an edge is formed between the inner hole wall 120 of the earring structure 100 and the chamfered surface 110.

[0053] The method for extruding the inner hole edge of the metal part provided in this embodiment includes the following steps:

[0054] Step S101: Apply a first extrusion force to the edge between the inner hole wall 120 and the chamfered surface 110 of the earring structure 100 by using the extrusion surface of the first extrusion tooling 300, so as to extrude and form a first extrusion layer 140 between the inner hole wall 120 and the chamfered surface 110.

[0055] Step S102: Apply a second extrusion force to the edge between the first extrusion layer 140 and the chamfered surface 110 by using the extrusion surface of the second extrusion tooling 400, so as to extrude and form a second extrusion layer 150 between the first extrusion layer 140 and the chamfered surface 110; wherein, the extrusion surfaces of both the second extrusion tooling 400 and the first extrusion tooling 300 are conical surfaces, the taper of the extrusion surface of the second extrusion tooling 400 is greater than the taper of the extrusion surface of the first extrusion tooling 300, and the taper of the extrusion surface of the second extrusion tooling 400 is less than the angle between the chamfered surface 110 and the axial direction of the earring structure 100.

[0056] It should also be noted that referring to Figures 3 to 5 as shown, Figure 3 and Figure 4 show schematic diagrams of the earring structure 100 and the bearing 200. Figure 5The schematic diagram shows the bearing 200 assembled in the earring structure 100 in a flanging-rolling manner. After the bearing 200 is flanged by rolling, the outer peripheral surface of the bearing 200 contacts the inner peripheral surface of the earring structure 100, and the flanging part 210 of the bearing 200 contacts the edge of the earring structure 100. Under dynamic loads, wear will occur between the outer peripheral surface of the bearing 200 and the inner peripheral surface of the earring structure 100, and fretting fatigue wear will occur between the flanging part 210 of the bearing 200 and the edge of the earring structure 100. However, due to the stress concentration existing between the flanging part 210 of the bearing 200 and the edge of the earring structure 100, under dynamic loads, the fretting fatigue wear between the flanging part 210 of the bearing 200 and the edge of the earring structure 100 is likely to cause cracks to initiate at the edge of the earring structure 100. The purpose of the extrusion method provided in this embodiment is to eliminate the fretting fatigue wear existing at the edge under dynamic loads and improve the fatigue performance of the entire earring assembly.

[0057] In the embodiments of the present application, the edges inside the hole of the earring structure 100 are sequentially extruded by a plurality of extrusion tools with different tapers, so as to extrude the edges between the chamfered surface 110 and the inner hole wall 120 to form a compressive stress layer composed of a first extrusion layer 140 and a second extrusion layer 150, realizing the extrusion strengthening of the edges; by designing the taper of the extrusion surface of the second extrusion tool 400 to be greater than the taper of the extrusion surface of the first extrusion tool 300, and designing the taper of the extrusion surface of the second extrusion tool 400 to be less than the angle between the chamfered surface 110 and the axis of the earring structure 100, such that the compressive stress layer presents as a continuous curved surface in morphology. Thus, after a part similar to the bearing 200 is assembled in the earring structure 100 in a flanging-rolling manner, it can achieve the elimination of the fretting fatigue wear existing at the edge under dynamic loads, and the compressive stress layer formed by extrusion at the edge can effectively reduce the stress level of the earring structure 100 under dynamic loads, thereby improving the fatigue performance of the entire earring assembly.

[0058] Of course, it should also be noted that the edges on the inner sides of the two ends of the earring structure 100 along its axis need to be extruded according to the above steps S101 and S102.

[0059] Next, the above method in the present exemplary embodiment will be described in more detail.

[0060] In one embodiment, before applying the first extrusion force to the edge between the inner hole wall 120 and the chamfered surface 110 of the earring structure 100 by the extrusion surface of the first extrusion tool 300, it further includes:

[0061] Determine the extrusion deformation amount according to the inner diameter of the earring structure 100, determine the first extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the first extrusion tooling 300, and determine the second extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the second extrusion tooling 400; wherein, the extrusion deformation amount is the deformation amount of the edge in the radial direction of the earring structure 100.

