Materials Science Forum Vols. 532-533

Abstract: Simulation of the velocity field of gas-solid-liquid three-phase flow inside and outside the abrasive water jet nozzle was studied by the computational fluid dynamics software (CFD). The complicated velocity field of the flow in the abrasive water jet (AWJ) nozzle and the abrasive track in the nozzle were obtained. In the course of the simulation, the inter-phase drag exchange coefficient model uses Gidaspow model (gas-solid), Wen-yu model (water-solid), Schiller-Naumann model (water-gas) respectively. The simulation results indicate that the swirl is produced in the nozzle and the abrasives are accelerated and moved around the swirl, and they are all distributed along the inner surface of the nozzle, the gas is mostly distributed in the center of swirl. The dispersion of the flow happens when it flows out of the nozzle, it can be divided into three zones, that is core zone, middle zone and border zone. At the core zone the velocity changes little while the velocity changes greatly at the middle zone, the velocity fluctuates greatly at the border zone.

Abstract: With the increase of expanded functions, Open CNC system is getting overstuffed gradually, which leads to the decrease of flexibility and reliability. Also, it is hard for users to define their special functions of CNC system. The paper proposes a strategy of intelligent reconfiguration based on floating hierarchical structure. The stepwise control structure of CNC system is broken and a reticular structure is built. Each function unit is assigned a code-array representing its layer levels. By changing values of the code-arrays, the system adjusts layer levels of the function units to adapt change of external environment. Redundant structure and technology of switch circuit are applied to establish internal structure of function unit. Technology of redevelop based on self-conducted configuration and structured language description is put forward. Strategies of simulation and evaluation are applied to prevent the CNC system from being damaged by improper redevelop.

Abstract: To describe the shape and location of free surfaces in the mold filling simulation, parameters including volume filled ratio, surface dimensionless distance, and surface filled ratio for the DFDM (Direct Finite Difference Method) elements were proposed. A model of mold filling process was established, considering the mass, momentum and heat transfer in the vicinity of free surface. It had been applied to an experimental Al casting. In-situ observation and record of actual mold filling process of the casting with special X-ray apparatus were carried out, and were used to validate the simulation results. The validation showed that the model could predict the mold filling process well. It was found that back pressure of gas in the mould cavity had minor effect on change of liquid flow when using pressurized feeding system and sand mould with good air permeability.

Abstract: In this study, hard turning GCr15 bearing steel with high cutting speed is experimental investigated the influence of the CB7015WH insert with chamfer edge and Safe-Lock and the CB7015 insert with a combination of hone radius and a chamfer edge on cutting forces and surface roughness of machined surface. Experimental results show that the cutting forces of the chamfer edge and Safe-Lock is smaller than that of the combination of hone radius and a chamfer edge. Moreover, surface roughness of machined surface with the CB7015WH insert is better. A coupled thermo-mechanical 2D finite element model with general finite element analysis software Deform 2D.8.1 is developed for the influence of two kinds of inserts on cutting forces and effective stress. The simulation results are compared with experimental data and found to be in good agreement.

Abstract: Based on the analysis of geometric errors of mechanism assembling, this paper applies the multi-body system kinematics theory in building the orientation error model of three-axis turntable induced by assembling errors. The results using the model could be easily applied in controlling turntable by error’s compensation, and shows which assembling error item has the larger effect. Furthermore，referenced by the measuring means of three-axis turntable, this paper conceives the definitions of the volumetric and orientation accuracy aimed at the turntable system, enlightened from the conception of NC machine tool. This research may be helpful to the foundation of the systematic conception of the turntable accuracy no matter in theory or in measuring method.

Abstract: The polygon action and the meshing impact of silent chain can be reduced by the change of the link plate structure. However, the change of the link plate structure may result in the complexity of manufacture. A new modified involute profile for sprocket is put forward based on the law of motion between the link plate and the driving sprocket. The modified involute profile is obtained by use of a unified program between VB and AutoCAD. The kinematic and dynamic simulation of silent chain with the new profile is performed by use of ADAMS. The results show that the polygon action of silent chain mechanism can be reduced and the smoothness of the silent chain drive is effectively improved as the sprocket is of the new modified involute profile.

Abstract: With the increasing of environmental conscious, design and explore of ideal products that meet customer requirements, especially cost less and environment friendly has become the goal for most manufacturing organizations. Green Quality Function Deployment (GQFD) is a very useful technique to fulfill this objective. In this paper, the first phase of the GQFD is to establish the Quality House, Green House and Cost House structures. For evaluating how well the customer demands, environmental constraints and cost are achieved by the product concept, the QFD method, eco-indicator method and input-output analysis are applied. In the second phase, to select the best product concept, a multi-criteria selection method--the analytic hierarchy process (AHP) is used. At the end of this paper, an application case of the bridge crane design according to the consumer demands and with a reduced cost and environmental impact is applied.

Abstract: The process of precision gear forging has been developed recently because of its advantages of giving high production rates and improved strength. For complete filling up, predicting the power requirement and final face width is an important feature of the forging process. A finite element analysis is utilized to investigate the maximum forging force and final face width under different process parameters such as modules, number of teeth, and the ratio of the height to diameter of billet. The abductive network is then applied to synthesize the data sets obtained from the numerical simulation, and a prediction model is established ultimately. Employing the predictive model can provide valuable references in prediction of the forging force and final face width under a suitable range of process parameters.

Abstract: The parameters such as aniotropic property, blank holder force and friction coefficient between tool and blank are not only effect on the forming force, stress and strain distribution of the worpiece, but also on the earing in products. In this paper, the finite element method is used to investigate the earing of the deep drawing process. In order to verify the prediction of FEM simulation of the earing in the cylindrical cup drawing process, the experimental data are compared with the results of the current simulation. A finite element analysis is also utilized to reduce the earing profile of the drawn products, a reverse forming method for obtaining the initial blank’s shape according to the forward cup deep drawing simulation is proposed.

Abstract: Five-axis CNC machining tools can improve the efficiency and accuracy obviously in machining industries, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the verification of the tool path is very important and necessary before machining the part. A new algorithm for 5-axis machining verification based on the stencil buffer has been presented in the paper. Based on the tool path and the cutter geometry, the cutter’s swept profile is determined. The swept envelope is subtracted from the sliced blank part model by using the stencil buffer. Considering the complexity of five-axis tool motions, examples are necessary to verify the reliability of the proposed algorithms. The experiment results indicate that the method is superior to the traditional methods on the processing time and the image quality. This proposed method can further be applied to machining error analysis, collisions interference.