CN110408756A - Rotary Hole Cold Extrusion Strengthening Device and Method - Google Patents

Abstract

The invention discloses a rotary hole cold extrusion strengthening device and method, which are used to solve the technical problem that the existing cold extrusion device causes the uneven distribution of the residual stress range around the hole along the thickness direction. The technical solution is that the device includes a mandrel, and also includes a trapezoidal extruding block, an extruding driving table, a driving handle and a braking block. In the method, the mandrel uses circumferential rotation instead of axial movement to complete the strengthening process. That is, the threaded mandrel at one end moves axially with the cooperation of the driving handle to push the trapezoidal extrusion block to complete the partial extrusion of the hole wall, and the mandrel is fixedly connected with the extrusion drive table and the driving handle by using the brake stopper. Rotate the driving handle for one circle to evenly apply the extrusion amount of the trapezoidal extrusion block to the circumference of the hole. The method of rotary extrusion strengthening solves the technical problem of uneven residual stress in the thickness direction of the hole wall, so that a higher residual stress value can still be obtained at the entrance of the mandrel, which improves the overall fatigue strengthening effect around the hole.

Description

Rotary Hole Cold Extrusion Strengthening Device and Method

technical field

The invention relates to a rotary hole cold extrusion strengthening device, and also relates to a rotary hole cold extrusion strengthening method.

Background technique

In the field of aviation manufacturing, the cold extrusion strengthening process of the hole can well solve the problem of fatigue crack initiation around the hole under the influence of fatigue external load in the mechanical connection hole. The process method is to force a conical mandrel with lubricated surface, large diameter and high hardness through the hole. This process forces the hole wall to undergo a series of elastic-plastic deformation, and eliminates the residual stress while introducing residual stress around the hole. The mechanical damage of hole making is eliminated, and the occurrence of fatigue damage of hole structure is fundamentally reduced.

Refer to Figure 4. The document "Research Progress and Prospects of Hole Extrusion Strengthening Technology. Acta Aeronautics Sinica. 39-(2018): 1-17." discloses a cold extrusion device. The device includes a mandrel 3 , a slotted bush 8 , a top cap 9 and a pulling gun 10 . In the strengthening process, the slotted bushing 8 is first installed on the small diameter end of the mandrel 3, and then the mandrel 3 and the top cap 9 are respectively installed in place from the two ends of the hole 2 to be strengthened, and the pulling gun 10 is started to pull the mandrel 3 into place. Pull out from the hole to be strengthened 2 to complete the strengthening process of the connecting hole. During the strengthening process, because the hole will eventually be expanded, the hole wall material bears a huge extrusion force and is converted into friction force during the relative displacement with the extrusion device, resulting in plastic flow of the hole wall material with the mandrel. The final result is that the material of the hole wall gradually gathers toward the extrusion end of the mandrel 3, causing the actual extrusion amount at the extrusion end to be greater than that at the extrusion end. After the strengthening process is completed, the residual stress range will be distributed in a trapezoid along the thickness direction of the hole wall, the extrusion surface of the hole is the largest, and the extrusion surface is the smallest. The contribution of the small residual stress on the extrusion surface to the fatigue strengthening effect is limited, and this area becomes the weak link of the material around the hole to resist fatigue damage. Therefore, in order to further improve the cold extrusion strengthening effect of the hole, the problem of uneven distribution of residual stress along the thickness direction of the hole wall must be properly resolved.

Contents of the invention

In order to overcome the disadvantage of the existing cold extrusion device that the residual stress range around the hole is unevenly distributed along the thickness direction, the present invention provides a rotary hole cold extrusion strengthening device and method. The device includes a mandrel, and also includes a trapezoidal extruding block, an extruding driving table, a driving handle and a braking block. In the method, the mandrel uses circumferential rotation instead of axial movement to complete the strengthening process. That is, the threaded mandrel at one end moves axially under the cooperation of the driving handle to push the trapezoidal extrusion block to complete the partial extrusion of the hole wall, and the mandrel is fixedly connected with the extrusion drive table and the driving handle by using the brake stopper. Rotate the driving handle for one circle to evenly apply the extrusion amount of the trapezoidal extrusion block to the circumference of the hole. The method of rotary extrusion strengthening solves the technical problem of uneven residual stress in the thickness direction of the hole wall, so that a higher residual stress value can still be obtained at the entrance of the mandrel, which improves the overall fatigue strengthening effect around the hole.