[0062] The above method determines the extrusion force applied by the extrusion tooling to the edge according to the extrusion deformation amount and the taper of the extrusion surface of the extrusion tooling, so as to ensure that the compressive stress layer formed by extrusion at the edge presents a continuous curved surface in terms of topography. Therefore, after a part similar to the bearing 200 is assembled in the earring structure 100 in a rolling flanging manner, the fretting fatigue wear existing at the edge under dynamic load can be eliminated. It should be noted that the above extrusion deformation amount is determined according to the inner diameter of the earring structure 100 before the extrusion process is implemented.

[0063] Furthermore, the extrusion deformation amount is:

[0064] (2)

[0065] Wherein, represents the inner diameter of the earring structure 100, represents the extrusion deformation amount, represents the deformation coefficient, The value of is 0.5% - 2.0%.

[0066] The above determines the extrusion deformation amount quantitatively according to the inner diameter of the earring structure 100, so as to further determine the numerical range of the extrusion force applied by the extrusion tooling to the edge according to the extrusion deformation amount and the taper of the extrusion surface. It should be noted that since the extrusion deformation amount is determined according to the inner diameter of the earring structure 100, when the first extrusion tooling 300 is used to extrude the edge between the inner hole wall 120 and the chamfer surface 110, and when the second extrusion tooling 400 is used to extrude the edge between the first extrusion layer 140 and the chamfer surface 110, the extrusion deformation amounts in these two cases are equal.

[0067] Furthermore, the calculation formulas for both the first extrusion force and the second extrusion force are:

[0068] (1)

[0069] Wherein, when calculating the first extrusion force, represents the first extrusion force, represents the taper of the extrusion surface of the first extrusion tooling 300. When calculating the second extrusion force, represents the second extrusion force, represents the taper of the extrusion surface of the second extrusion tooling 400; represents the extrusion allowance coefficient, The value of represents the extrusion deformation amount, and represents the elastic modulus of the earring structure 100.

[0070] Refer to Figure 6 As shown in F represents the first extrusion force applied by the first extrusion tooling 300 along the axial direction of the earring structure 100, F sin θ represents the extrusion force transmitted from the extrusion surface of the first extrusion tooling 300 to the edge, θ

[0070] represents the taper of the extrusion surface of the first extrusion tooling 300. When extruding with the extrusion surface of the second extrusion tooling 400, F F represents the second extrusion force applied by the second extrusion tooling 400 along the axial direction of the earring structure 100, F sin θ θ represents the extrusion force transmitted from the extrusion surface of the second extrusion tooling 400 to the edge, θ represents the taper of the extrusion surface of the second extrusion tooling 400.

[0071] By quantifying the first extrusion force applied by the first extrusion tooling 300 to the edge and the second extrusion force applied by the second extrusion tooling 400 to the edge through the above formula (1), it can be ensured that the compressive stress layer formed by extrusion at the edge presents a continuous curved surface that fits the bearing 200 in terms of morphology, achieving the elimination of fretting fatigue wear existing at the edge under dynamic loads. As can be seen from the above formula (1), the values of the first extrusion force and the second extrusion force both consider the size and material of the earring structure 100, the taper of the extrusion surface, and the extrusion allowance coefficient. It can be seen that the extrusion method provided in this embodiment can determine the appropriate extrusion force according to different extrusion conditions.

[0072] Preferably, in one embodiment, the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 is 10 - 20°.

[0073] It should be noted that for the sake of explanation, the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 is defined as the first difference. By setting the first difference within the numerical range of 10 - 20°, the first extrusion tooling 300 and the second extrusion tooling 400 can be applicable to the working condition when the angle between the chamfer surface 110 and the axial direction of the earring structure 100 is close to 45°. In this way, it can be ensured that the second extrusion tooling 400 extrudes the edge between the chamfer surface 110 and the first extrusion layer 140 extruded by the first extrusion tooling 300, so as to ensure that the compressive stress layer formed by extrusion at the edge presents a continuous curved surface in terms of morphology.

[0074] Optionally, determine the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 according to formula (3), and formula (3) is:

[0075] (3)

[0076] Wherein, represents the taper of the extrusion surface of the first extrusion tooling 300, represents the taper of the extrusion surface of the second extrusion tooling 400, represents the angle between the chamfered surface 110 and the axis of the earring structure 100.

[0077] According to the above formula (3), based on the angle between the chamfered surface 110 and the axis of the earring structure 100, determine the value relationship that the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 need to satisfy, so as to ensure that the second extrusion tooling 400 extrudes the edge between the chamfered surface 110 and the first extrusion layer 140 extruded by the first extrusion tooling 300, so as to ensure that the compressive stress layer formed by extrusion at the edge presents as a continuous curved surface in terms of morphology.

