Automobile drive shaft universal joint friction welding

The largest-volume friction welding application — universal joints on car drive shafts, welded in 1.5 seconds per part.

The ultrasonic welding of plastics is probably the largest application for ultrasonic welding, because of all these things we said about their properties. Now where do we use friction welding for metals? The knuckle of the drive shaft on most automobiles. The drive shaft is a tube that goes from the engine to the differential of the car. You have a universal joint. A universal joint is basically just a U-shaped piece of metal and another U-shaped piece of metal with a cross piece, a cruciform in between, shaped like a cross, and bearings. This has two degrees of freedom. You can wobble along the axis that you're spinning your shaft. When you hit a bump you don't put tremendous stresses on and fatigue your drive shaft, because the universal joint can take the angular misalignment when your car flexes. Usually you have at least one if not two universal joints on every car.