International Journal of Engineering
Volume:24 Issue: 1, Feb 2011

Abstract An investigation into the mixed mode fracture of steel fiber reinforced concrete (SFRC)beams with one percent volume fraction of steel fiber is presented. A series of notched beams withdifferent notch depths and locations are tested under three-point bending. The test results for apparentfracture toughness, crack trajectories, and fracture energy are presented. The crack paths for SFRCand plain concrete beams are compared. The apparent fracture toughness values were more scatteredfor SFRC than for plain concrete. The load-deflection curves were used to obtain the fracture energy.To this end, two methods were utilized for center notched beams, and the results were comparable toeach other. It is observed that fracture energy is a more reliable material property than apparentfracture toughness, and its scatter is less.

In design of a parallel resonant induction heating system، choosing a proper capacitancefor the resonant circuit is quite important. The capacitance affects the resonant frequency، outputpower، Q-factor، heating efficiency and power factor. In this paper، the role of equivalent seriesresistance (ESR) in the choice of capacitance is significantly recognized. Optimal value of resonancecapacitor is achieved by using genetic algorithm method under voltage constraint for maximizing theoutput power of an induction heater، while minimizing the power loss and inverter switchingfrequency at the same time. Based on the equivalent circuit model of an induction heating system، theoutput power، and the capacitor losses are calculated. The effectiveness of the proposed method isverified by computer simulations.

The advent of e-commerce has prompted many manufacturers to redesign their traditionalchannel structure by engaging in direct sales. In this paper, we present a dual channel inventory modelbased on queuing theory in a manufacturer-retailer supply chain, consisting of a traditional retailchannel and a direct channel which stocks are kept in both upper and lower echelon. The systemreceives stochastic demand from the both channel which each channel has an independent demandarrival rate. A lost-sales model which no backorder is allowed is supposed. The replenishment leadtimes are assumed independent exponential random variables for both warehouse and the retail store.Under the replenishment inventory policy, the inventory position is kept constant at a base-stocklevel. To analyze the chain performance, an objective function included holding, lost sales andtransportation cost is defined. Simulated Annealing is used to find a good solution for inventory levelin each echelon. At the end, we conduct a parametric analysis to study the effect of replenishment ratebetween warehouses on total cost and indicate how to decrease total cost by choosing a suitabletransportation system.

In this paper, the transportation problem under the carbon emission trading program ismodelled by mathematical programming and genetic algorithm. Since green supply chain issuesbecome important and new legislations are taken into account, carbon emissions costs are included inthe total costs of the supply chain. The optimisation model has the ability to minimise the total costsand provides the best solutions, which are both cost-effective and environmentally friendly.Moreover, a mathematical model and genetic algorithm are used to simulate the developments whencarbon emission costs are changed and when companies are committed penalty charge. Finally, theresult is shown the genetic algorithm technique is feasible in transportation network planning.

The cup drawing is a basic deep drawing process. Thus, understanding the mechanics ofthe cup drawing process helps in determining the general parameters that affect the deep drawingprocess. There are mainly two methods of analysis; experimental and analytical/numerical.Experimental analysis can be useful in analyzing the process to determine the process parameters thatproduce a defect free product. However, experimental work is usually very expensive and timeconsuming to perform. On the other hand, the Analytical/Numerical modeling can be used to modeland analyze the process through all stages of deformation. This approach is less time consuming andmore economical than experimental analysis. There have been several efforts to solve and analyze thedeep drawing problem. Among these are the attempts to analyze the cup drawing process, by fewresearches who developed analytical models for the cup drawing process to solve for stresses andstrains over the deforming sheet metal. However, they did not explain how to determine the movingboundaries in the deforming sheet. This paper deals with the analysis of deep drawing of circularblanks into axi-symmetric cylindrical cups forming using numerical modeling. A rigid plasticmaterial model with the variational approach is used for this analysis. The amount of draw obtainablein the drawing process has been related both theoretically and experimentally with the initial diameterof the blank. The strains in the radial and circumferential directions have been measured. Acorrelation on the flange thickness variation by taking into account the work hardening with theanalytical and experimental values also has been arrived at.

The tests were carried out with the spark timing adjusted to the maximum brake torquetiming in various equivalence ratios and engine speeds for gasoline and natural gas operations. In thiswork, the lower heating value of gasoline is about 13.6% higher than that of natural gas. Based on theexperimental results, the natural gas operation causes an increase of about 6.2% brake special fuelconsumption, 22% water temperature difference between outlet and inlet engine, 3% exhaust valve seattemperature, 2.3% brake thermal efficiency and a decrease of around 20.1% maximum brake torque,6.8% exhaust gas temperature and 19% lubricating oil temperature when compared to gasolineoperation. The results also revealed that, over the entire range of engine speed and equivalence ratio, theexhaust gas temperature and the lubricating oil temperature for gasoline operation is higher than that ofnatural gas operation while the exhaust valve seat temperature for natural gas operation is higher.

In this paper, we develop a mathematical model of sprinting in which anaerobicmetabolism is included. This model is simplified by considering the broad changes of energy leveland the cyclic variation associated with the strike pattern. We consider the effect of the centre of massto the overall energy balance along with force of resistance during initial motion of body. Results areobtained for the model from an event of a sprint championship. These computed results closelypredict the overall average performance of the participants over the course of entire race.

The present work involves numerical simulation of a steady, incompressible forcedconvection fluid flow through a matrix of porous media between two parallel plates at constanttemperature. A Darcy model for the momentum equation was employed. The mathematical model forenergy transport was based on single phase equation model which assumes local thermal equilibriumbetween fluid and solid phases. Single phase equation was derived by volume averaging on controlvolume. This model was modified by addition of dispersion terms.The results of this investigation were compared with two phase simulation’s results. Implementationof two phase model was expressed by separate energy equations of each solid and fluid phase. Theresults show that in many cases there are no significant differences between two approaches.However better compatibility of single phase model’s results with empirical results and no possibilityof determining the empirical parameters of two phase model, was observed.

numerical investigation has been carried out for mixed convection flow in a rectangularventilated cavity with a heat conducting solid circular cylinder at the center. Forced convection flowconditions were imposed by providing an inlet at the bottom of the left wall and an outlet vent at the topto the other sidewall. In this paper, the effect of cavity aspect ratio as well as the mixed convectionparameter on the flow and heat transfer characteristics were analyzed. Finite element method was used tocarry out the investigation. Computations were done for mixed convective flow with the Richardsonnumber Re ranging from 0.0 to 5.0, cavity aspect ratio from 0.5 to 2.0 and Reynolds number, Re of 100. The basic nature of the resulting interaction between the forced external air stream and the buoyancydrivenflow by the heat source was explained by the patterns of the streamlines and isotherms. Thecomputational results indicated that the flow and thermal fields as well as average Nusselt number at thehot wall, average temperature of the fluid and the temperature at the cylinder center strongly dependedon the cavity aspect ratio and mixed convection parameter Ri.