Iranian Journal of Science and Technology Transactions of Mechanical Engineering
Volume:38 Issue: 1, 2014

In this paper, the Hamilton's principle is implemented to derive the coupled partial differential equations of motion of composite sandwich beams with viscoelastic core. The sandwich beams model is based on the higher order theory for composite sandwich beams with viscoelastic core, which regards independent transverse displacements for the face sheets with linear variations along the depth of the core. The core Young's modulus and the beam rotary inertia effects are also taken into account. Frequency response analysis is examined by applying the Galerkin discretization approach on the adimensional equations of motion. The results are validated by comparison with the existing literature. An interesting study is managed for the frequency response sensitivity analysis to the core shear modulus variation. The novelty of this work, besides the study of the fiber angle effects on the frequency response, is finding more logical relationships for regarding or discarding the core Young's modulus and the beam rotary inertia contributions, during the frequency response analysis of the beam. The results indicate the significant role of the core Young's modulus and the beam rotary inertia effects on the frequency response of the beam. The outcomes illustrate regarding the core Young's modulus, contribution hardens the structure while consideration of the beam rotary inertia softens the structure.

A study on the effect of fiber length and fiber surface modification on tensile property of alkaline treated coir fiber reinforced epoxy composites is presented in this paper. The fiber surface treatment was carried out using Sodium Lauryl Sulfate (SLS) solution at five different concentrations, 2%, 4%, 6%, 8% and 10% respectively. Each group of the coir fiber was treated for 10 days. For each group the coir fibers experiments were conducted for different fiber lengths namely 10, 20, and 30mm. The SLS treated coir fiber was used as a reinforcement and epoxy was used as a matrix to fabricate the composites. The tensile strength of different samples of composites was measured. Increased SLS concentration in fiber treatment was found to increase the tensile strength up to 4% and further increase in SLS concentration reduced the tensile strength, also, experimental results showed that an increase in fiber length increased tensile strength. The maximum tensile strength of the composite was found to be uniformly occurring for 4% SLS with 30mm fiber length composite samples. Based on the nonlinear regression analysis the tensile strength equation was proposed for coir fiber reinforced epoxy composites.

Isogeometric analysis is a recently developed numerical technique that uses NURBS basis functions instead of Lagrange polynomial basis functions used in standard finite element method. This allows the analysis to be done with the exact CAD geometry that it is based on. However, the non interpolatory property of NURBS basis functions makes the essential boundary condition imposition to be no longer applicable, directly on the control values. Therefore, a technique such as penalty method or fitting of the boundary data onto the span of the basis functions is needed. Such techniques usually lead to additional computational complexity or cost. In the present paper, a simple pointwise approach is proposed to accurately impose essential boundary conditions in the isogeometric analysis. The method is based on the collocation of boundary conditions in distinct points on the boundary using NURBS basis functions. Some numerical examples in heat conduction and linear elasticity are used to evaluate applicability and accuracy of the proposed method. It is shown, through demonstrative numerical examples, that the present method can improve the accuracy of the isogeometric analysis.

In this paper, the meshless local Petrov-Galerkin (MLPG) method is used to analyze the dynamic fracture of an isotropic FGM plate containing a center crack. The dynamic stress intensity factors are studied under the influence of various non-homogeneity ratios. Both the moving least square (MLS) and the direct method have been applied to estimate the shape function and to impose the essential boundary conditions. The enriched weight function method is used to simulate the displacement and stress field around the crack tip. Normalized dynamic stress intensity factors (NDSIF) are calculated using the path independent integral, J*, which is formulated for the nonhomogeneous material. To validate the method, the homogenous center cracked plate problem is analyzed. The obtained results show good agreement between the analytical solution and the MLPG results for homogenous material. After validation, a center cracked plate made of FGM with two different material gradations (along and normal to the crack length) and three different lengths of FGM zone under the effect of step load are considered, and the following six distinct problems are studied here.

An attempt has been made to discuss the behaviour of a magnetic fluid based squeeze film between rough porous truncated conical plates by taking into consideration the effects of bearing deformation and slip velocity. Taking recourse to a different type of probability density function, the model of Christensen and Tonder has been adopted to evaluate the effect of transverse surface roughness and the concern stochastically averaged Reynolds’ type equation has been solved to derive the expression for pressure distribution. This results in the calculation of load carrying capacity. The graphical representations make it clear that although the combined effect of bearing deformation and slip velocity is relatively adverse the magnetic fluid lubricant saves the situation to a limited extent, at least in the case of the negatively skewed roughness. For an overall improvement of performance of bearing system, the slip parameter should be minimized. A suitable combination of aspect ratio and semi vertical angle may lead to some compensation for negative effect of deformation, especially when variance (negative) is involved.

