Friction Element Weld Element Modification To Increase Corrosion Resistance of Thermal Mechanical Joint

Abstract

A welded structural assembly and method are provided, which in one form includes at least one upper substrate, at least one lower substrate disposed adjacent the upper substrate, and a fastener extending through the upper substrate and into the lower substrate. The fastener is welded to the lower substrate and defines a head portion having an outer periphery and an underside. A sealing member is disposed under the head portion and contacts the underside thereof, and further extends beyond the outer periphery of the head portion.

What is claimed is: 
     
         1 . A welded structural assembly comprising:
 at least one upper substrate;   at least one lower substrate disposed adjacent the upper substrate;   a fastener extending through the upper substrate and into the lower substrate, wherein the fastener is welded to the lower substrate, the fastener defining a head portion having an outer periphery and an underside; and   a sealing member disposed under the head portion, the sealing member contacting the underside and extending beyond the outer periphery.   
     
     
         2 . The welded structural assembly according to  claim 1 , wherein the sealing member is a coating applied to at least one of the fastener and the upper substrate. 
     
     
         3 . The welded structural assembly according to  claim 2 , wherein the coating is selected from the group consisting of a thermoplastic polymer, lead, foam, and paper. 
     
     
         4 . The welded structural assembly according to  claim 1 , wherein the sealing member is a strip of tape. 
     
     
         5 . The welded structural assembly according to  claim 1 , wherein the sealing member is a washer. 
     
     
         6 . The welded structural assembly according to  claim 5 , wherein the washer is a material selected from the group consisting of a thermoplastic polymer, a closed cell foam, a wax-dipped fiber mat, and a non-ferrous metal. 
     
     
         7 . The welded structural assembly according to  claim 1 , wherein the head portion of the fastener comprises a recess extending proximally into the head portion, wherein the sealing member is plastically deformed to fill the recess. 
     
     
         8 . The welded structural assembly according to  claim 1 , wherein the underside of the head portion defines a distal face that extends normal to a shank of the fastener. 
     
     
         9 . The welded structural assembly according to  claim 1 , wherein the underside of the head portion defines a distal face that extends at an obtuse angle relative to a shank of the fastener. 
     
     
         10 . The welded structural assembly according to  claim 1 , wherein the underside of the head portion defines a distal face that extends at an acute angle relative to a shank of the fastener. 
     
     
         11 . The welded structural assembly according to  claim 1  further comprising a second head portion disposed on the head portion, the second head portion configured to shear off during installation of the fastener. 
     
     
         12 . The welded structural assembly according to  claim 1 , wherein the upper substrate is one of an aluminum material or a magnesium material, and the lower substrate is a steel material. 
     
     
         13 . The welded structural assembly according to  claim 1 , wherein the fastener is friction welded to the lower substrate. 
     
     
         14 . The welded structural assembly according to  claim 1 , wherein the fastener is resistance welded to the lower substrate. 
     
     
         15 . A method joining at least one upper substrate and at least one lower substrate comprising the steps of:
 placing a fastener into an aperture formed at least partially through the upper substrate;   providing a sealing member between a head portion of the fastener and the upper substrate; and   welding the fastener to the lower substrate while simultaneously forming the sealing member under the head portion such that the sealing member extends beyond an outer periphery of the head portion.   
     
     
         16 . The method according to  claim 15 , wherein the sealing member is a material that is cured by heat from the welding step during installation of the fastener. 
     
     
         17 . The method according to  claim 15 , wherein the sealing member is a material that is cured by a heat source separate from the welding. 
     
     
         18 . The method according to  claim 17 , wherein the separate heat source is heated air flowing through an installation tool. 
     
     
         19 . The method according to  claim 17 , wherein the separate heat source is induction heating of the fastener and sealing element prior to installation. 
     
     
         20 . The method according to  claim 15  further comprising the step of providing a lateral tooling barrier along the upper substrate to control the extension of the sealing member beyond the outer periphery of the fastener.