PSI - Issue 57

Matthias Winkler et al. / Procedia Structural Integrity 57 (2024) 510–517 Matthias Winkler / Structural Integrity Procedia 00 (2019) 000 – 000

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2.1.2. Hammer peening Hammer peening (or high frequency mechanical impact treatment - HFMI) also increases the notch radius by plastically deforming the weld toe with a hardened steel pin that is accelerated by a pneumatic actuator. Additionally, the plastic deformation increases the material hardness and introduces compressive residual stresses in the vicinity of the weld toe resulting in an improved fatigue resistance. However, the amount of the positive effect is dependent on the yield strength of the treated material f y (higher f y means greater effect) and the stress ratio R of the cyclic load (higher R means lower effect). Hammer peening is considered in the IIW-recommendations (Hobbacher, 2016) and (Marquis and Barsoum, 2016) and in annex F of prEN1993-1-9 ( prEN 1993-1-9 , 2021) that evolved from the German guideline DASt-026 ( DASt-Richtlinie 026 , 2019). Table 1 shows exemplarily an overview of improvement factors for a transverse stiffener treated by hammer peening that are given in the implied design codes.

Table 1. Improvement factors for the fatigue resistance of a transverse stiffener in reference to EN 1993-1-9 (nominal stress concept, Δσ C = 80 N/mm², l < 50mm, t < 25mm, σ max < 0,8*f y , Δσ < 1,5*f y )

Design code

f y [N/mm²]

R [-]

Δσ c,HFMI [N/mm²]

Improvement [%]

prEN 1993-1-9 / DASt-026 IIW - Hobbacher IIW - Marquis

235 - 700 235 - 900 235 - 950

-1 – 0.5

80- 160

0 - 100

0 – 0.4

80 - 125 90 - 180

0 - 56

0.15 – 0.52

13 -125

2.2. Test specimens, concept and set-up Out of a variety of structural details that are common for crane runways the 3 most typical have been chosen – 1. rail clamp, 2. transverse stiffener and 3. lateral attachment – to be subject of numerical and experimental investigations. The dimensions of the specimens, made from the steel grade S355, are given in Figure 2.

Figure 2. a) Typical components of a crane runway, specimens of investigated structural details: b) rail clamp, c) transverse stiffener, d) lateral attachment