We are pleased to announce that the Scientific Council of the IPPT PAN has awarded Adam Brodecki the degree of Doctor in Engineering and Technical Sciences, in the discipline of Mechanical Engineering. The title of his dissertation is: “Monitoring the Development of Fatigue Damage in Boiler Steels Supported by Optical Measurement Systems.” The supervisor of the dissertation was Prof. Zbigniew L. Kowalewski and the assistant supervisor was Assoc. Prof. Mateusz Kopeć at IPPT PAN.
Conventional fuel-powered power plants are still the main source of Poland's energy security, guaranteeing over 85% of the demand for electricity. However, most Polish power plants were put into operation in the 1960s or 1970s. During the construction of these power units, their durability was design to withstand a certain number of operating hours under specific conditions. The safe operating time for most units has already been significantly exceeded, thus many approaches have been performed to monitor the condition of structural elements. During the commissioning of these energy facilities, the heat-resistant materials used for heating devices and steam transportation exhibited significantly lower strength as compared to the contemporary materials. During repairs and the construction of new structures, increasingly advanced heat-resistant materials such as stainless steels or nickel-based alloys are being used. Despite the application of such advanced materials, there is still a lack of sufficient research focused on predicting their behaviour prior to failure. Therefore, this study proposes a methodology to assess the effectiveness of non-destructive testing based on optical measurement systems in damage development monitoring in heat-resistant steels subjected to cyclic loading. The comparative studies were conducted on heat-resistant, power engineering steels, X10CrMoVNb9-1 (P91) and 10CrMo9-10 (10H2M), used in the construction of pipelines and supercritical steam distribution systems. Comparative tests were carried out on materials in the as-delivered state and after prolonged operation for 80,000 hours (P91) and 280,000 hours (10H2M) at temperature of 540°C and internal pressures ranging from 2,9 MPa to 8,4 MPa. A series of strength and microstructural tests were conduct, including uniaxial tensile tests, and high and low cycle fatigue tests under stress amplitudes ranging from 250MPa to 650MPa, to characterize the damage mechanisms depending on the material's damage degree. The damage development due to fatigue was monitored using optical measurement methods: Electronic Speckle Pattern Interferometry (ESPI) and Digital Image Correlation (DIC). Additionally, measurable parameters of material damage, such as the strain-based fatigue damage measure ϕ and the fatigue damage parameter D, were utilized to characterize the dynamics of material damage development.
