Influence of Porosity on Fatigue of Cast Nickel Aluminum Bronze and AProposed Method to Reduce scatter of data

In this study, the effect of casting porosity on the strength of cast nickel aluminum bronze (NAB) was investigated. For this purpose, four-point fatigue tests were carried out under R = -1 and 50 Hz on this alloy. Experimental results and plotted fatigue curve indicated high values of scattering in fatigue data, increased at applied stress levels higher 150 MPa. To reduce scattering and to obtain a more realistic fatigue strength, pore sizes were measured from the fracture surfaces of the specimens by using image processing technique. The fatigue strength was, then, calculated based on the effective area and fatigue curves were re-plotted. Results indicated that S - N curves obtained by this method are independent from casting defects and could present a better index for fatigue strength of the casting alloy. Therefore, it was concluded that the strength was obtained from this method could be an appropriate reference value when considering the fatigue properties of cast nickel aluminum bronze.