Papers by Author: Dun Wen Zuo

Abstract: Strain films in the thin film resistance strain gauge are prepared by magnetron sputtering method. Some results concerning the electromechanical and structural properties of nichrome (Ni80Cr20 wt.%) thin films are presented. As compared to the well-known Ni-Cu (constantan) alloy film, which are widely used for manufacturing pressure and force sensors, nichrome (Ni80Cr20 wt.%) thin films exhibit gauge factor values of the same order of magnitude, but they are much more corrosion resistant and adherent to the substrate. The influences of composition and post-deposition annealing on the electrical resistance, temperature coefficient of resistance (TCR) and gauge factor of nichrome (Ni80Cr20 wt.%) thin films are discussed.

Abstract: According to lateral powder system due to gravity, the controllable rapid powder switch is first tried based on the principle that air pressure can change the direction of power. Then, three kinds of modified schemes are provided based on the experiment to remedy the lack of first try. Finally, one scheme is selected and realized, which can solve the problem of synchronization of laser and powder, and advance powder utilization factor.

Abstract: The machining accuracy and the surface roughness of workpieces machined by the PKM named BJ-04-02(A) are evaluated by machining experiments in this paper. The machining accuracy includes that of size, shape and position. Size includes the diameter and length. Shape accuracy includes straightness, roundness and cylindricity. Position accuracy includes perpendicularity, parallelism, inclination and concentricity. The experiment results show that the surface roughness and the straightness basically meet the demand of JB/T8771.7-1998, but other accuracy indexes are not consistent well with the mechanical standard. However, the machining accuracy becomes bad when machining tool is far away from the center of the workspace.

Abstract: Many thin-walled aero-parts have complex structure, and high machining accuracy is required. But because of their poor rigidity, it is easy to bring machining deformation caused by the existence of the clamping residual stress, and influences machining accuracy of workpiece. At the present time it is a focal point how to reduce the deformation the machined surface. Present studies mainly focus on the influences of clamping points, clamping order and clamping force on residual stresses. It is few studied for clamping schemes how to influence the residual stresses and the fatigue resistance of the machined parts. To reflect the relationship between clamping schemes and residual stresses and fatigue resistance, finite element models with different clamping schemes were built and the clamping process was simulated. A conclusion is obtained that it is advisable to adopt even and symmetry distributed clamps and multi-point clamps to reduce the workpiece distortion of aero-multi-frame components due to the clamping. This study conclusion has been validated by the actual production.

Abstract: Effects of running state and spindle speeds on the sound signals produced from a drill press are investigated. And the obtained sound signals by using of a sound level meter are analyzed in both time domain and frequency domain. It is evident that there is more high frequency energy for drilling sound signals with load than without load. And spindle speeds still affect their energy distribution of drilling sound signals. Using wavelet decomposition and wavelet packet decomposition, drilling sound signals are decomposed into a number of frequency bands. And energy percentages of the divided frequency bands are extracted to be the effective characteristics to recognize spindle speeds. Meanwhile, training error of different BP networks is compared to obtain the effective network for recognition spindle speeds. By using of the obtained network structure named 16-30-5, the study rate for training samples and the recognize rate for testing samples are all above 95%.

Abstract: It was carried out that a HSM test for aluminum alloy (2A70) rotor with carbide cutter. It was investigated and analyzed that the influence of different cutting speed and feed speed on the roughness of blade’s finished surface. The experiment showed that high quality surface was easy to obtain by increasing the cutting speed and decreasing the feed. But when the cutting speed crossed the critical value, increase in the cutting speed caused slight decrease in the surface roughness. The feed decreased to a very small value, the roughness increased a little. It was expected that best surface roughness and machining efficiency could be obtained by selecting the appropriate cutting speed and feed.

Abstract: In this paper, a new polishing technique was proposed to polish concave spherical surface by diamond spherical shell deposited by DC-Plasma Jet CVD(chemical vapor deposition), and preparation was studied from both experiment and theory. The deposited films were investigated by some techniques including: scanning electron microscopy (SEM), atom force microscopy (AFM), Raman spectroscopy, and roughness-profile-meter, which were used to analyze surface phase, microstructure, internal quality and surface roughness. The results show that the deposited diamond spherical shell film has some remarkable properties, such as high surface density, high hardness. Compared to traditional polishing techniques, it will have some potential advantages as convenient, flexible, efficient and precious. To adjust some important parameters as methane concentration, depositing time, and it can deposit the different size grain diamond spherical shell films, which are used to polish different precision degree concave spherical surfaces. Meantime, to change curvature of diamond spherical shell, it can adapt to polish various curvature radius concave spherical surfaces.

Abstract: The uniform distribution and the stability of the substrate temperature are the most important factors that deeply affect the quality and the growth rate of diamond films. In this paper, cemented carbide cutters were chosen for substrates, the 3D finite element (FE) model of filaments and substrates was developed in ANSYS 8.0, the calculated results show that the substrate temperature is influenced by the filament temperature, filaments diameter, the quantity of the filaments and the distance between the filaments and the substrates. The 3D finite element model of filaments and substrates also provides a basis for selecting the parameters to obtain uniform diamond films in miniature EACVD system.

Abstract: Diamond spherical shell thick film was prepared by high power DC-plasma jet CVD. Atom force microscopy, scanning electron microscopy, Raman spectroscopy and roughness-profile-meter were used to characterize microstructure, morphology, impurities and orientation evolution of diamond spherical shell thick film. The results show that, when nucleation begins, grains grow random orientation. The grain size of spherical diamond film prepared is compact, clear, uniform, continuous and no remarkable bigger grain over the whole surface of film. On the growth surface, (100) facets were dominant, and the cross-section SEM indicated that film columnar spreading grew from the substrate surface to the diamond film surface. The roughness of the growth surface was much more than that of the nucleation surface. To adjust some important parameters as methane concentrate, depositing time, and matrix temperature, and high quality diamond spherical shell thick film was deposited.

Abstract: High residual stress that includes thermal and intrinsic stress is an obstacle to the further application of chemical vapor deposited diamond thick film. In this paper, CVD diamond thick film was deposited on silicon substrate by hot filament chemical vapor deposited (HFCVD) system. The finite element analysis (FEA) simulation and experimental research were carried out on the thermal and intrinsic stress of large area diamond thick film. The FEA model is set up to investigate the distribution and magnitude of thermal stress. The intrinsic stress is studied by X-Ray diffraction “sin2ψ” method. The thermal stress and intrinsic stress are both compression stress. Simulation results show the discontinuous sharp of the diamond film result in the stress concentration and low cooling velocity is a good way to reduce thermal stress. The intrinsic stress is correlative with the microstructure and non-diamond component of diamond film. The origin of the intrinsic stress is discussed in detail in this paper.