Papers by Author: Hong Jun Wang

Abstract: The surface integrity of NAK80 steel by grinding and electrical discharge machining (EDM) was studied in this paper. Microhardness, 3D topography and surface roughness of machined surface precipitation hardening layer were measured respectively. And the residual stress of the machined steel surface was measured with X-ray diffraction. Further experiments indicated that, compared with EDM, grinding method can obtain better surface integrity, and lower stress concentration sensitivity of NAK80 steel. But when machining the parts with complex shapes, EDM has the unparalleled advantages to grinding method.

Abstract: The residual stress distribution of fillet of the diesel engine crankshaft on laser shock processing was analyzed by ANSYS software. The simulation results compared with the experimental data, to get results as follows: the simulation results were basically consistent with the experimental data. This fully proved that the finite element simulation method and related simulation parameters were correct. The parameters of laser impacting were optimized by ANSYS simulation, and the residual stress favorable distribution of the crankshaft fillet was obtained.

Abstract: The effects of discharge parameters on micro-surface topography in mirror-like surface electrical discharge machining (EDM) process were investigated, and the optimization scheme was obtained. The realization of the process parameters and their effects were analyzed by the Taguchi method. The surface roughness amd 2D micro-surface topography were measured. An L16 (44×23) Taguchi standard orthogonal array was chosen for the design of experiments. The level of importance of the parameters parameters on surface roughness was determined by using analysis of variance (ANOVA). The experimental results confirmed that peak current and open discharge voltage have more influence on the surface roughness on mirror-like surface EDMed workpiece in comparison with pulse duration and pulse off-time.

Abstract: The ideal of genetic algorithm was introduced in optimizing tap parameters for internal thread cold extrusion of high strength steel. The use of genetic algorithm was analyzed in the optimization design of the extrusion tap. Based on optimal result, the extrusion tap was machined to reduce the extrusion force effectively. It was completely feasible to using genetic algorithm to optimize tap parameters for internal thread cold extrusion of high strength steel. Results from this study provide important basis for practical application of internal thread cold extrusion of high strength steel.

Abstract: The heat source model and the heat input model were built by analyzing welding process. The rationalities of model were verified by finite element simulation. The method of prestressed welding was employed in order to reduce welding residual stress. The welding residual stress would be widely impacted by imposed prestress of 90% yield strength welding. At the same time the propagation of welding heat cracking in the heat-affected zone was properly controlled by prestressed welding.

Abstract: The crater diameter and depth of the surface machined by electrical discharge machining (EDM) were used to evaluate indexes for EDMed surface. The influence of discharge parameters selected on the crater diameter and depth in mirror-like surface EDM process was investigated, and the optimization scheme was obtained. An L16 (44×23) Taguchi standard orthogonal array was chosen for the design of experiments. Experimental results indicate that peak current and open discharge voltage have more influence on the crater diameter and depth in comparison with pulse off-time and pulse duration. Also the results confirm that the crater depth is about 10 to 20 percent of its diameter while the near-mirror EDM conducted in the NAK80 steel with fine discharge parameters.

Abstract: The mathematic model was established between finished surface residual stress and milling parameters by orthogonal regression testing. The rationality of the model was certified by FEM and test. The simulation hypothesis and process were verified by the model. The test showed that the model and FEM were feasible.