Method of forming a riveted joint

Abstract

According to a first aspect of the application, there as provided a method of forming a riveted joint comprising a UHSS layer and a non-UHSS layer using a self-piercing rivet comprising a head and a shank, an outer diameter of a top of the shank being greater than an outer diameter of a bottom of the shank before insertion of the rivet, the method comprising pushing the self-piercing rivet into the UHSS layer such that the lower portion of the shank flares outwards and cuts a slug from the UHSS, and pushing the flared shank of the self-piercing rivet and the slug into the non-UHSS layer such that the non-UHSS layer deforms into a die recess and flows around an outer surface of the flared shank.

1 . A self-piercing rivet comprising:
 a head and a shank, a bottom portion shank comprising a recess;   wherein the recess includes a cylindrical portion that defines a cylindrical wall portion of the shank, and wherein a shank wall thickness of the cylindrical shank wall portion has a ratio of between 0.16 and 0.3 relative to the outer diameter of the shank at the cylindrical shank wall portion.   
     
     
         2 . The self-piercing rivet of  claim 1 , wherein the recess defines a recess depth and the self-piercing rivet defines a rivet length, the recess depth being less than half of the rivet length. 
     
     
         3 . The self-piercing rivet of  claim 1 , wherein the cylindrical wall portion has a thickness in the range 1 mm to 1.5 mm. 
     
     
         4 . The self-piercing rivet of  claim 3 , wherein the diameter of the cylindrical portion of the recess is between 2.5 mm and 3.5 mm. 
     
     
         5 . The self-piercing rivet of  claim 1 , wherein the recess comprises an inwardly tapered portion. 
     
     
         6 . The self-piercing rivet of  claim 5 , wherein the inwardly tapered portion is a chamfered portion. 
     
     
         7 . The self-piercing rivet of  claim 6 , wherein the chamfered portion defines an included angle in the range 60 to 120 degrees. 
     
     
         8 . The self-piercing rivet of  claim 6 , wherein the shank defines a tip that is disposed at a lowermost end of the chamfered portion of the recess. 
     
     
         9 . The self-piercing rivet of  claim 8 , wherein the tip comprises a rounded portion. 
     
     
         10 . The self-piercing rivet of  claim 9 , wherein the rounded portion of the tip is disposed at a lowermost end of the chamfered lower portion of the bore. 
     
     
         11 . The self-piercing rivet of  claim 9 , wherein the rounded portion of the tip defines a radius of between 0.05 mm and 0.3 mm. 
     
     
         12 . The self-piercing rivet of  claim 9 , wherein the rounded portion of the tip adjoins the outer surface of the bottom portion of the shank. 
     
     
         13 . The self-piercing rivet of  claim 1 , further comprising a foot that comprises a flat surface that is substantially perpendicular to an axis of the rivet. 
     
     
         14 . The self-piercing rivet of  claim 6 , wherein the shank defines a tip that is disposed at a lowermost end of the chamfered portion of the recess, and wherein the self-piercing rivet further comprises a foot that comprises a flat surface that is substantially perpendicular to an axis of the rivet, and wherein the tip is disposed at an outer edge of the flat surface. 
     
     
         15 . The self-piercing rivet of  claim 1 , wherein the chamfered portion terminates at an upper end of the recess, the upper end of the recess being domed, conical, or planar. 
     
     
         16 . The self-piercing rivet of  claim 1 , wherein a lower portion of the recess has an inwardly tapering form. 
     
     
         17 . The self-piercing rivet of  claim 16 , wherein the lower portion has a curved inwardly tapering form. 
     
     
         18 . The self-piercing rivet of  claim 16 , wherein the lower portion of the recess has a concave form. 
     
     
         19 . A self-piercing rivet comprising:
 a head and a shank, a bottom portion shank comprising a recess;   wherein the recess comprises an inwardly tapered portion, the inwardly tapered portion defining an included angle in the range 60 to 120 degrees.   
     
     
         20 . A self-piercing rivet comprising:
 a head and a shank, a bottom portion shank comprising a recess;   wherein the recess defines a cylindrical portion that defines a cylindrical wall portion, the cylindrical wall portion having a thickness in the range 1 to 1.5 mm.