LEE- Malzeme Mühendisliği Lisansüstü Programı

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http://hdl.handle.net/11527/19378

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Konu "Sonlu elemanlar yöntemi" ile LEE- Malzeme Mühendisliği Lisansüstü Programı'a göz atma
  • Öge
    Wear behaviour analysis of different metals by the finite element method
    (Institute of Science And Technology, 2020-06-15) Demir, Canay ; Baydoğan, Murat ; 506171407 ; Materials Engineering ; Materials Engineering
    Material losses occur because of the damage caused by friction between materials relatively moving in contact with each other. Wear damage can significantly reduce the life cycle of the materials and can significantly affect their operating performance. To prevent or minimize this damage, wear mechanisms of material and material pairs must be determined under certain service conditions. Accordingly, wear testing and wear prediction have gained great importance. Wear is a very common type of damage in systems operating in motion. Wear can take place with more than one different mechanism. These are mainly classified as adhesive wear, abrasive wear, fatigue wear and corrosive wear. There are many factors that affect the wear phenomenon: crystal lattice structure, hardness, elasticity modulus, work-hardening, plastic deformation behavior, surface roughness of the materials etc. and they depend on the properties of materials. Additionally, the service or ambient conditions (temperature, humidity, etc.) very effective for the wear behavior. In order to minimize wear damage, wear behavior must be carefully examined. However, the most common is the method of determining the friction coefficient by the wear of the pin or ball, which is constantly under a certain force on the rotating disk with the pin-on-disk assembly, or vice versa. With this method, the wear loss is determined by measuring the wear traces on the wear disc or pin / ball. This experiment can be carried out under different loads, at different sliding speeds and distances, even at different temperatures. In all cases, it may not be possible to access all materials or wear surfaces can be complex geometries. In such cases, it is possible to obtain an approach to experimental results in cases where it is not possible to experiment using the Finite Element Method (FEA) as a numerical analysis method. Studies on wear modeling have been developed taking into account the classical wear theory put forward by Archard. In wear analysis using finite element analysis, Archard wear theory is still the most commonly used method today. The aim of this study is to obtain ball-on-disc type wear test results carried out in a laboratory environment via modeling in 3-dimensional in finite element analysis software. In this context, Inconel 718, 316L stainless steel, grey cast iron, spherical graphite cast iron, Zamak, Ti6Al4V, 7075 and 6082 aluminum alloys, AZ91 magnesium alloy and pure copper as metals with different crystal structure, hardness and microstructure have been subjected to wear test against alumina (Al2O3) ball. It is expected to verify that the validity of the finite element model used by comparing the results obtained from these experiments with the 3-dimensional wear model created with ANSYS Workbench and the results obtained by using Archard theory. In this way, it is aimed to make accurate predictions about the results of the wear analysis by using the finite element method. In line with the determination of wear loss in the specified materials, Inconel 718, 316L stainless steel, grey cast iron, spherical graphite cast iron, Ti6Al4V, 7075, AZ91, Zamak, 6082 and pure copper metals were tested under different loads in ball-on-disc wear test configuration. The wear loss is used in Archard`s wear equation to calculate the wear coefficient K and the coefficient of friction is used as an input to the simulation with hardness of material. SEM and Raman spectroscopy analysis of wear tracks were done. Using the 3-dimensional model of the ball-on-disc test setup was used to perform numerical analysis. Results from the numerical analysis were compared to the experimental analysis. There was a good correlation with the results in general. However, relatively higher error values were recorded for some metals like 7075 alloy and grey cast iron. The difference between these results were investigated both experimentally and numerically. First, the simulation is accepting that all surfaces are perfect. Secondly, the contact pressure was calculated as constant during the simulation. However, the in experiments the contact area is changing throughout the sliding thus, the contact pressure is expected to decrease. Furthermore, the contact pressure values calculated at the numerical model is differs from the Hertzian contact theory. Because in simulation assumes that bodies are elastic. Another reason is that oxide formations were found in wear tracks on sliding surfaces. The oxides created lubrication effect for the coefficient of friction of grey cast iron; however, it was kept constant during the simulation. Similarly, the metallic layer formation on the alumina ball against the Ti-6Al-4V resulted to metal-metal wear and the experimental K values was became different than the K value calculated from the Archard's equations. There are any many factors that can be found for accuracy of the simulation. Despite all that, the results were very promising to create a simulation tool for wear analysis of different materials.