A Method for Monitoring Vibrational Fatigue of Structure and Components

A vibration fatigue monitoring system has been developed by Framatome to assess, in real time, the evolution of industrial structures, systems and components lifetime expectancy. Its originality comes from the fact that only one or a few acceleration measurements are necessary to re-construct the complete stress history in the whole structure, including on welds or bolted connections that could not have been directly instrumented. From this stress history, a fatigue analysis with a rainflow counting algorithm is conducted and the cumulative usage factor of each weld or bolt is determined. The remaining life duration is then estimated. The method has been numerically and experimentally validated in that sense that the reconstructed stress histories were successfully compared to direct stress calculations and measurements. The system was then installed on five industrial structures submitted to transient dynamic excitations. It is expected that it will soon find further applications notably in monitoring vibrations induced during power plants transients that may induce some temporary resonance of piping equipment. Finally, the vibration monitoring system can also be combined with a thermal fatigue monitoring system, many of which are already deployed, at least on nuclear power plants, and the reconstructed stresses might include both thermal and mechanical effects. Installing such a fatigue monitoring on a set of sensitive systems and components could be a valuable brick in the present trend of building digital twins of power plants or other industrial structures.

Effect of Shot Peening on the Surface Oxidation of P92 Steel in the Steam Environment at 600°C

A vibration fatigue monitoring system has been developed by Framatome to assess, in real time, the evolution of industrial structures, systems and components lifetime expectancy. Its originality comes from the fact that only one or a few acceleration measurements are necessary to re-construct the complete stress history in the whole structure, including on welds or bolted connections that could not have been directly instrumented. From this stress history, a fatigue analysis with a rainflow counting algorithm is conducted and the cumulative usage factor of each weld or bolt is determined. The remaining life duration is then estimated. The method has been numerically and experimentally validated in that sense that the reconstructed stress histories were successfully compared to direct stress calculations and measurements. The system was then installed on five industrial structures submitted to transient dynamic excitations. It is expected that it will soon find further applications notably in monitoring vibrations induced during power plants transients that may induce some temporary resonance of piping equipment. Finally, the vibration monitoring system can also be combined with a thermal fatigue monitoring system, many of which are already deployed, at least on nuclear power plants, and the reconstructed stresses might include both thermal and mechanical effects. Installing such a fatigue monitoring on a set of sensitive systems and components could be a valuable brick in the present trend of building digital twins of power plants or other industrial structures.

Damage comparative analysis of needled C/SiC composite under vibration fatigue loading and monotonic tensile loading

Needled C/SiC composite is composed of fiber and matrix, witch fatigue limit is related to the vibration loading frequency. A kind of plate specimen made of needled C/SiC composite was tested on a shaking table, and the vibration fatigue life of each specimen was obtained. In addition, the monotonic tensile test of needled C/SiC composite specimen was also carried out. Furthermore, the fracture morphologies from vibration test and monotonic tensile test were compared by scanning electron microscope. And the mechanism causing these differences was also explained.