Abstract: Advanced light metals have recently attracted the interest of the aerospace and automotive industry. The need for accurate description of their cyclic inelastic response under various loading histories becomes increasingly important. Cyclic mean stress relaxation and ratcheting are two of the phenomena under investigation. A combined kinematic isotropic hardening model is implemented for the simulation of the behavior of Aluminum and Titanium alloys in uniaxial mean stress relaxation and ratcheting. The obtained results indicate that the model can perform well in these cases. This preliminary analysis provides useful insight for the evaluation of the models capabilities.
Abstract: This study describes how the control of bath pH allows different types of phase formation in the ternary Co-Ni-Fe nanocoating. The acidity of the plating bath has been known as a main factor to the properties of coatings. The Co-Ni-Fe coating was fabricated using a commercial electrodepostion process. Several pH solutions (3, 7 and 9) were employed to determine the optimum condition for Co-Ni-Fe synthesis. The bath pH was varied by using sodium hydroxide (NaOH) and sulphuric acid (H2SO4). Other parameters such as temperature, electrolyte composition, deposition time and current density were kept constant. The experiment was performed at 50°C. This temperature is commonly used in the industrial plating process. XRD analysis indicated the presence of both phases: body centred cubic (BCC) and face centred cubic (FCC) dependent on the pH value. Co-Ni-Fe nanocoatings obtained from the electrolyte of low pH showed the fine-grain morphology. The hardness of the Co-Ni-Fe nanocoatings was closely related to the obtained morphology.
Abstract: In this paper, three-dimensional finite element model of titanium alloy TC4 was established by using three-dimensional finite simulation software-Deform.Change rule of cutting force and cutting temperature can be obtained in different cutting parameters including cutting speed, feed rate and cutting depth.
Abstract: This study investigate the role of hydroxide ions (OH-) in the synthesis of Ni nanoparticles through polyol method at the temperature of 180°C. Ni nanoparticles were prepared using ethylene glycol (EG) as the solvent and hydrazine (N2H4) as the reducing agent. Sodium hydroxide (NaOH) was used to introduce the OH- in solutions. Amount of OH- has been controlled through manipulation of OH- /Ni2+ ratios. The role of OH- has been discussed in terms of size, morphology and reaction rate. Particles size and morphology were determined by Transmission Electron Microscopy (TEM). X-Ray Diffractometer (XRD) was used to verify the chemical composition of as-synthesized particles. The results demonstrated that at temperature of 180°C, Ni nanoparticles can be synthesized even without the existance of OH-. Although there no significant particles size changes,synthesis without OH- showed the most rapid reaction as compared to samples with OH-. Probable mechanisms for formation of Ni nanoparticles with and without OH- are also discussed. This finding contribute to a new rapid and facile synthesis of Ni nanoparticles.
Abstract: The indentation size effect (ISE) in Vickers test using steel as a typical model material group with selected heat treatments (annealed or tempered) has been investigated and analysed. Systematically hardness test were performed within a commonly used micro-load range. The ISE data was analysed by fitting data following the Meyer power law and the proportional specimen resistance (PSR) models and the link between ISE and the hardness-to-modulus ratio (H/E) was discussed. The results show that the ISE data correlated well with the Meyers power law (P= A.dn) and the PSR (P/d=a1 +a2d) models. The ISE power law index n exhibited a reasonable agreement with the hardness-elastic modulus ratio (H/E), which potentially could be used the relative contributions of plastic and elastic deformation contact area under indentation load and as a measurable input for inverse material parameter prediction.
Abstract: Stockpile wastewater consisted of ferrous metal, manganese metal and total suspended solid (TSS). In addition, it also has high acidity (pH) which is possibly harmful to the environment. This research objectives were to reduce ferrous and manganese metal in coal stockpile wastewater using electrocoagulation technique using aluminum electrode with variation in electrics current and processing time. The most effective conditions in reducing ferrous and manganese concentrations with electric current of ± 2.5 A in 90 minutes. Effectivity in ferrous and manganese metal reduction was 98.7% and 99.6%, respectively. The final concentration of ferrous and manganese metal was 0.08 mg/L and 0.01 mg/L respectively. Optimum concentration of TSS reduction was 83.7% with the final concentration of 72 mg/L. The wastewater pH value became 7,1. Finally, the results demonstrated that the electrocoagulation process using aluminium electrode is a reliable technique for removal of pollutants from coal stockpile wastewater.
Abstract: The ilmenite mineral (FeO.TiO2) from Bangka Island-Indonesia is an important source for synthesizing TiO2 nanoparticles. However, the process is rather difficult since this mineral still contains many impurities and minor elements. Therefore, controlling the synthesizing route parameters is essential for obtaining the desired TiO2 nanoparticle characteristics. In the current work, we proposed a modified process involving the use of sulfuric acid through sol-gel method to provide titanyl sulfate (TiOSO4) solution as the inorganic precursor. For investigation purposes, several parameters were varied including volume ratio of water and titanyl sulfate, addition of iron powder (seeding) and dextrin coagulant, calcination time and temperature. The results showed that TiO2 nanoparticles can be succesfully synthesized using TiOSO4 precursor derived from Bangka ilmenite. Under all processing conditions, the resulting TiO2 nanoparticles have sphere-like shape and were indexed as the anatase TiO2 phase. The results also showed that the average particle size was reduce from 96 188 nm to 32 40 nm when the volume ratio of water and titanylsulfate was increased from 3:1 to 6:1. The addition of iron powder as seeding has improved the purity of TiO2 to ~ 95.01 wt%, in comparison to that of without seeding, which is ~92.78 wt%.
Abstract: Ramie fibers and albizia wood, which are abundantly available in Indonesia, were used in fabricating hybrid sandwich composite for wind turbine propeller. A prototype was fabricated by modification of NACA 4415 standard airfoil, intended for low speed wind and environmental friendly operations. Hand lay-up method was applied for fabrication of this hybrid composite with one and two layers of ramie fiber. Mean volume fiber fraction (vf) of one-layer and two-layer composite are 47,12% and 44,82%, respectively. The highest measured bending stress is 30.88 MPa for two-layer composite with modulus of elasticity 2.02 GPa and bending strain 1,795%. Microstructure of this hybrid composite is unchanged significantly after 5.5 months operation. With ultimate simplicity and low manufacturing cost, hand lay-up method is suitable for small scale production.
Abstract: Glass Fiber Reinforced Plastics composites have an increased application in recent days, due to its enhanced structural properties, Mechanical and thermal properties. Drilling of holes in GFRP becomes almost unavoidable in fabrication. The heterogeneous nature of this kind of materials makes complications during machining operation. However, drilling is a common machining practice for assembly of components. The quality of holes produced in the GFRP material is severely affected by surface roughness, Circularity and Delamination. The objective of the study is to apply the Taguchi method and ANOVA to achieve an improved hole quality considering the minimum surface roughness through proper selection of drilling parameters. The regression method is employed in the Experimental investigation and Mathematical modelling of drilling of GFRP material using HSS drill bits.