INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2007 | Volume:18 | Issue:1 (SUPPLEMENT OF MECHANIC ENGINNERING)|Papers Count:13

In this paper, two dimensional analytical solution of heat conduction equation in a hollow sphere, which is subjected to a harmonic boundary condition with an arbitrary function along meridian is presented. The material is assumed to be homogenous and isotropic with time independent thermal properties. To solve the problem, first of all, the boundary condition is assumed to be a constant and by applying the separation of variables method, the temperature distribution in hollow sphere is obtained. Then applying Duhamel's principle, the temperature field under harmonic boundary condition is determined. The validity of the solution is demonstrated by comparing the results for the hollow sphere with the results available for a solid sphere under the same boundary condition.

On of the appropriate methods for evaluating the vibrational behavior of cracked beams is the use of special crack elements in the finite element method. In this method, a crack is considered in the element and the finite element formulation is derived for this special element using the crack tip elastic stresses. In the present research, first a general approach for deriving the stiffness matrix of the special cracked elements is described. The stiffness matrix is then determined for a cracked beam element and for a rectangular element containing an edge crack. Each of these two elements can be used individually for calculating the natural frequencies of a beam containing one or several edge cracks. It is shown that there is a good consistency between the numerical values of natural frequencies obtained from the present research and those of the earlier experimental or computational research studies. The computational time and cost required for the analysis of cracked beams using the special crack element are much less that those of the classical methods.

A method for fatigue life assessment of turbine blades under gas dynamics induced loads is presented. The bending caused by the flow of hot gases over the blade face is determined via flow analysis in turbine cascade. A static bending analysis of the blade is carried out to acquire the stress distribution. The required equivalent dynamic stress coefficients and the damping coefficient of the system (blade attachment to the turbine wheel) are obtained from modal analysis. Using the magnified dynamic bending stresses and the centrifugal stresses, the fatigue life of the blade under resonance and working speed are assessed. The method is applied to J79 turbine blade and the results are in good agreement with given manufacturing specifications. This method is proposed for evaluation of locally manufactured turbine blades.

Reliable operation and long life lasting of engines is very much dependent on accurate engine lubrication system design. A proper design would lead to reduction of fuel consumption, better emission control and power output.Nowadays, numerical methods can be used effectively and economically in engine lubrication system design. In this paper the engine lubrication system is divided to subsystems where these have been studied in detail and governing equations are obtained. An "EngineLubSim" code is developed that has the capability of analyzing the engine lubrication system. This code uses "linearized head correction" method and a successive over relaxation (SOR) approach is used to solve the system of equations. Also a "Bear Load' computer code is developed to calculate the eccentricity in journal bearings resulting from dynamic loading. The combination of these two codes gives a strong tool to analyze the engine lubrication system. The final code is applied to "Peykan" engine which is locally produced. Results show that insufficient oil reach to the middle crankshaft bearing.

The limitation on allowable temperature range of nickel cadmium (Ni-Cd) requires the designers to analysis their thermal behavior with respect to its parameters. Ni-Cd batteries are use in many applications including cordless and portable devices, emergency and standby power, telecommunication equipments, photovoltaic systems, electric vehicle, satellite and spacecraft and power plant supporting equipments. To date, most studies have utilized averaged properties in their analysis. In addition, the chemical reaction effect on the source term has been neglected. The purpose of this study is to numerically investigate the transient thermal behavior of Ni-Cd batteries. The governing equation is the transient and non-linear differential energy equation subjected to non-linear radiation boundary conditions and source term. In formulation of the governing differential energy equation, the Ni-Cd properties (K, C, p) are not constant and the chemical characteristic of the Ni-Cd batteries, source term, vary with location and time. Calculated thermal characteristic of each battery is then compared to experimental results.

In this paper, free vibration of a rotating beam is studied. Cross sectional area, elasticity modulus, moment of inertia, shear modulus, density and rotational speed are modeled as random variables. To study uncertainty, the stochastic [mite element method and second order perturbation technique are applied. The effects of rotational speed, setting angle and random property variances on "Coefficient of Variation" of first mode eigenvalue are investigated. This analysis is carried out for the Timoshenko and Bernoulli-Euler beam theories. Also, to determine the significance of random properties on response variation, a sensitivity analysis is applied. Results show that the first eigenvalue sensitivity curves for Bernoulli-Euler and Timoshenko beam models are approximately identical.

