Papers by Author: Er Liang Liu

Abstract: The high temperature oxidation phenomenon will occur on the tool-workpiece contact area when machining the superalloy. Two kinds of cemented carbide tools (YG6X, YG8) are selected, the coated carbide tool and coated ceramic tool which are suitable for machining superalloy are selected. The resistance furnace is used for heating tool material, and the oxidation resistance experiments are carried out. The results show that: WC which is included in the cemented carbide tool is oxidized to WO₃ and the Co is oxidized to Co₃O₄, Ti which is included in the coated carbide tool is oxidized to TiO₂. The grain of the tool is smaller, the oxidation resistance is better. The oxidation resistant of coated carbide tool is better than the non-coated tools. The coated ceramic tool is not substantially oxidized in high temperature situation. The merits order of the oxidation resistant properties is that: coated ceramic tool>coated carbide tool > YG6X>YG8.

Abstract: Cutting force, cutting heat and tool wear are closely related to the friction characteristics of tool-chip interface in the process of metal cutting. The variation of the cutting speed and temperature have been analyzed by the distribution of stress and strain in the primary and the secondary shear zone. A new friction model has been established to analyze the contact length between cutting tool and chip and local friction coefficient at the sliding zone. Cutting experiments have been performed in the process of carbide tools cutting the titaniumTi6Al4V, the contact length of sticking zone and sliding zone and friction coefficient have been analyzed by measured cutting force. The simulation of cutting process has been carried out based on Deform software, then the simulation results have been compared with the test ones, which verifies the accuracy of the established model.

Abstract: The research focused on the finite element simulation of the surface residual stress and took an experiment to get cutting temperature and cutting force by changing different groove and coated tools. Then it analyzed the influence of cutting and tool parameters on cutting force and temperature. Finally, the results reached a conclusion about the way that the tools with different groove and coating influenced the residual stress. The coated tools reduced the residual tensile stress in the machined surface. The axial and tangential residual stress was tensile stress and the tangential residual stress was larger than the axial in machining.

Abstract: In titanium alloy machining, under different cooling lubrication conditions, the variation of tool wear and chip morphology have a certain effect on the surface roughness. Under different cooling lubrication conditions, in order to analyze the variation of tool wear, chip morphology and surface roughness, the surface roughness values are measured ​​and the variation in tool wear and chip morphology are observed, and then the interaction relationship between the tool wear and the chip morphology is analyzed. The results show that the tool wear and chip morphology influence on the surface roughness. Under different cooling lubrication, the rake face wear do not change significantly, but wet cooling and MQL play a protective role for the flank face wear.

Abstract: The various feed rate and cutting speed have an important influence on cutting force, tool wear and chip morphology in machining titanium alloy. Cutting experiments are carried out analyzing the titanium alloy Ti6Al4V under different cutting speed and feed rate, the cutting force values are obtained. The analysis results show that the dominant wear pattern is adhesion wear and chipping. And the tool wear also has an influence on chip morphology.

Abstract: In the process of turning high-temperature and high-strength steel, it is an effective method for chip breaking with complicated groove insert. In this paper, chip breaking mechanism is analyzed using the coated complicate groove insert for cutting high-temperature and high-strength steel. The model of chip curl radios is constructed though analyzing the effect of complicated groove insert on chip formation. The mathematical formulation of chip section profile coefficient is built through analyzing influential effect of complicated groove on chip section profile. The chip breaking model is developed according to chip-breaking criterion. Finally, a full experimental validation of the model is presented for chip breaking when the workpiece is high-temperature and high-strength steel, 2.25Cr-1Mo-0.25V. The tested results show the chip breaking model is reasonable, and the optimization cutting parameters are obtained.

Abstract: Traditionally, the magnetic field is always vertical to the electrical field in a magnetic-electrochemical compound polishing.The magnetic field is set to parallel the electrical field in this paper. The mathematical model of the charged particles movement in a magnetic field is established through the analysis of its movement process when using Coulomb laws and Lorentz force. Through constructing the velocity formulation and loci formulation, the function of the magnetic field is proved. Because of the magnetic field, the concentration polarization of electrochemical reaction can be reduced more and the electrochemical reaction can be accelerated easily than the traditional polishing in which the magnetic field is vertical to the electrical field. Finally, to verify the model, the magnetic-electrochemical compound polishing process has been tested and the results, compared with those obtained from the model, have shown the movement model is reasonable and the analysis to function of magnetic field is correct.

Abstract: Magnetic-electrochemical compound polishing is applied in difficult-to-process materials little by little. The influence of the magnetic field to electrochemical process is very complicated. In the paper, using Coulomb laws and Lorentz force, the two kinds of math model of the movement of the charged particles are established according to the different magnetic field whose direction is vertical or parallel to the electrical field. The velocity equations and loci equations of three typical particles are concluded in two kinds of magnetic field’s directions. To be compared and analyzed carefully, the influence of the magnetic field’s direction to polishing is concluded. This study can guide how to determine the magnetic field’s direction in magnetic-electrochemical compound polishing, and build the theoretical basis to study the mechanism of magnetic-electrochemical compound polishing.

Abstract: This paper deals with the effect of cutting speed on chip fracture strain in high speed cutting. Firstly, a chip-fracture-strain-measuring device is designed and made according to chip breaking principle. Secondly, experiments are performed by the chip-fracture-strain-measuring device. The experiment results show that chip fracture strain increases first and then diminishes as cutting speed increasing in high speed cutting while feedrate and depth of cut are constant values. Lastly, the effect of cutting speed on chip fracture strain is theoretically analysed from three main factors which affect chip fracture strain. The study above lays a theory and basis for future investigation of chip fracture strain of the other metals and for future investigation the mechanism and chip breaking forecast system of 3-D groove insert in high speed cutting.

Abstract: Chip control is a major problem to be solved in automated machining system. It involves a total system to produce chips that can be evacuated easily and reliably from the working zone and can be disposed of efficiently. In order to realize those, prediction of chip-breaking in machining is one of effective methods. In this paper, to predict the chip breakage systematically, the equivalent parameters concept is used. Through presenting a study of the effect of complicated groove insert equivalent parameters on chip formation and breaking, a predictive model of chip-breaking is constructed. Finally, chip-breaking experiments are made and the tested results show that differential chip-breaking point’s ratio is fewer than five percent, so it proves that the chip-breaking predictive model is reasonable.