Christian Doppler Labor für Defekttoleranz von Stählen im Bereich hoher und sehr hoher Belastungszyklen

The so-called green transition – which refers to a general concept that shall allow for turning the current non-sustainable into a climate-neutral scenario – is one of the most urgent challenges for today´s generation. In this context, the sustainable and resource-efficient use of materials makes a significant contribution to ecological change and to a modern, competitive economy. Material fatigue is the most common reason for failure of technical components, and therefore must be considered as one of the determining mechanisms for the period of use. The optimal component design enables economical use of materials – which considers the energy-efficiency of lightweight constructions – and durability (i.e. very long lifetime). The defect-tolerance approach is based on the assumption that structures do contain crack-like defects. Designing components for maximum service life according to this methodology therefore means that crack growth must be prevented. Applying this concept enables to correlate endurable stresses with the size and geometrical parameters of defects by the use of fracture-mechanics principles. Such defects may be material-inherent (e.g., pores, cavities, nonmetallic inclusions, material inhomogeneities) or production- and application-related (e.g., scratches, punch marks, surface roughness, corrosion pits) and cannot be completely avoided. A safe component design, therefore, ensures that cyclic stresses occurring at relevant locations do not exceed a critical value – which depends on the expected maximum defect size (and geometry). Furthermore, it must be considered that with progressing service life, failure mechanisms may change: fatigue cracks can initiate in the interior of a material rather than on the surface or environmentally degrading effects may become relevant (corrosion fatigue). The declared goal of the CD laboratory is to systematically investigate the high and very high cycle fatigue properties of steels as well as to identify the underlying fracture mechanisms and the relevant parameters for predicting the cyclic strength. Using innovative methods, such as the ultrasonic fatigue testing systems developed at the Institute of Physics and Materials Science (IPM-BOKU), will serve to obtain comprehensive material data within reasonable time and – highly relevant nowadays – with minimum input of energy. Based on fracture-mechanics principles, the obtained data will be evaluated with the aim to develop an appropriate fatigue-strength prediction method. In addition, artificial intelligence (machine learning) is applied to enable optimisation of properties under cyclic loading. The results will enable the company partner to develop competitively viable, resource- and cost-efficient steel belt systems and the project leader and his team at BOKU to further strengthen their expertise in defect-tolerance and very high cycle fatigue.