PSI - Issue 58

Lucie Malíková et al. / Procedia Structural Integrity 58 (2024) 68–72 Lucie Malíková et al. / Structural Integrity Procedia 00 (2019) 000–000

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design light-weight structures. Two of the problems arising in HSS structures is to achieve a balance between tensile strength and fatigue performance without losing weldability and to overcome corrosion that is the greatest disadvantage for instance of steel bridges. Corrosion pits and defects are the typical surface damages and can cause crack nucleation and/or additionally decrease of mechanical and fatigue properties, see e.g. Balbín et al. (2021), Cui et al. (2020), Fatoba and Akid (2022) or Guo et al. (2021). Initiation of fatigue cracks based on the existence of corrosion defects/pits is described for instance in Bastidas-Arteaga et al. (2009), Chen et al. (2021) or Xu and Wang (2015). In this work, the mutual interaction of two corrosion pits is investigated. Via the finite element method (FEM) the stress field is analyzed and stress concentration is evaluated for various geometries of corrosion pits and their various mutual distances. Geometry of the numerical model is based on the real specimens prepared for fatigue tests under various levels of corrosion. Previous results on this topic can be found for instance in Malíková et al. (2023).

Nomenclature CC

mutual distance of the adjacent corrosion pits

corrosion pit depth specimen length corrosion pit length corrosion pit radius

D L

LC RC

W specimen width   appl applied stress range  xx

stress tensor component in the horizontal direction stress tensor component in the vertical direction

 yy

 vonMises von Mises stress

2. Numerical model Cylindrical specimens were produced for the experimental campaign from three different HSS, i.e. S460, S690 and S960 to investigate their fatigue behavior affected by various levels of corrosion, see Fig. 1a. Dimensions of the specimens can be seen in Fig. 1b and finally the schema of the suggested numerical model of the middle part of the corroded specimen is presented in Fig. 2c. The numerical model is two-dimensional and represents a longitudinal central plane of the specimen. The dimensions of both the specimen and the corrosion pits used within the numerical simulations are as follows:

 specimen length, L = 24 mm;  specimen width, W = 4 mm;  corrosion pit depth, D = 0.1 to 0.5 mm;  corrosion pit length, LC = 4× D = 0.4 to 2 mm;  corrosion pit radius, RC = ( LC 2 +4 D 2 )/8 D ;  mutual distance of the adjacent corrosion pits, CC = 0.1 to 1 mm.

The numerical simulations were performed via ANSYS commercial software and PLANE183 elements with quadratic displacement behavior were used to create the specimen. Refinement of the regions along the surface of the corrosion pits and their neighborhood was defined. The size of the smallest element used at the corrosion pits surface as well as in their closest vicinity was 0.005 mm in all configurations under the study. Due to symmetry, only one half of the specimen could be modelled. Plane strain conditions were applied. Model of the HSS was considered to be linear elastic with the following constants: Young’s modulus of 210 GPa and Poisson’s ratio of 0.3. Tensile loading range was assumed 100 MPa on both upper and bottom side of the specimen. The stress distribution along the specimen centre (path 1 in Fig. 1c) as well as on the corrosion pits surface (path 2 in Fig. 1c) was investigated. The results obtained and their discussion can be found in the following section.