Applied Mechanics and Materials Vols. 110-116

Abstract: A Platinum nanoparticles modified Au electrode has been successfully fabricated by using an in situ growth method. In this method, the Platinum nanoparticles could be grown on the Au electrode surface via the one-step immersion into the mixture of H2PtCl6 (analytical grade, 1g/L), NaBH4 (analytical grade) and polyvinylpyrrolidone K30 (PVP, analytical grade). A certain amount of PVP was added into the reaction system to prevent the coagulation of the Platinum nanoparticles, which obtained by the chemical redox reaction of H2PtCl6 and NaBH4. The structures and morphologies of the Platinum nanoparticles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) . The direct electrochemical behavior of ascorbic acid in 0.3 mol/L NaCl medium at the Platinum nanoparticles modified electrode has been investigated in detail. Compared to a bare Au electrode, a substantial decrease in the overvoltage of the ascorbic acid was observed at the Platinum nanoparticles modified electrode with oxidation starting at ca. 0.20 V vs. SCE (saturated KCl). At an applied potential of 0.18V, this modified electrode produced high and reproducible sensitivity to ascorbic acid and linear responses were obtained over a concentration range from 0.600 to 3.267 μmol/L with a detection limit of 1.9 nmol/L(S/N=3). The fabrication method of this sensor, which has highly sensitive, low working potential, and fast amperometric sensing to ascorbic acid, is simple and without using complex equipment. In addition, the sensor has been successfully used to detect ascorbic acid in real sample, thus is promising for the future development of ascorbic acid sensors.

Abstract: Sr-ferrite powders were preparated by mechanochemical treatments using SrCO3 and Fe2O3 as raw materials. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM) were employed to evaluated the morphologies, structures and magnetic properties of samples. The results indicated that the starting mixture became amorphous stage after ball-milled for 30h, and single phase SrFe12O19 could be obtained after annealed at 900°C for 2h. And the saturation magnetization was 58.2Am2/kg, and coercivity was 281.2 kA/m at room temperature. In comparison with the traditional firing method , the mechanochemical method benefited achieving the higher coercivity, which indicated that the samples had a better magnetic properties.

Abstract: This paper presents a three dimensional thermo-mechanical analysis to investigate the effect of welding technique on welding deformations in pipe-pipe joints of SUS304 stainless steel type. Single-pass TIG and MIG welding with V-joint geometry in pipes having a diameter of 274 mm and a thickness of 6.2 mm is studied here. Two different welding techniques are analyzed. It has been shown that selecting a suitable welding technique can modify the amount of welding distortions in this pipe geometry.

Abstract: Hydroforming is one of the forming technique which paves the way for the easy production of light weight and high strength automotive and aerospace components. The different approaches presented by the various authors in the field of hydroforming and its applications are reviewed in this paper. The authors have used Finite Element Analysis using different simulation tools like Abaqus, Ansys, LS-Dyna and Autoform 3D that help to minimize the failure cost of materials and dies. This paper deals with those disparate approaches, discussing exhaustively the process and application of hydroforming, providing sufficient data to make readers identify the burgeoning areas of research.

Abstract: Application of tailor welded blanks (TWBs) in automobile industry and aircraft manufacturing have been increased during past few years. Efficient material distribution and decreasing weight of the final part are some of the most important advantages of TWBs. Since tailor welded blanks are produced with at least two dissimilar and uniform or non-uniform thickness materials, they show different behavior than uniform materials during deep drawing process. In this research, the effect of weld line orientation on formability in deep drawing of tailor-welded blanks is examined using finite element simulation and experiments. The thinning behavior of the circular TWBs during a deep drawing in a square die is studied for different weld line orientations between two mild-steel blanks with different thicknesses. The numerical and experimental results indicate that the orientation of the weld line direction of the blank sheet has significant influence on the deformation behaviour. It is seen that thinning behavior is similar for two sections of TWB for the same weld line orientation. In addition, the most thinning occurs at 45 degree rotation of weld line, thus appropriate weld line orientation or the tailor blank sheets direction orientation can improve the formability of the tailor-welded blank in a deep-drawing of square cup.

