Advanced Materials Research Vol. 500

Abstract: Silicon nitride nanoscale cutting model was established by molecular dynamics simulation, and interactions force between atoms of work-piece was calculated by Tersoff potential function. Through the three-dimensional simulation of silicon nitride nanocutting process, the changes of cutting force, kinetic energy and potential energy in the nanoscale cutting process, and the effects of cutting thickness and cutting speed on the entire cutting process were analyzed. The results showed that the kinetic energy, potential energy and cuting force increased along with the cutting thickness increasing, both kinetic energy and potential energy decreased with cutting speed increasing.

Abstract: Turn-milling technology can replace turning with milling to high speed machining rotationally body parts. So, micro-turn-milling has superiority on the productivity and the quality of workpieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. Micro-turn-milling can be used for the machining of micro-parts in its hardened state. In this paper, the influence of cutting parameters on surface topography and tool wear is presented in micro-turn-milling of micro-screw. The interaction effect of parameters to surface topography and tool wear is investigated. The results show that micro-turn-milling technology has its peculiar advantages in realizing high-speed cutting and ensuring machining quality.

Abstract: The process parameters used in the hybrid superplastic forming have been optimized. Since the hybrid process was a combination of hot drawing and gas blow forming, the effects related with the two forming phases were taken into account to facilitate the process design. The punch shape has been modified. A two-stepped punch in accordance with the die geometry with length of 43 mm was used in this work. Finite element modeling (FEM) was carried out to detect the low-plastic-strain areas, where the materials would have capabilities to be deformed more as the temperature increased. The non-isothermal heating system was then adopted to heat up these selected areas to improve the material formability during deformation. The maximum thickness thinning of the formed sample was 40%. Microstructures observed via electron backscattered diffraction (EBSD) have shown the occurrence of grain growth and recrystallization. It is clear that no big structure defect resulting from large plastic deformation was found.

Abstract: The curved die plays a significant role in reduction of extrusion load, refinement of microstructure and improvement in quality of product. In the present investigation, a numerical FEM modeling has been carried out for extrusion of triangular section from round billet through a curved die using DEFORM-3D software for steady state deformation using rigid plastic material. The extrusion load has been predicted. The effective stress, strain, strain rate velocity and temperature distribution have been determined. An experimental test rig has been fabricated. The experimental results are compared with the theoretical results. The results of computations are found to be in good agreement with those of the experiments.

Abstract: Die casting is a high productive method to produce non ferrous castings such as Al, Mg alloy. And die temperature field paid important effects on the casting quality and die life. Die temperature field was controlled mainly by water cooling channel in die. In this paper, some factors influenced the die temperature such as the temperature of cooling water, the location of cooling water channel, the diameter of cooling water channel, the amount of cooling water channel were discussed and analyzed by FEM. These results are very practical in die casting process.

Abstract: A well-defined boundary condition is important for generating an accurate model for simulating metal forming process. It is important to characterize the features of the oxide scale in hot rolling of stainless steel strip. Short time oxidation tests in humid air with water vapor content of 7.0 vol. % were carried out using Gleeble 3500 thermo-mechanical simulator. The deformation, surface morphology of oxide scale, and the friction in hot rolling were studied by conducting hot rolling tests. The results show that the surface roughness decreases with an increase of reduction. The effect of oxide scale on friction and surface roughness transfer in hot rolling depends on oxide scale generated during reheating. When reheating time is increased, the average thickness of oxide scale increases and a relatively rough surface was obtained after hot rolling. Thick oxide scale of 301 steel shows the high lubricative effect.

Abstract: The linearly converging die plays a significant role in the extrusion process of section products in terms of reduction in extrusion load and improvement of product quality. With the help of upper bound method based on dual stream function method. Very few investigations have been reported when product and billet geometry are dissimilar using linear converging die. Dual stream function method is incapable of predicting kinematically admissible velocity field in the above case, SERR technique (Spatial Elementary Rigid Region) is the only alternative. In the present investigation, a reformulated SERR technique has been used to determine non-dimensional extrusion pressure and optimum die profile both for frictionless and friction conditions. SERR technique based on discontinuous velocity field is applicable for this case. In the present investigation, non-dimensional extrusion pressure and optimum die length has been determined for extrusion of pentagonal from round billet and the results are compared with the FEA results by using DEFORM 3D.

Abstract: The stress with different shapes of the same thickness of the leaflet under the same load is analysed and compared by us. We create the spherical and ellipsoidal curved surface in accordance with geometrical features. The experimental results of the finite element analysis show that stress distribution of the different bioprosthetic heart valve leaflets with the same thickness is different. This work is very helpful to manufacture reasonable shaped valvular leaflets and to prolong the lifetime of the bioprosthetic heart valve.

Abstract: Current stone countertop production process is worn the following problems: long handling distance, long handling time, loose process cohesion, low balance rate, etc. In order to solve these problems, an automatic production line is proposed. In the production line, roller conveyer is used as the logistic system. The selected CNC equipment adopts an open structure and an oblique base. The equipments are arranged into a U-shape line combined with unit layout. In order to increase the flexibility of the production line, the whole production line is divided into two level modules. According to the design rules of the automatic production line, two examples are planned and are simulated based on EM-Plant. The simulation results show that, compared with the current production process, the automatic production line has the following advantages: the transit distance is shortened more than half, the transit time is reduced to about 1/7, and the balance rate increases by 20%, the output is nearly doubled, while the number of workers does not increase.

Abstract: An universal open-architecture CNC development platform for further designing all kind of numerical control devices is study, which is beneficial to making considerable reduction of development cycle and cost. The platform adopts IPC+Clipper construction to achieve the open-architecture of hardware, adopts modular programming technique to implement the open software according to user requirement. The control system consists of closed outer position loop and closed inner speed loop.As a result, the combination of position loop and speed loop achieve high precise and good stability of the motion control.