Showing papers in "International Journal of Engineering - Transactions C: Aspects in 2014"

Analytic approach to free vibration and buckling analysis of functionally graded beams with edge cracks using four engineering beam theories

Abstract: A complete investigation on the free vibration and stability analysis of beams made of functionally graded materials (FGMs) containing open edge cracks utilizing four beam theories, Euler-Bernoulli, Rayleigh, shear and Timoshenko, is performed here. It is assumed that the material properties vary along the beam thickness exponentially and the cracked beam is modeled as two segments connected by two mass-less springs, extensional and rotational spring. Afterward the equations of motion for the free vibrations and buckling analysis are established and solved analytically for clamped-free boundary conditions. A detailed parametric study is also performed to examine the influences of the location and depth of the crack, material properties and slenderness ratio of the beam on the free vibration and buckling characteristics of cracked FGM beams for each of the four engineering beam theories.

A Size-dependent Bernoulli-Euler Beam Formulation based on a New Model of Couple Stress Theory

Abstract: In this paper, a size-dependent formulation for the Bernoulli-Euler beam is developed based on a new model of couple stress theory presented by Hadjesfandiar i and Dargush. The constitutive equation obtained in this new model, consists of only one length scale parameter that is capable of capturing the micro-structural size effect in predicting the mechanical behavior of the structure. Having one length scale parameter is claimed to be an advantage of the model in comparison with the classical couple stress theory. The governing equations and boundary conditions of the Bernoulli-Euler beam are developed using the variational formulation and the Hamilton principle. The static bending and free vibration problems of a Bernoulli-Euler beam with various boundary conditions are solved. Numerical results demonstrate that the value of deflection predicted by the new model is lower than that of the classical theory. It is also found that natural frequencies obtained by the present couple stress model are higher than those predicted by the classical theory. The differences between results obtained by the present model and the classical theory become significant as the thickness of the beam gets close to the length scale parameter of the beam material

Optimization of Double Pipe Fin-pin Heat Exchanger Using Entropy Generation Minimization

Abstract: In the current work optimization of double pipe fin-pin heat exchanger has been studied The effective parameters those are controlling the heat exchanger performance are divided in two categories; geometrical and operating conditions Using the Brent’s optimization algorithm and handling the thermodynamically design concept, one can minimize entropy generation in different length of heat exchanger In this paper, pins longitudinal SL and transversal ST distances are chosen as the design variables in different heat exchanger length between 200 and 920 mm In all calculations a constant value was applied for the ratio of heat flux to the heat exchanger length as Results showed that, in all conditions entropy generation number decreased and consequently lead to reduction in pumping power and manufacturing costs

A Node-based Mathematical Model towards the Location Routing Problem with Intermediate Replenishment Facilities under Capacity Constraint

Abstract: In this paper, we study the location routing problem with intermediate replenishment facilities (LRPIRF), an extension of the location routing problem (LRP), where the vehicles can replenish at some intermediate facilities. Vehicles leave the depot with load on-board, serve customers until out of load, may return to an intermediate facility to replenish, and finally return to the depot, completing their route. In this paper, we initiate a mathematical mixed integer programming model with new kind of subtour elimination constraints for this problem. Moreover, the facility location phase is considered besides vehicle routing phase in our problem. The objective of the problem is to find routes for vehicles to serve all customers at a minimal cost in terms of total travel cost and total facility location cost, without violating the capacity constraint of the vehicles. The solution to the LRPIRF is obtained through CPLEX solver in commercial software GAMS 23.5.1 ,Genetic Algorithm and Tabu Search algorithm. Computational results are obtained on a set of randomly generated instances and indicate the effectiveness of the proposed algorithms in terms of solution time and quality.

Tracking and Shape Control of a Micro-cantilever using Electrostatic Actuation

Abstract: In this paper the problems of state estimation, tracking control and shape control in a micro-cantilever beam with nonlinear electrostatic actuation are investigated. The system’s partial differential equation of motion is converted into a set of ordinary differential equations by projection method. Observabillity of the system is proven and a state estimation system is designed using extended Kalman filter (EKF) algorithm. A tracking control system is designed to make a specific point of the beam follow a reference signal. The effect of mode selection to include in model on controller performance is also investigated. Based on the tracking controller a shape control algorithm is designed to form the shape of beam into a desired shape. The proposed algorithms are validated by numerical simulation and resulted in a promising performance.

