Advanced Materials Research Vols. 314-316

Abstract: High deformation hardening, low thermal conductivity, high built-up edge tendency of austenitic stainless steels were the main factors that make their machinablity difficult. For determination of the suitable cutting parameters in machining austenitic stainless steel by PcBN cutting tools, the samples which were prepared to be used in the experiment, 300 mm in length and 60 mm in diameter, were dry machined in a numerical control lathe. During experiments, dry turning parameters, such as feed rate, cutting speed and cut depth were investigated. The suitable cutting speed and feed rate were determined according to workpieces surface roughness, cutting tools flank wear. Finally, cutting speed of 160 to 200 m/min, feed rate of 0.06 to 0.08 mm/rev and cut depth of 0.10 mm gave the satisfied results.

Abstract: GMAW with strip electrode is a new method, which uses the flat wire with a rectangular cross-section to replace the conventional round wire as consumable electrode. In the present study, the welding system was established. Then the typical arc behavior and metal transfer were analyzed. After that, high-speed-high-current welding experiment was carried out in both GMAW with strip electrode and conventional round wire. The results show that, Compared with the conventional GMAW with round wire, the welding arc of GMAW with strip electrode has much lower arc pressure, and the impact of the droplet on the weld pool is weakened remarkably. These two characteristics make GMAW with strip electrode suitable for high efficiency welding on the basis of maintaining the original advantages of GMAW.

Abstract: Packing problem, which occurs frequently in sheet metal, clothing and furniture industry, cut product patterns from raw materials most efficiently and maximize material utilization. In this paper, an adaptive memetic algorithm is proposed to solve the problem of irregular shapes packed on the rectangular sheets. First, operators and parameters of evolution is researched, and second, local search method is proposed. Finally, this study compares benchmarks presented by other authors. The results show that the material utilization efficiency by using the adaptive memetic algorithm is higher compared to other methods.

Abstract: Dissimilar metal welded joints are widely used in engineering structures nowadays. Among the various types of material combinations, dissimilar welded joints of carbon steel and austenitic stainless steel are very common in shipbuilding, nuclear and chemical industries. In this study the finite element software MSC.Marc is employed to calculate the welding residual stresses in dissimilar butt-welded Q235 steel and 304 stainless steel pipes with different welding currents. The calculation results indicate that the welding residual stresses present asymmetric distribution, peaks of residual stresses on inner surface tend to be in 304 stainless side which can be significant higher than the yield stresses of parent metals. Changing in welding current does not have a significant effect on the peak of stress in weld center line.

Abstract: Thermal cycling was applied to assess the effect of tin-lead solder 63Sn37Pb and lead-free solder 95.5Sn3.8Ag0.7Cu on the reliability of 3D PLUS solder joints. Nonlinear finite element method and viscoplastic Anand model were used to evaluate the stress and strain distribution and dangerous position of solders under the thermal cycling condition. The law of solder joints stress and plastic strain were finally obtained and showed significant cyclical changes. The stress and strain emerged the trend of accumulated enhancement with the process of time, then ultimately stabilized. Comparing two curves of equivalent stress and plastic strain obtained from lead-free and tin-lead solder, it was found that the reliability of 95.5Sn3.8Ag0.7Cu was better than that of 63Sn37Pb.

Abstract: With the gearbox of a large-scale wind turbine as a study object, the virtual prototype model of gearbox is created based on UG and ADAMS softwares according to its design parameters such as structure and size. By rigid and flexible dynamics analysis for gearbox, the angular velocity and acceleration curves of the in-out shaft are obtained. Gear meshing forces and flexible body stress cloud using ADAMS are also obtained. It is verified that these results are coincided with the theoretical value through analysis and the simulation results of ADAMS are valid. The simulation results show that the design level of wind turbine gearboxes can be improved using the virtual prototype technology and lay a good foundation for further optimal design.

Abstract: The experiments were performed with the self-made inverter power source of CO₂ arc welding under constant power control and constant voltage control. Electrical signals in welding process were analyzed by Hanover analyzer and Matlab software, and the effects of the two control methods on welding stability and arc energy were compared. The results show that the weld appearance under constant voltage control is worse due to less energy in arc burning period, the method of constant power control increases the arc energy effectively and improves weld formation and welding stability.

Abstract: A solving method with complex variable function which is fit for numerical calculation for stress concentration phenomena on an infinite plate where there are curvilinear holes is described in this paper. According to the method, the computer programs are made to study the stress concentration problems with curvilinear holes (hexagonal form and oblate form) that are often used in ship and other engineering structures. The maximum of the stresses at the edge of the holes and the distribution of the stresses under axial loading and pure bending moment are calculated respectively. Furthermore, the variations of factors of stress concentration with the different proportions of length and width for oblate holes are considered. The influence on factors of stress concentration due to the change of plate width is indicated. The solutions are consistent with the numerical results of boundary element method, finite element method and related articles.

Abstract: Cryogenic machining is considered as an eco-friendly machining process in manufacturing industry. In order to study the influence of cryogenic gas mixture of nitrogen gas and compressed air on machining performance, the experiments of turning 0Cr18Ni9 stainless steel were performed . The experimental results show that cryogenic machining technology can remarkably improve the surface integrity, cutting tool life and chip-breaking performance. Its advantages of improving machinability are especially obvious at higher cutting speeds.

Abstract: Based on the data obtained by the strength test of simply supported Reactive Powder Concrete (RPC) plate, the calculation method of simply supported RPC plate is studied and the method is proved to be feasible. In addition, based on the analysis of the steel fiber in the simply supported RPC plate, some suggestions, which can improve the flexural strength of simply supported RPC plate, are proposed。