Advanced Materials Research Vols. 154-155

Abstract: The mathematical model of five-axis NC machine tools was established based on the transformation matrix. A new decoupling and linkage-compensation method for five-axis NC machine tools is proposed. The error caused by linear axes and rotary axes was compensated by using the linkage-compensation approach. In the real-time error compensation process, the rotary axes error was compensated firstly, and then the linear error caused by linear axes and rotary axes was compensated. The new decoupling method can effectively compensate machining errors for five-axis NC machine tools, which was verified by simulation and actual machining.

Abstract: The feasibility of electroless Ni-plating was explored in order to solve the problem of the restoration of the parts of aircraft made of high strenth steel. The flow and criterion of the restoration technology were were preliminarily investigated. We have measured the hardness, adhesion strength and antiwear performance of the coating. The results show that the electroless Ni-plating process for restoring the scuffed surface of aircraft parts made of high strenth steel has the advantages of simple procedure, easy operationg, and low cost. The coating is well adhered to the substrate and meets with the requirement for performance. In one word, the restoration technology of aircraft parts made of high strenth steel is good for extending.

Abstract: As lack of a efficiency theoretical approximate solution for the surface effect mechanism analyzed during continuing and local vibrational plastic deformation process, according to vibrational rotary forging deforming characters, a three-dimension visco-elasticity plasticity constitutive equation was built by Kelvin model and Liewei-Mises model. After this constitutive equation was to be matrixing and to be introduced to tetrahedral solid elements, a visco-elasticity spatial stiffness matrix and a visco-plasticity spatial stiffness matrix were respectively derived. According to experimental parameters given, some simulation experimental projects were designed, a FEM models were established, and some FEM experiments were done on condition that amplitude and vibrational frequency were respectively changed, then different normal load-time curves were obtained. It is shown from experiment results that surface effect will appear during vibrational rotary forging forming process with little amplitude, the surface effect is related to the amplitude and the frequency, and this effect generation should be in special conditions, then preparatory research of surface effect mechanism of continuing and local vibrational plastic deforming process.

Abstract: Metal injection moulding was performed with gas atomized 316L stainless steel powders. Feedstocks were prepared using a paraffin wax/polyethylene/stearic acid binder system and subsequently molded into tensile bar specimens. Solvent extraction done at 80○C has shortened the debinding process to 30 minute. Single step of thermal binder debinding and sintering was done in a vacuum furnace. Sintering at 1380○C has reduced the porosity and associated with grain growth that result in an increase in ultimate tensile strength to 444 MPa while the elongation increased to 29% before fracture.

Abstract: The casting process design and simulation of a high-manganese steel roller were presented in this paper. The casting process design principle, process parameters, points of attention, and the simulation parameters were introduced. Huazhu CAE was used to simulate the casting process. The STL document used in Huazhu CAE was converted from the 3D moulding of the casting process using the Solidwork software. The simulation results and practical production showed that the casting process can reduce shrinkage defects of the casting. And practical production also showed that the produced rollers, according to the technique, met the quality demands, such as no crack, no misrun, etc, and they were successfully used at the thermal power plant.

Abstract: As a force being non-homogenous during incremental forming process, sheet metal tended to instability easily, then the deposition, wrinkle and fracture will be appearing concomitantly. If the vibration technique is introduced to the incremental forming process, its deformation mechanism will be changed, and forming quality is improved. Then some force equations are built by force analyzed for a element in local forming contact zone, some solutions of the force equations are obtained. With process parameters, mechanical performance parameters and vibra parameters given, stress curves are got. It is shown from simulation that the sheet metal stress has prominent variation with vibration，and forming-angle condition and frequency-condition should be met with vibration.

Abstract: According to the characteristics of aircraft subassembly, an optimal method for task balancing under resource constraints is presented. Firstly, the judgment indexes are abstracted to represent the running state of the assembling task, and mathematic model of assembling task balancing was established by available resources. Considering feature of aircraft subassembly, a fitness function is proposed based on two-stage priority targets, which are specific to task sequence and resource allocation respectively. Afterwards, Genetic-Tabu hybrid operations are executed to get the optimal solution. Finally, the effectiveness of this method is verified by applying to assembly task balancing of an outer flank.

Abstract: The effects of gravity and kinetic undercooling upon the melt/crystal interface in a vertical Bridgman-Stockbarger crystal growth system by numerical simulation. Thermal transport, melt convection and kinetic undercooling are simulated by two-dimensional transient calculations. Time evolution of the centerline interface location difference is tracked. This study then compares and discusses the results among the different gravitational acceleration. We also investigate the effects of the undercooling on the interface.

Abstract: The disadvantages of the conventional twin-roll caster for aluminum alloy are low casting speeds and limited choices of alloys that are castable by this processing. It is known that strip casting of aluminum alloy 5182 is very difficult because of their wider freezing zones. The vertical-type high-speed twin-roll caster used in the present study was devised to overcome these disadvantages. Features of the high speed twin roll casters are as below. Mild steel rolls were used in order to increase the casting speed and to be made at a lower equipment cost. Roll coating is produced in casting of Al-Mg alloy. Therefore lubricant, that resists heat transfer, was not used in the present study. Heat transfer between melt and the roll was improved by hydrostatic pressure of the melt. Low superheat casting was carried out in order to improve microstructure of the strip. In the present study, effectiveness of a high-speed twin roll caster for recycling aluminum alloy was investigated. The effects of the high-speed twin roll caster on alleviating the deterioration of mechanical properties by impurities were investigated. Properties of the cast strip were investigated by metalography, a tension test, and a deep drawing test.