Projeto, fabricação e operação de uma máquina de ensaio de erosão por cavitação

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The present work deals with the design, fabrication and operation of a cavitation erosion equipment and with the preliminary results obtained by its testing. A new cavitation erosion testing machine was designed, fabricated and tested, using a rotating disc with holes for generating cavitation. The developed equipment has as main advantages, in relation to the existing ones, low fabrication cost due to its smaller size and reduced number of components, the specimen quantity of up eight per test and a lower power needed to carry out the testing. It is small size equipment, capable of generating the necessary bubbles for causing the erosion by cavitation on the specimen surfaces at the speed of 4400 rpm and maximum power of 30 kW. Two types of rotating discs were investigated: with cavitation inducers holes and with pins. The rotating disc with inducer holes was more efficient as its power consumption was only 14 kW and the disc with inducer pins was 23 kW for practically the same erosion rate obtained by bronze and aluminium, both at the rotation speed of 4400 rpm. The cavitation erosion is responsible for surface damage caused exposure to this phenomenon. The equipment is capable of testing simultaneously 8 specimens of different materials, what shows the variety of possible materials which can be performed simultaneously in short period of time. The specimen erosion was confirmed by its loss of mass, using an analytical balance with accuracy of 0,2 mg and by the analyses of the eroded surface through the photograph analyses from the scanning electron microscope, MEV. The occurrence of cavitation due to micro-jets impact was confirmed by the microphotographs of circular craters in the aluminium specimens. The tested and discussed materials in this work presented different behavior when exposed to cavitation erosion. Bronze and brass showed a practically constant and linear erosion rate as seen in the lost mass versus testing time graphs. But, aluminium presented much lower wear, except for 10 to 15 hours of testing. After this period of time, a substantial reduction in the wear rate was occurred due to the formation of a fine layer of alumina which provided an increase in the aluminium wear resistance. According to the results obtained by the nodular cast iron specimens, it was observed that the cemented layer increased the erosion resistance to cavitation and decreased the specimen surface oxidation, however, the occurrence of surface oxidation prejudiced a more accurate analyses.

ASSUNTO(S)

projeto design cavitação erosão disco rotativo cavitation erosion engenharia de materiais e metalurgica rotating disc metals

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