Abstract: Nickel-based alloys provide high corrosion resistance and high-temperature strength but these alloys possess poor machinability. Hastelloy-X is a nickel based alloy that has been used for high temperature use. There are many studies about finite element modeling of aerospace alloys but studies in literature with Hastelloy-X are limited. In the present work, machining characteristics of Hastelloy-X were investigated and a numerical model was developed for the turning operation of Hastelloy-X. Two input parameters (cutting speed and feed rate) were variated in the operations and the results were evaluated considering process outputs such as cutting forces, cutting temperature, effective stresses and chip morphology. Based on the verification of the numerical model using experimental results, presented material model is appropriate for the turning operation of Hastelloy-X at low and medium cutting speed machining conditions.
Abstract: The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.
Abstract: The formation mechanisms and characterization (distribution, size and morphology) of the inclusions during continuous casting process of steels were investigated in this study. Samples were took out from several steps of the process and then, fully characterized via metallographic techniques, microscopic investigations and elemental analysis. Results showed that the addition of ferroalloys can intensify the formation of inclusions in some steps of the steelmaking process. Also, it was confirmed that the total oxygen content of the samples can be considered as a criteria of the clarity (purity and inclusion-free) of the steels, if the samples prepared carefully.
Abstract: In order to search the correlation between textural properties and geometrical heterogeneity in clays, as characterized by the surface fractal dimension, we used, three different cationic clays; namely Kaolin of Hamam Dbagh, Montmorillonite (Mt) of Maghnia and a sample prepared from Sodium Montmorillonte (Na-Mt)) and three different synthetic anionic clays, ZnAlCO3, MgAlCO3 at a molar ratio equal to three (R=3), and NiAlCO3 with different molar ratios (R=2, R=3 and R= 4). This DS parameter was evaluated from nitrogen (N2) analysis gas. the fractal Frenkel-Halsey-Hill (FHH) (DS) models was used to estimate the surface fractal dimensions at two ranges of relative pressure, the first between 0.08 and 0.22, which were found Ds to be 2.59, 2.53 and 2.68 from Kaolin, Montmorillonite and Sodium Montmorillonte clays respectively and 2.33, 2.61, 2.53, 2.56 and 2.56 for ZnAlCO3 and MgAlCO3, NiAlCO3 (2, 3 and 4) respectively, and other at medium relative pressure, which there was an excellent linear adjustment for F-H-H equation within the range between 0.37 and 0.82, which were found Ds to be 2.77, 2.64 and 2.82 for Kaolinite, Montmorillonite and Sodium Montmorillonte clays respectively, and 2.68, 2.64, 2.40, 2.60, 2.47 for ZnAlCO3, MgAlCO3, NiAlCO3 (2, 3 and 4) respectively. SEM Characterization confirmed the heterogeneous distribution of the particles and the BET analysis confirmed the fractal nature of the surface of these materials. The zeta potential of the sample which is most used as an indicator of dispersion stability, show a proportionality between increases of zeta potential with increase of dimension fractal (DS), for the same type of clays ( (NiAlCO3) with (R=2, 3 and 4) and Mt, Na-Mt). Key words: Anionic clays; Cationic clays; Fractal dimension; geometrical heterogeneity; Frenkel-Halsey-Hill model.
Abstract: This paper examines the modeling, simulation and optimization of CMOS–MEMS integrated pressure sensor based on suspended gate MOSFET. The pressure Sensor consists of a square poly silicone suspended membrane, which is the movable gate of the NMOS. This NMOS is designed using 2 μm CMOS technology. The mathematical model describing the complete behaviour of the PSFET pressure sensor has been described. Finite element method (FEA) based COMSOL Multiphysics is utilized for the simulation of pressure sensor. The simulation results show that, the output current of the pressure sensor varied from 355 to 3624 μA as the pressure changed from zero to 180 kPa and high pressure sensitivity of 15,18μA/kPa. Furthermore, this study emphasizes on the influence of the channel geometric parameters on the aforementioned characteristics to optimize the sensor performance.
Abstract: This work consists of the analysis of the bending responses of porous Ceramic-Metal functionally graded (FG) rectangular plates are investigated according to high order shear deformation theory. The proposed theory contains four unknowns unlike the other theories which contains five unknowns, but it checks the boundary conditions without constraints on the upper and lower plate surfaces. Both the effect of shear strain and normal deformation are included in the present theory and so it does not need any shear correction factor. The equilibrium equations according to the porous FG plates Ceramic-Metal are derived. The solution of the problem is derived by using Navier’s technique. Numerical results have been reported, and compared with those available in the open literature for non-porous plates. Effects of the exponent graded and porosity factors are investigated.
Abstract: Shear wall system is used as one of the most lateral load resisting systems in mulit-story building. Shear wall is quite effective in resisting wind and seismic load in medium-rise and high-rise building. Shear wall provided high stiffness and strength, which can be used to resist large lateral as well as vertical load, making the performance of the building beneficial in various wind load conditions. This study has been focused on the displacement of the different lateral load resisting system for high-rise buildings under various wind load conditions. In this paper, a study was carried out by changing the locations of shear wall radically to determine the structural configuration of a multistory building accordantly. This study has been focused on the effect of addition of shear wall at different location and configuration in buildings without shear wall as well as with shear wall. Besides that, from the software results, the behavior of the shear wall with and without opening was able to observed by obtaining the lateral displacement when acted by 10kN point load at the top left of the wall. The accuracy of the software was able to verify by comparing the result obtained from ETABS and SAP2000 and it was found that the percentage difference between values obtained from that two software is below 20 percent. The maximum lateral displacement at 40m/s and 50m/s is 1.8 and 2.8 times bigger than maximum lateral displacement at 30m/s respectively. The lateral displacement of the shear wall increases as the opening size increases.
Abstract: The Stirling Duplex concept, in which a Stirling engine drives a Stirling heat pump, has many energy and environmental benefits. This machine is essentially composed of three movable elements, a working piston and two displacers, in the same enclosure. The machine has two circuits of non-polluting working fluid, in both parts, engine and refrigerator.The compatibility of the Stirling machine with any type of thermal energy as an external combustion engine contributes to its industrial interests and scientific research. In this paper, a study is presented to estimate Stirling Duplex$'$s parameters and efficiencies by considering the adiabatic model. It appears that the Stirling Duplex is more efficient as a heat pump than as a refrigerating machine.