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چكيده انگليسي :

Wear Modeling in Nanocomposite Materials Sara Adibi Sara adibi@gmail com Date of Submission 2010 07 12 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Saeed Ziaei Rad szrad@cc iut ac ir Abstract Aluminum based metal matrix nanocomposites are ideal materials for structural application in the aircraft and automotive industries on account of their excellent mechanical characteristics and low cost component production with respect to other alloys Also it is well known that this kind of materials exhibit marked improvement in wear resistance when compared to unreinforced alloys In operating conditions components made of Al based composites are usually subjected to elevated temperatures high contact loads and widely used to fabricate mechanical parts that are involved in sliding contact Therefore prediction and experimental determination of their wear properties has become very important Experimental determination of life parameters in terms of wear has both a cost and time impact Therefore the ability to predict wear at the development stage enables the designers to come up with a better design longer useful life and more reliable products Despite the marked interest the simulation of wear is still in its early stages due to its complexity In this work an experimental programme on a pin on disk test on Al Mg Si Al2O3 nanocomposites and the corresponding unreinforced alloy was carried out at different loads and sliding distances A finite element model to simulate wear tests was also developed In order to predict wear and eventually the life span of such materials several hundreds of thousand operating cycles have to be simulated An FE post processor is the most optimum choice considering the computational expense of such large deformable deformable contact simulations Our approach is to include a wear model based on Archard s wear law in a FE post processor that works in association with commercial FE package ANSYS for solving the general deformable deformable contact problem Local wear is computed and then integrated over the sliding distance using the Euler integration scheme After every wear step the geometry is re meshed to correct the deformed mesh due to wear The wear on both the pin and disc surface are computed using the contact pressure distribution computed from a two dimensional FE model of the pin and disk included Coulomb friction at the contact The simulation was validated from a series of experiments Experiments were conducted on a POD rig to measure the friction coefficient as well as the wear depth two parameters needed for the simulation In general good agreement with the experimental results was observed under tested conditions of contact pressure and sliding speed Morever this paper deals with preparing Carbon Nanotube CNT Reinforced Nanocomposite CNRAC and predicting its mechanical and surface properties using the finite element method To prepare the reinforced nanocomposite a pre alloyed powder was milled in a planetary ball mill under the argon atmosphere Carbon nanotubes were then added to the powder in a particular procedure Next a finite element model consisting of CNTs as the fibers and Aluminium as the matrix was constructed A series of nano indentation tests were carried out to obtain the mechanical and surface properties of the material thus constructed The finite element models were then used to predict the results obtained from real indentation tests The predicted hardness and elastic modulus from the FE model show good agreement with experimental findings Keywords Wear modeling Wear simulation Pin on disk FEA Aluminum based metal matrix nanocomposite

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مدل سازي سايش در نانو كامپوزيت ها

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