Papers by Author: Sheng Qin

Abstract: High strength carbon fiber reinforced polymers (CFRP) with unidirectional laminate structure have gradually developed into major materials in load-bearing aerospace components, and the cutting demand of CFRP is increasing. In this work, orthogonal cutting tests were conducted on T700 high-strength CFRP laminates to get the mechanistic force model of special cutting tools. Also cutting force coefficients were obtained when cutting T700 high-strength CFRP laminates under different fiber orientations. Experimental results showed that the lowest cutting force was obtained when fiber orientation was between 120° and 150°.

Abstract: Carbon fiber reinforced polymers (CFRP) are increasingly used in aerospace and other industries, due to its high specific strength and stiffness. Machining operations are involved between forming fabrication and assembling as a fining process, during which defects like delamination, burrs and splintering are the main cause of substandard products. This is because that CFRP is a typical difficult to machine material with distinct anisotropy and heterogeneity. Thus machinability of CFRP material under different fiber orientations is a main issue. This paper intensively investigated on cutting forces and temperatures when orthogonal cutting of 0° T700/LT03A CFRP uniform laminates, with fiber orientation from 0°to 180°. Material removal mechanisms and carbon fiber fraction modes under various fiber orientations were discussed. The results showed that fiber orientation of 90°is the worst scenario of cutting, under which condition the force and temperature of the highest level, while that of 150°indicates the other. The results of cutting temperature indicated that it is mainly from the friction heat in the zone III generated by the thrust force.

Abstract: Both aluminum alloy and titanium alloy have been widely used in aerospace, aviation, military and automotive industries. This research presents a study of modified drills for drilling aluminum alloy and titanium alloy. The modified drills can be expected to reduce the cutting forces and torque. A set of experiment was carried on to investigate the performance of the modified drills. A method to quantitative assess of the reduction of the thrust force and torque was given below, and the calculation shows that the modified drills can reduce the thrust force and the torque by as high as 21.16% and 90.48%, respectively, as compared to the conventional drills under the same conditions.

Abstract: Carbon fiber reinforced plastics (CFRP) has increasing applications in aerospace and other fields, due to low density, high strength, high stiffness, great resistance to corrosion, etc. Although, delamination damages in drilling holes for assembly influence the final characteristics of CFRP components. This paper presents an experimental investigation to analyze delamination damage, in which acoustic emission and thrust force are monitored during drilling CFRP laminates to clarify the relationship between AE signals and delamination damages. The results show that delamination damage has close correlation with thrust force and acoustic emission energy. AE root mean square (rms) is recommended to be selected as AE signal parameter. Abrupt peak feature of AE rms can be used as a dependable trigger for delamination monitoring. The number of abrupt pulses of AE rms can be counted online to predict the degree of delamination damages, based on which delaminations can be monitored and controlled online.

Abstract: Since metal matrix composites (MMCs) have increasing applications in industries, this paper presents an experimental investigation on machinability of SiC_p reinforced aluminium metal matrix composites. 14 wt.% of SiC_p reinforcement addition composite was studied in end milling using CVD coated carbide tools under different cutting parameters. By experimental results, the relationships of cutting force and surface roughness with cutting speed and feed were discussed. Some defects concerning surface topography such as ploughed furrow, pits, matrix tearing, etc. were examined by SEM.

Abstract: nconel 718 is a typical difficult-to-machine material, and its high speed end milling process has wide applications in manufacturing parts for aerospace and power industry. Surface integrity of these parts greatly influences the final characteristics. This paper presents an experimental investigation to evaluate surface integrity behaviors of Inconel 718 with finishing cutting parameters in terms of surface topography, surface roughness Ra, residual stresses and subsurface microstructure and microhardness. The results show that high cutting speed is advisable to get better surface topography and roughness. Residual stresses and subsurface microhardness barely increase after 80m/min. Microstructure in surface layer has only slight deformation after high speed milling.