[0078] In one embodiment, after applying the second extrusion force to the edge between the first extrusion layer 140 and the chamfered surface 110 by using the extrusion surface of the second extrusion tooling 400, it further includes:

[0079] Apply a third extrusion force to the edge between the second extrusion layer 150 and the chamfered surface 110 by using the extrusion surface of the third extrusion tooling 500, so as to extrude and form a third extrusion layer 160 between the second extrusion layer 150 and the chamfered surface 110;

[0080] Wherein, the extrusion surface of the third extrusion tooling 500 is a conical surface, the taper of the extrusion surface of the third extrusion tooling 500 is greater than the taper of the extrusion surface of the second extrusion tooling 400, and the taper of the extrusion surface of the third extrusion tooling 500 is less than the angle between the chamfered surface 110 and the axis of the earring structure 100.

[0081] After the second extrusion tooling 400 applies the second extrusion force to the edge, further apply the third extrusion force to the edge between the second extrusion layer 150 and the chamfered surface 110 by using the third extrusion tooling 500, so as to improve the curved surface radian of the compressive stress layer formed after the edge is strengthened by multiple extrusions for the case where the angle between the chamfered surface 110 and the axis of the earring structure 100 is large, thereby better eliminating the fretting fatigue wear existing at the edge under dynamic load, and the more orderly multiple extrusions can also improve the effect of extrusion strengthening of the edge and enhance the strength of the compressive stress layer.

[0082] It should be explained that in the above, the edge between the second extrusion layer 150 and the chamfer surface 110 is extruded by the extrusion surface of the third extrusion tooling 500. In this case, the extrusion deformation amount is still determined according to the inner diameter of the earring structure 100, that is, determined according to the above formula (2). And it should be noted that for the same earring structure 100, when using the first extrusion tooling 300 to extrude the edge between the inner hole wall 120 and the chamfer surface 110, using the second extrusion tooling 400 to extrude the edge between the first extrusion layer 140 and the chamfer surface 110, and using the extrusion surface of the third extrusion tooling 500 to extrude the edge between the second extrusion layer 150 and the chamfer surface 110, the extrusion deformation amounts in these three cases are equal.

[0083] It also needs to be explained that in the above, the third extrusion force is applied to the edge between the second extrusion layer 150 and the chamfer surface 110 by the extrusion surface of the third extrusion tooling 500. Among them, the third extrusion force is determined according to formula (1); and when calculating the third extrusion force according to formula (1), represents the third extrusion force, represents the taper of the extrusion surface of the third extrusion tooling 500.

[0084] Optionally, the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 is equal to the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the third extrusion tooling 500. Through the above limitation, it is beneficial to improve the curved surface radian of the compressive stress layer formed by extrusion at the edge.

[0085] It should be noted that for the sake of easy explanation, the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the third extrusion tooling 500 is defined as the second difference.

[0086] Preferably, in one embodiment, both the first difference and the second difference are 10 - 20°, that is, the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the first extrusion tooling 300 is 10 - 20°, and the difference between the taper of the extrusion surface of the second extrusion tooling 400 and the taper of the extrusion surface of the third extrusion tooling 500 is 10 - 20°.

[0087] By setting the first difference and the second difference within the numerical range of 10 - 20°, the first extrusion tooling 300, the second extrusion tooling 400, and the third extrusion tooling 500 can be applicable to the working condition when the angle between the chamfered surface 110 and the axis of the earring structure 100 is close to 45°. This can ensure that the second extrusion tooling 400 extrudes the edge between the chamfered surface 110 and the first extrusion layer 140 extruded by the first extrusion tooling 300, and the third extrusion tooling 500 extrudes the edge between the chamfered surface 110 and the second extrusion layer 150 extruded by the second extrusion tooling 400. Thus, for the case where the angle between the chamfered surface 110 and the axis of the earring structure 100 is relatively large, the compression stress layer formed by extrusion at the edge still presents as a continuous curved surface in terms of morphology.

[0088] Optionally, when the first difference is equal to the second difference, the taper of the extrusion surface of the first extrusion tooling 300 , the first difference , and the angle between the chamfered surface 110 and the axis of the earring structure 100 need to satisfy the following formula:

[0089] (4)

[0090] Wherein, represents the taper of the extrusion surface of the first extrusion tooling 300, represents the angle between the chamfered surface 110 and the axis of the earring structure 100, represents the first difference.

