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17 results on '"Liu, Niancong"'

9. Surface integrity investigation and multi-objective optimization in high-speed cutting of AISI 304 stainless steel for dry cutting and MQCL conditions.

Author

Wang, Yinzhi, Zheng, Chengli, Liu, Niancong, Wu, Long, and Chen, Yun

Abstract

To realize green production in the manufacturing industry, it is important to reduce or even eliminate the discharge of cutting fluid. In this study, the impact tendency of the cutting parameters on the surface roughness of 304 steel was analyzed by establishing variance analysis models. The surface quality profile parameters and the main cutting force under minimum quantity cooling lubrication (MQCL) and dry cutting conditions were analyzed and compared. The characterization of the morphology of the machined surface was evaluated, and the wear mechanisms of the two machining methods were analyzed. A hybrid machining strategy was developed in which dry cutting is used at the beginning of cutting and dry cutting is replaced with MQCL before the quality of the machined surface deteriorates sharply. This strategy obtains the optimal parameter combination through a genetic algorithm. The most important factor affecting the surface roughness was the feed rate, whereas the change in cutting depth had no obvious effect on the surface roughness. In addition, the parameters of low cutting speed and feed rate were advantageous under dry cutting conditions. However, with increases in the feed rate and cutting speed, the peak and valley of the surface profile gradually increased, and the MQCL conditions were more conducive to obtaining a smoother surface. Furthermore, the MQCL and higher cutting speed could reduce the main cutting force. The surface roughness under hybrid cutting was 5.19% and 18.76% lower than that under MQCL and dry cutting, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
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11. Performance evaluation of castor oil-ethanol blended coolant under minimum quantity lubrication turning of difficult-to-machine materials

Author

Zou Xing, Yun Chen, Liu Niancong, Wu Shenghong, and Yuan Jia

Subjects
0209 industrial biotechnology, Materials science, Strategy and Management, Metallurgy, 02 engineering and technology, Management Science and Operations Research, 021001 nanoscience & nanotechnology, Hardness, Industrial and Manufacturing Engineering, Coolant, 020901 industrial engineering & automation, Vegetable oil, Castor oil, medicine, Lubrication, Surface roughness, Tool wear, 0210 nano-technology, Intensity (heat transfer), medicine.drug
Abstract

A recent trend in the processing of difficult-to-machine materials is the replacement of traditional coolants with vegetable oil, which is environmentally friendly. In this study, a new type of blended coolant that is suitable for minimum quantity lubrication (MQL) was developed by leveraging the mutual solubility of castor oil and ethanol. The physicochemical properties of the blended coolant and its effects on cutting vibration, surface hardness, surface roughness and tool wear mechanism under different working conditions were studied. Turning experiments on AISI 304 steel under dry cutting, flood cutting, vegetable oil (castor oil) minimum quantity lubrication (VMQL), 95 % ethanol MQL (EMQL), and blended coolant MQL (BMQL) conditions were conducted using a coated carbide tool. Among all the cooling methods tested, the minimum vibration in the axial and radial axis directions occurred in the BMQL, with vibration intensity reductions of 2.46 % and 3.38 %, respectively. Furthermore, the tool wear and changes in the matrix material surface hardness were the smallest under the BMQL, and the surface roughness decreased by 4.50 % or more. The average wear, VB, of the flank face decreased by more than 7.72 %. The blended coolant proved to be more conducive to cooling for cutting processes under MQL.

Published
2020

13. Quantitative analysis for effects of structural stiffness on vibration characteristics of machine tool feed system

Author

Liu, Niancong and Liu, Niancong

Abstract

The vibration of the feed system remains a long-standing challenge in a machine. Toward this objective, the effects of bearing stiffness, nut rigidity, coupling stiffness, screw length, screw speed and radial stiffness of worktable on the torsional vibration and axial vibration of the table are explored. In this paper, a mathematical model of multi-degree-of-freedom coupling torsional and axial vibration considering various factors is established by the second Lagrange equation, and simulation analysis and experimental verification are carried out. The effects of the variable lead and variable torsional stiffness of the nut on the torsional vibration of the workbench are analyzed. Results show that nut stiffness is the main factor affecting the vibration of the workbench. As the workbench mass, motor speed, screw length and lead increase, the axial vibration of the workbench increases. In the case of lead change, as the axial stiffness of the nut increases, the effect on the torsional vibration of the workbench is reduced. Under the variable torsional stiffness of the nut, with the increase of the lead, the influence of the lead on the torsional vibration of the workbench will increase. The experimental results provide a reference for further research and provide a theoretical basis for vibration reduction and structural optimization.

Published
2020

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