Simulação do desgaste abrasivo via interações múltiplas

Abstract

Abrasive wear is currently classified according to different particle dynamics: a) the sliding of active particles on the sample surface and b) the rolling of abrasives between the surfaces. The prevailing particle dynamics depends on the system features. In this thesis, instrumented laboratory tests are used to present a new methodology for the simulation of abrasive wear. The rolling of the abrasives is represented by a sequence of indentations, and the sliding of the active particle by a sequence of scratches. Two new equipments were especially developed to reproduce the action of an abrasive particle: a macro-simulator and micro-simulator. Two high resolution sliders drive the sample horizontally while the indenter is moved vertically by another slider. A 3D load cell controls the intensity of the process. The load limit of the macro-simulator is 500 N and that of the micro-simulator is 18 N. A high resolution piezoelectric translator is used to control the indenter movement in the micro-simulator. A worn surface produced in an abrasive test was used as a reference for the simulation. Its topography was assessed using laser interferometry and scanning electron microscopy. The morphology of the wear surface is defined by the predominant abrasive wear mechanism, and this defines the simulation configuration as follows: indentation alone, scratches alone and a mixture of indentations and scratches. The effect of the simulation parameters on the morphology was studied in the preliminary tests. The macro-simulator and tool-steel samples were used for the tests. The preliminary results showed that the simulation process was not possible when using the macro simulator because the load cell is out of range for the required loads. The micro-simulator was used to simulate the rolling of the particles on tool steel, glass and 1010 steel. The indentations were randomly positioned. The controlling variables were the normal load (0,29; 0,44; 0,49; 0,59; 0,98; 1,47 and 1,96 N) and the quantity of interactions (1000; 1500; 2000; 3500 and 5000). The results showed that the superimposition of indentations has a great effect in the morphology and topography of the simulated surfaces. A special method to describe the average depth of the indentations/scratches in function of the distance between them was developed. The ratio of the distance between the events to the size of a single event defined the value of superimposition. These tests showed that positive values of superimposition affect the average depth of the events. Wear occurs when superimposition is greater than 50%. The average depth of the deformation marks increased according to an elevation in the degree of superimposition and to the augmentation of normal load. The study of superimposition was used to relate the topography of the reference to the control parameters in two cases of simulation: a) the rolling and b) parallel sliding of the abrasive particles. In both cases, the simulation methodology produced surfaces topographically and morphologically similar to these of the respective references. The simulation process produces information relative to the position and to the interaction forces associated with each event. This information opens up great possibilities for a computational simulation of abrasive wear.