تعيين ثوابت الاستيك فلزات متخلخل گازار به كمك شبيه سازي اجزا محدود

چكيده انگليسي :

Determining the Elastic Constants of Gasar Porous Metals by Means of Finite Element Simulation Seyyed Shoya Mohseni Mofidi ss mohsenimofidi@me iut ac ir 10th April 2013 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor M R Forouzan Assoc Prof forouzan@cc iut ac ir Abstract Gasar or Lotus type porous metals are a new type of porous material which is distinguished by elongated unidirectional pores Such unidirectional pores contribute to many advantageous mechanical and thermal properties which cannot be observed in any other type of porous material This makes the gasar porous metals very attractive for use in modern engineering applications Using of these materials for designing new and special structure requires a complete understanding of deformation behavior of these materials Since preparing various types of test specimens from a Gasar ingot is usually impossible or very costly finite element simulation can be a useful tool to get a better understanding of behavior of these materials In this study a homogenization process is used for determining the elastic constants of Gasar porous metals The concept of homogenization is the replacement of a heterogeneous medium by a homogeneous equivalent one and to make a bridge between these two mediums a certain volume of the heterogeneous specimen for which predicted behavior is identical to behavior of the whole specimen called representative volume element RVE is needed Therefore determining a proper RVE to predict the elastic constants with a good accuracy is the most important goal of this study An algorithm is proposed to generate computational model for volume elements In this algorithm some statistical information about pore topologies obtained by analysis of Gasar real microstructure is considered The pores diameter distribution in surface perpendicular to pores elongation direction is assumed to have a normal distribution Also pores diameter distribution is kept constant along the pores elongation direction throughout the volume and all the pores have an identical aspect ratio In numerical approaches an exact RVE according to the classical definitions cannot be used and using RVE with a smaller size is inevitable This RVE results to apparent values for desired properties that differ from the effective properties Thus averaging over the several realizations can be used to diminish this difference between apparent and effective properties In this study a numerical statistical approach based on statistical analysis of the results obtained for several realizations is applied to determine suitable size for RVE by which desired properties can be predicted with a given and acceptable accuracy In order to examine the effects of increasing the width and the length of volume elements separately on determining the proper size of RVE two series of volume elements are considered After determining the proper RVE for Gasar porous magnesium with 40 porosity in first step in second step for verifying the accuracy of proposed algorithm for generating computational models the elastic constants of Gasar porous copper with 17 4 31 1 and 59 1 porosities are predicted by RVE determined in first step then the obtained results are compared with experimental data and it is shown that the proposed algorithm for generating computational models with defined RVE size can predict the elastic constants of Gasar porous metals with low and intermediate porosities with a good accuracy Keywords Gasar or Lotus type porous metals homogenization process representative volume element RVE elastic constants PDF created with pdfFactory trial version www pdffactory com

محسني مفيدي، شعيا

تعيين ثوابت الاستيك فلزات متخلخل گازار به كمك شبيه سازي اجزا محدود

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