Qing Long An

Fundamentals of BK7 Glass Removal in Micro/Nano-Machining

The confine of ductile-mode cutting and brittle-mode cutting seems to be a crucial step for designing a brittle material removal process. However, the existing transition from ductile-mode to brittle-mode for BK7 material makes the confine of different mode very difficult. Through a series of micro/nano-machining tests, measurements of cutting forces and morphological appearance of cutting groove as well as the cross section at the certain depth of cut, the confirmation of ductile-mode cutting, transition-mode cutting and brittle-mode cutting has been clearly described in the paper. This lays a foundation for the fundamental understanding of cutting physics concerning of material characteristics and cutting tools, and thereafter for the development of optimal process technology.

Study on the Effect of Grinding Parameters to the White Layer Formation in Grinding SKD-11 Hardened Steel

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.

Experimental Study on Turning of Alloy Cast Iron with Coated and Uncoated Tools

Alloy cast iron cylinder is the mainstream product used in engine nowadays. However, the machinability of alloy cast iron is poor because of its enhanced mechanical properties. In this paper, turning experiment has been conducted to study machinability of alloy cast iron with uncoated and coated carbide tools under dry cutting condition. The results of the experiment indicated that the turning performance of alloy cast iron with coated tool was much better than uncoated tool in terms of cutting force coefficients and tool wear. Feed rate has a great influence on surface roughness, and appropriate tool wear is benefit of finished surface roughness.

Optimization of Surface Roughness by Uniform Design of Experiments in Milling of 1Cr18Ni9Ti

This paper presents the optimization process of a surface roughness model for the milling 1Cr18Ni9Ti. The model is developed in term of milling speed, feed per tooth and radial depth of cut. Therefore, the regression model predicting formula for surface roughness has been established by means of uniform design of experiment, and then the response surface methodology was applied to generate response contours of surface roughness. The experimental results indicate that the material removal rate can be improved by selecting optimal milling parameters without increasing the surface roughness. Moreover, it is seen that the feed rate is the most significant factor on the surface roughness.

Study on the Residual Stress Induced by Dry Turning of Buttress Thread

Stainless 2Cr13 is used as petroleum pipe material for its good performance in condition of high temperature, high pressure and corrosive environment. Buttress thread turning is a type of heavy machining, which has a great influence on the residual stress of workpiece. Residual stress is usually determined by cutting parameters and tool geometries. Experiments with different geometrical tools were carried out and a finite element model was used to study the influence of tool geometries on the residual stress. Experimental and simulated results showed that relatively bigger rake angle and smaller corner radius make a relatively lower tensile residual stress of workpiece surface in dry turning buttress thread.

Study on the Machinability of Two Different Sulfur Free Cutting Steels

Research has been done on microstructure and machinability of two different free-cutting steels by using cutting tools coated and uncoated at the condition of different cutting parameters. The cutting force, surface quality, chip morphology and tool wear are investigated, which reveal the influence of the size and shape of sulphide inclusion on machinability. The experiment shows that the shape of spindled sulphide inclusion has relatively better machinability than stripped sulphide inclusion and the size of sulphide inclusion also plays some influence.

Study on the Surface Topography and Residual Stress for Dry Turning of GH80A

GH80A has been widely used in industry for its excellent property under high temperature. The surface integrity is one of the key factors that determine the lifetime. Hence, it’s worth to study surface topography and residual stress which are two important indexes used for evaluating the surface integrity. They are both resulted from the coupling of the mechanical and thermal effect during the turning which can not be well explained with experiment and numerical calculation. In this paper, workpiece surface topography was studied under different cutting parameters. The residual stress is measured and simulated to show more details about the effect of cutting parameters. The cutting temperature which is difficult to pick up in experiments is also simulated to explain the machining process.

Experimental Research on the Cooling Effects of a New High Efficiency Green Cooling Method

With more attention paying to the environment, green manufacturing (GM) has become inevitable trends in 21st century. Green cooling technology as one branch of GM always was one research hotspot in manufacturing. In this paper, a new high efficiency cooling technology based on GM is proposed, called as CPMJ. In this technology, a little quantity of 0 °C water is carried by high pressure cryogenic air (–20 °C) and reaches the grinding zone in the form of high speed mist jet to enhance heat transfer and gain the best cooling effect. Heat transfer experiments and grinding experiments were carried out to evaluate the cooling effects of CPMJ. Experimental results indicated that CPMJ can offer better cooling effects compared with cold air jet and flood cooling method. Grinding temperature was effectively reduced during grinding of titanium alloys with CPMJ.

FEM Analysis and Experimental Study on Residual Stress Induced by Form-Milling and Rolling of Rotor Steel 26NiCrMoV145

Rotor steel has been widely used in marine engineering and power industry because of its high yield stress and anti-fatigue performance at high temperature. The surface integrity must be guaranteed due to severe working environment. Hence it is worth studying residual stress (RS) for its significant influence on the quality of machined part. In this paper, an effective model is built with the help of finite element method (FEM) to evaluate RS induced by machining of rotor steel 26NiCrMoV145. An adaptive mesh control is introduced in this work to avoid excessive element distortion. Johnson-Cook flow stress model is proposed to model workpiece material. Rolling process is necessary to obtain desired RS according to the performance of form-milling process. In order to validate FEM predictions, both milling and rolling experiments have been carried out. The predicted RS profiles are in reasonable agreement with the experimental ones.

Study on Burr Formation in Face Milling of Stainless Steel with Chamfered Cutting Tool

Due to the properties such as high strength and high toughness, burr was commonly produced in the machining of stainless steel 1Cr18Ni9Ti, especially when a chamfered cutting tool was used. This study investigated the effects of chamfering geometry of cutting edge and machining parameters on burr formation and presented active control methods to minimize burr size on the exit end based on the experimental research in milling of 1Cr18Ni9Ti. Experiments of face milling with various cutting edge geometric features were conducted. Maximum height and thickness of exit burr and exit side burr were measured. As a result, a proper chamfering geometry that combined the advantages of enhancing the cutting edge strength and obtaining favorable burr types was presented. The experimental results also showed that a relatively high cutting speed was helpful in reducing burr formation; proper medium feed rate and axial depth were favorable for the minimization of burr size. This research is beneficial for precise machining of stainless steel.