Quantitative relationship between weld defect characteristic and fatigue crack initiation life for high-cycle fatigue property

The microstructure, mechanical, and fatigue behaviours of MAG welded G20Mn5 cast steel

“…The shrinkage surface or subsurface defects introduced by the casting become the primary failure origins. Therefore, the fatigue failure is prone to initiating from the near‐surface shrinkage introduced by the casting process rather than those welded defects . Furthermore, in each case, a single dominant crack originating from a critical defect is evidently observed on the fracture surface.…”

Analysis on peculiar fatigue fracture behaviour of shot peened metal using new threshold stress intensity factor range equation

“…The ability of shot peening to hinder the initiation and retard the subsequent propagation of surface cracks was discussed on the basis of a model combining a multiaxial fatigue criterion and a fracture mechanics approach. Shao et al 12 investigated the effect of interior defects on the high-cycle fatigue life of welded joints made by narrow-gap arc welding. The threshold value of the stress intensity factor at R = 0 (ΔK th, 0 ) was a suitable parameter for the fatigue life partition by considering the incremental life in the near-threshold regime.…”

Structural integrity assessment of rail steel failure modes and mechanism

“…It shows that the shape changing of mould will significantly improve the service cycles of thermite welding. The continuously welded joints are the weak points of the rail [28][29][30][31]. The past studies showed that more than 60% of rail failures are resulted from welded joints failures [32] and among these welding failures thermite welding was the most frequent compared with other welding methods [33].…”

“…The thermite welded rail joint, particularly the weld-toe region or the interface between the fusion zone and heat affected zone, is susceptible to fatigue damage formation [37][38][39]. The assessment of structural integrity is required to take account of the effects of the unusual service loadings [9,32,[40][41][42][43] including the residual stress state, and the presence of discontinuities [14,30,[44][45][46] or other circumstance with respect to the potential failure modes by fracture or fatigue. The unusual service load, together with the residual stress arisen from the welding process plays a role in the structural deterioration of the welded joint.…”

“…The welding process causes localized changes of material characteristics across the welded joints, causing the assembled rails susceptible to fatigue failures [58]. It is found that around 60~80% of rail weld failures occur at the heat affected zone (HAZ) [28,29], especially at the fusion line [30,31]. Based on the literature review of Chapter 2, the comprehensive material characterizations of thermite welded rail joints have not been clearly revealed.…”