Modeling the Frictional Contact Geometry in Machining Using Fractals

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This grant will research friction at the tool-chip interface in machining and will attempt to quantify the extents of seizure and sliding islands. Preliminary analysis conducted through a prior exploratory grant will be extended to better examine the non-Euclidean nature of frictional contact. The role of cutting conditions, tool and work materials, tool preparation and atmospheric oxidation will be determined in evaluating map areas and perimeters. The primary objective of this research is to develop a fractal model of the frictional contact geometry at the tool rake face in machining. The physics and mathematics of friction will be investigated using a fractal geometric approach, to determine relationships for cutting variables such as area of contact, cutting forces, energy consumed, tool temperatures and wear, extending on preliminary work. These models will be validated and improved with data obtained from conventional as well as specialized experiments. Seizure will be examined at a fundamental level and the role of physical mechanisms in its creation and extinction at the interface quantified. Seizure will be studied by varying tool surface preparation, oxidation, controlled tool coatings, work material prior processing and tool wear. The material and cutting conditions leading to different fractal dimensions will be physically modeled and validated experimentally. Issues of similarity, scaling and stationarity will be suitably studied to develop predictive models of the cutting process.This project is expected to lead to improved models of the cutting process and consequently to its imminent automation. This research will be useful in cutting tool design, tool coating evaluation, and process optimization. The scalability of frictional models to finer scales of machining will also result from this treatment.