FRICTION WELD

Another variant of the friction welding process, linear friction welding, uses servo-hydrauHcs pumps to vibrate parts back and forth against each other. Bond areas of approximately 1000 mm can be joined the attachment of turbine blades to rotors is a prevalent apphcation of this technology. 

Excellent high strength welds have been produced by inertia-welding, or friction-welding, which develops essentially no heat-affected zone. The actual interface is wrought molybdenum because the molten metal and the adjacent soHd metal that has been raised to very high temperatures have been expelled from the joint. 

Friction welding Heat zone effect Heli-arc welding Pressure welding Spot welding... 

The tool joints made by forging are heat treated by quenching and tempering. They are either friction welded or flash welded to the pipe body. For friction... 

Inertia (friction) welding in the solid state, which is useful for joining dissimilar metals, i.e., aluminum to steel and stainless steel. At least one of the pieces to be welded must be circular and capable of being rotated at high velocities before being brought into contact with pressure to the second member. 

Friction welding is the most common solid-state process. One type, direct-drive friction welding, is accomplished by spinning one piece rapidly against a second, stationary piece to produce frictional heating. When the metal is at a forging temperature below the solidus, rotation is stopped and axial force is applied. Heated metal, together with oxide and surface contamination, is squeezed out of the interface between the two pieces in the form of a metal flash, which can be trimmed to form a smooth surface. 

Yet another boundary condition encountered in polymer processing is prescribed heat flux. Surface-heat generation via solid-solid friction, as in frictional welding and conveying of solids in screw extmders, is an example. Moreover, certain types of intensive radiation or convective heating that are weak functions of surface temperature can also be treated as a prescribed surface heat-flux boundary condition. Finally, we occasionally encounter the highly nonlinear boundary condition of prescribed surface radiation. The exposure of the surface of an opaque substance to a radiation source at temperature 7 ,-leads to the following heat flux ... 

Frictional Welding Two pieces of PMMA are to be welded frictionally. Estimate the normal pressure that has to be applied in order to raise the interface temperature from 25°C to 120°C in 1 s. The relative velocity between the sheets is 10 cm/s. The thermal conductivity of PMMA is 4.8 x 10-4 cal/cm s, the thermal diffusivity is 9 x 10 4cm2/s, and the coefficient of friction is 0.5. 

Polymer Engineering and Science 40, No.8, Aug.2000, p.1931-41 FRICTION WELDING OF SIMILAR AND DISSIMILAR MATERIALS. PMMA AND PVC... 

The effects of spin friction pressure and time on the friction welding between PMMA-PMMA, PVC-PVC and PMMA-PVC are discussed. Data are presented for the the three heat-affected zones and the three sections of tensile fracture morphology. 19 refs. 

Spin/friction welding primarily finds usage with engineering plastics such as acetal. It is occasionally used with plastic components found in packaging. 

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