Advanced Materials Research Vols. 287-290

Abstract: Fatigue test of AF1410 steel and two thickness of electron beam have been done, and fatigue properties of the base metal and EB-welded joints have been studied. The results showed that fatigue limit of electron beam welded joints was close to that of base metal under this test conditions, and the welded thickness has little effect on S-N curves of electron beam welded samples under this test conditions. From SEM fracture morphology, it can be seen that fracture morphology of the welded samples was not obvious different form base metal. In the instant-off area of electron beam welded sample, there was dimple-like morphology showing good ductility.

Abstract: It is very crucial to accurately identify the parameters of contact dynamics in predicting the chatter stability of spindle–tool holder assemblies in machining centers. Fast and accurate identification of contact dynamics in spindle–tool holder assembly has become an important issue in the recent years. In this paper, the receptance coupling substructure approach is employed for identification the stiffness and damping of the interface in a simple manner, in which the frequency response function of the tool holder is derived from the Timoshenko beam finite elements model. A BT 50 type tool holder is adopted as an application example of the method. Although this study focuses on the contact dynamics at the spindle–tool holder interfaces of the assembly, the approach might be used for identifying the dynamical parameters of other critical interface.

Abstract: The distribution and appearance characteristics of porosities in laser penetrated weld of aluminum alloy were observed, and the formation mechanisms of porosities were analyzed in detail, and the influences of twin spot laser energy distribution on porosities were investigated. It showed that there are two kinds of porosities, metallurgical and technologic porosities, in laser penetrated weld of aluminum alloy. The formation of metallurgical porosities is related to the separation, congregation and incorporation of hydrogen in the weld pool, while instantaneous instability of the keyhole is an essential reason for the occurrence of technologic porosities. Twin spot laser energy distribution can enlarge diameters of the opening and the root of the keyhole, improve fluctuating conditions of the wall of the keyhole, increase stability of the keyhole, and consequently decrease technologic porosities in number, but it has no obvious influence on metallurgical porosities.

Abstract: Aiming at the cleaning operation of high-rise building glass wall, a novel pneumatic wall-climbing robot was developed. According to the configuration and the characteristics analysis on the robot, the kinematics equations were derived and PWM / PFM algorithm was proposed based on PID control. The simulation results show that the motion and control for the robot has advantages of fast speed , flexible movement, strong obstacle avoidance ability and simple control features, and so on.

Abstract: The ZnFe₂O₄ and TiO₂ nanocomposite films was prepared by Sol-Gel method on conductive glass, and the influence factors of it’s photoelectrocatalytic performence such as the film layer, pole and voltage was investigated. The results indicated that: the photocatalytic effects of composite films with ZnFe₂O₄+ TiO₂+ ZnFe₂O₄ was the best. The decomposing ratio of methyl orange with the photoelectrocatalysis of composite films at voltage 0.2-6V all increased unstably.At the same time, the distance from films to pole plank also had the effects on the photocatalytic activities of the films.

Abstract: Diamond-like carbon (DLC) films have been given great attention in the last twenty years and applied in many fields due to its super mechanical property. In this paper, DLC films were prepared by filter cathodic vacuum arc (FCVA) deposition under different negative bias voltage. No spalling was found in all of as-prepared DLC films. X-ray photoelectron spectroscopy (XPS), Raman spectra were employed to analyze composition and structure, the results showed that as-prepared DLC films had tendency of graphite with increase of negative bias voltage. Mechanical properties were characterized by micro-hardness and pin-on disc tests, the results showed that the hardness of DLC films decreased with bias voltage, but still kept good wear resistant.

Abstract: In order to obtain a real shape of membrane structure, a new shape finding method was developed based on real material property. The curved shape is first obtained by raising the control points above the projection plane. The convergence was improved using pseudo material properties to get a preliminary shape, and then the real properties to get the final shape. A large number of examples were analyzed to verify the validity and practicality of this method. The results showed that the final curved surface after the second shape finding process was always quite similar to the first one. Moreover the curved surface obtained after the second shape finding process is accurate and will be realized in real.

Abstract: Freestanding diamond film was prepared by hot filament chemical vapor deposition (HFCVD) method. Inter-Digital Transducer (IDT) was formed on the nucleation side of freestanding diamond film by photolithography technique. Then piezoelectric AlN film was deposited by RF reactive magnetron sputtering to obtain the AlN/diamond film structure. Surface morphologies of the nucleation side and the IDT were characterized by atomic force microscopy (AFM) and optical microscopy. The results indicated that the surface of nucleation side was very smooth and the IDT was of high quality without discontinuity and short circuit phenomenon. Room temperature frequency dependence of dielectric constant and dielectric loss for freestanding diamond film suggest a good stability of dielectric properties in high frequency region for diamond film. X-ray diffraction (XRD) pattern of the structure of AlN /diamond film structure showed a strong diffraction peak of AlN (002), which indicated that as-sputtered AlN film was highly c-axis oriented.

Abstract: Nanocrystalline ZnO and Zn₂TiO₄ porous film electrodes were prepared by sol-gel method and spin coating method, and the nanocrystalline porous films were characterized by XRD and SEM. Using ZnPc dye and PbS quantum dots as sensitizers. The nanocrystalline film electrodes of ZnO series and Zn₂TiO₄ series were prepared separately, and their absorption characteristics observed by UV-vis spectrophotometer. The results showed that ZnPc dye and PbS quantum dots could well sensitize the film electrodes, and the effect of ZnPc dye and PbS quantum dots composite sensitization was optimal. Then, the solar cells were fabricated. In simulation sunlight, the overall photoelectric conversion efficiency by Zn₂TiO₄/Q-PbS/ZnPc electrode increased by 22%, relative to the ZnO/Q-PbS/ZnPc electrode’s.

Abstract: In the paper, a new type of high-frequency microwave heating method for windshield forming process was investigated. In order to obtain the effects of forming process parameters and windshield properties on the forming qualities of windshield, the distributions of electromagnetic energy and temperature were simulated by coupling electromagnetic analysis with multi-physics analysis. Moreover, the influence of different microwave input frequencies on electromagnetic energy and temperature distributions was analyzed. The results show that a travelling-standing wave distribution of electromagnetic energy is formed within windshield. And the temperature distribution and heating time are determined by combined influences of windshield properties and microwave frequency. And the necessary temperature distribution can be realized by electing appropriate microwave frequency.