Research on the failure of the induced draft fan's shaft in a power boiler

The failure of the induced draft fan's shaft in a power boiler was been analyzed. The performances of material applied satisfied the design requirement. The order torsional vibration showed anomaly at the shaft's smallest diameter for the design condition and the actual radius of that chamfer less than the design radius caused more significant stress concentration. The additive effect of the abnormal torsional vibration and the higher stress concentration induced the microcrack's initiation along the network pearlite's interface. The vibration and the alternating torsional loading in the induced draft fan's service led to crack growing along the different direction and fracture presenting the typical ratchet-like characteristic.