A well known method in nonlinear QFT is to substitution of nonlinear plant by an equivalent linear family of plants. This method is based on the selection of a family of desired functions of the time response of the system. In this paper, a previously developed approach is applied to control an inverted pendulum. This approach is based on the arbitrary selection of output functions. The results show that the implementation of the method is more straightforward and lead to satisfactory results.

Dynamic crack propagation and arrest have been considered. Finite element analysis and remeshing technique have been used to analyze the mode I fracture problem in a DCB specimen. Plane stress condition is invoked in the present two dimensional analyses. Specimens have been made from Epoxy resin (Araldite B). Dynamic fracture toughness criterion has been considered to find the crack propagation velocity and crack tip location in each time step and also is described in detail. According to the new crack tip position, a remeshing technique has been used based upon this new position and then nodal data is transferred from the old mesh to the new mesh according to the elements shape functions. Obtained results involving specimen kinetic and strain energy during crack growth, crack tip velocity, dynamic stress intensity factor and arrest length have been presented. ANSYS 7.0 standard Finite element code and the related APDL programming facilities have been employed for modeling the problem. Comparison of the results with those cited in the literature has been shown good agreement.

Slope stability analysis is a branch of engineering science where there are great uncertainties. Although these uncertainties have strong effects on predicting process, however in common stability, analysis methods their direct effects are not considered. Probabilistic slope stability analysis method is a suitable tool for considering uncertainties in design process. First order Taylor series approximation method is the most common probabilistic slope stability method that is almost verified in all practical cases. In research program Proba_Slope software was written. This software has the ability to do deterministic slope stability analysis utilizing Bishop's method and probabilistic slope stability analysis based on above approximation method. The results gained from Proba_Slope were then verified using commercial software.

Good understanding of In-Cylinder fluid flow during the induction process and compression stroke has effective role in optimization engine design to aid best operation, fuel consumption and also decrease of environment pollution. In recent years, various turbulence models are widely developed and used to predict turbulent flow. The standard k- e turbulent model shows poor prediction in engine fuid flows; therefore, researchers study and investigate other engine turbulence models. In this paper, Reynolds Stress Turbulence Model (RSM) is used for calculations of flow phenomena in an internal combustion engine chamber during the induction process and compression stroke and the abilities of the model are examined. The results are compared with k-e and ASM turbulence models for various engine types of piston and cylinder socket and also compared with experimental data.Qualitative consideration of the results shows that the Reynolds Stress Turbulence Model predicts additional flow structures and very good agreement with physical expectations and other numerical and experimental data, although it is very expensive to compute.

A new damage detection (crack locating) approach for pipe is introduced based on sensitivity analysis. The method is also validated by modal test results. As far as the applications concern, pipes are mostly slender structural members, therefore the Euler-Bernoulli beam theory is adopted here in the pipe Finite Element model. The damage is modeled by a stiffness reduction of the element (within the FE model) containing the crack. The minor variation of the mass matrix due to crack is neglected. Expressions relating the sensitivity of modal frequencies to the changes of stiffness (and mass) matrices are presented. Using this method, the crack is connected to the changes of natural frequencies with a simple relation. This relation then forms the basis of inverse solution to find a pipe crack from changes of few modal frequencies. First, the direct problem is formulated. A typical case with numerical simulation is presented. Then, the inverse problem is solved for-the same case presented in the direct simulation. Finally, the experiments conducted on a pipe (undamaged and damaged) instrumented for modal testing is fully reported. The computational method is verified. The experimental results confirm the validity and applicability of the method for crack detection in slender pipes.

Using dust combustion apparatus, proper experiments is done to recognize the aluminum dust flame structure. In this work, using a computer code, images that have been taken from the flame with a high speed camera is filtered and extra lights will omit. Then another code is used to calculate the area of burning agglomerates and then with respect to this area and applying a correction coefficient, actual diameter is calculated and then with using another code, dependence between agglomerates diameter and time is calculated and when diameter is zero, time of burning will be calculated and then burning time has been calculated with respect to the initial diameter of agglomerates and effects of change in oxidizer and carrier gas have been studied. Experimental tests in different carrier gases and different values of oxidizer indicate asymmetric combustion in aluminum particles.