Rivet for friction self-piercing riveting and friction self-piercing riveting connection system thereof

Abstract

A rivet rotational feeding method for friction self-piercing riveting (F-SPR) system, comprising: a semi-hollow rivet, a driving spindle and a die. The bottom surface of the rivet head is connected to the semi-hollow rivet shank. The semi-hollow rivet shank has a wedge-shaped end. The rivet head has rotation driving structures and positioning structure on the top end. The rotation driving structures are central symmetric concave or convex surfaces. The positioning structure is a central symmetric and mirror symmetric concave or convex surface. The matching between the driving spindle and the rivet can improve the rotation reliability and positioning accuracy of the riveting at a high rotational speed during F-SPR process, which is beneficial to solve the problems of poor stability and non-coincidence between the geometry axis and the rotation axis of the rivet.

Claims

1. A friction self-piercing rivet (F-SPR), comprising: a semi-tubed rivet shank, with a wedge shaped cone tip at its bottom end, wherein the rivet has a rivet head that connecting with an upper end of the rivet shank; the rivet head has a chamfering and rotary driving structures at its upper end, and a positioning structure in its center; the rotary driving structure is a central symmetric, concave or convex surface; the positioning structure is a central symmetric and mirror symmetric, concave or convex surface; wherein the rotatory driving structure has several wedge-shaped notches, plum blossom shaped bosses or a plum blossom shaped grooves evenly distributed along a circumferential direction of the rivet head; the wedge-shaped notch has two intersecting planes, one of which is perpendicular to surface of the rivet head, designed for bearing a circumferential torque, and other one is tilted from the surface of the rivet head to lower end of the rivet head for dynamic matching; the plum blossom shaped bosses contain several petals evenly distributed along circumferential direction of the rivet head, which are used to bear circumferential torques; and the plum blossom shaped grooves contain several petals evenly distributed along circumferential direction of the rivet head, which are used to bear circumferential torques; wherein the concave or convex surface of the rotatory driving structure is a non-mirror symmetric structure.

2. The friction self-piercing rivet of claim 1, wherein the tip has a vertex conforming to an inner wall or an outer wall of the rivet shank or between the inner wall and the outer wall of the rivet shank.

3. The friction self-piercing rivet of claim 1, wherein the positioning structure is a cone shaped groove or a conical protruding platform.

4. The friction self-piercing rivet of claim 3, wherein the cone shaped groove is coaxial with a semi-hollow rivet shank to ensure that a rotation axis of the rivet is coincided with its geometric axis when a driving torque is applied.

5. The friction self-piercing rivet of claim 3, wherein the conical protruding platform is coaxial with a semi-hollow rivet shank to ensure that the rotation axis of the rivet is coincided with its geometric axis when a driving torque is applied.

6. A friction self-piercing riveting (F-SPR) system comprising: a driving spindle that is capable of driving a rivet for axial translational motion and circumferential rotational motion; a rivet comprising: a semi-tubed rivet shank, with a wedge shaped cone tip at its bottom end, wherein the rivet has a rivet head that connecting with an upper end of the rivet shank; the rivet head has a chamfering and rotary driving structures at its upper end, and a positioning structure in its center; the rotary driving structure is a central symmetric, concave or convex surface; the positioning structure is a central symmetric and mirror symmetric, concave or convex surface; a die on the bottom of a workpieces; wherein a driving spindle has a lower surface matching with an upper surface of the rivet head; wherein the matching is: {circle around (1)} when a rotatory driving system is in the form of several wedge-shaped notches, the driving spindle has several wedge-shaped projections evenly distributed along a circumferential direction on bottom; wherein the number of wedge-shaped projections is equal to the number of the wedge-shaped notches; wherein the shape of the wedge-shaped projections is complementary to the shape of the wedge-shaped notch, and: {circle around (2)} when the positioning structure is cone-shaped groove, the driving spindle has a positioning protruding on bottom; wherein the positioning protrusion has a same taper with the positioning grooves; wherein the positioning protrusion has a height smaller than the depth of the positioning groove.

7. The F-SPR system of claim 6, wherein the wedge-shaped notch and wedge-shaped protrusion have chamfering on each edge for avoiding over positioning.

8. The F-SPR system of claim 6, wherein the die has an upper surface designing with fixed structures on top end to control plastic flow of the workpieces in riveting.

9. The F-SPR system of claim 8, wherein the fixed structure includes a die with a flat surface, a pip die, a die with a concave flat bottom and a die with a through hole.

