Atlas Copco has developed a fully hollow self-pierce rivet. With the Henrob T-rivet (T = tubular), up to four layers of high-strength, low-deformability 6,000 mm aluminum alloys can be safely joined.
According to Atlas Copco IAS, the new T-rivets meet the requirements of the automotive industry for mechanical joining processes for new lightweight constructions and multi-material design. As a result of these trends, more and more aluminum is being used in body-in-white construction. Modern aluminum alloys have very low ductility (formability), which is a challenge for the joining process. If several layers of high-strength aluminum had to be joined up to now, conventional semi-hollow self-pierce rivets would often cause cracking in the component or asymmetrical expansion of the rivet. This made the joint unstable and susceptible to corrosion — or even impossible.
The new joining element differs from semi-tubular self-pierce rivets in particular by its completely tubular structure, as it is called. Conventional semi-tubular self-pierce rivets require a deep die to accommodate the displaced material. In the case of T-rivets, the material that the rivet displaces in the joining process can, on the other hand, move further upwards in its bore and thus flow in two directions, the manufacturer argues. This displaces less material downwards, so that the die can be very flat. This in turn avoids cracks in the lowest material layer because the brittle aluminum is not deformed that much.
Reliable Joining of Thick Layers
The tip of the T-rivet also improves the process by allowing more uniform penetration of the material. A special coating reduces friction and facilitates the flow of aluminum into the cavity. In this way, even thick layers can be joined reliably and safely.
6,000 aluminum alloys are often used for the construction of impact surfaces, such as the A and B pillars and other safety-critical applications in car body construction. Therefore, a permanently strong, multi-layer joint is particularly important in these areas, Atlas Copco reports.
