Hong Jie Pei

Study on Forming Mechanism of Surface Hardening in Two-Pass Grinding 40Cr Steel

We had done the two-pass grind-hardening experiment on 40Cr steel using the conventional aluminum grinding wheel on a surface grinder, compared the structure and performance of the hardened layer of one-pass grinding with those of two-pass grinding and analyzed the forming mechanism of two-pass grinding hardened layers. The results show that there are a similar martensite structure and change rules of hardened layer of one-pass grinding and two-pass grinding in spite of the different of initial structures, for martensite has tempered by the action of the creep feed grinding temperature field. The depths of hardened layer, microhardness and wear resistance have further improved, but the maximal compressive residual stress and its influencing depth of hardened layer have decreased. The forming mechanism of the two-pass grinding hardened layer is the same as that of the grinding hardened layer of quenched steel.

Formation and Simulation of Cutting-Direction Burr in Orthogonal Cutting

The cutting-direction burr is one of the important factors that influence the edge quality and performance of precision parts. The cutting-direction burr formation process is simulated with DeformTH3D. The mechanism of cutting-direction burr formation is analyzed in terms of the results of the simulation. The negative shear zone and initiation negative shear angle are discussed too. Study results show that the deformation of CDE is an important factor affect the cutting direction burrs’ size and shape.

Research of Surface Hardening Based on Transverse Feed Grinding

The structure and performance of the hardened layer in this paper has been researched by means of transverse feed grinding 40Cr steel on a plane grinding machine, the result shows that under the action of the grinding temperature field, there are different structural change rules and distributing characteristics of micro-hardness. Although there is always a softened band, which is made up of a transitional area and an unhardened area or a temper area in the hardened layer, the reasonable softened band is conducive to the improvement of wear-resistant quality of a hardened layer under the condition of oil lubrication.

Research and Development of LM Neural Network Prediction System for Grind-Hardening

An improved neural network based on L-M algorithm has been applied to the prediction of the grind-hardening parameters against to the slow convergence rate of conventional BP neural network. And the the neural network model for grind-hardening is established. The neural network prediction system for grind-hardening process has been developed based on L-M algorithm. The functions of system is analyzed, particularly and some pivotal technology to realize the system are put forward.

Application of Castor Oil-Based Cutting Fluids in Precision Turning

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.

Thermal Stress Simulation of the Surface Grinding

Thermal stresses of grinding plays an important role on the fatigue and wear resistance of the component. A comprehensive analysis of thermal stress induced by surface grinding has been conducted with aid of the finite element method. To obtain a reliable figure of thermal stress induced by grinding, temperature-dependent properties of workpiece materials were taken into account. The developed finite element procedure has also been applied to calculate the surface and sub-surface thermal stress induced by moving source of triangular heat when convection and radiation is occurred over the whole work. Based on an analysis of the effects of wheel velocity on the thermal stress distributions in an elastic-plastic solid, some important conclusions were given.

CFD Analysis and Experimental Investigation of Jet Orientation in MQL Machining

MQL (minimal quantity lubrication) machining produces almost similar cutting performance to conventional flood supply machining while using much less metal working fluid. To take full advantage of MQL machining and expand its applicability, an understanding of its jet orientation is critical. Through computer fluid dynamics (CFD) analysis of MQL flow field surrounding the workpiece and tool, it was found that a zone of negative pressure (ZNP) existed between workpiece and flank tool face in turning and was in favor of coolant particle arriving at tool tip. Cutting force was minimal and discontinuous chip effect was best of all when spraying from principal flank face and at range of target 20mm.

Characteristic of Residual Stress Distributions at Workpiece Surface in Grind-Hardening

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.

Study on the Performance of Braze Cemented Carbide Cutting Tool

The Cemented carbide cutting tool is widely used in more machining factory, the 5 types of cemented carbide materials: YT30+Ta, YTS25, YH1, 726 and 758 and Selected to make brazing and cutting test. The experiment results shown that: (a) the hardness of cemented carbide cutting tool after being brazed does not change, redoes HRA0.1~0.2; (b) YT30+Ta, YTS25 types of cemented carbide could be brazed using 105# solder, brazing quality could be very well; (c) Wear characteristic of machine-clamping and brazed cemented carbide cutting tool is normal and hardly change in T<150 minutes. The study makes theory and experiment foundation to widely use cemented carbide cutting tools.

Application of Taguchi Method in Vibration Tapping Process

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.