[0091] When the angle between the chamfered surface 110 and the axis of the earring structure 100 is known, according to the above formula (4), the numerical relationship that the taper of the extrusion surface of the first extrusion tooling 300, the taper of the extrusion surface of the second extrusion tooling 400, and the taper of the extrusion surface of the third extrusion tooling 500 need to satisfy can be determined. This can ensure that the second extrusion tooling 400 extrudes the edge between the chamfered surface 110 and the first extrusion layer 140 extruded by the first extrusion tooling 300, and the third extrusion tooling 500 extrudes the edge between the chamfered surface 110 and the second extrusion layer 150 extruded by the second extrusion tooling 400. Thus, it can be ensured that the compression stress layer formed by extrusion at the edge presents as a continuous curved surface in terms of morphology.

[0092] Optionally, the taper of the extrusion surface of the first extrusion tooling 300 is 10°. Considering that after the bearing 200 is roll-formed and flanged, the outer peripheral surface of the bearing 200 contacts the inner peripheral surface of the earring structure 100, and the flanged part 210 of the bearing 200 contacts the edge of the earring structure 100, the taper of the extrusion surface of the first extrusion tooling 300 should neither be too small nor too large to prevent the formation of new wear points between the earring structure 100 and the flanged part 210 of the bearing 200.

[0093] Exemplarily, taking the angle between the chamfered surface 110 of the earring structure 100 and the axis of the earring structure 100 as 45° as an example, one can select two extrusion toolings with different tapers or three extrusion toolings with different tapers to extrude the edge inside the hole of the earring structure 100. For example, one can select the first extrusion tooling 300 with a taper of 10° for the extrusion surface and the second extrusion tooling 400 with a taper of 20° for the extrusion surface to sequentially extrude the edge; or select the first extrusion tooling 300 with a taper of 10° for the extrusion surface, the second extrusion tooling 400 with a taper of 20° for the extrusion surface, and the third extrusion tooling 500 with a taper of 30° for the extrusion surface to sequentially extrude the edge.

[0094] Taking the sequential extrusion of the edge by the first extrusion tooling 300 with a taper of 10° for the extrusion surface, the second extrusion tooling 400 with a taper of 20° for the extrusion surface, and the third extrusion tooling 500 with a taper of 30° for the extrusion surface as an example, the extrusion method provided in this embodiment will be further described below.

[0095] It should be noted that for the sake of explanation, the edge between the inner hole wall 120 and the chamfered surface 110 of the aforementioned earring structure 100 is denoted as the first edge 131, the edge between the first extrusion layer 140 and the chamfered surface 110 is denoted as the second edge 132, and the edge between the second extrusion layer 150 and the chamfered surface 110 is denoted as the third edge 133.

[0096] Before performing the extrusion process, it is determined that the extrusion allowance coefficient is taken as 1.8, the inner diameter of the earring structure 100 is 17.462 mm, the material of the earring structure 100 is selected as 15-5PH, 15-5PH represents martensitic precipitation hardening stainless steel, the extrusion allowance is determined to be 0.087 mm according to the inner diameter of the earring structure 100, and the elastic modulus of the earring structure 100 is determined to be 190 GPa according to the material of the earring structure 100. According to formula (1) and the above parameters, the first extrusion force that the first extrusion tooling 300 should apply to the first edge 131, the second extrusion force that the second extrusion tooling 400 should apply to the second edge 132, and the third extrusion force that the third extrusion tooling 500 should apply to the third edge 133 can be determined.

[0097] Reference Figures 7 to 9As shown in [reference], first, use the first extrusion tooling 300 with a taper of 10° on the extrusion surface to extrude the first edge 131. The extrusion surface of the first extrusion tooling 300 acts on the first edge 131 between the chamfered surface 110 and the inner hole wall 120, and applies a first extrusion force of 23410 N. After the first extrusion tooling 300 finishes extrusion, a first extrusion layer 140 is formed between the chamfered surface 110 and the inner hole wall 120. The angle between the first extrusion layer 140 and the axial direction of the earring structure 100 is 10°.

[0098] Reference Figures 10 to 12 As shown in [reference], then, use the second extrusion tooling 400 with a taper of 20° on the extrusion surface to extrude the second edge 132. The extrusion surface of the second extrusion tooling 400 acts on the second edge 132 between the first extrusion layer 140 and the chamfered surface 110, and applies a second extrusion force of 11883 N. After the second extrusion tooling 400 finishes extrusion, a second extrusion layer 150 is formed between the chamfered surface 110 and the first extrusion layer 140. The angle between the second extrusion layer 150 and the axial direction of the earring structure 100 is 20°.

