Advanced Materials Research Vols. 602-604

Abstract: The subject of study is the vertical extrusion of P91 large diameter thick-walled seamless steel tube, simulate the variation of microstructure during the abbreviated ratio test. Compare the simulation results and the results of Steel pipe specimens metallographic which were in different extrusion ratio, research the influence of extrusion ratio on microstructure and properties from micro-organizational level, and verify the accuracy of the microstructure evolution of the mathematical model.

Abstract: 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.

Abstract: Precision grinding experiment and process optimization of YG3 cemented carbide materials was conducted with various grinding parameters using resin-bonded diamond grinding wheel. Different rotation speed of workpiece, feed rate and grinding depth were chozen in precision cross grinding. Surface roughness was measured for studying the removal mode and grinding charateristics. A set of ideal grinding parameters of YG3 cemented carbide were obtained by changing the process parameters. The research result has guiding significance for reducing the wheel wear and processing costs, improving grinding quality and efficiency while precision grinding hard and brittle materials.

Abstract: Hot forming is a method to make products with ultra high strength steels which typically used in automotive sector. 22MnB5 is one of the most typical hot forming steels. In this paper, hot forming process of 22MnB5 steel is simulated by thermo-mechanical coupled FE software Pam-stamp 2011. Through the simulation the temperature distribution and martensite phase fraction of hot forming part can be obtained. Besides, a hot forming experiment was set up. The tensile strength and Vickers hardness of hot samples which take from the hot formed part are measured. The experimental results indicate that the value of Vickers hardness in side wall is higher. The microstructure investigations have shown that the part after hot forming mostly fully martensitic microstructures. The result from simulation show good agreement with experimental results.

Abstract: For the stiffness of the cutting face is nonuniform, the evenness of the machining face may not be ensured during a gearbox back shell’s cutting process. By reasonably simplifying the machining process, a cutting stiffness contrast analysis of three design schemes is performed in this paper, and then improvement advice is brought forward to the design engineer. The paper has some engineering value and can be used for reference in similar analysis.

Abstract: At present, the finish machining process of workpiece with free-form surface has the disadvantages of complex trajectory planning, low machining efficiency and precision. To solve these problems, an idea of uniform ER finishing with changeable removal rate model is proposed in this paper. The rheological effect of ER fluid is used to change the magnetic field distribution in finishing areas; then the finishing pressure distribution is changed, that makes the material removal rate of every point in the contact area be approximately equal, so the aim of uniform removal is achieved. In this paper, the quantitative relationship between electric field intensity and finishing pressure is studied. Contrast experiments of finishing and removal effects are performed under the different conditions of electric field distribution. The ER finishing equipment is developed and the proposed finishing method is feasible and has the potential of obtaining the ultra precision.

Abstract: In this paper, the parameter optimization problem for face-milling operations is studied. A mathematical model is developed in order to minimize unit machining time. The machining process needs one finishing pass and at least one roughing pass depending on the total depth of cut. Maximum and minimum allowable cutting speeds, feed rates and depths of cut, as well as tool life, surface roughness, cutting force and cutting power consumption are constraints of the model. Optimal values of machining parameters are found by a genetic algorithm (GA). The influence of tool replacement time and GA operators is evaluated.

Abstract: In order to stop the drill feeding accurately once the workpiece is drilled through, the Key issues of determination are analyzed. Then a determining method based on axial force is presented. The axial force is smoothed and monitored online to determine the drill-out period and drill-through point. Finally, experiments are carried on and the results demonstrate that this method can stop the drill feeding accurately with an accuracy of 0.04mm once the workpiece is drilled through in vibration drilling.

Abstract: In this paper, the cutting acreage model of every cutting edge point in turn-milling is established firstly. Then according to the calculation of the above model, the cutter wears with different cutting parameters are analyzed. Aiming at balancing the wears of different areas along the cutting edge, the cutting parameters are changed to optimize the cutter wears. Finally the model and the optimization are proved correct by machining experiments with different cutting parameters.

Abstract: This paper introduces the theoretical basis and function of developing spindle rotary device. A technological method of wire electro-discharge grinding(WEDG),which is based on the wire electrode cutting machine, is presented. The main factors that influence the machining of engineering ceramic material surface quality are analyzed. And the conclusion is that there are main factors: the main structure and conductivity of the spindle rotary device, and the changes of power in the process of single pulse machining discharge. The conclusions from the experiments provide the theoretical basis for further study on the factors that influence the rotary workpiece surface quality and for the discussion on methods of improving the rotary workpiece surface quality; the conclusions also expand the process scope of WEDM.