Papers by Author: Hong Jie Pei

Abstract: The importance of the surface integrity in modern machining is represented. Based on the notion of the surface integrity that was put forward by Michael Field, a new method of surface integrity characterization is presented in this paper. This method consists of surface quality, surficial coat quality and the edge quality. Then an evaluation system of surface integrity based metrology is constructed and has been applied in a machining process of nickel-base alloy turbine disk. The manufacturing time decreased by approximately 10%. In all, this characterization and the evaluation system of surface integrity are rational and efficient. This work let us be capable of breaking through in the systematical evaluation of present machining surface.

Abstract: The grinding process is currently used for machining the parts requiring for good precision. However, the apparition of some damage related to this process is still uncontrolled, in which the major deterioration is from the residual stress. Through grinding and hardening test, the residual stress distributions under different grinding speeds are obtained, and then numerical simulation for thermal stress of the workpiece surface is carried out by finite element software ANSYS to deduce the distribution of phase transformation stress under different grinding speed.

Abstract: Green high-speed cutting is one of the main development directions of advanced processing technology.The defects of the traditional cooling and lubrication conditions and the deficiencies of external MQL (Minimum Quantity Lubrication) were analyzed in this paper. A new way of cooling and lubrication named internal MQL was highlighted, and an internal MQL system applied to turning was researched and designed. By high-speed turning of bearing steel GCr15 under different cooling lubrication conditions as dry turning, external and internal MQL, the comparative study of cutting force and surface roughness was carried out systematically. The results showed that the internal MQL has a comparative advantage, showing a good application prospect.

Abstract: Large quantities of coolant-lubricants are still widely used in metal working industry, generating high consumption and discard costs and impacting the environment. An alternative to current practices is to use biodegradable cutting fluids that doesn’t pollute environment or require new setups. In current study, biodegradable base oils, synthetic ester and castor oil, are chosen and compounded into cutting fluids which correspond with the national standards. The tests have been performed to high speed turn AISI 1045 steel in ester-based fluid, castor-based emulsion, kerosene and dry condition. The results indicate that the application of cutting fluids is inevitable in metal machining and can not be replaced by dry machining. The lubricating and cooling properties of the ester-based fluid and castor-based emulsion are better than kerosene and can wholly replace mineral oil.

Abstract: Vibration tapping is capable to tap the deep and small hole in difficult-to-machine materials. Taguchi method is utilized to optimize the parameters in vibration tapping process in order to get the lowest maximum torque. Besides these parameters, this investigation includes the lubrication conditions comprised of dry cutting, conventional flooded lubrication and minimum quantity lubrication (MQL). The results show that the frequency and lubrication condition are significant and interaction effects exist due to these two factors.

Abstract: To solve the problems caused by the cost of metal working fluids in manufacturing processes, many methods have been employed. MQL (minimum quantity lubrication) is a successful application as a green manufacture strategy. Vibration tapping is a workable tapping method with good performance. An application of MQL technique in vibration tapping was studied. Maximum torque and chip morphology were used to evaluate the performance of MQL operation. A comparison among MQL, flooded and dry operations was carried out. The results showed that MQL decreased the maximum torque value obviously and the chip morphology under this condition was good.

Abstract: Green machining is a process that implements sustainable development strategy. In order to reduce cost and decrease environmental pollution in manufacturing process, a sort of biodegradable castor oil-based emulsion is developed, whose physical and chemical properties can correspond with the national standards. The cooling and lubricating properties of the emulsion are better while machining steel materials through comparative experiments with certain imported commodity synthetic cutting fluid. The emulsion can successfully substitute for commodity fluid because of its high performance-price ratio.

Abstract: The grinding process is currently used for most of the parts requiring good precision. However, the apparition of some damage related to this process is still uncontrolled. The major deterioration is from residual stress. In order to investigate the residual stresses caused by mechanical plastic deformation, thermal plastic deformation and phase transformation in ground components, a feasible numerical method was developed to accommodate appropriately thermal stress and phase transformation in a workpiece experiencing critical temperature variation during grinding. The change of the material properties was modeled as function of temperature history. The wheel velocity V_s is a key factor in determining the distribution of residual stress; both the surface residual stress and the depth of residual stress are induced with the increase of the wheel speed.

Abstract: The present study aims to investigate the temperature field by using the different heat fluxes, such as rectangle heat flux, triangular heat flux, inclined triangular heat flux, circular heat flux. To obtain a reliable figure of temperature field induced by grinding, temperature-dependent properties of work materials were taken into account and a convection model with an effective cooling factor was introduced. A thorough analysis using the finite element method showed that predictions were very agreed with the results of the experiment. Finally, the present paper showed that the contact angle must be taken into account in future models.

Abstract: In order to study the mechanism of cutting fluid penetration during minimum quantity lubrication (MQL) machining, the flow field in cutting area was investigated through both theoretical analysis and computational fluid dynamics (CFD) simulation on the basis of cutting experiments. Combining the capillary model of cutting fluid penetration, the flow field in the wedge-shaped area beside major flank of the tool was analyzed in detail. It was found that the flow pressure at the wedge angle was lower than the outer. It was favorable for cutting fluid to penetrate into the main cutting edge. Besides, the air supply pressure of MQL has great impact on cutting fluid droplet track. Proper air supply pressure was in favor of cutting fluid penetration.