[0099] Reference Figure 13 and Figure 15 As shown in [reference], finally, use the third extrusion tooling 500 with a taper of 30° on the extrusion surface to extrude the third edge 133. The extrusion surface of the third extrusion tooling 500 acts on the third edge 133 between the second extrusion layer 150 and the chamfered surface 110, and applies a third extrusion force of 8128 N. After the third extrusion tooling 500 finishes extrusion, a third extrusion layer 160 is formed between the chamfered surface 110 and the second extrusion layer 150. The angle between the third extrusion layer 160 and the axial direction of the earring structure 100 is 30°.

[0100] Reference Figure 15 and Figure 16 As shown in [reference] and [reference], after the above-mentioned first extrusion tooling 300, second extrusion tooling 400, and third extrusion tooling 500 complete the extrusion operations in sequence, the inner hole edges of the earring structure 100 are extruded and strengthened to form a compressive stress layer. The compressive stress layer includes the first extrusion layer 140, the second extrusion layer 150, and the third extrusion layer 160. It presents as a continuous curved surface in morphology, realizing the elimination of fretting fatigue wear at the edges under dynamic loads. And this compressive stress layer can effectively reduce the stress level of the earring structure 100 under dynamic loads, thereby improving the fatigue performance of the entire earring assembly. It should be noted that the compressive stress layer composed of the first extrusion layer 140, the second extrusion layer 150, and the third extrusion layer 160 is morphologically close to a curved surface with a radius of 0.3 mm - 0.5 mm.

[0101] For the earring structure 100 made of 15-5PH material with an inner diameter of 17.462 mm, fatigue life tests were respectively carried out on multiple earring components without extrusion strengthening and multiple earring components after extrusion strengthening using the extrusion method of this embodiment. Among them, for the earring components without extrusion strengthening, the fatigue life of the earring components was 140,000 to 1,200,000 cycles, and the life dispersion coefficient was very large. For the extrusion method of this embodiment, for the earring components after sequentially extruding and strengthening the earring structure 100 using the first extrusion tooling 300 with a taper of 10° on the extrusion surface and the second extrusion tooling 400 with a taper of 20° on the extrusion surface, the fatigue life of the earring components reached 2,000,000 cycles, far higher than the life requirement of 1,200,000 cycles, and the life dispersion coefficient was small. The test results show that the extrusion method of this embodiment effectively improves the fatigue performance of the earring components.

[0102] Furthermore, in this exemplary embodiment, an extrusion tooling for the inner hole edge of a metal part is also provided, which is applied to the extrusion method for the inner hole edge of the metal part in the above embodiment. Refer to Figure 17 As shown in, the extrusion tooling is columnar, and one end of the extrusion tooling along its axial direction is provided with an extrusion portion 600, and the outer peripheral surface of the extrusion portion 600 is a conical surface for extruding the inner hole edge of the metal part.

[0103] Among them, the metal part is the earring structure 100. Chamfered surfaces 110 are provided at the two ends of the earring structure 100 along its axial direction. The chamfered surfaces 110 are annular surfaces and are located between the inner hole wall 120 of the earring structure 100 and the end surface of the earring structure 100. The angle between the chamfered surfaces 110 and the axial direction of the earring structure 100 is an acute angle, so as to form an edge between the inner hole wall 120 of the earring structure 100 and the chamfered surfaces 110. The outer peripheral surface of the extrusion portion 600 of the extrusion tooling provided in this embodiment is used to extrude the edge inside the hole of the earring structure 100.

[0104] It should be noted that the taper of the outer peripheral surface of the extrusion portion 600 in this embodiment can be processed into different tapers according to the extrusion working conditions, and this embodiment does not make specific limitations on the taper of the outer peripheral surface of the extrusion portion 600. The other end of the extrusion tooling in this embodiment is used to connect to a driving device, and the driving device is used to control the extrusion tooling to apply an extrusion force to the edge.

[0105] By extruding and strengthening the edge inside the hole of the earring structure 100 through the outer peripheral surface of the extrusion portion 600 of the extrusion tooling and forming a compressive stress layer, the compressive stress layer formed at the edge can effectively reduce the stress level of the earring structure 100 under dynamic loads, and further improve the fatigue performance of the entire earring component.

