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Contract summary report OZM-LCF-2023: Experimental evaluation of low cycle fatigue properties of steel 1.4529
Štefan, Jan ; Parma, Slavomír
This technical report was prepared within the framework of the contract "OZM-LCF-2023: Experimental evaluation of the properties of steel 1.4529 in terms of low cycle fatigue". The report clearly documents all relevant information concerning the technical performance of the contract, starting from the design of the experimental program, through the protocols of the experiments performed, to the summary evaluation of the program, including proposals for possible contract extension and follow-up experimental activities.
Overview documentation of notches produced by laser burning technology into pipe bodies within the project TK01030108 (NEMENUS)
Štefan, Jan
This technical report has been prepared within the project DP_04_02_04: Research of applicability of modern SHM (Structural Health Monitoring) systems for increasing reliability and economic efficiency of nuclear power plant operation (existing, new and small modular reactors). The purpose of this report is to provide an overview documentation of the experience with laser technology, which has been successfully applied in the previous TAČR project TK01030108 (NEMENUS project, 2020 and 2022) for the production of notches into pipe test specimens, and which is expected to be advantageously used also in the experimental program of the current project. The information gathered in this document will help in the specification of the assignment to the provider of this service (ATG, s.r.o.), and in the optimization of the laser parameters for the purpose.
Review of report ÚJV DITI 2301/1308 – Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR
Štefan, Jan ; Gabriel, Dušan
This technical report has been elaborated for the State Office for Nuclear Safety (SÚJB) in the framework of expert support in the field of strength and durability assessment. The report was elaborated as a review on the technical report: ÚJV DITI 2301/1308: Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR elaborated by the staff of the Strength and lifetime evaluation department of ÚJV Řež, a. s. The purpose of the report T575/23 was to provide the SÚJB with an independent review of the statements made by the authors of the ÚJV report. In accordance with the requirement of SÚJB, the emphasis was placed on the material aspects of the issue. The reviewer expressed a favourable attitude towards the submitted UJV report with only one major objection to one aspect of the issue of radiation swelling and a few minor comments of a mostly formal nature.
Development of autonomous experimental system to analyse yield surfaces distortion due to multiaxial ratcheting
Svárovský, Jiří ; Parma, Slavomír ; Štefan, Jan ; Ciocanel, C. ; Feigenbaum, H. P. ; Marek, René ; Klepač, Vilém ; Plešek, Jiří
Multiaxial ratcheting is a failure mode of structures characterized by the accumulation of plastic strain due to cyclic loading. Despite several models having been developed to predict multiaxial ratcheting, they often fail when validated with experimental data collected under a wide array of loading conditions. In this study, an experimental setup was developed and an autonomous testing procedure was used to experimentally analyze the evolution of the yield surface shape due to cyclic biaxial loading. Thin-walled tubular test specimens were made of 304L steel with a diameter of 40mm and underwent axial-torsional testing using the Instron 8852 system. The total axial strain was increased from 0 to 1% while the total shear strain underwent 5 cycles with the strain amplitude of 0.5% and the mean strain of 0.5%. Three yield surfaces were measured after the straining sequence was completed. Results showed strong directional distortional hardening and good agreement between the flow vectors and the normals to the yield surface, lending support to the associative flow rule.
Deep learning methods for the acoustic emission methods to evaluate an onset of plastic straining
Parma, Slavomír ; Kovanda, Martin ; Chlada, Milan ; Štefan, Jan ; Kober, Jan ; Feigenbaum, H. P. ; Plešek, Jiří
Development of phenomenological plasticity models, hardening rules, and plasticity theories relies on experimental data of plastic straining. The experimental data are usually measured as the stress–strain response of the material being loaded and do not provide any clues or information about the local response of\nmaterial. In this paper, we analyze the plastic deformation of the material using the acoustic emission method and current state-of-the-art neural network models such as the InceptionTime architecture.
Calibrated finite volume method-based simulation framework for laser shock peening
Isoz, Martin ; Gruber, Pavel ; Schmidt, Jaroslav ; Kubíčková, Lucie ; Štefan, Jan ; Kaufman, Jan ; Brajer, Jan ; Gabriel, Dušan
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening processes, such as the shot peening, are widely used in both automotive and aerospace industries. The laser shock\npeening (LSP), i.e. hardening of the material surface by a laser-induced shock wave, is a modern alternative to the standard peening. Concurrently, the industrial applications of LSP are promoted by recently emerged affordable high power-density lasers. However, the nascent LSP applications are still mostly a trial-and-error\nprocesses based on an extensive experimental testing. Consequently, we focused on a highly application-driven development of a framework for LSP modeling, and the internal workings and results of which are the focus of the present contribution.
V5: Report on further collaboration with R6 Panel
Joch, Jaroslav ; Štefan, Jan
This report presents obligatory output V5 of project TAČR TK01030108: Innovative methods for nuclear plant safety evaluation based on SHM technologies and related procedures - NEMENUS (NEw MEthods for NUclear Safety). The report presents program of further collaboration with R6 Panel and other foreign partners established during the project.
V7: Summary report NEMENUS for SÚJB
Štefan, Jan ; Joch, Jaroslav ; Převorovský, Zdeněk ; Gabriel, Dušan ; Krofta, Josef ; Chlada, Milan ; Kober, Jan ; Masák, Jan ; Kunz, J. ; Ashhab, B.
This is the final report of project TAČR TK01030108: Innovative methods for nuclear plant safety evaluation based on SHM technologies and related procedures - NEMENUS (NEw MEthods for NUclear Safety). In this report, the most important project results and outputs are presented, as well as a summary of its contributions with respect to long-term technological horizons.
V6: Report on functional sample NEMENUS
Štefan, Jan ; Joch, Jaroslav ; Převorovský, Zdeněk ; Gabriel, Dušan ; Krofta, Josef ; Chlada, Milan ; Kober, Jan ; Masák, Jan ; Materna, A. ; Kovářík, O. ; Čech, J.
This research report is an integral part of mandatory output V6: FUNCTIONAL SPECIMEN of project TAČR TK01030108: Innovative methods for nuclear plant safety evaluation based on SHM technologies and related procedures - NEMENUS (NEw MEthods for NUclear Safety). The report presents full technical description of the elaborated representative functional specimen (the representative SHM model) and the description of a four-year experimental program.
Development of autonomous experimental setup to investigate directional distortional hardening under biaxial loading
Svárovský, Jiří ; Parma, Slavomír ; Štefan, Jan ; Ciocanel, C. ; Feigenbaum, H. P. ; Klepač, Vilém ; Marek, René ; Plešek, Jiří
Plastic deformations alter the shape of the yield surface in the stress space. Models for predicting the shape of the yield surface according to the direction of loading are being developed. Experimental data are the key factor in development and validation of phenomenological models, such as the model of directional distortional hardening cited in this study. The objective of this paper is to present the experimental setup for investigation of the directional distortional hardening. A new autonomous method was developed using an axial-torsional testing machine and the Labivew 2017 graphical programming environment to monitor the yield surface in axial stress – shear stress space. A suitable yield condition in form of effective plastic strain was used for the determination of the yield points. Initial yield surface obtained by this method shows promising agreement with von Mises model of the yield surface. Several outstanding yield points were measured which disrupt the assumption of the yield surface convexity. Therefore, possible shortcomings caused by the methodology are being investigated.

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3 Štefan, Jakub
4 Štefan, Jiří
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