Fatigue Life Assessment of Screw Blades in Screw Sand Washing Machine under Extreme Load

The aim of this study is to estimate the fatigue life of the screw blades in the screw sand washing machine under the extreme load (i.e., the load caused by the full load condition). Firstly, the extreme load is taken into consideration in the fatigue life assessment of screw blades by means of the finite element analysis (FEA). Next, the P-S-N curve is fitted by the fully reversed rotating bending testing on standard specimens and theory deduction. Then, s are generated according to the maximum and minimum stresses of the root of screw blades under different thicknesses. Finally, the service life of screw blades is assessed based on the P-S-N curve, s, and Soderberg mean stress correction method. In particular, the effects of the surface finish factor, fatigue notch factor, and residual stress on the fatigue life of screw blades are considered. The results show that the stress concentration is at the root of screw blades; the screw blades with the thickness of 10 mm, whose service life is around 35 years, are the optimum in terms of the screw sand washing machine proposed in this study; the safety factor of screw blades should be 2, considering the influence of the fatigue load.