Experimental and analytical modeling of near-dry turning operations with coated grooved tools for improved sustainability

Traditionally, cutting fluids are known to enhance machining performance despite conflicting studies in the past. The primary purpose of the application of cutting fluids is to carry the heat and chips away from the cutting point. Mist generated by flooding cutting fluids, leave behind bacterial colonies in fluid sumps. The generation of toxic fumes and the disposal costs do not make the use of cutting fluids a healthy and economical option any more. Under these circumstances dry, near-dry and cryogenic machining becomes more viable options. In this dissertation, the role of near-dry machining is investigated based on its performance comparison with dry and conventional flood-cooled machining methods.; Machining performance comparisons were carried out on AISI 4140 alloy steel and A380 aluminum alloy under all three different cooling/lubrication conditions (flood cooling, near-dry and dry). For the alloy steels near-dry machining provided lower cutting forces, lower surface roughness values, better chip breaking and better progressive tool-wear patterns. Aluminum alloys performed better under flood cooling conditions, unlike steel.; The tool temperature measurements obtained using infrared techniques showed that the maximum tool temperature is always found at the point where the maximum rate of tool-wear is located. Cutting forces decreased over the machining time while tool temperature was increasing. Comparison of progressive tool-wear patterns under different cooling/lubrication conditions showed how the low tool temperature enhances tool-life.; To better understand the relationship between the tool-wear and type of cutting fluids used, a series turning tests were carried out under dry, near-dry and flood-cooled conditions. Tool-life was significantly different when different cutting fluids are used and the results were instrumental in broadly defining the tool coatings effect factor in the existing tool-life equation. In addition, to that the ratio between cutting force and thrust force was seen as an indicator to detect forthcoming tool failure.; To understand the interfacial frictional and temperature conditions much better, metallographic examinations were carried out on chips produced by tools with different coating thicknesses and cooling/lubrication conditions. Results showed complex interactions between the tool-chip interface temperature and the frictional conditions and clearly shows how chip formation is affected by this behavior.; The project is concluded by simulating the cooling and temperature effects on the tool by finite element analysis methods. The existing FEM program developed earlier was modified by adding a coating layer and cooling boundary conditions to simulate the tool cooling under dry, near-dry or flood cooling conditions. The tool geometry as well as the cutting conditions affects the tool temperature and friction at the tool-chip interface significantly.