Research On Temperature Filed Of Surface Grinding Applied Nanofluid For Minimum Quantity Lubricant

The grinding energy ratio is very high during the grinding process, especially for hard-to-cut materials. Moreover, most of the grinding energy is converted into grinding heat and accumulated in the grinding zone. If this grinding heat cannot be taken away in time, the temperature in grinding zone would be risen sharply, which has serious influence on the quality and service life of the component. However, the lubrication and cooling performance of the traditional flood cooling technology has been limited by vapour film and gas barrier layer. Moreover, a large volume of grinding fluid has caused high costs and environmental problem. Therefore, looking for an effective cooling method has great significance on controlling the grinding temperature, improving the workpiece quantity and reducing costs. A new technology of cooling for grinding is proposed in this study. The nanofluid with better lubrication and heat transfer properties is prepared, and it will be split into droplets with a micron grade diameter by compressed air. Furthermore, high speed and kinetic energy is obtained by the droplets which can break through the vapour film and gas barrier layer, and be injected into the grinding zone. Then, an effective lubrication and cooling performance is obtained during grinding. The temperature field of minimum quantity lubrication (MQL) grinding applied nanofluid is investigated deeply through theoretical analysis, numerical simulation, and experimental verification. The following is the achievements of this article:(1) The suspension stability of nanofluid is investigated. The ultrasonic vibration time, the concentration of dispersant and PH value of the base fluid that have effect on the suspension stability for nanofluid is discussed by experimental and theoretical analysis.(2) The heat transfer enhancement of Al2O3-DW nanofluid applied in MQL grinding is analysised. The density, specific heat and thermal conductivity of nanofluid are studied. Based on the atomization mechanism, the influencing factors about the velocity and the diameter of the droplet were analyzed. And the mathematical model of heat transfer during the grinding is established based on the temperature distribution of grinding surface and the boiling properties of nanofluid.(3) The mathematical model for heat transfer and the temperature field during grinding is studied. Heat input and distribution on grinding surface are calculated according to the grinding mechanism. The mathematical model of three-dimensional transient temperature flied for grinding is established by dispersing structural model with finite element method and taking boundary conditions of cooling technique into consideration.(4) The three-dimensional numerical simulation of the temperature filed in surface grinding is investigated. The layers and curve model is established according the contact state of grinding wheel-workpiece. The birth-death element method is used for simulation of material removal. The surface effect unit is established so that heat flux and heat convection can load on the same boundary. Based on the undeformed chip thickness, the parabolic model of heat flux is analyzed. The simulation result is verified with experimental result. The temperature distribution and changing are compared with dry grinding, pure water MQL grinding and Al2O3-DW nanofluid MQL grinding respectively. It is found that Al2O3-DW nanofluid has the best heat transfer performance.