Performance of UT creeping waves in crack sizing

Crack sizing is of fundamental importance for achieving safety and reliability in design and validation of mechanical structures, especially considering wide-spread and well-known fatigue design methodologies such as the “Damage Tolerant Approach”. From this point of view, the present paper analyses the so-called “Creeping Waves”, sub-surface longitudinal waves sometimes suggested in the literature as particularly useful in crack sizing. To this aim, experimental results obtained from a dedicated sample block have been compared with suitable numerical simulations carried out by means of both CIVAnde® v. 9.1 and WAVE2000® Pro v.2.2. From the results, some advantages of the CW technique remain confirmed, but some strong limits of their application to crack sizing could also be defined.