An Optimized PID for Capsubots using Modified Chaotic Genetic Algorithm (RESEARCH NOTE)

Abstract: This paper proposes a design for a mesoscale capsule robot which can be used in gaining diagnostic data and delivering medical treatment in inaccessible parts of the human body. After modeling the capsule robot system and determining its transfer function, an approach is presented for the capsule robot to control it: A PID-controlled closed-loop approach. A modified chaotic genetic algorithm is proposed in order to optimize the coefficients of the PID controller. Then, simulations are conducted to demonstrate the results for the proposed approach. Finally, the results are compared with those of similar works in the literature. doi: 10.5829/idosi.ije.2014.27.09c.07

Hotel Location Problem Using Erlang Queuing Model under Uncertainty (RESEARCH NOTE)

Abstract: Determining and selecting an appropriate location to construct a hotel is one of the most challenging concerns which hotel industry investors are facing with. In this study we attempt to find a suitable response to this research/application need by a mathematical model using the queueing theory and the fuzzy logic. Therefore hotel, the reception system and travelers accommodations are formulated by appropriate queueing models. Considering the fact that the arrival rate for hotel and the amount of time spent in hotel is uncertain thus a profit function is defined using the fuzzy logic and the fuzzy queueing models. Using the values of this function, candidate locations for constructing a hotel are compared and the one with maximum profit for the investors is selected. Due to using fuzzy parameters in the profit function, the amounts of profit obtained for different locations are in the form of fuzzy numbers, thus we use fuzzy ranking techniques to prioritize the candidate locations for constructing the hotel.

Optimal Thermodynamic Design of Turbofan Engines using Multi-objective Genetic Algorithm

Abstract: The aim of this study is to optimize the performance functions of turbofan engines. In this way, the multi-objective genetic algorithm is employed to optimal design of turbofan with considering the offdesign model of engine. The design variables are high-pressure compressor pressure ratio, lowpressure compressor pressure ratio, fan pressure ratio and bypass ratio. They are calculated in such a way that the performance functions are at their best conditions simultaneously. The performance functions are specific thrust at take-off, and thrust specific fuel consumption, propulsive, thermal, and overall efficiencies at cruise. The optimization is carried out using the modified NSGA II which is among the best multi-objective genetic algorithm methods. The results of this optimization will be a set of vectors which the designer may choose one of those according to the problem conditions.

Young s Modulus of Single and Double Walled Carbon Nanocones Using Finite Element Method(TECHNICAL NOTE)

Abstract: In this paper a three-dimensional finite element (FE) model of carbon nanocones (CNCs) is proposed and used for obtaining Young\'s modulus of CNCs. In this model, stretching and bending forces between carbon atoms are simulated using truss elements in ANSYS software. Then the model is subjected to the tension and by obtaining the stiffness of the CNC and using elasticity theory, Young’s modulus is calculated. The results showed that for a fixed length of CNC, the modulus increase with the increase in diameter whereas it decreases by increasing the apex angle. Also, Young’s modulus of double walled carbon nanocoes (DWCNCs) obtained between the values of each layer. Furthermore, it is showed that elastic modulus can be effected by defects and their positions in CNC.

Magnetic Saturation Impacts on Fault Analysis of Squirrel-cage Six Phases Induction Motors using Winding Function Approach

Abstract: Multiple coupled circuit modeling (MCCM) of squirrel-cage induction motors (SCIMs), or winding function approach is the most detailed and complete analytical model used to analyze the performance of faulty SCIMs. Already, in variate papers this approach was used to 3phases SCIMs, but this paper extends the above-mentioned model to 6phases SCIMs. Various simulations of variative faults are carried out on faulty 6phases SCIMs, and then, results obtained the simulation were presented. The innovation in this paper is the first time simulation of broken bars and stator winding faults on 6phases SCIMs using winding function approach with considering magnetic saturation effect that the precise results as well as were presented.

Synthesis of Ethylenediamine-modified Ordered Mesoporous Carbon as a New Nanoporous Adsorbent for Removal of Cu(II) and Pb(II) Ions from Aqueous Media

Abstract: The mesoporous carbon (CMK-3) functionalized with ethylenediamine (EDA) has been synthesized (CMK-3-EDA) and applied as a new mesoporous adsorbent for removal of Cu(II) and Pb(II) cations from aqueous solutions. Nitrogen adsorption–desorption measurements (BET) show that surface area, pore size and pore volume of CMK-3 were significantly changed after amine modification. The BET surface area and pore diameter of functionalized product were 344.74 m2 .g−1 and 28.61A, respectively. The adsorption conditions including contact time, pH value and adsorbent dosage of the sample solution were investigated in batch system and then determined by means of flam atomic absorption spectroscopy. Under experimental conditions, the adsorption capacity was 188.2 mg. g−1 and 196.64 mg. g−1 for Cu(II) and Pb(II) ions, respectively. The obtained high adsorption capacity of CMK-3 functionalized with EDA is due to the amine functional groups formed on the surface of CMK-3 which can react with Pb(II) and Cu(II) ions. Results show that the new synthesized porous material is a highly effective material for sorption of Pb(II) and Cu(II) ions in comparison to other adsorbents.