Advanced Materials Research Vols. 690-693

Abstract: The ultrasonic transmission model is established in the ultrasonic cutting process based on the ultrasound oval cutting device made by ourselves and the different vibration cutting effects is analyzed under the ultrasonic cutting process in this paper. The ultrasonic transmission at the contact interface is vulnerably affected by preload force factors and so on by the vibration experiments of the ultrasonic vibration cutting system.

Abstract: The finite element method was adopted to predict the cutting temperature filed of workpiece surface when machining aerospace aluminum alloy 7050-T7451. Some key techniques such as the materials flow stress behavior, the separation of the chips with the workpiece, failure and fracture criterion, the tool-chip friction model were discussed in details. To validate the finite element model, the cutting temperature field of the chip was obtained by infrared thermal imaging system. The result revealed that the prediction model is credible. Based on the model, the effects of tool geometrical parameters such as flank wear, cutting edge inclination and corner radius on cutting temperature were analyzed.

Abstract: Molecular dynamics model of the polysilicon material under the micro/nanoscale is established by using molecular dynamics method, make variety of the typical defects distribute to the polysilicon model reasonable and relax the simulation model, obtain the system potential energy curves in the relaxation process and the atomic location figure after the relaxation. Conduct molecular dynamics simulation of nanometric cutting process relying on the development of simulation program, get instant atom position image and draw the cutting force curve. Discusses the typical defects impact on the polycrystalline silicon nanometric cutting process, those mainly include cutting force changes in the cutting process, potential energy changes and processed surface quality etc.

Abstract: The writer successfully obtained brazed Cu-Al joint by using vacuum brazing method, and also conducted an analysis for the microstructure morphology of the joint. The result shows that: The interface of the brazed Cu-Al joint includes three parts---the transition area on the Cu side, the central brazing seam area and the transition area on the Al side. Formed between the brazing seam area and the Cu substrate are the Cu₃Al₂ and CuAl₂ layers, and the average width of the transition area of Cu₃Al₂ is 12 μm while that of CuAl₂ 8 μm. The brazing seam area is mainly composed of α-Al solid solution, Cu₃Al₂ and CuAl₂ metal compounds, in addition, the ε-Cu₁₅Si₄ phase, the Al-Si phase and CuZn₂ phase are also formed. These phases present themselves in the state of acicular compounds, which are dispersed in the brazing seam area.

Abstract: In this investigation, in order to research the influence of magnetic field on microstructure and properties of magnesium alloy welded joint, the AZ91 magnesium alloy plates were welded by GTAW under AC longitudinal magnetic field. The tensile test, EDS and XRD were used to analyze the properties and microstructure of welded joint under different magentic field current. The acting mechanism of magentic field on welded joint was studied. The results show that, the optimal mechanical properties will be obtained when I_m=1A, which the ultimate tensile strength is 270MPa and the elongation precentage is 7.1%.The magnetic field can produce electromagnetic stirring, which can refine crystal grain and improve the solubility of alloy element. The properties of welded joint will been improved by these fine crystal grain.

Abstract: The hot-dipping Al coating was developed on 22MnB5 steel surface. Effects of heat input with different welding parameters were investigated in this paper. It describes an approach to optimum the heat input of Al coating on 22MnB5 steel. The results of optimum heat input show that ~3840J/cm has the best tensile strength, whose corresponding welding parameters are optimum for hot-dipping Al coating steel. The proper hot-dipping time (~2min) of Fe-Al compounds between Fe substrate and Al coatings must be selected (750°C, hot-dipping 2min) in order to decrease the finger-like growth of 22MnB5 steel surface coatings.

Abstract: Reflow soldering process parameters have distinct effect on the lead-free reflow profile and its key indicators. To determine the relationship between reflow soldering process parameters and lead-free reflow profile is significant for obtaining the correct reflow profile. The result of orthogonal experimental shows that the most influential factors of the change rate of heat-up R_S are conveyor speed S, temperature set value of the heating zone 1 T₁ and the temperature set value of heating zone 2 T₂ in sequence; the most influential factors of the soaking time T_S are conveyor speed S, the temperature set value of heating zone 4 T₄ and the temperature set value of heating zone 2 T₂ in sequence; the most influential factors of the reflow peak temperature P_T are conveyor speed S, the temperature set value of heating zone 7 T₇ and the temperature set value of heating zone 6 T₆ in sequence; the most influential factors of the reflow time T_AL are conveyor speed S and the temperature set value of heating zone 6 T₆ in sequence.

Abstract: This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Al-Cu dissimilar metals welding product case study to demonstrate its use in evaluating alternative design strategies for an energy efficient welding product. The energy consuming characteristic and the life-cycle model of welding product have been studied by the energy analysis method. The energy consumption model of welding product throughout life-cycle has been modelled. The energy properties of different welding method has been studied and described quantitatively by the energy analysis method of total life-cycle. The results show that an effective brazing technology is the key to improve the utilization ratio of energy.

Abstract: Hot pressure welding (HPW) is one of the inner lead bonding process which is widely used in microelectronics manufacturing. This paper presents a practical digital temperature controller for HPW. Based on the step response, an identification method is developed to obtain a nonlinear time-delay model for heating-up control design. The input-output linearization problem is solved by means of second-order Pade approximation and static inverse transform, and an optimal controller is obtained for the welding machine. The experimental equipment on the temperature control is designed based on LabVIEW and data acquisition card. Simulation and experimental results show that the dynamic performance, steady stage error and overshoot satisfy the designed requirements.

Abstract: For detecting weld seams deviation during the industrial actual welding process, IPG YLR-10000 high power fiber laser welding equipment was used during laser welding experiments. A high-speed near-infrared camera was used to capture the dynamic welding pool image sequences. Through studying the change of the features of near-infrared images of the weld pool when the laser beam deviated the weld seam, the centroid of the welding pool could be used as the deviated parameter of the weld seam. The welding pool images coordinates were established, and the ways of rotating and shifting the coordinates were used to build a model to test the welding spots deviation. Finally, the model of the relationship of the actual weld seam deviation and the tested weld seam deviation had been set up by using the regression analysis method. Its validity and feasibility had been tested by analyzing the models correlation R parameters.