Advanced Materials Research Vols. 418-420

Abstract: The mathematic model of CVC-Plus work roll curve is built. The ratio of the initial shifting value to the target crown is determined, and the mathematical model considering the relationship between the coefficients A₂, A₃, A₄, A₅ and is established. According to the theoretical analysis, the distance between the maximum or minimum point of the high order equivalent crown for work roll with CVC-plus roll curve and the rolling central point is the times of the roll barrel length. In general, the initial shifting value of the CVC-plus roll curve is not equal to the initial shifting value of the 3-order CVC roll curve . The coefficient A1 can also be obtained by optimizing the target function with minimizing the axial force.

Abstract: A novel machining method which is a combination of electrical discharge machining (EDM) and electrorheological fluid-assisted polishing (ERP) is presented to finish hard materials. The ER fluid is used as work fluid, which resulting in the material removal and polishing simultaneously. In this study, a series of machining experiments on aluminum alloy material are carried out to obtain the microstructures of machined surface using the different mode of material removal. Moreover, the ERP process can finish the micro-craters on workpiece surface after EDM to obtain better profile of removal region.

Abstract: In this paper, varying weight percentages of Ni-coated carbon nanotubes (Ni-CNTs) was incorporated into Sn-Ag-Cu (SAC) solder matrix, to form composite solder. Up to 0.05% of Ni-CNTs were successfully incorporated. After that, the electrochemical behavior of Sn-Ag-Cu with varying weight percentages of Ni-coated carbon nanotubes (Ni-CNTs) composite solder were investigated in 0.3% Na₂SO₄ solution by using potentiodynamic polarization method. Scanning microscopy was used to characterize the samples after the electrochemical tests. It was observed that the corrosion resistance decreased when the content of Ni-CNTs reached a certain level.

Abstract: The milling of titanium alloy has been widely used in aerospace field for the advantages of high-quality and high-efficiency. In order to provide the theoretical basis of practical production through optimizing the milling parameters of titanium alloy material and improving the milling property of Ti-6Al-4V, the orthogonal design approach is adopted to analyze the milling force experiment of three typical microstructure of Ti-6Al-4V titanium alloy, utilizing the algorithm of least squares establishes the multivariate linear regression equations of the milling parameters on the main milling force and conducts the regression analysis, obtained more accurate empirical formula of milling force of Ti-6Al-4V titanium alloy under different heat treatment process. Furthermore, the significances of the regression equation and regression coefficients are testing with using MATLAB statistical software. Consequently, the optimum heat treatment processing and the optimal milling parameters are obtained through analyzing the results above.

Abstract: Controlled metal transfer in gas metal arc welding (GMAW) and its modifications including the double-electrode GMAW implies controllable heat and mass inputs and better assured weld quality. To understand, analyze, and control the metal transfer process, the droplet should be monitored in real time. Due to the fast development and transfer of the droplet, the monitoring speed is a key. A tracking method that takes advantage of results from previous images to speed the processing is advantageous. In this paper, Kalman Filter tracking and Least Square Match tracking algorithms are developed to track a droplet in the innovative double-electrode GMAW after its original position is identified. Experimental results showed that the Kalman Filtering algorithm is not suitable for this application due to the limited life span of each droplet. Instead, the Least Square Match algorithm is effective in tracking a droplet if a universal droplet template can be found and defined. However, there are no universal templates suitable for all the droplets. Hence, a real time template updating and LSM tracking method is proposed to track the droplet effectively. Experimental results verified its tracking accuracy.

Abstract: In order to investigate the effect of heat input on the microstructure and mechanical properties of low matched high-tensile steel welded joint, the metallurgical structure and mechanical properties of welded joint obtained with different heat input were analyzed using optical microscope , welded joint tensile test and impact test of weld metal. The results show that the optimal values are obtained when the heat input is 11.9KJ/cm,where the tensile strength is 798.45MPa and ballistic work is 69J; Weld metal microstructure is mainly composed by the primary ferrite and acicular ferrite. The width of the dendrite and grain size of the weld metal microstructure increase with the increasing of the heat input.

Abstract: It mainly focuses on the research of the occurred problems and the suggested solutions when the dimension of the injection part die is calculated. The algorithm we usually use in enterprises is mid-value difference method, but it often appears parts working dimensions out of tolerance; So a compensatory algorithm based on mid-value difference method was developed, and the compensation algorithm and modified formula used in the thickness direction are put forward for sheet part. A series of sheet part are analyzed by ANSYS thermal transient analysis module, and the parameters in the compensation algorithm in the thickness direction are determined. The compensation results show that parts working dimensions in the thickness direction is in tolerance.

Abstract: Based on generalized non-Newtonian fluid with seven parameters Cross-WLF viscosity model and modified 2-double Tait model, the numerical simulation was carried out for the short glass fiber reinforced PP injection molding process of rectangular part. The influence of main process parameters on fiber orientation is investigated. The results show that fiber orientation can be generally divided into three-regional layers in injection molding, that is outer-surface, subsurface and core layer. The degree of fiber orientation in subsurface layer is the highest and that in core layer is the lowest. The influence of fibers interaction coefficient (C_i) and fibers aspect ratio (r_e) on fiber orientation is significant. There is obvious difference between simulation results and practical results without consideration of C_i. The effect of melt temperature, mold temperature and cooling tubes number on fiber orientation isn’t obvious.

Abstract: It is an important method to machine revolution aspheric with Arc Envelope Grinding Method（AEGM）. In this article, the relationship between the grinding point of the wheel and its position is analyzed, and motion law of the grinding point is discussed in grinding aspheric. According to motion velocity of the grinding point , the concrete position of severe wear for the wheel can be calculated out theoretically. It is possible to achieve even angular velocity of the grinding point by adjusting the wheel feed rate, so the angular velocity of wheel movement is optimized, which provide confirm base for improving the precision of grinding aspheric.

Abstract: To reduce welding residual stress (WRS) of a class 3 pressure vessel during the reconstruction, temper bead welding technique (TBWT) was applied to the container. To compare WRS causing by common welding and TBWT, WRS of the two different kinds of welded specimens of 16Mn steel were measured and evaluated by X-ray method. To study the effect of butt weld reinforcement height on WRS, welds with and without weld reinforcement were measured. The results show that longitudinal stress was reduced obviously and the lateral stress is the maximum principal stress for TBWT; WRS of TBWT T-shape specimens were obviously decreased which proves TBWT is better than common welding procedure; WRS was decreased by more than 25% after removing the weld reinforcement and further proves that it is one of effective ways to reduce WRS in engineering application.