The Need

The aircraft industry requires robust methods for joining metal sheets, structures, and assemblies together in wings, fuselages, and engines. Fusion-based welding methods cannot always be used because they create heat-affected zones, which reduce the mechanical performance of material around the weld. In addition, there is a need for repair of parts that have been damaged, worn, or corroded during operation. This is particularly important for life critical and high value components often used in aerospace, automotive, and oil and gas applications. A common practice is to scrap parts when damage is detected, adding cost and downtime. This invention enables ultrasonic additive manufacturing (UAM) to provide solutions for both metal sheet joining and damage repair. In addition, this technology allows high-strength reinforcement or sensors to be embedded during the repair and joining processes.

Additive manufacturing (AM) can significantly optimize the speed and costs of prototyping, manufacturing, and customization of products. Recent innovations have expanded the breadth of material choices possible for AM and thus its applicability. A recent BCC research summary (IAS102C) reports that additive manufacturing of metals is expected to grow from a global market of 91.5 million USD in 2017 to 5.3 billion USD by 2023 with a CAGR of 34%. UAM utilizes a cylindrical sonotrode to grip layers of foil feedstock and apply lateral (y-direction) displacements via ultrasonic vibrations to create a scrubbing action and plastic deformation between the foil and the material to which it is being welded. The scrubbing action displaces surface oxides and collapses asperities. This creates intimate metal-to-metal contact which results in solid-state welding. More information on UAM process details and applications can be found here: https://smsl.osu.edu/uam/research. The sonotrode rolls over the foil longitudinally (x-direction) to weld the layer. This scrubbing motion, however, is unable to produce good welds for interfaces that are normal to the x-y plane. Therefore, while robust parts and features can be built utilizing wide sheet feedstock, the edges of foil layers cannot be sufficiently welded to adjacent foils or base part material to fill channels or provide flush, seamless joints between parts without leaving cracks or weak areas in the build. This invention allows UAM to fill channels and gaps without leaving defects in the perpendicular plane.

The Technology

This invention uses UAM with a modified sonotrode to fill a channel that has been cut, formed, or otherwise created in a metal structure or between two metal structures. This technology utilizes standard foil feedstock without special processing or handling. The foil alloy may be the same or different than the part material and may be welded over reinforcing fibers, sensors, electronics, or other materials to embed them in the metal part. Multiple layers of metal foil can be welded into the channel until the entire channel is filled in. At this point, unwanted welded material can be removed using milling or other methods to achieve a flush surface where the channel once was. This invention enables the generation of strong, stable welds in channels required for joining structures or repairing damage and defects.

Commercial Applications

• Aerospace structures: manufacturing, joining, or reinforcement of wings, fuselages, engine components, and supports
• Automotive structures: manufacturing, joining, or reinforcement of body structures and components such as seat frames
• Oil and gas: repair of pipeline cracks and damage or wear on drilling equipment
• Industrial processes: repair of wear and damage to expensive components
• Smart structures: embedment of sensors and electronics in aerospace, automotive, medical, and consumer products

Benefits/Advantages

• Solid-state joining method
• High integrity welds without heat-affected zones or thermally induced stresses
• Applicable to a wide variety of metals and alloys
• Seamless, flush joints or repairs
• Minimal effect on the original temper of the parts and foil feedstock