RESIDUAL STRESS REDUCTION OF FILLET BOX WELDED JOINTS BY LOCAL HEATING USING INDUCTION HEATING DEVICE

To improve the fatigue life of welded joints in steel bridges, a series of experimental and analytical investigations was conducted on a method of welding residual stress reduction by local heating with an induction heating (IH) device. The IH coil of 110 mm x 40 mm was installed around the fillet weld and heated to 350 °C . The tensile residual stress of about 340 MPa was reduced to under 30 MPa. The local heating experiment was simulated by the thermal elasto-plastic analysis to examine the mechanism of residual stress reduction. A four-point bending fatigue experiment was conducted. The fatigue life of the locally heated joints became two to five times longer than that of the joints without heating under the applied stress conditions of 70 to 100 MPa.