Cutting Parameters Influence Analysis on Residual Stress Generation in Iron Turning Operation Cast Nodular Austempered
Elifas Levi da Silva1; Durval Uchôas Braga2; Deibe Valgas dos Santos3
1 Centro Universitário de Formiga; 2 Universidade Federal de São João Del Rei; 3 Centro Universitário UNA
doi:10.20906/CPS/COB-2015-1547
Resumo
The austempered ductile iron (ADI) is a modern cast iron class obtained by austempering treatment performed in a nodular cast iron. Residual stress are the tensions that remain in a component even when it is free of external forces or temperature gradients. The machining process is a source of residual stress generated in the material. The mechanical properties of materials such as, fatigue, dimensional stability, corrosion resistance, resistance to fracture, can be influenced by residual stresses. The machining ADI has a difficulty to be a hardened material besides the transformation of austenite into martensite during the machining process, the residual stresses generated during processing. In this sense, it was decided to conduct this research in order to study the effects of cutting parameters in the generation of residual stresses after ADI turning operation. We used factorial design randomized by levels and fixed effect model for the analysis of the results of the experiments. The turning tests were performed in the center of turning Romi GL 240M, with carbide tools k group. For analysis of residual stress were performed micro hardness tests of Ultra Micro Hardness Tester DUH-211S laboratory of the Federal University of São João del Rei, being made of micro hardness measurements in three regions of machined specimens, beginning, middle and end of machined nominal length. Had as control variables: cutting speed, the advance of the tool, number of pass and length of machining. The dependent variable was the micro hardness generated in the process. The results indicated that the ADI turning caused the generation of residual tensile stress, all control variables, except for variable length machining caused a reduction in the value of micro hardness when leaving a lower level to the higher, which indicates the generation of residual tensile stress. The intensity of the tensile residual stress generated during the machining length was significantly different proved to be lower when cutting starts.
Palavras-chave: Turning; Nodular cast iron austempered; Residual Stress; Cutting Parameters