Weldment Design and Service Life Under Constant Amplitude and Single Tensile Overload Conditions

Abstract

4140 parent steel was used to determine the behavior of fatigue fracture development at room temperature. Heat treatment, as-welding, R", 0 constant amplitude loading, and single tensile overloads with a 2.5 over load ratio were all applied to the parent steel. The goal of this study is to add to the body of knowledge required for the safe design and long-term service life of weldments that are subjected to single tensile and continuous amplitude overloads. The region II Paris equation is satisfied by the data, which are virtually log-log linear. For all material test settings, the overload cycles to failure for a given R ratio fell within a factor of 3.0 or less, which is again a relatively modest variance between materials. The range of retardation cycles, or NR, is roughly 3.0 x 110 to 5.0 x 110 cycles. This indicates that for R ≈ 0, fatigue crack growth life rises from roughly 300 to 500%. This shows that every material condition that was examined reacted well to the single tensile overloads. In the Paris log-log linear zone, the resistance to fatigue fracture growth was constant for all four material situations. There was just a factor of two difference between fatigue life and fatigue crack growth rates.