Papers by Author: Zhi Qiang Liu

Abstract: Research has been done on machinability of two different kinds of free-cutting steels by using coated cutting tool at the condition of different cutting parameters. Orthogonal tests are adopted in order to compare the cutting performance of the two materials. The cutting force, surface roughness, chip morphology and tool wear are investigated, which reveal the influence of Pb and other composition on machinability. The experiment shows that 1215 has more or less better performance than 12L14. It is of great significance for the development of environmental friendly products.

Abstract: As a typical high strength material, titanium alloy Ti-6Al-2Sn-4Zr- 2Mo-0.1Si (TA19) is used to manufacturing the compressor power-brake of aircraft engine and the aircraft skin. All the machining experiments were carried out on a CNC-milling center under the stable conditions of cutting speed, feed rate, and depth of cut. The performance and wear mechanisms of coated- and uncoated carbide tools have been investigated in this paper to evaluate the machinability of TA19 in face milling. The three tools used were PVD-TiN+TiAlN, CVD-TiN+Al2O3+TiCN and uncoated carbide inserts. The results indicated that PVD coating had the best performance than other tool materials in milling titanium alloy TA19, and the cutting force and the wear value were the smallest than that for CVD-coated and uncoated tools. The failure types of PVD-, CVD- and uncoated inserts were the crater wear and micro tipping; the crater wear and tipping; tipping. Abrasive wear and adherent wear were the predominant mechanism of PVD-TiN+TiAlN carbide insert in face milling TA19 alloy. For CVD- and uncoated carbide, adherent wear was predominant.

Abstract: Different parameters of Minimum Quantity Lubrication (MQL) system, including air pressure, oil quantity, nozzle position, might have different influences on the cutting force and the cutting temperature. This paper presents an experiment of end-milling titanium alloy with MQL system. The objective of the experiment is to investigate the influences of MQL parameters in milling of Ti-6Al-4V. The results of experiment show that there are different effects on the cutting force and the cutting temperature with different MQL parameters, which will help to select different parameters in the end-milling process of Ti-6Al-4V.

Abstract: As two kinds of advanced titanium alloys, TC18 and TA19 were introduced in this paper. The machinabilities of TC18 and TA19 alloys were described in the grinding process. Grinding experiments were completed using green silicon carbide grinding wheel with the coarser 100 grit. Grinding forces and specific energy in surface grinding were investigated. And then, for studying the grinding characteristic, SEM images of the workpiece material were obtained. The results indicated that specific chip formation had the great effect on the mechanism of grinding TC18 and TA19 alloys, and the scratch was the main characteristic of surface grinding. TC18 alloy had the poor grinding performance compared to TA19 alloy.

Abstract: Turning parameters are subject to processing efficiency, cutting force and surface quality, etc. A method, called the coupling method of response surfaces, is presented in this paper to select cutting parameters subjected to several constraints. An experiment of turning free cutting steel is made in order to set up the model. The results from the optimal selection provide a basis prototype for the cutting parameters. It can meet the needs of the turning process in industrial production.

Abstract: This paper investigates the surface integrity of Ti-6Al-4V in conventional grinding using SiC abrasive, it includes surface roughness, surface topography, surface residual stress and metallurgical structure alteration. The experiment result indicated that grinding depth and feed rate have significant effect on surface roughness. Workpiece ground surface was free of crack, but severe plastic deformation layer and light burn appeared because of chemical reactions and mechanical factors. Ground surface was in a state of high tensile residual stress, thermal cycling of surface layer had the greatest effect. The machined surface experienced microstructure alteration on the top layer of ground surface, a heat-affected zone (HAZ) was observed.