10. The F-SPR system of claim 6, wherein a process for rivet rotational feeding includes: Step 1, placing the rivet vertically under the driving spindle and applying appropriate resistance to restrain an axial translational motion and rotational motion of the rivet; Step 2, feeding the driving spindle straightly downwards to the upper surface of the rivet; Step 3, feeding the driving spindle axially downward slowly and, at the same time, rotating the driving spindle to match the positioning structure of the driving spindle automatically with the positioning structures in the center of the rivet head; making the rotary driving structures on bottom of the driving spindle contacting with the driving structures on the top of the rivet head; the surfaces of the rivet head and on the driving spindle contact with each other, wherein bottom surface of the driving spindle contact with the top surface of the rivet head; during the mating of the driving spindle and the rivet, when an axial pressing force or a circumferential torque exerted on the rivet by the driving spindle exceeds external resistance applied to the rivet, the rivet starts to move axially or circumferentially with the driving spindle; Step 4, when the driving spindle and the rivet move together approaching the surface of the workpieces, speed of the axial and circumferential motion of the driving spindle switch to required process parameters of F-SPR process and drive the rivet to finish the F-SPR process under setting process parameters.

Description

(1) FIG. 1 is the schematic of the rivet in this invention.

(2) FIG. 2 is the top view and cross-section view of the rivet in this invention.

(3) Wherein, a is the top view and b is the cross-section view along the A-A cutting surface

(4) FIG. 3 is the driving spindle of the F-SPR process in this invention.

(5) FIG. 4 is a schematic of the rivet head designed with the driving structures of plum-shaped-protrusion and a positioning structure of the conical-shaped groove.

(6) FIG. 5 is a schematic of the rivet head designed with the driving structures of plum-shaped-groove and positioning structure of the conical-shaped protrusion.

(7) FIG. 6 is a schematic of the first example of implementation.

(8) Wherein a-c shows the matching process of the rivet and the driving structure; d shows the relative positions of the rivet and the driving spindle after the F-SPR process; e shows the F-SPR joint profile.

(9) FIG. 7 is a schematic of the second example of implementation.

(10) Wherein a-c shows the matching process of the rivet and the driving structure; d shows the relative positions of the rivet and the driving spindle after the F-SPR process; e shows the F-SPR joint profile.

(11) FIG. 8 is a schematic of the third example of implementation.

(12) Wherein a-c shows the matching process of the rivet and the driving structure; d shows the relative positions of the rivet and the driving spindle after the F-SPR process; e shows the F-SPR joint profile.

(13) FIG. 9 is a schematic of the forth example of implementation.

(14) Wherein a-c shows the matching process of the rivet and the driving structure; d shows the relative positions of the rivet and the driving spindle after the F-SPR process; e shows the F-SPR joint profile.

BEST MODE

Example 1

(15) As shown in FIG. 1 and FIG. 2, the rivet 101 has a semi-hollow rivet shank 103 and a rivet head 104, which includes six wedge-shaped notches 105 and a positioning groove 106.

(16) Wherein the semi-hollow rivet shank 103 has an inner diameter of 4.0 mm, an outer diameter of 6.0 mm and a depth of 5.0 mm.

(17) Wherein the rivet head 104 has a diameter of 8.0 mm and a height of 2.0 mm.

(18) Wherein the semi-hollow rivet 103 has a wedge-shaped end 110 with the tip 109 locating between the inner wall and the outer wall with 0.4 mm from the surface of the inner wall and 0.6 mm from the surface of the outer wall.

(19) Wherein the rivet head 104 has chamfering 111, with the cone angel of 60.

(20) Wherein the six wedge-shaped notches 105 are distributed evenly along the circumferential direction and on the edge of the rivet head 104, which contains two intersecting planes 112 and 113. Wherein plane 112 is perpendicular to the top surface of the rivet head 104, plane 113 tilts from the top surface of the rivet head 104 to the bottom edge of the rivet head. The angle between plane 112 and plane 113 is 75.

(21) Wherein the positioning groove 106 is in the center of the rivet head 104 and has a conical shape, with the cone angel of 20 and the depth of 1.5 mm.

(22) Wherein the positioning groove 106 has a coaxiality error of less than 0.0014 mm with the semi-hollow rivet shank 103.

(23) Wherein angel between the bottom surface of the rivet head 104 and the outer surface of the semi-hollow rivet shank 103 is 80.

(24) Wherein the radius of the transition circle between the bottom surface of the rivet head 104 and the semi-hollow rivet shank 103 is 0.5 mm.

(25) As shown in FIG. 4 and FIG. 5, the rotation driving structure is a centrally symmetric concave or convex surface. The positioning structure has a centrally and mirrored symmetric convex or concave surface. Wherein, the rivet head shown in FIG. 4 has a rotation driving structure of a plum shaped convex platform and a positioning structure of a conical groove. The rivet head shown in FIG. 5 has a rotary driving structure of the plum blossom groove and the positioning structure of the cone shaped protrusion.

(26) As shown in FIG. 6, the F-SPR system contains a driving spindle 102, a die 15 and two workpieces 14 to be joined setting on the die 15, wherein the driving spindle 102 has a bottom surface that matches with the structures on the top surface of the rivet 101.

(27) The matching means that the bottom surface of the driving spindle 102 has six wedge-shaped protrusions 107, the shape of which is complementary to the shape of the wedge-shaped notch 105.

(28) Wherein the positioning protrusion 108 has a cone angle of 20 and a depth of 1.2 mm.

(29) Wherein the six wedge-shaped notches 105 and the six wedge-shaped protrusions 107 have a 0.2 mm chamfering on each edge.

