International Journal of Advanced Design and Manufacturing Technology
Volume:5 Issue: 3, Sep 2012

Recently, offshore and ocean engineering have been dealing with novel materials that play a significant role in reducing the weight of structures used in the ship construction industry. 5XXX series of aluminum alloys are of the novel alloys are suitable for construction of ship hulls and the topside structures of offshore platforms. Within different 5XXX aluminum alloys, AA5083 is of great importance which is extensively used in the ship construction industry. In the present study, formability of AA5083-H111 aluminum alloy is investigated in room temperature by using uni-axial tensile tests and hydraulic bulge tests. Tensile tests were performed to evaluate materials anisotropy in different directions with respect to rolling direction. Anisotropy coefficients were then used to correct flow stress curves obtained by balanced biaxial bulge tests. Moreover, flow stress curves obtained from both tests were separately introduced to an explicit commercial finite element code. Comparisons showed that numerical simulation done in this study stand in according with the experiments.

Porous materials are commonly found in nature and as industrial materials such as wood, carbon, foams, ceramics and bricks. In order to use them effectively, their mechanical properties must be understood in relation to their micro-structures. Foam made from non-flammable metal will remain non-flammable and the foam is generally recyclable back to its base material. This research work is mainly concentrated in producing porous aluminum castings using melt route Metallic foams typically retain some physical properties of their base material thus density and % Porosity is found. Porous castings were developed by melt route using soaked Precursors, steel net, aluminum net and by casting around granules technique.

One of the methods to reduce the emissions in a diesel engine is by oxygen introduction into the combustion chamber which can be done by supplying the oxygen into the inlet manifold during suction stroke. Oxygen affects different parameters such as brake thermal efficiency, fuel consumption, NOx and smoke at different load conditions. Load test was conducted for various concentrations of oxygen (21 to 27 percent) in terms of 2%. It is found that oxygen enrichment leads to better combustion which in turn results in less fuel consumption and an increase in brake thermal efficiency. It was found that about 25% oxygen enrichment in the inlet air results in the optimum performance and emission characteristics. The result shows that varying oxygen enrichment in the inlet air increases brake thermal efficiency and subsequently decreases brake specific fuel consumption. It was also found that an oxide of nitrogen (NOx) increases exponentially whereas smoke intensity falls bellow the normal level. One of the methods to reduce the emissions in a diesel engine is by oxygen introduction into the combustion chamber which can be done by supplying the oxygen into the inlet manifold during suction stroke.

Fused deposition modeling (FDM) is a filament based rapid prototyping system provides us to manufacture real parts with multiple production-grade materials, such as ABS-M30, PC, PPSF and PC-ABS blend. Fused deposition modeling technology, essentially perform using layer manufacturing process. More complex 3D physical models can be efficiently fabricated without geometric limitation by this technology; a remarkable reduction in production life cycle has been achieved. However, due to the Layer Manufacturing process, stair case effect is unavoidable which results in poor surface finish. In this paper, the surface roughness of a model having surfaces at different angles produced by fused deposition modelling machine is analyzed to understand the effect of different angled surfaces on the surface roughness of the model of FDM produced part model.

In this paper an efficient dual time implicit approach is used to solve viscous laminar flow around two bodies with general motion. Therefore, the grid includes a background grid and two sets of grids around the moving bodies. Rotational and translational motions of two bodies are managed separately in this grid arrangement. In this work the overset concept for hybrid grid is used and flow variables are interpolated with a simple method. The unsteady two dimensional Navier-Stokes equations are discretized using an implicit dual time stepping method. To accelerate convergence, the local pseudo-time stepping and implicit residual averaging are applied. To evaluate the present method, moving cases including rotational and translational motions are solved and the results are compared with experimental and numerical data.

Investigations are carried out to evaluate the performance of a low heat rejection (LHR) diesel engine consisting of air gap insulated piston with 3-mm air gap, with superni (an alloy of nickel) crown and air gap insulated liner with superni insert with different operating conditions of crude jatropha oil with varied injection timing and injection pressure. Performance parameters of brake thermal efficiency (BTE), exhaust gas temperature (EGT) and volumetric efficiency (VE) are determined at various magnitudes of brake mean effective pressure. Pollution levels of smoke and oxides of nitrogen (NOx) are recorded at the peak load operation of the engine. Combustion characteristics of the engine of peak pressure (PP), time of occurrence of peak pressure(TOPP), maximum rate of pressure rise (MRPR) and time of occurrence of maximum rate of pressure (TOMRPR) are measured with TDC (top dead centre) encoder, pressure transducer, console and special pressure-crank angle software package. Zero dimensional, multi-zone combustion model is assumed to predict combustion characteristics and validated with experimental results. Conventional engine (CE) showed deteriorated performance, while LHR engine showed improved performance with crude jatropha oil operation at recommended injection timing and pressure and the performance of both version of the engine is improved with advanced injection timing and higher injection pressure when compared with CE with pure diesel operation. Peak brake thermal efficiency increased by 4%, smoke levels decreased by 4% and NOx levels increased by 37% with vegetable oil operation on LHR engine at its optimum injection timing, when compared with pure diesel operation on CE at manufacturer’s recommended injection timing.

Hydro-forming is a fabrication process that uses a fluid medium to form a piece by using high internal pressure. In tube hydro-forming, a tubular blank is placed between two dies, sealed and pressurized water injected, deforming the tube walls in the cavity form of the dies. Exist Several typical hydro-forming processes such as T- shapes, cross-shapes and Y- shapes. Successful hydro-forming depends on selection of proper tubular blank, sound preform shape and internal pressure. In this paper, 3D model of hydro-forming process of T-shape tube has been simulated by finite element method. Two damage model, coupled with von Mises plastic criterion, have been applied to predict where and when onset of ductile and MSFLD rupture occur in the process. All studies presented in this paper have been carried out on aluminium alloy EN AW-7108 T6.

