Magnetohydrodynamic-based Internal Cooling System for a Ceramic Cutting Tool: Concept Design, Numerical Study, and Experimental Evalidation.

Abstract

The effective removal of the heat generated during mechanical cutting processes is crucial to enhancing tool life and producing workpieces with superior surface finish. The internal cooling systems used in cutting inserts employ a liquid water-based solvent as the primary medium to transport the excess thermal energy generated during the cutting process. The limitations of this approach are the low thermal conductivity of water and the need for a mechanical input to circulate the coolant around the inner chamber of the cutting tool. In this context, this paper proposes an alternative method in which liquid gallium is used as the coolant in combination with a magnetohydrodynamic (MHD) pump, which avoids the need for an external power source. Using computational fluid dynamics, we created a numerical model of an internal cooling system and then solved it under conditions in which a magnetic field was applied to the liquid metal. This was followed by a simulation study performed to evaluate the effectiveness of liquid gallium over liquid water. The results of experiments conducted under non-cooling and liquid gallium cooling conditions were analyzed and compared in terms of the tool wear rate. The results showed that after six machining cycles at a cutting speed V_c = 250 m min ^-1, the corner wear VB_c rate was 75 µm with the coolant off and 48 µm with the MHD-based coolant on, representing a decrease of 36% in tool wear. At V_c = 900 m min^-1, the corner wear VB_c rate was 75 µm with the coolant off and 246 µm with the MHD-based coolant on, representing a decrease of 31% in tool wear. When external cooling using liquid water was added, the results showed at V_c = 250 m min^-1, the difference between the tool wear rate reduction with the internal liquid gallium coolant relative to the external coolant was 29%. When the cutting speed was increased to V_c = 900 m min^-1, the difference observed between the internal liquid gallium coolant relative to the external coolant was 16%. The study proves the feasibility of using liquid gallium as a coolant to effectively remove thermal energy through internally fabricated cooling channels in cutting inserts.