PSI - Issue 17

Peter Trampus et al. / Procedia Structural Integrity 17 (2019) 262–267 Trampus et al / Structural Integrity Procedia 00 (2019) 000 – 000

265

4

to-brittle transition temperature) and can contribute to the propagation of cracks due to fatigue and/or corrosion or, in case of radiation environment, irradiation assisted fatigue or irradiation assisted corrosion. Consequently, the true assessment of structural integrity should take into consideration a continuous decrease in safety margins. This decrease will compromise the component’s integrity and put its safety at risk . For a reliable assessment, all three inputs are equally important. Since the energy requirement for ductile failure is far greater than required for fracture in the brittle mode, the basic tool of structural integrity assessment is the fracture mechanics. The assessment may either be deterministic or probabilistic. Fracture mechanics allows the calculation of the limit of loading conditions for the material, complete with its mechanical properties and intrinsic flaws (e.g. cracks, lack-of-fusions), such that these flaws remain stable and not propagate. To be able to take ageing effects into consideration, a vast knowledge on materials science is also inevitable.

Loading, environment

Crack propagation (e.g. fatigue, corrosion)

Change in material properties (e.g. embrittlement, loss of toughness)

K I < K Ic or

P f < 5∙10

-6 /y

Material properties

Flaws

Decrease in safety margin

Fig.1. Scheme of structural integrity assessment and the interrelations of the elements (K I and K Ic are the stress intensity factor and its critical value; P f is the probability of failure)

5. The NDT integrity engineer competences

We have recognized and briefly introduced the role and the evolution of NDT in a safety conscious world. Furthermore, we demonstrated the explicit need for ensuring the integrity of both high-performance engineering structures and components as well as structures and components of ageing assets, such as power and process plants, petrochemical and off-shore facilities. We have also recognized the gap between the NDT person delivering inspection results and managers making decision based on the results. We are strongly convinced that this subject matter expertise can and must be added to the NDT/structural integrity assessment quality process and most importantly to the safe and reliable operation of high-risk facility structures and components. It was stated in the introduction that the up-to-date and future NDT belongs to STEM. With other words it means that NDT participates in the revolutionary process triggered by spreading of digitalization, cyber-physical systems, cloud-based informatics and artificial intelligence, i.e. the basic attributes of Industry 4.0. Under the name of NDT 4.0 clear concepts have already been elaborated which are trying to find the right position for the development in the field of NDT with regard to and within the Industry 4.0. NDT integrity engineering is an inseparable element of this process.