Advanced Materials Research Vols. 463-464

Abstract: In this paper, a 2D boundary element approach able to model viscoelastic functionally graded materials (FGM) is presented. A numerical implementation of the Somigliana identity for displacements is developed to solve 2D problems of exponentially graded elasticity. An FGM is an advanced material in which its composition changes gradually resulting in a corresponding change in properties of the material. The FGM concept can be applied to various materials for structural and functional uses. Our model needs only the Green’s function of nonhomogeneous elastostatic problems with material properties that vary continuously along a given dimension. We consider the material properties to be an exponential function of Cartesian coordinates x. As application, a numerical example is provided to validate the proposed boundary integral equation approach.

Abstract: An observation during screw fixing activities on kitchen cabinet installation was carried out. In collaboration with Signature Kitchen Ptd. Ltd., a kitchen cabinet manufacturer in Malaysia, twenty-eight (28) houses in Kelang Valley, Malaysia were selected for the study. Almost all of the sites selected have shown some damages of the particleboard during the screw fixing activities. Generally, there were cracks, chip-off or swelling occurred in between the panel surface and the screw head edges. The damages observed on the screw joint during installation are in the form of split holes, loose holes and delamination. All damages then were identified for its type of failure mode especially at the screw-driving slot and particleboard surface. Six type of failure mode were identified, documented and discussed.

Abstract: The realising of complex parts by welding together and then deep-drawing metal sheets made of different steel types or even different metal types can have many advantages, such as decreasing the part’s weight, reducing the manufacturing costs and an increased dimensional precision. In order to benefit from these results, a detailed knowledge of the metal sheets’ behaviour during deep-drawing is necessary. The current paper aims to compare, using numerical simulations based on the finite element method, the deep-drawing behaviour of parts made of steel sheets of different thicknesses welded together in three different manners and also of a part made of a monoblock blank.

Abstract: This paper combines an artificial neural network (ANN) with a traditional genetic algorithm (GA) method, called hybrid genetic algorithm (HGA), to analyze the warpage of multi-cavity plastic injection molding parts. Simulation results indicate that the minimum and the maximum warpage of the hybrid genetic algorithm (HGA) method were lower than that of the traditional GA method and CAE simulation. These results reveal that, when HGA is applied to multi-cavity plastic warpage analysis, the optimal process conditions are significantly better than those using the traditional GA method or CAE simulation.

Abstract: The energy bandgap (Eg) of silicon thin film prepared by plasma enhanced chemical vapor deposition (PECVD) is greatly dependent on the deposition conditions. Although the influence of some deposition parameters on Eg has been studied individually, it is still not clear which parameter plays the most important role. Here, a 5-factor 5-level factorial experiment was designed and carried out for the deposition parameters: the flow rate of SiH4, the flow rate of H2, the plasma power, the total gas pressure, and the substrate temperature. By making main effect analysis to the influences of such 5 factors on Eg, not only the influence of each deposition parameter was obtained, but also the most critical parameters were selected out. It was found that the gas flow rate of SiH4 and the total gas pressure played the most important roles on determining Eg of silicon thin film. That is to say, in order to obtain an expected Eg for Si thin film prepared by PECVD, much attention should be paid to optimize the two parameters. However, other parameters, including the H2 flow rate, the plasma power and the substrate temperature, can be set as default values according to the experience. Thus, the optimization workload can be reduced greatly.

Abstract: The complex modeling and coordination program has been developed based on quality standards that are in line with the quality requirements specific to the production of turbojet engines and assures the guarantees and confidence of our European Partners in our ability to take part in complex international projects with high levels of scientific and technological difficulty. A particular feature of the project is the quality system integration. For this purpose, the hardware of the existing machine tools is modified to assure the active control of parameters and a report is issued on the actual parameters. The report printed on a barcode card accompanies the component throughout the technological workflow, assuring the traceability of the component history, and a quality report is issued.

Abstract: Cu₂ZnSnSe₄ (CZTSe) thin films with the advantages of low cost, abundance in resources, and the suitable band-gap of 0.9~1.1 eV have been the potential materials for solar cells, though the Cu(In,Ga)Se2 thin films have received most of the attentions. In this study, CZTSe thin films were prepared by direct-current (D.C.) sputtering using three self-made CZTSe targets in different compositions. The sputtered films displayed a preferred orientation in (112) by the X-ray diffraction analysis. The films were also characterized by field-emission scanning electron microscopy and energy dispersion spectroscopy. The films had the band-gap of 0.8~1.08 eV analyzed by absorption spectroscopy. CZTSe films were p-type and had a low electrical conductivity of 10-3 ohm-cm and a high carrier concentration of 10²⁰~10²¹ cm-2.

Abstract: The security risks of using tap-changer of main transformer in substation to adjust remote operation and automatic sequence operation were analyzed, the tap-changer slider gear urgent stop devices of main transformers integrated into RGT were designed and developed and the functions of the system, hardware construct and software system were discussed in this paper. The vigorously developing of smart grid construction and practice application of this device are shown that the method has the urgency and effectiveness

Abstract: The effect of N₂ gas pressure during the rapid thermal process (RTP) on the structural and morphological properties of CIGS films was investigated. The precursor was prepared by sputtering from a single quaternary CIGS target. XRD characterization demonstrated that there were two phase of CuIn_0.7 Ga_0.3 Se₂ and Ga-rich CuIn_{Subscript text}1-xGaxSe_{Subscript text}2 chalcopyrite structure in all of the selenized CIGS films. Too low and too high N₂ gas pressure induced compact but small grain-size morphologies due to the insufficient Se supply. Furthermore, all of the samples exhibited delaminated cross-sectional morphologies. Finally, Photovoltaic devices prepared from absorbers selenized under 4 Torr N₂ gas pressure resulted in efficiency of 4.8%.

Abstract: Crack detection by Piezoelectric Wafer Active Sensors (PWAS) is one of the emerging methods of Non-destructive Evaluation (NDE). These sensors can assess the health state of the structure in far filed through the analyzing the high frequency Lamb wave propagation. As PWAS is the essential part of this method, simulation and modeling of these sensors and their interaction with the host structure, strongly affect the accuracy of results. In this study, unlike the previous works, in which some certain areas of the host structure were considered as a sensor and actuator, the direct simulation of electro-mechanical interaction of the PWAS and the host structure is modeled among modeling the PWAS with a FEM coupled-field element. After verification of the FEM analysis with theoretical group velocity of S0 mode, capability of the S0 mode in crack detection was examined. Different length and angles of the crack in an aluminum plate modeled. The crack growth effect was defined among a damage index by using the strain energy magnitude that received by sensor localized behind the crack. The result showed that transmitted energy from the cracks decreases as the crack length increases. In addition, as the angle crack to the sensor increases, the ability of sensor to crack detection will increase.