In this study, the temperature distribution of an AISI 304 stainless steel during gas tungsten arc welding is modeled by using the Goldak's three-dimensional moving heat source. A C++ program is developed in order to employ the heat inputs into finite difference thermal simulation of the welded plate. By simulating the temperature distribution and shape of the weld pool, effect of welding parameters such as current and welding speed on the sensitization, weld width and weld depth are evaluated. Results show that the width and depth of weld and sensitized zone increase with raising the current while the sensitization location decreases. The effect of welding speed is vice versa. To verify the simulated results, currents of 160, 200 and 240 A and welding velocity of 2 mm/s are selected for experiments. Good agreement is obtained between the simulated and experimental results.

In this investigation, Control Volume based Finite Element Method is applied to simulate the effects of different governing parameters on natural convection heat transfer in an inclined L-shape enclosure filled with Cu-water nanofluid. The numerical investigation is performed at a fixed Prandtl number (Pr) equal to 6.2 and various values of non dimensional governing parameters namely, volume fraction of nanoparticles, Rayleigh number and different inclination angles. The results show that for Ra =104 the maximum and minimum average Nusselt number correspond to ζ = -45ͦ and 45ͦ, respectively, whereas an opposite trend is observed for Ra =105.

This project mainly focuses on maximising the production of distillled water by emphasizing three important factors: decrease in depth of water, increase in exposure area and temperature of the saline water. In this work, to augment the evaporation and temperature of the still basin water, the basin is made by glass material because of its good absorption. The stepped type basin is composed of four trays. Each tray is detached into top and bottom trays. The depending water enters the top trays (evaporating zone) where evaporation takes place depending on depth provided by the glass strip. The overflow water driven to the bottom tray (heating zone) through the gap provided in the separation glass will be further heated and made to flow through the subsequent trays. Modifications such as sponges to increase the exposure area, sensible heat materials like sand, and metal scraps to increase the saline water temperature, glass cubes with dry salt, camphor, aluminum scraps and charcoal to increase both saline water temperature and exposure area showed subtle improvement in the production rate. Experimental results were compared with ordinary basin type still. Theoretical evaluation was also done and is closer to the experimental values.

Direct injection diesel engine offers the benefit of better fuel economy over gasoline engine. Diesel engine with electronic control of high pressure, multiple injections per cycle, 4 valves per cylinder, turbocharged with intercooled, cooled EGR or SCR and DPF have now become the key features to meet the upcoming emissions in India. This paper describes the work done on multi-cylinder diesel engine to meet the requirements of Bharat stage 5 emissions and has the potential to meet Euro6 emission norms. Vehicle simulation model developed by using AVL cruise software was used to find out the engine steady state speed-load point’s equivalent to Bharat stage 5 emission test cycle. Engine emission development was done on test bench using these speed-load points. Engine was optimized with new hardware, namely piston bowl with reduced compression ratio, high capacity EGR cooler and turbocharger to attain the desired emission level. Diesel oxidation catalyst and coated diesel particulate filter (cDPF) loading were optimized to reach Bharat stage 5 emission norms. Vehicle with Selective Catalyst Reduction (SCR) with average 60% conversion efficiency has the potential to meet Euro6 norms.

In this paper, turbulent flow causing erosion in Tunnel 1 of Tarbela Dam using Reynolds Stress Model considering the effect of sediment particles is discussed. Velocity, pressure and erosion rate results are presented for three different water heads in the reservoir i.e., considering summer, winter and average seasons both for one-way and two-way/full coupling. Erosion rate is concluded the maximum at main bend and outlets at high head at full coupling. Numerical results are compared with the experimental erosion results for the scale down model of almost similar geometrical components. In addition, maximum loss of mass at T section in the loop with time is concluded.

In this study, thermal performance of a proposed point-focus solar collector for low power applications was estimated under different operating variables. For this purpose, theoretical analysis was employed with varying relevant parameters, using a set of thermodynamics and energy equations, i.e., ambient temperature, beam solar insolation, wind speed, wind incidence angle and wall temperature of the absorber. The results show decreasing trend of the wind incidence angle along with increasing the convective heat loss coefficient as the highest related values obtained under head-on wind flow, but the wall temperature of the absorber exerts negligible influence. The maximum thermal efficiency of 79.68% was obtained in August with the side-on wind flow of 4.9􀝉⁄􀝏 and an ambient temperature of 29.2􀔨 when the absorber wall temperature has a minimum value of 150􀔨.

Information about the temperature of drilling hole during the drilling process is important in work-piece quality and tools life aspects. In this study temperature of the drilling hole is determined using Artificial Neural Networks according to certain points’ temperature of the work piece and two parameters, drill diameter and ambient temperature. To achieve this aim, twodimensional model of work piece is provided; then by Computational Heat Transfer simulations based on Finite Volume Method, temperature in different nodes of the work piece is specified. Obtained results are used for training and testing the neural network. Temperature of specified points, drill diameter and ambient temperature are selected as inputs of the network and temperature of drilling hole is considered as an output data. Also, for comparison, temperature is obtained experimentally. Comparison between numerical results and experimental data shows that neural network can be used more efficiently to determine temperature of hole in a drilling process.