Abstract: Briquettes produced from agro-residues are fairly good substitute for coal, lignite and firewood. Briquettes from saw dust have high specific density of 1400 kg/m3 compared to bulk density of 210 kg/m3 (approx.) of loose saw dust. Loading/unloading, transportation and storage costs of agro-residues are drastically reduced if they are converted in the form of briquettes. Formation of briquettes at the very site of its production stops air pollution to a large extent. Hence briquetting of saw dust produces renewable and environment friendly source of energy. In this paper an attempt is made to design and fabricate briquetting machine for saw dust on lab scale to produce briquettes at the rate of 7kg/hr.Effect of moisture content in saw dust and binders used have been studied on briquette density, power consumption/kg of briquette produced and calorific value/kg of briquette. Thermal efficiency of chulha (local stove) using prepared briquette was obtained to be 5%.

Abstract: Voltage flicker and harmonics are power quality problems which are imposed on power system by electrical arc furnace. To study furnaces and find a solution to remove the negative effects of them, it is needed to have an appropriate electrical arc furnace model. Several methods in time and frequency domain have been presented. One of the time domain methods is Mayr model which has two problems. Firstly, it shows the harmonic components more than the real values. Secondly, it does not involve voltage flicker phenomenon. In this article with the comparison of harmonic components of Mayr model and measured values of arc furnace, an improved Mayr model is introduced. In the presented model, the problems of Mayr model are removed and it shows the real behavior of arc furnace

Abstract: Indonesia is rich in natural resources, including source of biofuel such as sweet potato starch. Sweet potato (Ipomoea batatas L) has a starch content of 22.4% which could be converted to sugar through hydrolysis process in order to yield ehtanol. This study aimed to examine the optimize ethanol yielded from starch of sweet potatoes using combination of acid and enzymatic hydrolysis. It used 0.5 HCl which combined with each Aspergillus flavus and Aspergillus niger, and mixture of both microbes for acid and enzymatic hydrolysis process. The highest sugar content resulted in hydrolysis process was fermented for 24, 48, and 72 hours to yield maximum ethanol. Data were analyzed using one-way analysis of variance (Anova). The highest reducing sugar produced by combination of HCl and Aspergillus niger was 12.61% (w/v). The highest ethanol produced was 46.17% (v/v) in 72 hours fermentation time.

Abstract: Parametric structural FEA (Finite Element Analysis) models of the orthogonal rib-stiffened thin walled cylindrical shells are established using APDL (ANSYS Parametric Design Language). An experiential optimization design method is then developed based on conclusions of series numerical analysis investigating the effects of parameters’ modification upon buckling loads and modes of the structure. The effects of single design parameter modification under both variational and fixed volume (mass) constraints upon the buckling loads and modes indicate that, only one design scheme is able to obtain maximum buckling load when deployment of the strengthening ribs and volume (mass) parameter were settled previously, and minimum mass would be obtained while this maximum buckling load equals to the required design load. Optimization calculations for aluminum alloy material and layered C/E (Carbon/Epoxy) composite material shells with three layering styles are implemented and discussed, and some useful conclusions are obtained. Method and approach developed in this paper provide certain reference value for the optimal design of such structures.

Abstract: In this paper an empty cylinder which is as a simulator for a ramjet engine has been studied by a cold flow. The air flow comes into the cylinder from one side and injection operation will be done by four nozzles which are located in the entrance of cylinder. By changing length to diameter ratio and injection angle, we have studied droplet sizing and efficient mass fraction of fuel vapor near and at the exit area. We named the mass of fuel vapor inside the flammability limit as the efficient mass fraction. To fulfill the calculation we used a modified version of KIVA-3V.