Hong Feng Wang

Numerical Simulation of the Prestressed Laser Welding of 7075－T7451 Aluminum Alloy Sheet

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.

Effect of Optimization of Shot Peening Parameters on Surface Integrity of NAK80

Shot peening is known to improve the fatigue performance of materials. The improvement in fatigue is that plastic deformation in the surface increases hardness, yield stress and microstrain of thinning Crystal block and dislocation density, and formed advantaged compress residual stress that are introduced into the near-surface of the components and which hinder crack initiation and growth. But over peening effect is produced when shot peening strengthening goes beyond a certain limit, which was adverse to improve surface quality. This paper adopted the optimization of the critical peening parameters to avoid appearing over peening effect. The experimental result showed that arc high value of optimal shot peening was 0.40mm.

Application of Stir Tool Force Measuring Dynamometer for Friction Stir Welding of Aluminum Alloys

In this study, a stir tool force measuring dynamometer was designed and manufactured to be suitable for use during the process of friction stir welding. The dynamometer meets the requirements needed for actual force measurements, with error percentage values in the x-, y-, and z-axis directions of 1.1, 1.3, and 1.2%, respectively, and a three-directional sensitivity range of 0.4–2.1%. At the same time, stir tool forces were measured under different process parameters using the manufactured dynamometer. The stir tool force mathematical model, to be used for friction stir welding processes, was established by function approximation and regression analysis methods. The model was set up with a significance level under 90%. Finally, a comparison between the model-calculated values and experimental values yielded a stir tool force average error of 10.4, 4.66, and 7.11% in the x-, y-, and z-axes direction, respectively. Therefore, calculated and experimental values are in agreement.

Analysis on the Friction and Wear Properties of Friction Stir Jointing for 7022 Aluminum Alloy Joining Region

The friction and wear properties of the friction stir jointing 7022 aluminum alloy joining region were tested in this paper. The friction coefficients and wearing capacities of the joining regions under different joining process parameters were obtained. The experiment results showed that the friction coefficients and wearing capacities of the joining regions had a certain relationship with the hardness, but not became direct ratio relation. The friction coefficient of the joining region was smaller than that of the base metal. This main reason was base metal was lath-shaped grain, and the joining region was isometric crystal. The wear volume under 400/30 parameters was minimum. The wear volume was greatly influenced by the hardness of the joining region, but was not direct proportion relationship. Due to the random factors influence in friction process, the law of the friction coefficient reflecting friction and wear was not the same with the law of wear volume reflecting friction and wear. The friction form was abrasive wear and adhesive wear.

Effect of the Impact Load on Joining Region of the Friction Stir Jointing for 7022 Aluminum Alloy

The impact experiment of the joining workpiece of the friction stir jointing for 7022 aluminum alloy was made by the impact load experiment machine. The objective was studying the effect of the different joining process parameters of the FSJ on impact toughness. The results showed the impact toughness of the joining region was lower than that of the base metal when the rotation speed of the tool was 300rpm and the feed speed was 30 and 50mm•min-1, the impact toughness of the joining region of the other joining process parameters was higher than that of the base metal. The impact toughness of the joining region was the best when the rotation speed of the tool was 400rpm and the feed speed was 100mm•min-1. It is higher than 22.3% of the base metal. The impact fracture of the joining region was mainly dimple; only fracture edge appeared a small amount of the quasi cleavage. The fracture presented good toughness.

Analysis on the Wear Resistance of the Cast Manganese Steel by Shock Excitation and Rotation Method

The casting machine of the shock excitation and rotation comprehensive effect was obtained by the improvement on the basis of the traditional casting technology. Mine manganese steel hammer was cast by the casting machine of the shock excitation and rotation comprehensive effect. The manganese steel hammer was analyzed by the microstructure and wear resistance. The casting mechanism of the casting machine of the shock excitation and rotation comprehensive effect was further discussed. The experiment result showed the cast manganese steel by the shock excitation and rotation method had the advantages of the grain fine and uniform, good wear resistance. Comparing to the traditional technology, the new casting technology could extend the service life of the casting manganese steel.

Study on the Mathematical Model of the Milling Force and Residual Stress

Metal milling processing principle and the elastic-plastic deformation theory were combined in this paper. The mathematical model of milling force and residual stress in the NC milling process was deduced by the theory. By the obtained mathematical model, could further analyze the effect of milling force on the residual stress and then obtain the law of milling force to milling deformation. This proved the strong a theoretic guarantee for controlling the machining deformation.

Analysis on Milling Deformation of 7022 Aluminum Alloy Blank Jointed by FSJ

Milling process of jointing blank of 7022 aluminum alloy was simulated by ANSYS. The results show that the maximum residual tensile stress and pressure stress are mainly concentrated in the jointing seam zone when the jointing blank is milled. The milling deformation of jointing blank is shown as “wave” shape. The milling deformation of key eye side is shown upwarp. The jointing initiating terminal is shown downward displacement. The maximum downward displacement is present to the middle of jointing seam central line. In additional, the milling deformation along sheet length direction is shown outward extension.

Optimization of Tap Parameters for Internal Thread Cold Extrusion of High Strength Steel Based on Genetic Algorithm

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.

Effect of Discharge Parameters on Micro-Surface Topography of NAK80 by Mirror-Like Surface EDM

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.