Turbulence-based Model Of Solid-liquid In Slender Channels Mixed Flow Study

Micro-deep-hole machining is a large removal cutting process performed under limited space conditions.Under the conditions of limited chip and debris space and insufficient tool rigidity,the smaller the aperture,the more difficult the machining,especially for the mechanical machining of slender deep holes with diameters below 1mm.This thesis focuses on the drilling of slender deep holes with a drilling diameter of 0.85 mm and a length-to-diameter ratio of 35 or more.The research content includes the establishment of a mathematical model for the flow characteristics of solid-liquid mixtures in slender deep holes;the design of the drilling tool for slender deep holes,simulation and optimization of key machining process parameters;and the investigation of the flow characteristics of solid-liquid mixtures under different inner diameters of the tool holder.Firstly,a chip removal model was established for the chip removal system in micro-deephole machining.The motion state of the chips under different cutting fluid forces was analyzed.By comparing and analyzing the theoretical and turbulence models of the flow inside the drill rod in the simulation experiment of slender deep-hole drilling,it was found that in the deep-hole drilling process,the Mixture physical model and Realizable k-ε turbulence model were more suitable for the flow characteristics of the fluid inside the rod in the experiment.Secondly,a tool suitable for internal chip removal in slender deep-hole drilling was designed.Simulation experiments were carried out under different processing parameters.The experimental results showed that under the condition of constant rotation speed,the axial force,torque,and temperature increase with the increase of feed rate;when the feed rate is determined,the axial force,torque,and temperature do not change much with the change of rotation speed.Finally,the optimal parameter combination was selected,with a feed rate of 0.01 mm and a processing speed of 15,000 r/min.The axial force during the machining process was 14.5 N,the machining torque was 2.4 N·mm,and the drilling temperature was 103℃.Then,the flow characteristics of the solid-liquid mixture inside the tool holder were analyzed for tool holder inner diameters of 0.3mm,0.35 mm,0.4mm,and 0.45 mm.Finally,simulation experiments showed that when the outer diameter of the tool holder was 0.75 mm and the inner diameter was 0.4mm,the simulated flow velocities of the solid-liquid mixture inside the tool holder were 6.5m/s,and the pressure of the solid-liquid mixture inside the tool holder was relatively low.The trajectory distribution of the solid-phase particles was more sparse and uniform.Finally,a drilling experiment of slender deep holes was conducted using 45# steel as the workpiece material.The results showed that the dimensional errors of the formed deep holes were0.0102 mm and 0.0068 mm,respectively.The axial deviation of the deep holes after processing was less than 1°,and the surface roughness Ra of the formed hole was 1.297μm,meeting the desired experimental indicators overall.