The technical solution adopted by the present invention to solve the technical problem is: a rotary hole cold extrusion strengthening device, including a mandrel 3, which is characterized in that it also includes a trapezoidal extrusion block 4, an extrusion driving table 5, and a driving handle 6 and brake stop 7. One end of the mandrel 3 is a tapered inclined surface and the other end is threaded, and the threaded end of the mandrel 3 is matched with the threaded hole at the center of the extrusion drive table 5 and the drive handle 6 . The extruding drive table 5 is a cylindrical boss with ribs, and there is a protruding part on the outside of the bottom round table, which is closely matched with the groove of the driving handle 6 to transmit torque. A trapezoidal extrusion block 4 is placed in the top groove of the extruding drive table 5 to match the conical slope of the mandrel 3 . The threaded end of the mandrel 3 is provided with a rectangular through slot, and the bottom of the driving handle 6 is provided with a square slot. The rectangular through slot and the square slot are used to put the brake stopper 7 to limit the circumferential rotation of the mandrel 3 relative to the driving handle 6. The conical inclined surface of mandrel 3 provides stable support for trapezoidal extrusion block 4 .

A rotary hole cold extrusion strengthening method is characterized in that it includes the following steps:

Step 1. Place the top of the assembly 1 in the hole 2 to be strengthened, and connect the threaded section of the mandrel 3 with the threaded holes at the bottom of the extrusion drive table 5 and the drive handle 6;

Step 2: Rotate the driving handle 6, the threaded section of the mandrel 3 enters the threaded hole of the driving handle 6, and drives the conical surface of the mandrel 3 to exert pressure on the inclined surface of the trapezoidal extrusion block 4, so that the trapezoidal extrusion block 4 expands radially outward, Complete the extrusion of the local hole wall of the hole 2 to be strengthened;

Step 3: After the extrusion of the local hole wall is completed, insert the brake block 7 into the through groove of the mandrel 3 threaded section and the square groove at the bottom of the drive handle 6 to limit the extrusion of the mandrel relative to the extrusion drive table 5 and the drive handle 6 degrees of circumferential rotational freedom.

Step 4: Rotate the driving handle 6 again, so that the trapezoidal extrusion block 4 rotates once in the wall of the hole 2 to be strengthened, and completes the entire rotary cold extrusion strengthening process.

The beneficial effect of the present invention is that: the device includes a mandrel, and also includes a trapezoidal extruding block, an extruding driving platform, a driving handle and a braking block. In the method, the mandrel uses circumferential rotation instead of axial movement to complete the strengthening process. That is, the threaded mandrel at one end moves axially under the cooperation of the driving handle to push the trapezoidal extrusion block to complete the partial extrusion of the hole wall, and the mandrel is fixedly connected with the extrusion drive table and the driving handle by using the brake stopper. Rotate the driving handle for one circle to evenly apply the extrusion amount of the trapezoidal extrusion block to the circumference of the hole. The method of rotary extrusion strengthening solves the technical problem of uneven residual stress in the thickness direction of the hole wall, so that a higher residual stress value can still be obtained at the entrance of the mandrel, which improves the overall fatigue strengthening effect around the hole.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is an assembly diagram of the rotary hole cold extrusion strengthening device of the present invention.

Fig. 2 is an exploded view of the rotary hole cold extrusion strengthening device of the present invention.

Fig. 3 is a principle diagram of the trapezoidal extruding block in Fig. 2 exerting a local extrusion amount on the hole wall.

Fig. 4 is an assembly diagram of a hole cold extrusion device in the background technology.

In the figure, 1-assembly, 2-hole to be strengthened, 3-mandrel, 4-trapezoidal extrusion block, 5-extrusion drive table, 6-drive handle, 7-brake block, 8-slit liner Set, 9-top hat, 10-pull gun.

Detailed ways

Refer to Figure 1-3. The rotary hole cold extrusion strengthening device of the present invention includes a mandrel 3 , and also includes a trapezoidal extrusion block 4 , an extrusion drive table 5 , a drive handle 6 and a brake block 7 . One end of the mandrel 3 is a tapered inclined surface and the other end has threads, and the threaded end of the mandrel 3 cooperates with the threaded hole at the center of the extrusion drive table 5 and the drive handle 6 . The extruding drive table 5 is a cylindrical boss with ribs, and there is a protruding part on the outside of the bottom round table, which is closely matched with the groove of the driving handle 6 to transmit torque. A trapezoidal extrusion block 4 is placed in the groove on the top of the extruding drive table 5 to match the conical slope of the mandrel 3 . In the stage of extruding the partial hole wall of the hole, each circumferential surface of the trapezoidal extruding block 4 is limited by the square slots on the cylinder of the extruding driving platform 5 . When the mandrel 3 is forced to move in the axial direction, since the trapezoidal extrusion block 4 is constrained on all sides, the reaction force on the inclined surface of the mandrel 3 can only push the trapezoidal extrusion block 4 to move to the right to complete the hole wall part. The amount of squeeze applied. The threaded end of the mandrel 3 is provided with a rectangular through groove, and when the local extrusion is completed, a brake block 7 is inserted into the square groove at the bottom of the driving handle 6 and the through groove of the mandrel 3 to limit the circumference of the mandrel 3 relative to the driving handle 6. To rotate, the conical inclined surface of the mandrel 3 provides stable support for the trapezoidal extrusion block 4, ensuring that the local extrusion amount is applied to the entire range of the hole wall when the driving handle 6 rotates one circle.

