Innovative technologies for nondestructive determination of fracture toughness for pipeline steels in transportation infastructure

In the inspection and quality assurance framework, coercimetry refers to non-destructive testing of mechanical properties based on measurements of the magnetic characteristics of a metal. This technology relies on the continuous and noticeable (100-400%) increase in the magnitude of the coercivity, while the metal passes from as-delivered to its final state. As both magnetic and mechanical properties are determined by intrinsic microstructure, it is possible to formulate empirically calculated correlations between them. This technology is widely used to assess fatigue state on metal pipes (Bezlyudko et al., 2010), but has never been used to evaluate fracture toughness. Having overcome the fundamental philosophical dilemma of characterizing limit properties through nondestructive methods, coercimetry offers a solid ground base for the development of the proposed innovative solution. COMET’s main objective is to develop the first coercimetry-based fracture toughness assessment solution. Phase I demonstrated the technical feasibility of a non-destructive testing solution, based on coercivity metering, to assess material fracture toughness of steel pipelines; evaluating the correlation between coercivity and facture toughness. Phase II will empirically stablish a correlation model between coercivity and fracture toughness trough extensive laboratory trials and develop a first prototype for field deployment. The scope of the project includes testing in samples of different materials subject to at least 5 different heat treatments, and also measurements on samples under load, a representative state of in-service pipelines.