Kinematics was my least favourite part of physics, mostly because I always had a rough time wrapping my head around the various rules and principles that govern the way things move in our world. However one lesson always stuck with me in my head, the one relating to friction and it’s various forms. Whilst I’m sure the teacher delighted in tricking us all by asking us what kind of friction a rolling tire has (hint: it’s either static or kinetic and it’s not the one you’d first think it is) that example rooted the principle firmly in my head. Understanding that made further concepts a lot easier to grasp although I’d never really considered friction a powerful force until I saw this:
What you’re seeing happen here is a process called Friction Welding although in technical terms it’s actually not welding at all. Instead it’s actually a type of forging as in traditional welding two pieces of metal are joined via melting whereas in friction welding no such melt occurs. This process has a lot of advantages most notably allowing 2 dissimilar metals, say high grade aluminium and steel (a common pair in space fairing missions), to be joined together. Doing this process via other means is extremely difficult due to the different melting points of each material and would likely lead to a much weaker bond. Friction welding by comparison always creates a full strength bond without the additional weight introduced via other methods.
Interestingly enough this process can also be used with materials other than metals, specifically thermoplastics which are a type of plastic that becomes pliable under heat. Friction welding can then also be used to join said plastics onto metal surfaces, enabling cross material bonds that are far stronger than those that could be achieved via other methods.
Pretty fascinating, isn’t it?