Advanced Materials Research Vol. 845

Abstract: Porous ceramics were produced by compaction method of Nigerian clay and cassava starch. The samples were prepared by adding an amount from 5 to 30%wt of cassava starch into the clay and sintered at temperature of 900-1300°C. The influence of cassava starch content on the bulk density and apparent porosity was studied. The result of XRD and DTA/TGA shows that the optimum sintering temperature was found to be 1300°C. The percentage porosity increased from 12.87 to 43.95% while bulk density decreased from 2.16 to 1.46g/cm³ with the increase of cassava starch from 5 to 30%wt. The effect of sintering temperature and cassava starch content improved the microstructure in terms of porosity and the thermal properties of porous clay for various applications which requires a specific porosity.

Abstract: As the electronic packaging industry is vastly being developed, the solder plays a crucial role in providing integrity electronic assemblies. Unfortunately, the traditional Sn-Pb solder is harmful to the environment and human due to lead (Pb) it contains. Hence, in this study, the Sn-Bi lead free solder alloy is investigated based on its physical properties together with melting temperature, hardness and microstructure. Investigation shows that this solder provides a low melting temperature of, T_m=141.08°C which is lower than the most used Sn-Pb, T_m=183°C and Sn-Ag-Cu, T_m=227°C. Moreover, the Sn-Bi solder also produces well-defined microstructures with Sn-matrix and bismuth precipitation on the matrix. The Sn-Bi solder also provides a higher hardness with average of 11.8Hv for Vickers hardness and 3.87BHN for Brinell hardness. All this results seem to satisfies the environment as well as producing better physical properties.

Abstract: The relationship between morphological parameter and different type of loading orientation on elastic behavior and yielding of trabecular may provide insight towards osteoporotic bone losses during normal activities. This paper attempts to predict the elastic and failure behavior of different loading modes (tensile and compression) on anatomic sites and morphological indices through finite element (FE) simulation. Specimens extracted from bovine femoral trabecular bone were imaged using micro computed tomography (μCT). Morphological studies were done followed by FE analysis. Results demonstrated differences between yield behaviors on anatomic sites were reflected onto the morphological indices and the type of loading modes. The yield initiated earlier in rod-like than plate-like trabecular in both loading condition but showed different failure behavior in rod-like trabecular with small differences in maximum stress between tensile and compressive. However, in many cases, trabecular models tend to have oblique fracture pattern in all anatomic sites. Through these findings, improved prediction of elastic properties and yield behavior by computational means provide insight in the development of bone substitute material depending on the anatomic site as well as in osteoporotic bone pathological treatment to monitor losses in trabecular struts.

Abstract: Transportation of Oil and Gas from the production site to the terminal or refinery requires the use of long pipelines which procure to develop slug flow regime. This slug may cause cyclic stresses leading to fatigue and results in damaging the pipelines. This paper aims to utilize that design guide and calculate the total fatigue life for the pipeline due to internal slug flow by performing evaluation of the stress range and fatigue life span of the pipeBeam 3element with moving loads in ANSYS commercial software have been used to simulate the slug flow across the pipeline and assess the dynamic response. The total fatigue life for different selected slug parametrs was calculated. The model was validated by comparing with analytical solution in a previous published research and reasonable agreement was revealed. The results show that increasing the slug to pipe weight ratio resulting in higher dynamic stresses and reduction in the fatigue life of the pipe. This model can be utilized for the offshore pipeline if the external environmental effects are considered.

Abstract: The partial discharge (PD) phenomenon is very harmful for electrical appliances and its early detection could be a cost effective approach for the industry. Although many techniques are used for PD detection yet no technique has presented widely acceptable solution. Still the subject needs parallel study of the detection techniques. In this study, partial discharge signal has been captured by the three techniques using fiber optic sensor (FOS), Piezoelectric Sensor (PZT), leakage current (LC) techniques. In these experiments, FOS shows good sensitivity in the range of applied high voltage > 5 kV. The sensitivity and noise level of PD signal was different in these two experiments.

Abstract: There is a high risk of insulation system dielectric instability when partial discharge (PD) occurs. Therefore, measurement and monitoring of PD is an important preventive tool to safeguard high-voltage equipment from wanton damage. PD can be detected using optical method to increase the detection threshold and to improve the performance of on-line measurement of PD in noise environment. The PD emitted energy as acoustic emission. We can use this emitted energy to detect PD signal. The best method to detect PD in power transformer is by using acoustic emission. Optical sensor has some advantages such as; high sensitivity, more accuracy small size. Furthermore, in on-site measurements and laboratory experiments, it isoptical methodthat gives very moderate signal attenuations. This paper reviews the available PD detection methods (involving high voltage equipment) such as; acoustic detection and optical detection. The advantages and disadvantages of each method have been explored and compared. The review suggests that optical detection techniques provide many advantages from the consideration of accuracy and suitability for the applications when compared to other techniques.

Abstract: Radial cracks formed in brittle materials by Vickers indentation were used as nanoscale tensile tests for very thin metallic films coated on the brittle substrates. For the purpose of evaluating the mechanical properties of the films, a fracture-mechanics-based model was proposed, in which the crack opening displacements (COD) of film/substrate crack systems were related with the plastic deformation and failure of the films. The application of this technique to gold film/glass substrate systems indicated the possibility of the measurement of mechanical properties of very thin metallic coatings with a thickness of several 10 nm.

Abstract: In the present study, the tensile and fatigue properties of extruded 7075 Al alloys subjected to re-solution treatment and then T6, T73 and retrogression-reaging (RRA) tempers were reassessed based upon the microstructural analyses by means of electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The microstructural analyses indicated that fibrous grains having orientations close to <111> and <001> were preferentially aligned in the extrusion direction and that re-solution treatment increased the fraction of <111> grains. Further the as-received T6 specimens had very high dislocation density as well as fine subgrains, while the re-solution treatment decreased dislocation density considerably and increased grain size. These characteristics explained tensile properties well, by taking into account the effect of precipitates formed by tempers. On the other hand, fatigue strength decreased prominently in all of the specimens, as the relative humidity (RH) was increased from 25% to 85%. T73 and RRA treatments which improve the resistance to stress corrosion cracking (SCC) in static loading were not effective in the humidity-enhanced deterioration in fatigue strength.

Abstract: Free vibration modes of foam-core sandwich plates with and without polymer columns were experimentally identified from frequency response tests. The responses were made at selected locations on the plate surface by attaching a single-axis accelerometer to measure out-of-plane response. Resonant frequencies, relative damping ratios and mode shapes were established for the lowest 3 out-of-plane modes found in the frequency range of 0-900 Hz. The results show that the vibration characteristics were affected by the sandwich structure configuration and material properties.

Abstract: In this paper, glass fiber reinforce polymer subject to quasi-static three point bending loading and tensile loading was studied experimentally. Glass fiber reinforced made of chopped strand mat (CSM) were used in this study. Several samples were prepared and tested by using Instron universal testing machine at different strain rate including 1mm/min, 10mm/min and 100mm/min and all of the tests were repeated three times in order to minimize experimental error and the average of the obtained results were used for further analysis. The load-extension curves and stress-strain curve of glass fiber reinforce subject to three point bending and tensile loading test were determined at different strain rate and the obtained results were compared together. As results of this study, it has found that the strain rate has effect on flexural and tensile behavior of glass fiber reinforce.