Patent of the Month – Joining Dissimilar Materials
Editor | On 12, Jan 2020
Our patent of the month this month takes us to a quartet of inventors at the Battelle Memorial Institute in Washington State. US10,369,748 was awarded to the team on August 6. The invention takes us on a rare foray into the world of manufacture, where we observe the rather more common challenge of joining together dissimilar materials.
Here’s what the background description has to tell us about the specific problem under consideration:
A world of rising energy necessitates approaches for reducing the amount of energy needed to perform standard tasks. Among approaches under development are lighter, more fuel efficient vehicles. Reducing the weight of vehicles can be accomplished in a variety of ways including replacing heavier steel regions with lighter weight materials. However, difficulty has arisen in attempting to find ways to robustly join dissimilar materials in a way that provides the needed strength and resiliency that exists in structures that are made from the same material. Preferably, and in some instances by requirement, these seams and interconnects must be welded together. Welding is fairly straight forward when the two materials have similar melting points but becomes more and more difficult when the materials have vastly different melting points or other characteristics.
Joining materials such as steel to aluminum, titanium, magnesium, copper, or any combination thereof, has proved difficult for a variety of reasons. The prior art generally teaches that when these materials are joined that the temperatures must be maintained generally low so as to prevent the formation of brittle intermetallic compounds, which are generally believed to cause the welds to be brittle and fail. Most prior art methodologies for joining dissimilar materials have focused on getting rid of these brittle intermetallic portions. However, the work arounds have generally proven to have negative side effects such as cost and complexity and in many instances simply do not provide an acceptable solution.
Hence what is needed is a process for forming high strength joints between dissimilar materials in ways that a simpler cheaper and more effective than the current methodologies. The present invention is a significant step forward in addressing these needs.
Which, if we take the problem back to first principles, as the inventors have sought to do, is all about a strength-versus-temperature contradiction, about which, the Contradiction Matrix has this to say:
And here, according to the main Claim of the patent, is how the inventors have solved the problem:
A method for solid state joining of dissimilar materials using a friction stir welding device, the method comprising the steps of: inserting a pin having two ends within an aperture defined in a first material and a carbon reinforced composite material; and friction stir welding each end of the pin to a portion of the first material.
Wow. Let’s look at that again, this time with the relevant Inventive Principles inserted…
A method for solid state joining of dissimilar materials using a friction stir welding device, the method comprising the steps of: inserting [Principle 7, Nested Doll] a pin [Principle 24, Intermediary] having two ends within an aperture [Principle 31, Porous Materials/Holes] defined in a first material and a carbon reinforced composite material [Principle 40, Composite]; and friction stir welding [Principle 9, Prior Counteraction] each end of the pin to a portion of the first material.
Five out of eight sounds pretty impressive to me.