PSI - Issue 5

G. Lesiuk et al. / Procedia Structural Integrity 5 (2017) 912–919 Lesiuk et al./ Structural Integrity Procedia 00 (2017) 000 – 000

918

7

the increasing of the fatigue crack length. This effect is manifested by the larger bright areas associated with growing crack.

Fig. 6. Fatigue crack growth curves for CT specimen obtained by experiment ( F max =4.5kN, no reinforcement), Paris law integration ( F max =6kN, no reinforcement), experiment ( F max =6kN, full CFRP patches).

3. Conclusions

1. The old mild steel from 1902 year was investigated under static and cyclic conditions. The basic material investigations were performed. The microstructural degradation processes (typical for this ancient type of steel) have been found; 2. The CFRP patches strengthening strategy is suitable for old structural members (from puddle iron or old mild steel) with fatigue cracks. However, the wrong preparation of the CFRP and metal surface can cause premature failure of strengthened joint; 3. The main mechanism of fatigue crack growth retardation is associated with local  K reduction due to CFRP patches; 4. Further experiments and numerical simulations are required in order to determine the optimal conditions of the CFRP patches (load state, fiber orientation etc.). Acknowledgements 1. This work was financial supported by the Wroclaw University of Science and Technology – Department of Mechanics, Materials Science and Engineering internal, fundamental research program. 2. The publication has been prepared as a part of the Support Programme of the Partnership between Higher Education and Science and Business Activity Sector financed by City of Wroclaw. 3. The authors also acknowledge the Portuguese Science Foundation (FCT) for the financial support through the post-doctoral grant SFRH/BPD/107825/2015. References ASTM E647-15a - Standard Test Method for Measurement of Fatigue Crack Growth Rates (2015). Bień J., Durability as a criterion in the management of bridge infrastructureD.W. Edukacyjne (Ed.), Trwalość obiektów mostowych, Politechnika Wrocawska, Dolnoślaska Izba Inżynierów Budownictwa, Zwiazek Mostowców Rzeczypospolitej Polskiej (2012), pp. 97 -114 (in Polish). Correia J.A.F.O., A.M.P. De Jesus, A. Fernandez-Canteli, R.A.B. Calçada, Fatigue Damage Assessment of a Riveted Connection Made of Puddle Iron from the Fão Bridge using the Modified Probabilistic Interpretation Technique, Procedia Engineering, Volume 114, 2015, Pages 760-