Contents of Journal of Mechanical Engineering 61, 1 (2010) 



ABDOLLAHPOOR, A., MARZBANRAD, J.: Crashworthiness study of axial 
impact in cylindrical aluminium tubes                                    1

SELAHI, E.: Investigation of tangential and radial modulus of 
elasticity effects on stress  components in thick composite 
pressure pipe                                                           19

BARADARAN, G. H., MAHMOODABADI, M. J.: Parametric study of 
the MLPG method for the analysis of three-dimensional steady 
state heat conduction problems                                          31



Crashworthiness study of axial impact in cylindrical aluminium tubes

A. ABDOLLAHPOOR, J. MARZBANRAD

A thin-walled cylindrical tube, when subjected to an axial load, will be folded and will absorb an impact energy. In the design of a frontal cylindrical tube for absorbing the kinetic energy during car accidents, there were a lot of theoretical and experimental researches that have defined the characteristics of the tube during cars accidents. After studying most of these researches, it was found that the theoretical approach usually simplified the problem and could not be used confidently in design. Experimental approach usually faced difficulty when the material was changed.

In this paper, a computer simulation program joined with the response surface methodology was planned to find the tube characteristics in axial impacts. The problem parameters were dimensional measures of an aluminium circular tube including thickness, diameter and length. The output of the work was to find the variation of the absorbed energy and mean crash force of the tube with the parameters in the applicable automotive ranges. Also, our results were compared with some available theoretical approaches.



Investigation of tangential and radial modulus of elasticity effects on stress components in thick composite pressure pipe

E. SELAHI

In this paper, the first time using Lekhnitskii's theory, an analytical modelling for analysing of stress components in thick pressurized composite pipe is introduced. In this method laminates have orthotropic properties; stacking sequences of layers can be either symmetric or asymmetric. Constants of the modelling equations can be found from boundary conditions of radial stress and displacement in the normal direction of layers. Governing equations of this model can be solved analytically. By using this modelling, for two cases of unidirectional and woven fabric laminated, relative magnitude of tangential to radial modulus of elasticity in stress components of thick composite pressurized pipe has been investigated and the results are compared together. Also these pressurized composite pipes are modelled with finite element modelling in MSC Nastran software and the results are compared with mathematical modelling results. The results of both mathematical and FEM are very close together.




Parametric study of the MLPG method for the analysis of three-dimensional steady state heat conduction problems

G. H. BARADARAN, M. J. MAHMOODABADI

A 3D Meshless Local Petrov-Galerkin (MLPG) method is presented for the solution of the steady state heat conduction problems. The spherical sub domains are used for the integration of the symmetric weak form. A concise mapping is introduced to compute the integrals efficiently. The Moving Least Squares (MLS) approximation is used for the interpolation schemes and the Heaviside step function is chosen for the test function. The penalty method is adopted to efficiently enforce the essential boundary conditions. Complete study of the effects of parameters including radius of sub domains, radius of support domains on the accuracy and efficiency of the solution is performed. The Genetic Algorithm (GA) is used to determine the optimum values of parameters for minimum computation time and highest accuracy. Results show that the optimum values of parameters in the considered 3D problems much differ from those obtained for 2D problems by the others.