PSI - Issue 77

João Nuno Silva et al. / Procedia Structural Integrity 77 (2026) 657–664

659

Joa˜o Nuno Silva et al. / Structural Integrity Procedia 00 (2026) 000–000

3

freight wagons. Part 2 is dedicated to structural requirements for freight wagons and is the principal reference for the present case study, which concerns a welded construction detail of a railway freight wagon. The EN 12663-2 standard formalizes a test-based philosophy for fatigue verification. It first specifies wagon specific fatigue load cases, considering vertical and transverse accelerations representative of track irregularities and operational actions. Also, prescribes that under the specified static loads, the measured stresses at defined locations (strain-gauge positions) shall not exceed the permissible stresses tabulated in the code. These permissible values are derived through Haigh (Goodman) mean-stress interaction, and use the same notch case classification as ERRI B 12 / RP60 technical code.

2.3. DVS 1612

The DVS 1612 technical code provides a structured methodology for assessing the fatigue resistance of welded railway structures. To select the appropriate notch-case lines and associated fatigue parameters, the welding process, stress orientation, weld geometry, and weld performance classification based on the standard EN 15085-3 (2023) must be considered jointly. Nominal stress components (longitudinal, transverse, and shear stresses) are extracted at representative points along the joint, typically at a distance of 1.0 to 1.5 times the plate thickness from the weld toe or root, as the guideline prescribes. The stress histories obtained for each load scenario identify the maximum and minimum values for every stress component, enabling the definition of stress ratios and the subsequent use of the code’s verification formulas. Allowable fatigue stresses are determined from the Moore–Kommers–Jasper (MKJ) diagrams, which provide stress limits for each notch case as a function of mean stress regime, stress component, material (structural steel grades S235 and S355), and notch case. Notch cases encompass welded joints, heat-a ff ected zones, and base materials, with normal stress components classes ranging from A + (highest resistance) to F3 (lowest), where most classes include sub-levels (e.g.,A + , A, A-) and F2–F3 are single curves; for shear stress component, the classification ranges from G + toH-.The permissible values for longitudinal and transverse normal stresses are evaluated separately for tensile and compressive mean-stress regimes via Equations 4 and 5, respectively. Being σ the normal stresses, τ the shear stress, R the stress ratio, and k the inverse stress ratio, in compression. The corresponding permissible value for shear follows Equation 6.

2 · (1 − 0 . 3 · R σ ) 1 . 3 · (1 − R σ )

σ zul = 150MPa · 1 . 04 − x ·

(4)

2 1 − k

σ zul = 150MPa · 1 . 04 − x ·

(5)

2 · (1 − 0 . 17 · R τ ) 1 . 17 · (1 − R τ ) ·

(6)

τ zul , R = − 1

τ zul =

These expressions depend on the notch-dependent parameters x and τ zul , R = − 1 defined by the code. All calculated permissible stresses are then corrected for thickness and finally limited by the material’s yield strength; for shear, the upper bound is the yield strength divided by √ 3. Verification proceeds by checking that the individual usage factors for the three nominal components satisfy Equation 7, and that the combined multiaxial interaction remains within the limit set by Equation 8. Compliance with these criteria guarantees a minimum fatigue life of 2 × 10 6 cycles with 97.5% survival probability.

σ ∥ σ ∥ , zul

σ ⊥ σ ⊥ , zul

τ τ zul ≤

U f ∥ =

≤ 1 ; U f ⊥ =

≤ 1 ; U f τ =

1

(7)

U f , Multi =

+

+

σ ∥ σ ∥ , zul

σ ⊥ σ ⊥ , zul

τ τ zul

2

2

2

σ ∥ σ ∥ , zul

σ ⊥ σ ⊥ , zul

≤ 1 . 1

(8)

−

·