Fatigue Crack Growth Rate of the Long Term Operated Puddle Iron from the Eiffel Bridge

Abstract

The paper summarises an experimental study on the fatigue crack propagation and cracks paths in ancient steel—19th-century puddle iron from the Eiffel bridge. The tests were performed with the load R-ratio equal to 0.05 and 0.5. All tests were performed under different notch inclinations (mode I + II). The fatigue crack growth rate in the tested material is significantly higher than its “modern” equivalent—low carbon mild steel. The crack closure phenomenon occurs in specimens during the process of crack growth. Understanding this aspect is crucial for the examination of a stress R-ratio influence on kinetic fatigue fracture diagram (KFFD) description. Both the experimental and numerical approach, using the HP VEE environment, has been applied to the crack closure as well as the crack opening forces’ estimation. These analyses are based on the deformation of the hysteresis loop. The algorithm that was implemented in the numerical environment is promising when it comes to describing the kinetics of fatigue crack growth (taking into consideration the crack closure effect) in old metallic materials.

Study of the Fatigue Crack Growth in Long-Term Operated Mild Steel under Mixed-Mode (I + II, I + III) Loading Conditions

“…Force components were defined to show a resultant force in the desired direction and a null resultant moment. Forces satisfying these conditions were calculated as presented in Equations (7)- (9). Pins were modelled as kinematic couplings, but rotation about the z-axis was allowed to prevent over stiffness.…”

“…While state of the art and test procedures are clear for uniaxial loads, despite the diversity of results, there is little work on the multi-axial fatigue of this type of material. Papers [7][8][9] of the authors' team devoted to the mixed-mode (I + II) fatigue fracture of puddle iron, show significant discrepancies in the expected fatigue-fracture behavior of puddle iron compared with existing mixed-mode criteria. On the other hand, realistic assessment of the structural integrity using modern tools such as the finite element method [10][11][12] requires the substitution of growth models for uniaxial states with models for mixed fracture growth modes.…”

Fatigue Crack Growth Rate in Long Term Operated 19th Century Puddle Iron

“…For the puddle iron from viaduct (1863) similar procedure (fully described in refs. [6,8]) was adopted. Due to material limitations, the size of the CT specimen was decreased.…”

“…According to the experimental procedure described in refs. [6,8], the crack closure point as well as corresponded and levels was estimated in order to evaluate the effective stress intensity range ( ) based on the Elber concept [10]. Finally, the Kinetic Fatigue Fracture Diagrams were constructed for both materials - A noticeable is R-ratio effect in KFFD represented by shifted / curves ( Fig.…”

“…This bridge is located in Viana do Castelo, Portugal, crossing the Lima River, having a total length of 645 m. Another part of an ancient iron member was extracted from the restored viaduct (1863) located in Brochocin (Low Silesia, Poland),. Due to limited knowledge of the fatigue crack growth behaviour [3], this paper fills the gap in the literature on experimental results of fatigue crack growth (FCG) behaviour based on the effective stress intensity factor range and of a new parameter using the strain energy density concept for the metallic materials under consideration [4]. These FCG results are of great importance, since it allows the residual lifetime assessment of old metallic bridges of the same historical period, reducing the uncertainties associated with this type of materials.…”