The new aluminum-bodied Jaguar XJ (X351) is the largest single automotive user of rivets, 3118 being applied per body using 88 Kawasaki robots, and complemented with the use of adhesive, which is applied over the specially pretreated sheet. Colored rivets are now possible for prepainted applications. The aesthetic appearance of self-piercing rivets is excellent, with the flat head of the rivet providing visual continuity on the sheet surface. In addition, a joint should be made from the thinner to the thicker material. Optimum performance is achieved when the joining direction is from the hard/brittle material to the soft/more easily deformable material. Commercial systems found on the market are generally in the form of manual, easy-to-handle devices, although there is the flexibility to incorporate them into automated robotic lines. The force needed to squeeze the rivet into the sheets is high and the overhang distance is limited because of the rigidity of the pliers. The rivets are pushed into the sheets by a small hydraulic power device with special overhang pliers. An exhaustive description of each mechanical fastening system is not possible in this book.įIGURE 6.13. They can provide an efficient solution, particularly when used in association with adhesive bonding, to a wide range of assembly problems. 10 In the last few decades some new systems have appeared on the market that are particularly applicable to the joining of mixed material designs. Mechanical assembly methods like screws and bolts have been used as an autobody materials joining technology for some time and some excellent texts are available, providing the relevant background science. The joining of materials where a long tool life is of high relative importance. The joining of materials in applications where a high fatigue life is critical compared to static strength. Many of the aluminum applications in autobody structures make use of mechanical fastening techniques to overcome the poor inherent weldability of aluminum. The joining of material combinations that cannot be easily welded such as prepainted steels or very dissimilar metals. Although resistance spot welding remains the major process for autobody materials assembly, mechanical fastening techniques such as spot clinching and self-pierce riveting offer benefits under certain circumstances. The forces used can be as much as five times those for spot welding. These systems need to be particularly rigid to withstand the high applications forces during the fastening process. The main drawbacks with these processes are the limited peel strength, particularly for clinched joints, and the high degree of access required and weight of the systems used to produce these joints. This method is called “laser-assisted self-pierce riveting” or LSPR, and it was employed for joining the components of the Demo-structure. used a laser beam at the joint location and showed that it can provide enough heat to prevent initiation of cracks in AZ31 magnesium alloy. The formability of magnesium improves at higher temperature because of the additional slip systems activated. Magnesium has hexagonal crystal structure which results in limited slip systems and poor ductility and formability at room temperature therefore, SPR generally causes cracking in magnesium alloys.

If the ductility of the materials being joined by the SPR is less than the required value, cracking might occur, especially in the bottom sheet, due to the severe plastic deformation. The SPR technique can be used for joining dissimilar materials and multilayer stacks, but it requires penetration into both materials, which means it is not suitable for brittle materials. Illustration of the self-pierce riveting. Although the principles of operation are basically the same, there are variations from one system to another in, for example, rivet and die shape.Figure 14.7. Self-piercing riveting is, essentially, a proprietary process. No fume or heat, low noise emission, low energy consumption.Little or no damage to pre-coated materials.Can be used on unweldable materials and dissimilar material combinations.The die shape also causes a button to form on the underside of the lower sheet ideally, the rivet tail should not pierce this.Īdvantages of self-piercing riveting include. The rivet may be set flush with the top sheet when using a countersunk rivet head.

The rivet pierces the top sheet and the die shape causes the rivet to flare within the lower sheet to form a mechanical interlock.

The semi-tubular rivet is driven into the materials to be joined between a punch and die in a press tool. The process starts by clamping the sheets between the die and the blankholder. National Structural Integrity Research Centre.Structural Integrity Research Foundation.

Self piercing rivet gun