A rotary hole cold extrusion strengthening method specifically includes the following steps:

Step 1. Place the top of the assembly 1 in the hole 2 to be strengthened, and connect the threaded section of the mandrel 3 with the threaded holes at the bottom of the extrusion drive table 5 and the drive handle 6;

Step 2: Rotate the driving handle 6, the threaded section of the mandrel 3 enters the threaded hole of the driving handle 6, and drives the conical surface of the mandrel 3 to exert pressure on the inclined surface of the trapezoidal extrusion block 4, so that the trapezoidal extrusion block 4 expands radially outward, Complete the extrusion of the local hole wall of the hole 2 to be strengthened;

Step 3: After the extrusion of the local hole wall is completed, insert the brake block 7 into the through groove of the mandrel 3 threaded section and the square groove at the bottom of the drive handle 6 to limit the extrusion of the mandrel relative to the extrusion drive table 5 and the drive handle 6 degrees of circumferential rotational freedom.

Step 4: Rotate the driving handle 6 again, so that the trapezoidal extrusion block 4 rotates once in the wall of the hole 2 to be strengthened, and completes the entire rotary cold extrusion strengthening process.

In the present invention, by changing the pulling extrusion of mandrel 3 to rotary extrusion, it effectively avoids the increase of the actual extrusion amount at the outlet of the hole wall caused by the axial flow of the hole wall material with the mandrel 3, and the remaining The technical problem of uneven distribution of stress along the thickness direction. The residual stress layer introduced by the strengthening method of the present invention is more uniform, the residual stress of the mandrel extrusion surface is increased, and the weak link of the strengthening effect is eliminated.

Claims (2)

1. A rotary hole cold extrusion strengthening device, comprising a mandrel (3), characterized in that it also includes a trapezoidal extrusion block (4), an extrusion drive table (5), a drive handle (6) and a brake Block (7); one end of the mandrel (3) is a tapered inclined surface and the other end is threaded, and the threaded end of the mandrel (3) is connected to the threaded hole in the center of the extrusion drive table (5) and the drive handle (6) Coordination; extrusion drive table (5) is a cylindrical boss with ribs, and there is a protruding part on the outside of the bottom round table, which is closely matched with the groove of the drive handle (6) to transmit torque; extrusion drive table (5) top groove The trapezoidal extrusion block (4) is placed inside to match the conical inclined surface of the mandrel (3); the threaded end of the mandrel (3) has a rectangular through groove, and the bottom of the driving handle (6) has a square groove, the rectangular through groove and the square groove. The groove is used to put the brake stopper (7) to limit the circumferential rotation of the mandrel (3) relative to the drive handle (6), and the conical slope of the mandrel (3) provides stable support for the trapezoidal extrusion block (4) . 2. A rotary hole cold extrusion strengthening method is characterized in that it comprises the following steps: Step 1. Place the top of the assembly (1) in the hole to be strengthened (2), and connect the threaded section of the mandrel (3) with the threaded hole at the bottom of the extrusion drive table (5) and the drive handle (6); Step 2: Rotate the driving handle (6), and the threaded section of the mandrel (3) enters the threaded hole of the driving handle (6), driving the conical surface of the mandrel (3) to exert pressure on the slope of the trapezoidal extrusion block (4), so that the trapezoidal The extrusion block (4) expands radially outward to complete the extrusion of the local hole wall of the to-be-reinforced hole (2); Step 3: After the extrusion of the local hole wall is completed, insert the brake stopper (7) into the through groove of the threaded section of the mandrel (3) and the square groove at the bottom of the drive handle (6) to limit the relative movement of the extrusion mandrel. Circumferential rotational degrees of freedom of the driving table (5) and the driving handle (6); Step 4: Rotate the driving handle (6) again, so that the trapezoidal extrusion block (4) rotates once in the wall of the hole to be strengthened (2), and completes the entire rotary cold extrusion strengthening process.