Abstract: A 3-D FEA has been carried out to determine the stress distribution in bolted double-lap bolted joints using ABAQUS CAE and compared with available closed-form equations. As friction load in bolted joint is transferred through-the-thickness, the 3-D finite element model gave more reliable stress distribution than simplistic 2-D closed form (incorporated with clamp-up). Similar trend in stress distribution were found for closed-form and FEA approaches.
Abstract: The high content of silica in geothermal waste can be used as a alternative source of amorphous silica for the production of silicon based materials. In this research, geothermal waste was used as silica sources in hydrothermal reaction of zeolite synthesis. Zeolite was synthesized by unstirred hydrothermal process. Hydrothermal process was conducted at variation temperature 100, 110 and 120 °C for 5 hours. To study the effect of holding time on hydrothermal product, hydrothermal process also done in variation of: 1, 3 and 5 hours holding time at temperature 120 °C. All of hydrothermal products were characterized by XRD. The results show hydrothermal process successfully converts geothermal waste into zeolite A and sodalite.
Abstract: The resonance frequency method is one of many non-destructive tests which allow us to evaluate construction materials. It was used to determine the dynamic properties of concrete, required in structures design and control, also considered as the key elements for materials dynamic. In this study, we chose a non-destructive approach to quantify-in laboratory-, the influence of adding “crushed limestone” and “natural pozzolan” on local concrete’s dynamic characteristics. However, several concrete mixtures have been prepared with limestone aggregates. The experimental used plan, allowed us to determine the dynamic modulus of elasticity, the dynamic modulus of rigidity of different formulated concretes.
Abstract: A top-down silicon nanowire fabrication using a combination of optical lithography and orientation dependent etching (ODE) has been developed using <100> Silicon-on Insulator (SOI) as the starting substrate. Initially, the samples were doped with phosphorus using the diffusion process resulting in carrier concentration of 2 x 1018 cm-3. After the silicon nanowires were fabricated, they were measured using a dual configuration method which is similar to the four-point probe measurement technique to deduce its resistivity. The data obtained had suggested that doping distribution in the silicon nanowires were lower and this may have been affected by the surface depletion effect. In addition, with respect to carrier mobility, the effective mobility of electrons extracted using the four-point probe data had demonstrated that the mobility of carriers in the silicon nanowire is comparable with the bulk mobility. This is most probably due to the fact that in this research, the quantum confinement effect on these nanowires is not significant.
Abstract: The treated palm oil fuel ash (POFA) is used as a substitute material in producing an improved porcelain ceramics. Most of the POFA is posed as waste in landfills, causing environmental and other problems. The POFA is grounded in a ball mill until the particle size is reduced to about 50 μm. Then it is heated at a temperature of 600 oC for 1.5 h in an electric furnace. About 5 wt% to 25 wt% of POFA is used to substitute quartz in porcelain composition. The mixed powder is then pressed into pellets at pressure of 91 MPa. All the pellets are sintered at a temperature of 1000 oC, 1100 oC, 1200 oC and 1280 oC for 2.0 h soaking times. It is found that the highest compressive strength, 45 MPa is obtained at 15 wt% of POFA and sintered at 1100 oC. The improvement in the properties could be attributed to the changes in the microstructural features as a result of an increase in mullite and cristobalite simultaneously.
Abstract: Joining sialon to as-received and nitrided AISI 420 martensitic stainless steels using diffusion bonding is reported in this paper. The samples were joined at 1200°C for one hour under uniaxial pressure of 17 MPa in a vacuum (1x10-5 Torr). After joining process, the microstructure, interdiffusion of elements, and hardness of the joint were studied. The interdiffusion and reactivity of the elements created the reaction layer. It consisted of interface layer on the sialon side whereas thicker diffusion layer was formed on the steel side. Thinner reaction layers were observed in joining sialon to nitrided steels compared to joining sialon to as-received steel due to less reactivity between the joined materials. However, more precipitates such as carbides were formed in the parent steel with longer nitriding time. Gaps were formed between the diffusion layer and the parent steel but the interfacial bonds were strong since no cracking occurred on the samples. Since the reaction layer had intermediate hardness, it contributed to the joint’s ductility that reduced the effect of thermal expansion mismatch between the joined materials by acting as a shock absorbing zone.
Abstract: The objective of thiswork was to investigate the microstructure and adhesion of NiAl coating whichformed by self propagation high temperature synthesis (SHS) process. Ni/Almixture and an underlayer material which used Ni and Al were compacted to forma bilayer pellet and subsequently put on a steel substrate. The Ni/Al reactionwas ignited using induction heating in a combustion chamber of argon gas. Themorphology and microstructure of the products were observed using SEM and XRD.The results showed that further reactions between NiAl coating and underlayermaterials formed several intermetallic phases. The role of Al and Ni underlayeron the microstructure, porosity and the adhesion between coating and thesubstrate was observed.
Abstract: In this work, the potential beneficial uses of palm oil fly ash (POFA) as a green pigment in paint technology via sintering process was studied. The POFA composites were sintered in the furnace at temperature 750°C. The obtained green pigment from POFA composites through the processes of mixing, reductive heating, ball milling and sieving was subsequently characterized by X-Ray diffraction technique.
Abstract: The effect of additive elements on impact toughness of Al-11Si-Cu alloy was investigated. The impact test bars were used as impact specimens. The energy of Al-11Si-Cu was improved with Sr modifier addition. The high ability of Ce and La to form large structure intermetallic in Al-Si-Cu will reduce the energy. The RE-intermetallic has an effect on impact analysis, which facilitates to increase the porosity pore.
Abstract: A welding coupon of AISI 304 austenitic stainless steel with thickness of 5 mm was welded by Gas Metal Arc Welding (GMAW) process using different welding parameters. The rectangular tensile test specimens (ASTM E8 standard) were subjected to cathodic hydrogen charging by immersed in 0.3 M sulfuric acid (H2SO4) solution and charged with current density rate of 110 mA per cm2 for 12 hours. The effect of cathodic hydrogen charging on the microstructural properties and fracture behavior in welding joints have been examined using an optical microscopy and scanning electron microscopy (SEM). The results showed that the percentage decay of UTS and elongation in welding coupons were reduced because of hydrogen charged. The fractured surfaces in weld joints zone appeared a formation of globular oxides.