Key Engineering Materials Vol. 748

Abstract: Based on the experiment of turning aluminium alloy (7075-T651), the relations between the fractal dimensions of cutting forces with machining parameters are studied. Cutting speed, feed speed and cutting depth are considered as the process parameters. The cutting force in turning aluminium alloy operation are measured and the fractal dimension are calculated using the algorithm of correlation dimension. From main effect plots the fractal dimensions of three directions of cutting forces are reduced with the increase of cutting speed, increased with the increase of cutting depth and insignificant with the increase of feed speed. The mathematic models of fractal dimension of cutting force are developed using response surface methodology (RSM). The results of the ANOVA show that cutting speed and cutting depth have remarkable influence to fractal dimension D_x, D_y and D_z.

Abstract: Based on the explicit dynamic analysis method, the finite element models of successive shots and multiple shots for shot peening process are established by using LS-DYNA software.The simulations of the elastic-plastic dynamic process of shots impacting on a metallic target during shot peening process were accomplished. For Al2024-T3 alloy plate, the surface roughness induced by shot peening is studied and the effect of overlapping on the general trend is evaluated.The analysis results show that the surface roughness increases rapidly at the initial stage of shot peening and forms micro-scale pits. With the increase of the coverage, the surface deformation increased slowly when the surface coverage reached 100%.

Abstract: This study investigates the effect of water flowrate on the copper alloy corrosion by using a hydrodynamic corrosion test in operating conditions of water flow rate range between 0.05 and 3.5 m/s, the temperature range between 20 and 45 °C. Dissolved oxygen concentration was in the range between 6.1 and 9.2 mg/l. The effects of water properties density, viscosity, and the tube geometric dimensions also considered. Corrosion rate determined by the weight loss calculation method and the tested samples microstructures characterized using FESEM. The results showed that the copper surface layer more affected by water flow at the beginning of turbulent flow condition, while at fully developed turbulent flow condition the surface covered with a fixed oxide layer. Therefore, corrosion found to be at higher rates during the initial stage of the turbulent flow condition, but it reduced at fully developed turbulent flow conditions at higher water velocity. These results indicate that the overall flow rate conditions, which include physical properties of the fluid, hydrodynamic parameters, and the geometric tube dimensions, have the dominant influence on corrosion rate.

Abstract: The microstructure and mechanical properties were investigated in an industrial Al-Cu-Mg alloy processed by Equal Channel Angular Pressing ECAP and heating. The die used is formed by two channels intersecting at an angle 90°. Transmission Electron Microscopy (TEM) and orientation (ASTAR) imaging were used in addition to hardness measurements. After heating, a sub-micron grain size is retained. In addition, a further hardening is observed due to secondary precipitation. Differential Scanning Calorimetry (DSC) showed that the activation energy of θ’ precipitation is strongly lowered after ECAP.

Abstract: This paper studies the effect of different solution temperature and quenching medium on Microstructure and hardness of Mg-9Li-4Al-1Zn-0.5Y alloy by means of optical microscope (OM), X-ray diffraction (XRD) and hardness testing. The results show that in the solution process, the higher of the solution temperature is, more of the second phase dissolved in β phase. In the quenching process, the higher of the cooling rate is, more of the second phase dissolved in the β phase precipitates from the super-saturation β matrix, which can greatly weaken the solution strengthening effect. The hardness of the investigated alloy reaches its highest value with solution treatment at 648K and water-quenched treatment, increased from 58HB to 108HB.

Abstract: In this paper, the aging treatment is performed to Mg-Zn alloy with different Zinc contents,the effect of aging treatment on the microstructure of Mg-Zn alloy was studied. The experimental results show that Zinc precipitated from the mg substrate, and exists in the form of Mg-Zn phase after aging treatment of Mg-Zn alloy, which greatly improves the Mg-Zn alloy's mechanical properties. After heat treatment of Mg-Zn alloy, the second phase along the grain boundary changes from the patch distribution to the network distribution with the increase of the content of Zn.

Abstract: Drilling experiments of titanium alloy Ti6Al4V were conducted. Taking the speed and feed as the process variables, a set of experimental cutting forces are obtained and compared. From the experimental results it is concluded that within the experimental extent the thrust force and torque of drilling process rises with the feed rate. The lower spindle speed resulted in the greater amount of thrust. Feed rates have greater influence on the thrust force than the spindle speed. The combination of greater feed rate and lower spindle speed results in the maximum amount of thrust. However, combination of greater feed rate and spindle speed resulted in maximum amount of torque.

Abstract: Based on the finite element model of high frequency welded pipe welded of composite aluminum alloy, the stress-time variation curves of welded pipe in different welding parameters were obtained. The analysis shows that the residual tensile stress in the weld zone is largest. At the same time, the weld tensile test and hydrostatic burst test were conducted. When the residual tensile stress in the weld zone is high, the blasting pressure which the weld can withstand is small, and the cracking position is often in the welded seam zone. To a certain extent, the change of the thermal stress in the welding process and the residual stress in the cooling process can be accurately reflected by the finite element analysis method.

Abstract: An investigation has been carried out on the effects of abrasive-aided ultrasonic cavitation machining process on improving the surface roughness of 3D-printed material. The test surface will be placed in a vertical orientation aligned with the central axis of the ultrasonic horn rather than horizontally as commonly practiced. Experimental parameters of abrasive concentration and size is used and the effect on surface roughness at both vertical and horizontal distances away from the horn is examined. It is found that larger abrasive concentration has a positive effect on the depth of surface roughness improvement while a limitation is observed for larger abrasive sizes. No trend in surface roughness improvement is found with respect to the horizontal distance from the horn’s central axis.

Abstract: A new self-lubrication concept based on the techniques including of dry grinding and solid lubricating was proposed for green grinding process. And a kind of self-lubrication grinding wheel was designed with solid powder lubricant and centrifugal impeller inside. The self-lubricating was achieved by the blow out of the solid powder lubricant from the inner cavity of the wheel by the centrifugal force to the grinding surface. The experiments were conducted to study the friction and wear properties of the new cylindrical wheel samples manufactured by the proposed concept. The results showed that the flow channel diameters of 1 to 1.5 mm are the best for the blowing out of the solid lubricant to realize the continuous lubricating. After grinding, the surface coating is even, and the sizes of the abrasive particles are relatively uniform with no peeling into blocks. Although there is a certain wear loss of the grinding surface, the wear rate of the particles on the sample wheels is less than that of the traditional grinding wheel. The computational simulation of the self-lubrication wheel is conducted with the RSM method with FLUENT software to analyze the flow field in the wheel cavity of solid lubricant inside, which is meaningful for the study of the motion of the solid lubricant and useful for optimum design of the wheel design to realize the best self-lubricating performance.