Papers by Author: Wei Wei Ming

Abstract: Based on the conventional chatter stability model, stability Lobes diagram in die & mould steel milling system is obtained. The derived diagram can be divided into two independent regions by a Lobes curve: absolutely stable and instable region. In fact, it is more reasonable that there should be a transition stage between the stable and instable state. That is to say, grade of stability (GOS) should be in a closed interval [0, 1], rather than Boolean logic. Due to the different stability sensibilities for different order Lobe curve in milling system, there should be different widths of transition belts for different order curve. Thus, with the help of Sigmoid transfer function widths of each order Lobe curve are studied. Finally, the fuzzy chatter stability is implemented by an adjustable slope coefficient.

Abstract: The two phase (α+β) titanium alloys are extensively applied in aerospace, automotive, and biomedical industries owing to their excellent comprehensive performance combining of high strength-to-density ratio, good corrosion resistance, and high strength at elevated temperature. However, the poor machinability of these alloys restricts the improvement of manufacturing productivity and cost savings. In this paper, machinability of three α+β titanium alloys was studied at the finish hard turning conditions.

Abstract: The α+2βtype Ti-5Al-4.75Mo-4.75V-1Cr-1Fe (TC18) is a very difficult machine material for its low thermal conductivity, low elastic modulus, and high chemical activity. So how to improve the machining efficiency and prolong the tool life have got more and more attentions. In this paper, wear mechanism and wear types of coated (TiN+TiAlN) carbide tool and uncoated carbide tool are presented when face milling the Ti-18 alloy under the same machining condition. The results showed that wear types of PVD coated tool are mainly adhesive, diffusion and crater wear, while the mainly failure mode of uncoated carbide tool is tipping. So it is more appropriate to select the PVD coated tool than uncoated tool in the milling TC18 alloy process.

Abstract: With the development of aerospace, biomedical and chemical industries, titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (TC18) is becoming widespread used. TC18 has even better mechanical property than Ti-6Al-4V (TC4). For better cutting TC18, simulation model was set up. PVD and CVD coated carbide inserts were used to machine titanium alloy TC18. The cutting forces were measured. Milling model was set up for the extraction of the cutting force coefficients and chip flow angle. Results were compared. All the coefficients of CVD coated carbide insert were found to be larger than those of PVD coated carbide insert. The model was proved to be reasonable after validation.

Abstract: Centerless grinding is a widely used manufacturing process in the mass production of precision parts. However, its productivity and precision is largely determined by the grinder set-up conditions, process stability and workpiece surface integrity. Grinding titanium alloys encounters difficulties due to its low thermal conductivity, high shear strength and extreme chemical reactivity. Therefore, the grindability of titanium alloy should be improved in order to increase the productivity for the sake of workpiece quality. In this paper, centerless grinding process was introduced initially and the research of impact factors on centerless grinding performance was reviewed. The problems occurred in the centerless grinding of titanium alloy were studied and optimum guidelines were proposed.

Abstract: Titanium alloys are extensively applied in aerospace, automotive, biomedical, and chemical industries owing to their excellent performance combining high strength-to-density ratio, good corrosion resistance, and high strength at elevated temperature. Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloys are used to replace the most common Ti-6Al-4V in some important applications such as some parts in aerospace engine. The purpose of this paper is to evaluate the machinability of TC11 alloys in the finish hard turning conditions. The paper presents the machinability results of TC11 alloys compared with Ti-6Al-4V, and analyzes the variables such as cutting force, surface integrity, and tool wear mechanism in the experiments.

Abstract: TC11 is an α+β heat resistance titanium alloy with high strength to weight ratio, good corrosion resistance and high service temperature up to 500°C. Response Surface Methodology (RSM) is an empirical statistical modeling technique employed for multiple regression analysis using quantitative data obtained from properly designed experiments to solve multivariable equations simultaneously. In this paper, a series of experiments were carried out to evaluate the machinability of TC11 alloy based on RSM. Optimum results show feed rate at 0.05mm/r, depth of cut at 0.25mm and moderate cutting speed at 110.9m/min giving the satisfied machining quality.

Abstract: Austenitic stainless steels are extensively used in the areas with high corrosion. The high heat resistance and strength make them difficult-to-cut materials. The tool life in machining austenitic stainless steels is restricted by the high cutting force and temperature which induce the tool wear and edge chipped. To achieve tool edge strength and reduce the edge-related problems, tool edge preparation is applied by introducing the chamfered and honed edges. In the current paper, the effects of the cutting edge preparation in face milling of austenitic stainless steels were studied using statistical method. The output cutting parameters as cutting force, temperature were obtained by finite element analysis. The purpose for this research is to give guidance to the tool edge preparation for machining stainless steels.

Abstract: Due to the high strength of austenitic stainless steels, it is essential for cutting tool to keep with appropriate chamfered edges during the face milling process. In this paper, face milling mechanics with chamfered edge based on cutting force and chip formation were analyzed through finite element analysis (FEA). Three kinds of tools with different chamfered edges were studied on face milling of 1Cr18Ni9Ti austenitic stainless steel. The primary research results indicated that FEA results showed good consistency with experimental results. This can provide references for development and application of tools during face milling process.

Abstract: White layer formed in the machined surface has been observed in many manufacturing processes. However, grinding has been considered more sensitive to form white layer due to the characteristics with high temperature and rapid heating and quenching. As an effective process to the difficult-to-machining die steel, grinding is widely used in the finishing of die and mould components with high precision. So study on white layer formed in ground surface is significant to improve the product quality and life. In this paper, grinding experiments focus on SKD-11 hardened steel with variable parameters were conducted to study the white layer formation and the parameter optimization to develop the favorable white layer and restrict the thickness of the dark-etching layer and the hot-affective region.