ROLE OF FRICTION IN ULTRASONIC CONSOLIDATIONDURING PROCESSING OF METAL MATRIX COMPOSITES

摘要

Ultrasonic consolidation (UC) is a free form solid state processing method that can be used tornfabricate layered metal matrix composites (MMCs). The technique generates energy at therninterface by ultrasonic vibrations to weld the metal foils. There are several advantages to thisrnprocessing method which include: the fabrication of multi-material composites, faster productionrntimes, and lower processing temperatures. Furthermore, because the materials do not completelyrnmelt, the thermal gradients and residual thermal stresses are low compared with other productionrntechniques. The objective of this paper is to experimentally explore the validity of a frictionrnmodel that provides energy at the interface of two foils being welded together. An energyrnbalance is performed to predict transient temperature of the foil with frictional heat beingrnsupplied as a heat flux at the interface. An infrared camera is used to record the temperature ofrnthe foil during welding under different consolidation pressures, speeds of the rotating sonotrode,rnand amplitudes of the ultrasonic device. The process parameters are chosen to minimize therncontribution of plastic deformation to the heat generation. It is found that in most cases that thernvalue used for the friction coefficient in the friction model results in predictions that are withinrn20% of the measured temperature. Better agreement can be obtained if the friction coefficient isrnallowed to be a function of pressure, speed, and amplitude.