A new model of cutting fluid penetration in the interface zone during metal cutting is proposed. This model includes three stages relating to processes in a single capillary: 1. liquid phase entry, 2. 'micro-droplet explosion', and 3. filling the capillary by gas phase lubrication. Calculations of model parameters have been done for two different liquids: water and castor oil. The correlation between model data and known experimental results is also given. Abstract cutting fluid, model, interface zone, liquid phase, gas phase, water, castor oil, capillary Keywords Nomenclature C FP Ffr cu oz U
A multistage mechanism of lubrication layer formation during cutting is described and the necessary conditions for the formation of a lubrication layer are formulated, I t is considered that the process of physical adsorption of the tribo-active components of the cutting fluid in the contact zone between tool and chip during metal cutting is one step in a multistage process which occurs in the interface capillary system. A mathematical model describing simultaneous diffusion and adsorption of tribo-active components in a single interface capillary is proposed. Some parameters for a model determining the efficiency of the lubricating action of surface-active additives are alsoproposed. Nomenclature 9 volumetric surfadant concentration in liquid phase D diffusion factor of surfactants k 1, 11 M m n n' 0.2 Boltzmann constant single capillary length depth of liquid phase penetration into capillary mass of surfactant molecule concentration of surfactant in liquid phase, per unit length of capillary dimensionless concentration of adsorbed surfactant non-adsorbed surfadant concentration, per unit length of capillary concentration of surfactant in 'steam cap' outside capillary (per unit length of capillary) axis along capillary length Lubrication Science 11-1, November 1998. (11) 51 0954-0075 $8.00 + $8.00 (868-1 198) 52 V.A. Godlevski, A.V. Volkov, V.N. Latyshev, and L.N. Maurin: A Description of the Lubricating Action of the Tribo-Active Components of Cutting Fluids P gas pressure in capillary r capillary radius S t present time T gas temperature tl = t/z, dimensionless time U velocity of chip movement z1 = z/Z, dimensionless coordinate a constant maximal effective cross-section for collision of surfactant molecules dimensionless concentration of surfactant adsorbed on capillary walls p' adsorbed surfactant concentration, per unit length of capillary P O equilibrium value of P on linear part of adsorption isotherm p(n>,p(P> chemical potentials, for unsorbed and adsorbed surfactants, respectively V proportionality factor (tangent of inclination angle of the isotherm) 77 constant, the reciprocal value of which is the adsorption time T , = Z$u capillary lifetime %h chemisorption layer formation time zP physical adsorption time =t thermo-catalytic destruction time Trn supramolecular (multilayer) film forming time z l = Z~/ D time necessary for diffusion movement of a surfactant particle (in gas phase at temperature 2') along full capillary length 1, time of adsorption processes on capillary walls P 22 = l/q
INTRODUCTIONThe lubricating action of cutting fluids is mainly determined by their chemical activity.' This property is, however, extremely problematic, in so far as it is harmful to the operator, can affect machine tool detail, and complicates the recycling of used lubricants. These factors mean a reduced concentration of chemically active additives in cutting fluids.To compensate for the reduction in the good tribological characteristics of cutting fluids, surface-active agents (surfactants) are used, the role of whic...
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