Detection of mechanical damage using Lamb or Rayleigh waves is limited to relatively simple geometries, yet real structures often incorporate features such as free or clamped edges, welds, rivets, ribs and holes. All these features are potential sources of wave reflections and scattering, which make the application of these types of guided waves for damage detection difficult. However, these features can themselves generate so-called ‘feature-guided’ waves. This article details the first application of the fundamental mode of transient edge waves for detection of mechanical damage. The fundamental edge wave mode (ES₀) – a natural analogue to Rayleigh waves – is weakly dispersive and may decay with propagation distance. The phase and group velocities of the ES₀ wave mode are close to the fundamental shear horizontal (SH₀) and symmetric Lamb (S₀) wave modes, at low and high frequencies, respectively. It is therefore quite challenging to excite a single ES₀ mode and avoid wave coupling. However, it was found experimentally that at medium range frequencies the ES₀ mode can be decoupled from SH₀ and S₀ modes, and its decay is small, allowing for distant detection of defects and damage along free edges of slender structural components. This article provides a brief theory of edge waves, excitation methodology and successful examples of distant detection of crack-like and corrosion damage in I-beam sections, which are widely applied in engineering and construction.

Additive manufacturing offers greater flexibility in the design and fabrication of structural components with complex shapes. However, the use of additively manufactured parts for load-bearing structural applications, specifically involving cyclic loading, requires a thorough investigation of material fatigue properties. These properties can be affected by many factors, including residual stresses and crack tip shielding mechanisms, which can be very different from those of conventionally manufactured materials. This research focuses on super duplex stainless steels (SDSSs) fabricated with wire arc additive manufacturing (WAAM) and investigates their fatigue crack growth rates and the net effect of crack tip shielding mechanisms. Using the compliance-based method, we measured crack tip opening loads in compact tension (CT) specimens with cracks propagating longitudinally and transversely to the WAAM deposition direction. It was found that fatigue crack growth rates were very similar in both directions when correlated by the effective stress intensity factor range. However, the differences in crack tip opening loads explain a quite significant influence of the deposition direction on the fatigue life.