Multi-objective Optimization of Crashworthiness of Cylindrical Tubes as Energy Absorbers
Multi-objective Optimization of Crashworthiness of Cylindrical Tubes as Energy Absorbers
مجله مهندسي مكانيك ايران
Ianian Journal of Mechanical Engineering Transactions of the ISME
ISSN 1605-9727
دوفصلنامه داراي رتبه علمي - پژوهشي (فني مهندسي) به زبان انگليسي
سال دوازدهم، شماره 1 (پياپي 16)، March 2011
Title:
Multi-objective Optimization of Crashworthiness of Cylindrical Tubes as Energy Absorbers
Author(s):
M.Mirzaei , M. Shakeri , M. Sadighi , S.E. Seyedi
Paper language: English
Abstract:
In this article, the multi-objective optimization of cylindrical aluminum tubes under axial impact load is presented. The absorbed energy and the specific absorbed energy (SEA) are considered as objective functions while the maximum crush load should not exceed allowable limit. The geometric dimensions of tubes including diameter, length and thickness are chosen as design variables. The Non-dominated Sorting Genetic Algorithm –II (NSGAII) is applied to obtain the Pareto optimal solutions. A back-propagation neural network is constructed as the surrogate model to formulate the mapping between the design variables and the objective functions. The finite element software ABAQUS/Explicit is used to generate the training and test sets for the artificial neural networks. To validate the results of finite element model, several impact tests are carried out using drop hammer.
Keywords:
Cylindrical tube, Energy absorption, Neural networks, Multi, objective optimization
Modeling of Upward Subcooled Flow Boiling of Refrigerant-113 in a Vertical Annulus
Modeling of Upward Subcooled Flow Boiling of Refrigerant-113 in a Vertical Annulus
Title:
Modeling of Upward Subcooled Flow Boiling of Refrigerant-113 in a Vertical Annulus
Author(s):
H. Aminfar and M.R. Haghgoo
Paper language: English
Abstract:
In this paper, a modified two-fluid model has been adopted to simulate the process of upward vertical subcooled flow boiling of refrigerant R-113 in a vertical annular channel at low pressure. The modified model considers temperature dependent properties and saturation temperature variation and was validated against a number of published low-pressure subcooled boiling experiments. The results show good agreement with experimental data including radial profiles of void fraction, phase velocities and liquid temperature. A sinusoidal axial distribution of wall heat flux was applied as well as constant wall heat flux. Results show that by increasing the wall heat flux, the bubble boundary layer will become thicker and the profiles of axial liquid velocity will gradually depart from those of singlephase flow.
Low Velocity Impact on Relatively Thick Rectangular Plate under In-plane Loads Resting on Pasternak Elastic Foundation
Low Velocity Impact on Relatively Thick Rectangular Plate under In-plane Loads Resting on Pasternak Elastic Foundation
Title:
Low Velocity Impact on Relatively Thick Rectangular Plate under In-plane Loads Resting on Pasternak Elastic Foundation
Author(s):
Sh. Hosseini Hashemi , R. Kalhor
Paper language: English
Abstract:
This study deals with the elastic-plastic impact on moderately thick rectangular plate subjected to uniform in-plane compressive loads resting on the Pasternak elastic foundation. The proposed rectangular plates have two opposite edges simply-supported, while all possible combinations of free, simply-supported and clamped boundary conditions are applied to the other two edges. The dimensionless equations of motion of the plate are obtained by applying the Reissner-Mindlin plate theory considering the first-order shear deformation and the rotary inertia effects. The exact closed form solution of the governing equations leading to more accurate result with less calculating time in comparison with the Rayleigh-Ritz method is used to obtain the dynamic response of the plat. The validity of the result is first examined by studying the convergence of the maximum impact force. Then, a comparison of results with those available in literature confirms the excellent accuracy of the present approach. Finally the effects of the dimensionless parameters such as uniaxial and biaxial in-plane loads and the effect of foundation stiffness parameters on force and displacement histories have been examined.
Keywords:
Low velocity impact, first order shear deformation theory, permanent indentation, in, plane loads, elastic foundation
A Comparative Study on the use of Butyl Esters of Soyabean and Sunflower Oils as Biodiesel Fuel for Compression Ignition Engine
A Comparative Study on the use of Butyl Esters of Soyabean and Sunflower Oils as Biodiesel Fuel for Compression Ignition Engine
Title:
A Comparative Study on the use of Butyl Esters of Soyabean and Sunflower Oils as Biodiesel Fuel for Compression Ignition Engine
Author(s):
Ajit Pal Singh , K. Anbumani
Paper language: English
Abstract:
To study the feasibility of using two edible plant oils as diesel substitute a comparative study was made. Oils were exacted from the seeds of soyabean (Glycine Max, Family: Leguminoceae) and sunflower (Helianthus annuus, Family: Asteraceae/Compositeae). Oils were esterified (butyl esters) before blending with pure diesel in the ratio of 10:90, 15:85, 20:80, and 25:75 by volume. Pure diesel was used as control. Studies have revealed that on blending vegetable oils with diesel a remarkable improvement in their physical and chemical properities took place. Cetane number came to be very close to pure diesel. Engine (C.I.) was run at different loads (0, 4, 8, 12, 16, and 20 kg) at a constant speed (1500 rpm) separately on each blend and also on pure diesel. Studies have revealed that soyabean oil at 20% blend with diesel gave best performance in terms of low smoke intensity, emission of HC and NOx. All the parameters tested viz., flash point, total fuel consumption, specific energy consumption, specific fuel consumption, brake thermal efficiency and cylindrical peak pressure were improved. Results have further indicated that at 20% blend engine showed a closer performance to pure diesel. 20% blend of soyabean oil exhibited better performance than sunflower oil blends. However, both the oils at 20% blends with diesel can be used as a diesel substitute. There studies have thus indicated that esterified soyabean oil at 20% blend satisfies the important fuel properties as per ASTM D975 specifications of biodiesel as it lead to the improvement of engine performance and emission characteristics without any modification in engine.
