Miikka Väntänen

• Global Boiler Works Oy

A model for the probabilistic cyclic R-curve has been derived. The model is based on the commonly used hypothesis of consecutive microstructural barrier fronts defining the erratic behavior of microstructurally short cracks and the transition to physically short cracks with declining importance of the microstructural features. The model can describ...

This work explores the effects of underloads on physically short fatigue cracks propagating under near-threshold zero–tension loading in various constraint conditions. A finite element model is employed to model the transient behavior of plasticity-induced crack closure and residual stress, from which propagation behavior can be inferred. The expec...

The purpose of present work is to deepen the understanding of crack propagation, non-propagation, and fatigue limit. Quantitative prediction of fatigue crack non-propagation in constant amplitude loading is attempted through extensive 3D elastic–plastic finite element analysis of near-threshold propagation of short cracks nucleating from surface de...

The microstructure and nodule count of large-size nodular cast iron components vary spatially. These variables are qualitatively known to affect the fatigue limit, yet no model exists to quantify the effects. Some of the physical aspects, such as the clustering of graphite nodules and the role of ferrite microhardness in ferritic-pearlitic nodular...

A hierarchical Bayesian approach to analysing fatigue test data including reinserted specimens is proposed. It is found that the inference model is capable of fitting the fatigue damage model to the observed data well. After the addition of rerun specimen data, the results show a significant change in the predictive SN curves. For the analysed 40Cr...

A novel approach for inferring the underlying non-metallic inclusion distribution from fatigue test fractography is presented. It is shown that the non-metallic inclusion size distribution obtained from fatigue testing differs from the extreme value distributions, which do not take fatigue into account. Fatigue, as a process, acts as a filter for t...

This article describes the fatigue testing of QT steel in ultrasonic frequencies. Different possibilities, challenges and prejudices are reviewed.

A Bayesian sequential experimental design for fatigue testing was implemented on the basis on D-optimality and a non-linear continuous damage model. The design accounts for the whole range of testing levels.