Key Engineering Materials Vols. 426-427

Abstract: In machining process, the workpiece is subject to cutting forces and torques. To resist these external loads, a fixture can supply clamping forces to completely restrain the workpiece. However, insufficient clamping forces cannot prevent the workpiece from translation and rotations, whereas excessive clamping forces may cause strongly the improper workpiece-fixture system deformations. Therefore, how to effectively determine the optimum clamping forces is the main objective of this paper. Firstly, a mechanistic model is proposed to measure the stability of clamping forces against these external loads. Secondly, a relaxation method is further established to true obtain the optimum clamping forces by solving the proposed model. The presented approach is conceptually simple and computationally efficient. It is particularly useful in the early stages of fixture design and process planning.

Abstract: An efficient mesh model repair method is proposed in this paper, which can repair the holes with boundary continuity. It is mainly composed of the following steps: Firstly, the hole boundary is triangulated to generate the initial surface patch, of which the edges are distributed along the boundary averagely similar to an curtain covering at a window. Secondly, the initial surface patch is refined, and the interior edges are relaxed while refining to get a Delaunay-like refinement surface patch, which approximates the density of the surrounding mesh. Finally, the refinement surface patch is reshaped based on the minimization of the surface energy solved by the order discrete Euler-Lagrange equation in order to realize the continuity repair. The proposed method is proved to be efficient and robust by experiments of different kinds of boundary conditions.

Abstract: Pinhole defect in the deposit is one of the ticklers which have not yet been solved fundamentally when micro-electroforming nickel into high-aspect-ratio (HAR) micro-molds. To obtain void-free micro-components, a new micro-electroforming technique, which was carried out under the complex circumstance of vacuum-degassing and temperature-gradient, was developed in this paper. Mechanisms of this micro-electroforming process were introduced using graphic and simulation methods. To investigate the feasibility of the exploited technique, a series of experiments were performed using special equipment developed by authors, followed by the evaluating of surface morphology of nickel micro-electroforms using a scanning electron microscope (SEM). Experimental results showed that, comparing with the conventional electroforming practices, a significant reduction in pinhole defects of the samples electroformed by the novel process was achieved.

Abstract: This paper presents a research on the effects of ultrasonic frequencies of 19.9 kHz, 23.6 kHz and 29.3 kHz on both of cyclic amplitude and fatigue life of Al2O3-ZrO2 nano-composite ceramics. According to the high-cyclic-life tests at low load level, some prohibition influence on the process of crack initiation and propagation under ultrasonic vibration is revealed as frequencies are raised from 19.9 kHz to 29.3 kHz. During the low load level tests, the toughness increment induced by the transcrystalline fracture is found in the scanning electronic micrographs of the fractures, which shows the existence of the inhibition effect on the crack initiation and propagation. At the same time, the fracture XRD indicates that t-m phase transition of ZrO2 under 29.3 kHz is higher than that under 19.9 kHz, which means that both the required cyclic amplitude and the fatigue life can be improved if the ultrasonic frequency is increased to 23.6 kHz. All the test results show that high frequencies exhibit stronger toughening improvements than the lower ones do. This paper is a pre-research for the ultrasonic ceramic grinding and the conclusions obtained are meaningful for the study of the crack propagation mechanism during the grinding.

Abstract: For the disadvantages of the lateral powder feeding and multi-lateral coaxial powder feeding process in laser cladding rapid prototyping process, a new process of hollow focusing laser, powder tube being middle and inside-beam powder feeding is put forward, which can be especially apply in laser cladding. In this paper, the finite element analysis model of temperature of the laser cladding using inside-beam powder feeding is established, temperature distribution of the single-layer in laser cladding is researched, which is theoretically useful for controlling the quality of microstructure and to prevent the cracks. When adopting finite element analysis software, Ansys, the layer unit is acted layer-by-layer, the full simulation of real cladding deposition process will be realized if moving boundary. Finally, some experiments validate the simulation results. Compared with the original mode, it can be found that if adopting the system of the laser cladding rapid manufacturing using inside-beam powder feeding, the temperature distribution is different and it will lead to a denser microstructure.

Abstract: At present, the rimed integral impeller is machined mainly by NC-electro-discharge machining (NC-EDM). To raise the efficiency of EDM process, the pre-channel is machined by NC-ECM to replace NC-EDM in rough machining process. The experimental results indicate that the whole process efficiency can be improved by not less than 20%, but the design of cathode and its feeding path in NC-ECM is a skilled and costly work. To improve machining accuracy and simplify design process, a new design approach based on simulating the shaping process of NC-ECM was put forward to design the cathode and its feeding path.

Abstract: Outer space target recognition is one of kernel functions of space-based surveillance system. This paper presents a new method on space target recognition based on image sequence using wavelet moments and DS evidence theory. Experimental results show our recognition system has a good performance (100%) which achieves need of practical application.

Abstract: Honeycomb paper has developed rapidly because of its hexagon core structure in casing area. One of the reasons is that honeycomb paper can prevent or lighten the vibration and concussion in the process of transportation. In this paper, the honeycomb paper with several different side lengths is studied. We studied the effect of their antivibration performance, offered certain theoretic direction to choose the side length of honeycomb paper and a method for antivibration analysis of honeycomb paper.

Abstract: Stability of cotton flow velocity determines the accuracy of foreign fiber detection system. There are many factors affecting fiber flow flux. In the process of operational control, recent research has been directed towards synthetically and effectively adjusting the relative parameters, and thus achieving a stable and economic foreign fiber detection system in textile sector. In the foreign fiber detection system, the parameters of flow velocity are affected by the temperature, pressure, density, which are also interrelated and redundant information. Based on Clustering Fusion, the design of the flow velocity used in the detection device is provided in this paper. Using captured parameter characteristic information, clustering fusion control, conducts the second fusion for ART-2 and BP neural network, and sends to fusion center, then fusion center process the data using neural network method. Linking with synthesis repository and global data base, different control strategies can be utilized to adjust velocity of flow parameter. The cluster control strategy that keeps output velocity of flow stable are proposed to improve the fiber measure precision in foreign fiber detection system. This system can be used in indigenous foreign fiber detection system, and significantly improve the performance of the entire system.

Abstract: The basic equation of axial flow pump is derived from the assumption， which axial plane velocity and circumferential velocity distribute linearly along the blade radius. Based on the basic equation, the axial plane velocity and circumferential velocity gradient of discharge blade are calculated, and the flow field of pump is built. Using arc method of design blade, a design case is given. The standard K- epsilon turbulence model is applied to simulate the flow field of axial flow pump by FLUENT software. The simulation results indicate that pump efficiency reach 91%, there aren’t impact or vortex in pump, and the pressure distribution on the blade suction surface is even and high, the anti-cavitation performance is improved.