Dissertation: High-Strength Steel structural members susceptible to fatigue failure

Demanding strength, manufacturability and critical weight limitations are generally the main criteria in the design and fabrication of structural components. According to the dissertation from LUT University by Mohammad Dabiri, titled The Low Cycle-Fatigue of S960 MC Direct-Quenched High-Strength Steel, the emergence and development of ultra-high and high-strength materials, especially steels benefiting from an excellent high strength to weight ratio, along with their acceptable manufacturability, led to the special role that these materials play in the industry. 

Although they are so promising for components that experience static loading conditions, their dominant field of application (i.e. mobile machineries and equipment) imposes fluctuating service loads on them, making these structural members susceptible to fatigue failure.

In addition, due to the inevitable presence of stress raisers in real components, the high-strength steels, with their high-notch sensitivity, could suffer more compared with other commercial low- and medium-strength steels.

According to Dabiri, the importance of knowing the material response and its characteristics specifically under cyclic loading and subsequent fatigue failure acted as the principal incentive to study particularly S960 MC Direct-Quenched High-Strength Steel. The study by Dabiri covers the aspects of microstructural analysis, experimental tests and numerical simulations. The main goals and contributions can be divided into two categories, as follows:

      I.        New results through experimental tests and measurements

     II.        Novelties created through utilizing the mathematical and numerical techniques


The findings of the current study are valuable in industrial and academic point of views. The results will be a huge help for the manufacturers seeking the microstructural analysis and techniques to improve their products and also designers and researchers to utilize or perform the further improvements to the proposed methods and approaches in this thesis.



Information for the intranet

Mohammad Dabiri, Master of Science in Technology, will defend his doctoral dissertation at LUT on October 18thin lecture hall 2303 at 12:00. His dissertation is titled The Low Cycle-Fatigue of S960 MC Direct-Quenched High-Strength Steel. Associate Professor Zuheir Barsoum from KTH Royal Institute of Technology, Sweden will act as opponent. Professor Timo Björk of LUT will act as custos.


Library information

The dissertation has been published in the Acta Universitatis Lappeenrantaensis research series number 807 of the university. ISBN 978-952-335-257-5, ISBN 978-952-335-258-2 (PDF), ISSN 1456-4491. The electronic version can be found from LUTPub-database. A printed version of the dissertation may be purchased from the Aalef bookstore, tel. +358 44 744 5511, or at kirjakauppa@aalef.fior online from the LUT Shop: https://lutshop.lut.fi/.