In situ 3D measurement of lubrication behavior at interface between tool and workpiece by direct fluorescence observation technique

A new direct observation method, which is based on an optical microscopy and a conventional fluorescence method, is developed in order to measure the oil film thickness at the interface between the tool and the workpiece in lubricated upsetting. The oil film thickness is measured using this method. The oil film thickness and the distribution at the interface during lubricated upsetting can be measured three dimensionally. The calculated central thicknesses at the instant of entrapment are in good agreement with the measured ones for lubricants with higher viscosity at higher compression speed. The 3D surface topography of workpiece at the end surface can be clearly visualized.