An Exact Solution for Quasi-Static Poro-Thermoelasticity in Spherical Coordinates
An Exact Solution for Quasi-Static Poro-Thermoelasticity in Spherical Coordinates
Title:
An Exact Solution for Quasi-Static Poro-Thermoelasticity in Spherical Coordinates
Author(s):
M. Jabbari , H. Dehbani
Paper language: English
Abstract:
In this paper the Quasi-Static poro-thermoelasticity model of a hollow and solid sphere under radial symmetric loading condition (r, t) is‡ considered. A full analytical method is used and an exact unique solution of the Quasi-Static equations is presented. The thermal, mechanical and pressure boundary conditions, the body force, the heat source and the injected volume rate per unit volume of a distribute water source are considered in the most general forms where no limiting assumption is used. This generality allows to simulate variety of applicable problems.
A General Form Solution for Elastic Buckling of Thin Cylinders Made of FGM under Axial Loading
A General Form Solution for Elastic Buckling of Thin Cylinders Made of FGM under Axial Loading
مجله مهندسي مكانيك ايران
Ianian Journal of Mechanical Engineering Transactions of the ISME
ISSN 1605-9727
دوفصلنامه داراي رتبه علمي - پژوهشي (فني مهندسي) به زبان انگليسي
سال دوازدهم، شماره 2 (پياپي 17)، sep 2011
Title:
A General Form Solution for Elastic Buckling of Thin Cylinders Made of FGM under Axial Loading
Author(s):
R. Shahsiah
Paper language: English
Abstract:
In this article, the axisymmetric mechanical buckling of thin cylindrical shell made of functionally graded material (FGM) is considered. The governing equations for a thin cylinder based on the first-order shell theory and Timoshenko's assumptions are obtained. The equations are derived using the Sanders simplified kinematic relations and the principle of work and energy. The constituent material of the functionally graded shell is assumed to be a mixture of ceramic and metal. It is assumed that the mechanical properties vary continuously through the shell thickness. The thin cylindrical shell is under uniform axial compressive load. The expression for the criticalmechanical buckling load is obtained analytically and is given by closed form solution. The results are validated with the Timoshenko's formula in the literature.
Thermo-elastic analysis of a functionally graded thick sphere by differential quadrature method
Thermo-elastic analysis of a functionally graded thick sphere by differential quadrature method
Title:
Thermo-elastic analysis of a functionally graded thick sphere by differential quadrature method
Author(s):
R. Akbari Alashti , M. Khorsand and M.H. Tarahhomi
Paper language: English
Abstract:
Thermo-elastic analysis of a functionally graded hollow sphere is carried out and numerical solutions of displacement, stress and thermal fields are obtained using the Polynomial differential quadrature (PDQ) method. Material properties are assumed to be graded in the radial direction according to a power law function, however the Poisson’s ratio is assumed to be constant. The governing partial differential equations are obtained in terms of displacement and temperature fields and expressed in the form of series equations. A comparison of numerical results with the analytical and finite element results is presented that shows an excellent agreement. The effect of the material grading parameter, temperature variation and thickness of the sphere on the distribution of stress, radial displacement and temperature fields is investigated.
A Linear Approach to the Control of Vortex Induced Vibrations of Circular Cylinders with a 2-D Van der Pol Model for Structural Os
A Linear Approach to the Control of Vortex Induced Vibrations of Circular Cylinders with a 2-D Van der Pol Model for Structural Os
Title:
A Linear Approach to the Control of Vortex Induced Vibrations of Circular Cylinders with a 2-D Van der Pol Model for Structural Oscillator
Author(s):
A. Farshidianfar , N. Dolatabadi
Paper language: English
Abstract:
In the present paper, a new 2-D Van der Polstructural oscillator model is introduced for the vortex induced vibrations of circular cylinders.The main purpose of this task is to control the recently introduced model by means of modern control definitions in state space. In order to control the system, the whole model is linearized about its equilibrium point by deriving state-space matrices. Then, the linear transfer function is obtained and controlled by pole-placement technique which is based on the state variables feedback. Afterwards, this linear controller is applied to the nonlinear system about its equilibrium point by assuming that there is no uncertainty in both physical and mathematical models. Eventually,the results for linear and nonlinear systems are compared.
Thermoelastic Analysis in Thick FGM Cylinders with Extended Profile
Thermoelastic Analysis in Thick FGM Cylinders with Extended Profile
Title:
Thermoelastic Analysis in Thick FGM Cylinders with Extended Profile
Author(s):
R. Poultangari , A. Bahtui , M.R. Eslami
Paper language: English
Abstract:
An exact solution is obtained for an axisymmetric steady-state thermo-mechanical stresses in a thick functionally graded cylinder. The material properties are graded along the radial direction ac- cording to an exponential function of radial direction with three con- stants. The advantage of the proposed model, compared to the mod- els with two constants such as the linear, power law, and exponential models with two constants, is that it satisfies the material boundary conditions at the inside and outside radiuses, leaving one more con- stant to be selected to produce different types of material variation profiles along the cylinder radius. Utilizing the assumed exponential model, the analytical solution of the problem, using the generalized Bessel function and the Lagrange method, is obtained employing the energy and Navier equations.
