PSI - Issue 75

Elena Sidorov et al. / Procedia Structural Integrity 75 (2025) 276–288 Elena Sidorov et al. / Structural Integrity Procedia (2025)

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4. Numerical investigations on contact surface imperfections The ANSYS software package is used to create a FE model in order to calculate the test specimens as shown in Figure 7a. A regular mesh of 8-node solid elements (SOLID185) is implemented for the rail with an element size of 1 mm at the bottom of the rail. The weld and the flange are meshed free with 10-node tetrahedron volume elements (SOLID187). Contact elements (CONTAC174) are placed on the bottom side of the rail. The corresponding target elements (TARGE170) are located on the top side of the flange. The following nominal cross-sectional dimensions are implemented for test-specimen type 1 as shown in Figure 5a: b r = 50 mm, h r = 30 mm, weld size a = 5 mm without penetration, t f = 13 mm, t = 17 mm, b sup = 30 mm, d = 17,50 mm. The relevant dimensions of type 2 as shown in Figure 5b are the same except for h r = 50 mm. For the test specimen type 3 as shown in Figure 5c with support along the entire flange bottom side, the following nominal cross sectional dimensions are implemented: b r = 50 mm, h r = 30 mm, weld size a = 5 mm without penetration, t f = 15 mm, b sup = 100 mm, d = 20 mm. Figure 5 also indicates the boundary conditions. An extended Lagrange contact formulation with a friction coefficient of 0.5 is used. An ideal elastic behaviour of steel with a modulus of elasticity E = 210 000 N/mm² and a Poisson's ratio = 0.33 is assumed. The load F = 100 kN is uniformly distributed over the top of the rail. To simulate the technical contact as visible in Figure 7b, a wedge shaped gap with a maximum value of g con as shown in Figure 7c is implemented in the FE model. The choice of this special shape of the gap is based on the investigations in (Sidorov & Euler, 2024). The weld toes and roots are not rounded off since the focus of the investigation is laid on the evaluation of the nominal stress level.

Fig. 7. Calculation of small-scale specimens: a) FE model, b) a) micro-section of test specimen No. 205 from type 1, c) wedge-shaped gap of the FE model to simulated the technical contact (exaggerated illustration of gap) 5. Comparison of experimental and numerical results 5.1. Introduction Due to the small dimensions of the test specimens, an unavoidable eccentricity of the test load was observed in the experimental investigations. For the comparison with the numerical results, that do not include any eccentricity, the bending portion of the experimental data was extracted by Eq. (3) that averages the strain value ε DIC obtained by DIC and that obtained by the strain gauge ( ε gauge ) at the same positions at the front and back side of the test specimens.

ε

+

ε

DIC gauge

ε

=

(3)

exp

2

5.2. Top flange being exclusively supported by the web Figure 8a compares the experimental and the numerical strains in the flange of the test specimens of type 1 with chain intermittent rails welds that are only supported by the web. The corresponding strains for the staggered intermittent rails welds (type 2) are illustrated in Figure 8b. For both types, the experimental results underneath the rail scatter around the result of the FE model. There is only a little difference between the numerical results for the assumed gap sizes g con = 30 µm and 50 µm.