Patent Application
20130106123
The invention relates to a welded assembly having improved structural integrity.
Welding is a fabrication or process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the substrates of the work-piece and adding a filler material to form a pool of molten material, a.k.a., the weld pool, at the substrate interface. After the weld pool at the substrate interface cools, a high strength joint is produced.
Depending on the type and quality of the materials sought to be joined, the same welding process may expend/consume vastly different amounts of energy to generate a robust weld. Additionally, a welding process that expends more energy may require larger, heavier, more powerful, and thus more expensive welding equipment. Such increased consumption of welding energy tends to reduce the overall efficiency of the welding operation, and, coupled with the higher cost and size of the welding equipment, tends to increase the effective cost of the finished assembly.
Some welding processes involve melting the base material microstructure at the weld interface, while others are configured as solid-state joining processes. One type of a solid-state joining process is friction-stir welding (FSW). FSW is frequently used for joining aluminum components, because, in comparison with alternative welding processes, FSW inputs smaller amounts of thermal energy and generates less thermal distortion in the components being joined.
A welded assembly characterized by improved structural integrity includes a first component disposed along a first plane. The first component includes first and second substantially parallel surfaces, and includes a channel arranged on the first surface. The assembly also includes a second component disposed along a second plane, wherein the second component includes a leading edge. The leading edge of the second component is inserted into the channel of the first component such that an interface is formed between the first and second components. A weld applied or generated on the second surface joins the first component with the second component at the interface such that the assembly is formed.
The first plane may be substantially orthogonal to the second plane.
The weld generated on the second surface may be a friction-stir weld. Such a friction-stir weld may penetrate into the channel without emerging on the first surface.
The first component and the second component may each retain a respective material microstructure at the interface following the generation of the weld.
In the first component, an aperture may connect the channel and the second surface. Additionally, the edge of the second component may include a projection configured to engage the aperture.
The first component may be a face plate and the second component may be a crash box, each for a vehicle bumper system. Accordingly, the weld may be used to at least partially join such a vehicle bumper support.
Each of the first and second components may be formed from one of aluminum, magnesium, titanium, copper, and steel.
A method of forming such a welded assembly is also disclosed.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the drawings, wherein like reference numbers refer to like components,
With renewed reference to
FSW is a solid-state joining process for components that are formed from metal, such as steel, aluminum, magnesium, titanium, and copper. FSW is termed a solid-state welding process because the base metal structure is not melted during joining of the components. Because the base metal structure is not melted during FSW, this process is especially useful for applications where it is desirable for the original metal characteristics to remain unchanged after the assembly is completed. Accordingly, FSW is frequently used to create large assemblies which cannot be easily heat treated to recover material temper characteristics after the weld has been completed.
As shown in
Frictional energy is generated between the tool 32 and the materials of the crash box 14 and the face plate 12. Such frictional energy, along with the energy generated by the mechanical mixing process within the materials of the crash box 14 and the face plate 12 at the interface 16, causes the stirred materials to soften without reaching their respective melting points. In turn, the softening of the stirred materials permits the tool 32 to traverse along the second surface 20 in a plasticized pool of metal while welding the face plate 12 and the crash box 14 at the interface 16.
During the generation of the friction-stir weld 30, the tool 32 is rotated and fed along the second surface 20. As the tool 32 is thus rotated and fed along the second surface 20, a leading face 34 of the tool forces the plasticized material to a back side 36 of the tool, while applying a substantial forging force to consolidate the weld material at the interface 16. Accordingly, the welding of the face plate 12 and the crash box 14 is facilitated by severe plastic deformation of the face plate and the crash box at the interface 16 in the solid state, subsequently culminating in dynamic re-crystallization of the base material. Accordingly, although the weld 30 entails plastic deformation and stirring of the base materials of the face plate 12 and crash box 14, the resultant joint nevertheless retains the respective material microstructures of the face plate and crash box at the interface 16.
As a result of the interface 16 being created by the edge 28 inside the channel 22, the placement of the friction-stirred region generated by the weld 30 may be controlled more reliably with respect to the first surface 18. Correspondingly, the process that generates the weld 30 may be sufficiently robust to consistently penetrate into the channel 22 and join the face plate 12 and the crash box 14, but without the weld sporadically emerging on or accessing the first surface 18. As observed from testing of friction-stir welded assemblies, such sporadic penetration of the first surface 18 by the weld 30 may produce welded assemblies with inconsistent structural integrity. Therefore, the ability to retain the first surface 18 undisturbed by the friction-stirred region provides an improved structural integrity welded assembly 10. For purposes of clarity,
After frame 62, the method proceeds to frame 64 with inserting the leading edge 28 of the second component, which in the described embodiment is the crash box 14, into the channel 22, thus forming the interface 16. Accordingly, in frame 64, the face plate 12 and the crash box are abutted for further processing. Following frame 64, the method advances to frame 66, where it includes joining the face plate 12 with the crash box 14 at the interface 16 via the weld 30 generated on the second surface 20 such that the assembly 10 is formed.
As described with respect to
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