(30) As shown in FIG. 6 (a), the workpieces 14 in this implementation are aluminum alloy AA6061-T6 and high strength steel DP780 with the thickness of 1.2 mm and 1.6 mm, respectively.

(31) As shown in FIG. 6 (a)-(c), the F-SPR method contains the following steps:

(32) Step 1: Locating the rivet 101 30 mm below the driving spindle 102 and apply resistance to the rivet 101 to restrain it axial translation or circumferential rotation motions.

(33) Step 2: feeding the driving spindle 102 at a feed rate of 50 mm/s downwards to the location of 3.0 mm above the top surface of the rivet 101.

(34) Step 3: feeding the driving spindle 102 at a feed rate of 2.0 mm/s and a spindle speed of 60 rpm. Under this motion of the driving spindle 102, the positioning protrusion 108 and the positioning groove 106 match with each other. The planes 112 on the six wedge-shaped notches 105 match with the corresponding planes on the six wedge-shaped protrusions 107. The bottom surface of the driving spindle 102 contacts with the top surface of the rivet 101. With the feeding and rotating motion of the driving spindle 102, the external resistance applied to the rivet 101 is destroyed and the rivet starts to move synchronized with the driving spindle 102 to rotate and to feed.

(35) Step 4, when the driving spindle 102 and the rivet 101 move together to 2.0 mm above the workpieces 14, the driving spindle 102 speeds up to the predefined F-SPR process parameters, i.e., 900 rpm and 20 mm/s and drive the rivet 101 to move until the end of the F-SPR process.

(36) After the F-SPR process described in this implementation, the final relative position of the rivet 101, the driving spindle 102 the workpieces 14 and the die 15 is shown in FIG. 6(d) and the final F-SPR joint cross-section profile is shown in FIG. 6(e).

(37) The averaged tensile-shear strength of the F-SPR joints of aluminum alloy to high strength steel is 9.27 kN, which increased by 42.2% compared to the tensile-shear strength of the F-SPR joints of the same workpieces using the bolt rivet, 6.52 kN. Besides, the gap between the rivet shank and the sheets in the joint is reduces, which is beneficial to the improvement of the fatigue performance of the joint.

The Second Implementation

(38) The rive 103 has a wedge-shaped end with the tip locating on the outer surface of the semi-hollow rivet shank.

(39) As shown in FIG. 7 (a), the workpieces 14 are aluminum alloy AA6061-T6 and magnesium alloy AZ31B, with the thickness of 1.2 mm and 1.6 mm, respectively.

(40) The workpieces 14 in this implementation are joined by F-SPR process using the rivet 101, the driving spindle 102 and the pip die 15.

(41) Other embodiment in this implementation is the same with those in the first implementation.

(42) After the F-SPR process described in this implementation, the final relative position of the rivet 101, the driving spindle 102 the workpieces 14 and the die 15 is shown in FIG. 7(d) and the final F-SPR joint cross-section profile is shown in FIG. 7(e).

(43) The averaged tensile-shear strength of the F-SPR joints of aluminum alloy to high strength steel is 7.85 kN, which increased by 97.2% compared to the tensile-shear strength of the F-SPR joints of the same workpieces using the bolt rivet, 3.98 kN. Besides, the gap between the rivet shank and the sheets in the joint is reduces, which is beneficial to the improvement of the fatigue performance of the joint.

The Third Implementation

(44) As shown in FIG. 8 (a), the workpieces 14 are aluminum alloy AA6061-T6 and aluminum casting Aural-2, with the thickness of 2.0 mm and 3.0 mm, respectively.

(45) The workpieces 14 in this implementation are joined by F-SPR process using the rivet 101, the driving spindle 102 and the die 15 with a flat bottom 17.

(46) Other embodiment in this implementation is the same with those in the first implementation.

(47) After the F-SPR process described in this implementation, the final relative position of the rivet 101, the driving spindle 102 the workpieces 14 and the die 15 is shown in FIG. 8(d) and the final F-SPR joint cross-section profile is shown in FIG. 8(e).

The Forth Implementation

(48) As shown in FIG. 9 (a), the workpieces 14 are aluminum alloy AA6061-T6 and carbon fiber reinforced plastic, CFRP, with the thickness of 1.2 mm and 2.0 mm, respectively.

(49) The workpieces 14 in this implementation are joined by F-SPR process using the rivet 101, the driving spindle 102 and the die 15 with a through hole 18.

(50) Other embodiment in this implementation is the same with those in the first implementation.

(51) After the F-SPR process described in this implementation, the final relative position of the rivet 101, the driving spindle 102 the workpieces 14 and the die 15 is shown in FIG. 9(d) and the final F-SPR joint cross-section profile is shown in FIG. 9(e).

(52) The above specific implementation may be partially adjusted by the technical personnel of the field without deviating from the principles and tenet of the invention in a different way. The scope of the protection of the invention is subject to the claim of rights and is not limited by the specific implementation, and the various implementation cases within its scope are bound by the invention.