[0106] Other embodiments of the present application will be readily contemplated by those skilled in the art in view of the specification and practice of the invention disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include common general knowledge or conventional technical means in the technical field not disclosed in the present application.

Claims

1. A method for extruding the inner hole edge of a metal part, wherein the metal part has an earring structure, characterized in that, Chamfered surfaces are provided at the orifice ends of both ends of the earring structure, and the method includes: Applying a first extrusion force to the edge between the inner hole wall of the earring structure and the chamfered surface by using the extrusion surface of the first extrusion tooling, so as to extrude and form a first extrusion layer between the inner hole wall and the chamfered surface; Applying a second extrusion force to the edge between the first extrusion layer and the chamfered surface by using the extrusion surface of the second extrusion tooling, so as to extrude and form a second extrusion layer between the first extrusion layer and the chamfered surface; wherein, the extrusion surfaces of both the second extrusion tooling and the first extrusion tooling are conical surfaces, the taper of the extrusion surface of the second extrusion tooling is greater than the taper of the extrusion surface of the first extrusion tooling, and the taper of the extrusion surface of the second extrusion tooling is less than the included angle between the chamfered surface and the axis of the earring structure.

2. The extrusion method for the inner hole edge of the metal part according to claim 1, characterized in that, Before applying the first extrusion force to the edge between the inner hole wall of the earring structure and the chamfered surface by using the extrusion surface of the first extrusion tooling, it further includes: Determining the extrusion deformation amount according to the inner diameter of the earring structure, determining the first extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the first extrusion tooling, and determining the second extrusion force according to the extrusion deformation amount and the taper of the extrusion surface of the second extrusion tooling; wherein, the extrusion deformation amount is the deformation amount of the edge in the radial direction of the earring structure.

3. The extrusion method for the inner hole edge of a metal part according to claim 2, characterized in that, The calculation formulas for both the first extrusion force and the second extrusion force are: （1） Among them, when calculating the first extrusion force, represents the first extrusion force, represents the taper of the extrusion surface of the first extrusion tooling. When calculating the second extrusion force, represents the second extrusion force, represents the taper of the extrusion surface of the second extrusion tooling; represents the extrusion allowance coefficient, has a value range of 1.2 - 1.8, represents the extrusion deformation amount, represents the elastic modulus of the earring structure.

4. The extrusion method for the inner hole edge of the metal part according to claim 2 or 3, characterized in that, The extrusion deformation amount is: （2） Among them, represents the inner diameter of the earring structure, represents the extrusion deformation amount, represents the deformation coefficient, The value of is 0.5% - 2.0%.

5. The extrusion method for the inner hole edge of the metal part according to claim 2, characterized in that, The difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the first extrusion tooling is 10 - 20°.

6. The extrusion method for the inner hole edge of a metal part according to claim 2, characterized in that, After applying the second extrusion force to the edge between the first extrusion layer and the chamfered surface by using the extrusion surface of the second extrusion tooling, it further includes: Applying a third extrusion force to the edge between the second extrusion layer and the chamfered surface by using the extrusion surface of the third extrusion tooling, so as to extrude and form a third extrusion layer between the second extrusion layer and the chamfered surface; Wherein, the extrusion surface of the third extrusion tooling is a conical surface, the taper of the extrusion surface of the third extrusion tooling is greater than the taper of the extrusion surface of the second extrusion tooling, and the taper of the extrusion surface of the third extrusion tooling is less than the included angle between the chamfered surface and the axis of the earring structure.

7. The extrusion method for the inner hole edge of the metal part according to claim 6, characterized in that The difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the first extrusion tooling is equal to the difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the third extrusion tooling.

8. The extrusion method for the inner hole edge of the metal part according to claim 7, characterized in that, The difference between the taper of the extrusion surface of the second extrusion tooling and the taper of the extrusion surface of the third extrusion tooling is 10 - 20°.

9. The extrusion method for the inner hole edge of a metal part according to claim 1, characterized in that, The taper of the extrusion surface of the first extrusion tooling is 10°.

10. An extrusion tooling for the inner hole edge of a metal part, characterized in that, Applied to the extrusion method for the inner hole edge of the metal part according to any one of claims 1 - 9, the extrusion tooling is columnar, and an extrusion part is provided at one end of the extrusion tooling along its axis, and the outer peripheral surface of the extrusion part is a conical surface for extruding the inner hole edge of the metal part.

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