Application of finite element method to analysis of tribological properties of aluminum oxide nano-layers

This article describes the research findings achieved by the application of Al₂O₃ nano-layers coated on aluminum alloys by an electrolytic method. With tribological applications, mainly thin and hard anti-wear coatings were used. Oxide Al₂O₃ nano-layers created by electrolytic method on aluminum alloys have very good tribological properties when pairing them with plastics and low friction composites. Self-lubricating coatings are a mixture of binding and lubricating agents, which after a putting on sliding surfaces create the coating being characterized by a low friction coefficient that enables a mutual movement of the rubbing areas without the need to apply an extra lubrication media. On the other hand, binding materials – polymers – guarantee the presence of the cohesive force which hold components of the layers together, as well as adhesive forces binding the layer with the base. Practically all polymers can be applied as a matrix for production of polymer composites, but because of excellent friction properties and chemical inertness polytetrafluoroethylene is the most attractive. The structure of the investigated nano-layers was described by the computer image analysis that enables its modeling. Analyzed nano-layers were tribological tested in pair with composites on the basis of polytetrafluoroethylene. In the course of examinations tribological properties were measured that described the quality of sliding pairs, i.e. friction coefficient and abrasive wear. The registered parameters were compared to these measured in other tribological pairs. The differences were analyzed and justified. For predicting stresses and strains generated during the experiment a finite element method was used. The achieved results are similar to the measured real values. Applied computer analysis with finite element method as the calculation method of the cube-plate sliding matching with reciprocating motion and simulation of real forces condition that affect the system, allowed to achieve the following maximal stresses: TG15 (3.02726 MPa), TGK20/5 (3.02732 MPa), TMP12 (4.25076 MPa), and strains: TG15 (0.0045573), TGK20/5 (0.0047507), TMP12 (0.0065434). The stress distributions indicate that the highest values appear in the contact cube-plate area and at the lower cube edges especially in the places being in accordance with the movement direction irrespective of the kind of material used. Material modification results in the change of achieved stresses and strain values according Hooke’s law.