The new generation naval grade high strength low alloy steel specifically designed for ship building applications due to its high strength to weight ratio. In general, the fusion welding of structural steels required attention on under dynamic loading conditions.

The fatigue failure of welded structures is more susceptible in cyclic loading due to heterogeneities of consumables and microstructure deformation. And these heterogeneities make weld under complicated during local stress-strain conditions.

Therefore, it is necessary to identify design safe regions to avoid these catastrophic failures of the welded joints.

In this investigation, the rotating-beam fatigue test was performed on the fusion-welded butt joints of naval grade steel and its results were correlated with mechanical properties. The fatigue testing was conducted at five different stress levels varied from 50 – 90 % of yield strength.

The S-N curve was constructed from the experimental data for a stress ratio R = -1. The mechanical properties such as tensile strength, impact strength, and micro hardness were evaluated as per the ASTM standard.

The evaluated fatigue strength of fusion-welded butt joints was 356 MPa. The maximum recorded transverse tensile strength and energy absorption of welded joint was 570 MPa &178 J respectively.

The results concluded that the fatigue strength of fusion welded naval grade steel obtained appreciably higher fatigue strength than standard IIW fatigue curve.

From the S-N curve, the safe region has been identified for infinite life design of gas metal arc welded butt joints of naval grade steels.

This article is shared by P. Hariprasath, P. Sivaraj, V. Balasubramanian, Srinivas Pilli and K. Sridhar.