Zhi Yuan Rui

Research on Cutting-Temperature Field and Distribution of Heat Rates Among a Workpiece, Cutter, and Chip for High-Speed Cutting Based on Analytical and Numerical Methods

High-speed cutting is widely employed in aerospace, automotive, die, and other industries. However, no comprehensive mechanism of high-speed cutting behavior was as yet comprehended completely. Models of thermal sources and fields of cutting temperature are proposed for analysis of thermal equilibrium between heat generation and energy consumption at high-speed dry cutting. Mathematic models of cutting temperature for three cutting deformation areas are developed to analyze heat generation and release behavior in high-speed machining. The ratios of heat distribution among a chip, cutter and workpiece were found for different cutting speeds using the MATLAB software.

Improved Method of Fatigue Life Assessment for TiAl Alloys

For rapid fatigue life assessment of TiAl alloys, the new method was proposed based on qualitative and quantitative analyses. The qualitative analysis was employed to illustrate the microstructure effect for TiAl alloys on their fatigue life. The new formula is derived for estimation of the interaction forces of dislocations, which yields quite satisfactory results. The results of qualitative and quantitative analyses were used to predict the fatigue life improvement by the addition of trace elements producing grain refinement.

Effect of the Microcrack Inclination Angle on Crack Propagation Behavior of TiAl Alloy

Molecular dynamics simulation was employed to make the model of crack propagation for singlecrystal γ-TiAl alloy. The effects of the angle between a microcrack and loading direction on crack propagation were studied through the analysis of the atomic configurations and stress–strain curves in the paper. The results show that the time for the emission of first dislocation and the yield stress value decrease with the angle. The crack propagation occurs by the submain crack mechanism, which becomes more obvious as the angle increases and the number of stacking faults and stair-rod dislocations decreases.

Influence of Temperature on Fatigue Crack Propagation in TiAl Alloys

Experimental investigations of fracture toughness for a TiAl-based γ-alloy were performed at different temperatures. The temperature effect on fatigue crack growth behavior is evaluated, the formula describing its rate in range to II (stable propagation) was derived, as well as specific values of equation constants were obtained on the basis of experimental results. Tests were conducted in vacuum at 25, 750, and 850°C. The experimental results demonstrate that temperature exerts great influence on fatigue crack growth rates. With an increase in temperature up to 750°C, the growth rate of such cracks increases, after reaching this temperature, the brittle-ductile transition of a TiAl-based alloy is taking place. A similar relationship is also observed for conventional alloys.

Model of Shear Slipping Deformation and its Cutting Energy Consumed for High Speed Machining

The characteristics of serrated chips were analyzed using the theory of shear-slipping deformation at high speed cutting, with geometric and mathematic models of the chip built. Deformation of continuous chip for scissile metal materials can be analyzed and controlled by analogous methods that are employed at normal cutting speed. Geometrical model about serrated chip for difficult-to-cut material under orthogonal cutting condition is offered by proper simplifying. The nonlinear equations of indices related to some factors for measuring deformation degree of chip have been ascertained. Based on the condition fo forces equilibrium with respect to single serrated chip at the moment when it is to be in shear instability, forces equilibrium equations are obtained, with shear force and shear velocity as well as friction force and flowing velocity for a chip segment found. Finally, energy equations of cutting are acquired from deformation energy and friction work consumed in the course of chip formation, which can be offered to the further study of mechanism of high speed machining and the design of high speed machine tool.

A New Method on Choosing Tool Materials at High Speed Machining

Aiming at the key problem of tool choice presented at high speed machining, this paper analyses the characteristic of existing materials of high speed machining tool from three aspects of mechanics, physics and chemistry, and sums up the cutting property of work materials combining with some experimental results and literatures. By integrated comparison of the property of materials of tool and workpiece, a method of choosing tool material for corresponding to workpiece is offered. Finally, some matched materials of tool and work are provided for convenient choice, which can acquire better effects than used testing or experience ways and means.

Thermal Error Modeling and Compensating of Motorized Spindle Based on Improved Neural Network

In a lot of factors, thermal deformation of motorized high-speed spindle is a key factor affecting the manufacturing accuracy of machine tool. In order to reduce the thermal errors, the reasons and influence factors are analyzed. A thermal error model, that considers the effect of thermodynamics and speed on the thermal deformation, is proposed by using genetic algorithm-based radial basis function neural network. The improved neural network has been trained and tested, then a thermal error compensation system based on this model is established to compensate thermal deformation. The experiment results show that there is a 79% decrease in motorized spindle errors and this model has high accuracy.

The Micro Crack Nucleation Rule and Fracture Behavior of Titanium Aluminum Alloy

Study on tensile fracture behavior of TiAl alloy by means of the macro fracture theory and micro dislocation block theory. A quantitative analysis method of micro crack nucleation and crack mechanism for TiAl alloy is performed with the help of the dislocation distribution model, and is based on the strain energy density theory and criterion, a crack criterion of TiAl alloy instability is established. The experimental results confirmed that the dislocation model and S criterion on tensile fracture behavior of TiAl alloys are effective.

Research on the Cooling System of High-Speed Motorized Spindle

In order to control effectively the temperature of the motorized spindle, based on thermodynamics, heat transfer theory and fluid dynamics control theory, the model of motorized spindle with cooling system is established and simulated. Based on the idea of orthogonal experiment and simulation experiment, the comprehensive tests are built, and the optimum matching relation between the heat flux of motor and the flow velocity of cooling liquid is determined in this article. The results show that the flow velocity of coolant can be adjusted according to the heat flux of motor which can control the temperature in the steady range and improves the cooling effect.

Calculations for Diffusion Probability and Diffusivity of Interstitial Atom in one Lattice for γ-TiAl Alloy

The motion of interstitial atoms (one of the point defects) in material is random under certain temperature. However, the diffusion of interstitial atoms has priority along some certain directions to the others, so it is necessary to reveal the phenomenon (the phenomenon also can be called anisotropic). In order to illustrate the anisotropic and reveal the magnitude of probability of the micro crack formation along crystal axes, some formulae derived from former literatures have been adopted, and the values of diffusion probability and diffusivity of interstitial atoms-Ti or Al along 〈110〉and〈100〉have been calculated. The conclusion that the diffusion of interstitial atoms along different crystal axis has different diffusivity is verified by the comparison of the results of calculations.