The present study analizes a trigeneration system based on an internal combustion engine and a steam ejector refrigeration system from an energy point of view.

This paper proposes a control strategy for a cable-suspended robot based on sliding mode approach (SMC) which is faced to external disturbances and parametric uncertainties. This control algorithm is based on Lyapunov technique which is able to provide the stability of the end-effecter during tracking a desired path with an acceptable precision. The main contribution of the paper is to calculate the Dynamic Load Carrying Capacity (DLCC) of a spatial cable robot while tracking a desired trajectory based on SMC algorithm. In finale, the efficiency of the proposed method is illustrated by performing some simulation studies on the ICaSbot (IUST Cable Suspended Robot) which supports 6 DOFs using six cables. Simulation and experimental results confirm the validity of the authors’ claim corresponding to the accurate tracking capability of the proposed control, its robustness and its capability toward DLCC calculation.

A thermodynamic analysis of the counter flow wet cooling tower (CWCT) in the Steelmaking unit of the Khuzestan Steel Company (KSC) is performed in this paper. We evaluated both energy and exergy formulations for analyzing the heat and mass transfer, exergy and second-law efficiency in this cooling tower. The Lewis factor Lef is an indication of the relative rates of heat and mass transfer in an evaporative process. In many performance analyses of the cooling tower, Lef is assumed to be 1 in order to simplify the heat and mass transfer equations between air and water. If so, evaporative loss is negligible. But in this paper, although heat and mass transfer equations and their numerical solutions are more complicated, Lef is calculated for all parts of the tower in order to achieve more accurate results in predicting air and water conditions into the cooling tower in the analysis on the performance of this cooling tower.

In this study, the effect of wall orientation on the optimum insulation position in the wall from different perspectives is studied numerically. Using Crank- Nicolson One dimensional transient heat conduction equation is solved for the wall with convection boundary conditions. Outdoor temperature is considered as a periodic function of time. Since natural night ventilation is used in the building, indoor temperature is constant during day time while air conditioning (AC) system is ON and is time dependent when AC is OFF. A time dependent indoor temperature is calculated and used as a boundary condition at the wall inner side. For the position of insulation in the wall six practical configurations are considered and time lag (TL), decrement factor (DF) and total conduction heat gain (TCHG) is calculated for all configurations. It is seen that, from minimum TCHG perspective, the best configuration for all directions is when insulation is used in the inner side of the wall. The minimum TCHG is occurred at an angle of 200⁰ from the south. It can be concluded that different perspectives may lead to different results for the optimum insulation position in the wall.

In this study, Al2O3–SiC nanocomposites have been fabricated by mixing of alumina powder containing 0.05% weight magnesium oxide and silicon carbide nano powders, followed by hot pressing at 16500C. The mechanical properties of Al2O3-SiC nanocomposites containing different volume fraction (2.5, 5, 7.5, 10 and 15%) of nano scale SiC particles were investigated and compared with those of alumina. The MgO additive was able to promote the densification of the nanocomposites. Al2O3-SiC powders were prepared by planetary milling in isopropanol. The fracture mode and microstructure of specimens was investigated by means of scanning electron microscopy. The nanocomposites were tougher compared to alumina when they were hot pressed at the same temperature. The young’s modulus is decreased by increasing the volume percent of SiC. The values hardness and fracture toughness of the nanocomposites is increased by increasing the volume percent of SiC up to 7.5% and then decreased slightly. The ballistic energy dissipation ability is decreased by increasing the volume percent of SiC up to 5% and then increased slightly. The Scanning electron microscopy observations showed that fracture mode is changed from intergranular for alumina to transgranular for nanocomposites. It also shows the growth of grain is decreased by increasing the volume fraction of SiC particles. Finally X-ray diffraction analysis indicated that there was no chemical reaction between Al2O3 and SiC particles.

Compaction under tractors tires is of special concern because the weight of these machines has increased dramatically in the last years. These machines and others associated with crop cultural practices weight enough to significantly compact the soil, especially if the soil is soft with high moisture content during tilling, planting, or harvesting. The stress distribution and the size and form of the tire-soil interface are decisive for the stress propagation in the soil profile. The finite element method is a very useful numerical tool in evaluating different effects of tire on the soil. The goals of this study are to model the response of a soft soil, in relation to tire pressure and axle load. To validate the model by comparison with measured responses in the literature for such a soil and develop the 2D symmetric multi-laminated model of a tractor tire interaction with soft soil and to verify the result with measured field response data reported in the literature. In this study we use a (2D) axisymmetric tire model for the numerical simulation of soil-tire interaction under different load and inflation pressure. The Maximum soil-tire pressure for 70 kpa inflation pressure and 15kN axel load was 83.7 kpa which were approximately 30% less than the stress at the tire contact patch in the field test as cited in the literature. Although in previous investigations with a 3D analysis the difference was 36%. Maximum vertical stress at contact area with 150kPa inflation pressure and 15 kN axel load was 98.6 kPa that was not significantly different than was 101 kPa reported with 3D analysis. In general, more accuracy in 2D compared than whit 3D analysis was obtained due to more accurate meshing in 2D analysis. This investigation shows that maximum stresses in tire occurred at the side wall. Results showed that a simple 2D axisymmetric model can show soil-tire stresses whit good accuracy.