Papers by Author: Guo Giang Guo

Abstract: This paper investigates the surface condition of 9Mn2V in conventional surface grinding using SG abrasive under different tempering processes, which includes metallographic structure, micro-hardness, specific grinding energy, surface roughness, surface morphology and surface residual stress. The experimental results indicated that the specific grinding energy increased after the completion of tempering. The ground surface quality improved evidently with the times of tempering increasing. Meanwhile the ground surface was in a state of high tensile residual stress after quenching. After the second time of tempering, the residual stress had significantly been reduced.

Abstract: High cutting force, high cutting temperature and severe adhesion will be produced in the machining process of Ti-6Al-1.5Cr-2.5Mo-0.5Fe-0.3Si. Furthermore, there are critical needs to reduce the use of cutting fluid in machining process. This paper presents a friction force model under MQL condition. An experiment of turning titanium alloy was presented to test and analyze MQL effects. The mainly results were: (1) MQL can reduce the friction at the chip-tool interface when cutting parameters and matching parameters of MQL were chosen properly. (2) Degrees of serrated chips and chip morphology affected by different lubrication conditions were different.

Abstract: This paper investigates the machinability of TC4 and TC11 in conventional grinding using SiC abrasive. The experiment result indicated that TC11 is more difficult to grind than TC4 because of its higher strength and ductility. Ground surface was in a state of high tensile residual stress to each material, thermal cycling of surface layer had the greatest effect. The ground surface experienced microstructure alteration, a heat-affected zone (HAZ) and plastically deformed layer were observed.

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: This paper investigates the surface grinding of Ti-6Al-4V under minimum quantity lubrication (MQL) condition. The experiment result indicated that grinding force ratio and specific energy have close related to grinding parameters. Due to the flow field of MQL mist has easy been affected by feed rate, the interaction between of MQL mist flow field and feed rates of worktable has great effect on surface roughness and surface quality. Additionally, comparing to dry grinding, MQL could help to improve surface quality by restrain chemical reactions and physical changes.

Abstract: Experimental results of Ti-6-2-4-2S, Ti-6-4 and Ti-5-5-5-1-1 are detailed in this paper with conventional surface grinding using SiC abrasive under dry conditions. Measurements of grinding forces, surface topography and metallurgical structure of ground surface were taken to investigate the grinding mechanism of these materials. The results showed grinding force ratios to these materials were between 1.35 to 2.25 at all material remove rates, but the specific energy to Ti-5-5-5-1-1 and Ti-6-2-4-2S were little higher than Ti-6-4. Evaluation of ground surface topography indicated they were visually free of crack and burn. At the same grinding parameters, Ti-5-5-5-1-1 had the maximum depth of heat-affected zone because of its poor high temperature properties.

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.

Abstract: 13%Cr stainless steel has good comprehensive performance, which makes it suitable to work under the condition of high temperature, high pressure and corrosive environment, such as petroleum industry. It can be used as materials of petroleum pipes with buttress thread. Buttress thread turning is a heavy-load machining, which places high requirement on the cutting tool. Based on the cutting characteristics of buttress thread, the machinability of 13%Cr stainless steel is studied by turning experiments. Two kinds of inserts with different geometries were employed in buttress thread turning experiments. Experimental results show that less cutting force, longer tool life, better chip curling effect and surface quality was acquired for the insert with rake angle of 12° , clearance angle of 3° and chip-curling groove during 13%Cr stainless steel buttress thread turning process.

Abstract: Rotor steel 26NiCrMoV145 has been widely employed in aerospace and power industry because of its unique properties. As to this new material that used widely in important places, it is worth studying its machinability. An experiment was carried out to study the cutting forces and tool wear mechanism during high speed dry turning using multilayer Al2O3 coated carbide insert. The orthogonal test was chosen, cutting forces were measured. SEM analysis has been carried out on worn tools to determine the tool wear mechanisms. Crater wear and coating peeling could be found in every cutting speed. Flank face wear appears smooth when cutting speed increases. At last, an optimization of the cutting condition was suggested when considering of material remove rate, cutting forces and tool wear.

Abstract: Aluminum alloy, as a kind of large-scaled structures, have been widely used in modern aerospace industry. In order to reduce its machining deformation, cutting parameter optimization is absolutely necessarily. By fuzzy synthetic evaluation, cutting parameters are optimized based on factors: surface roughness, residual stress, radial milling force and milling temperature. By maximal grade of membership rule, optimized values are obtained by different two methods. And by BP network with Bayesian regularization method the corresponding milling parameters are obtained too.