PSI - Issue 17

Mihaela Iordachescu et al. / Procedia Structural Integrity 17 (2019) 434–439 M. Iordachescu et al./ Structural Integrity Procedia 00 (2019) 000 – 000

439

6

The sketch and the images of Fig. 4 illustrate the process of slip band forming and its final state after having served as origin and propagation path of the wire fracture. Fig. 4b and 4c are higher magnification views in metallographic samples obtained from longitudinal cuts of broken LDS and ES wire specimens, respectively. These are showing the strong distortion of the microstructural layers once the slip bands are formed.

Fig. 4. a) Sketch of the slip band formation; higher magnification view of the wires failure: b) LDS; c) ES.

4. Conclusions

The experimental results presented in this paper show that transverse loads significantly reduce the tensile bearing capacity of the high-strength cold drawn wires used for structural strand-tendons manufacturing. The two types of studied wires, respectively made of eutectoid steel and lean duplex stainless steel, do not differ in the empirical fracture criterion found to predict their tensile bearing capacity as a function of the applied transverse load. The failure mechanism of the wires is basically the same due to the strong microstructure orientation produced by the drawing process. However, the pearlitic nature of the eutectoid steel and the austenite-ferrite duality of the duplex stainless steel produce strong qualitative differences. The failure propagates from the boundary of the notched area following an inclined plane with respect to the wire axis. The origin of the plane is an unstable plastic slip band that arises from the concentration of microcracks and of large plastic deformations in the microstructural layers simultaneously forced to bend and elongate in the proximity of the applied transverse load.

Acknowledgements

The authors gratefully acknowledge the financial support of the Spanish Ministry of Science and Innovation through the projects BIA 2014-53314 – R and RTI 2018-097221-B-I00 and the collaboration with INOXFIL S.A. who kindly provided the high-strength, duplex steel wires.

References

BBR HiAm CONA Strand stay cable system, 2009. BBR VT International, www.bbrnetwork.com. De Abreu, M., Iordachescu, M., Valiente, A., 2018. On hydrogen-induced damage in cold-drawn lean-duplex wires. Engineering Failure Analysis 91, 516-526. DYWIDAG bonded post-tensioning using strands, 2017. DYWIDAG-SYSTEMS International, 04 160-1/06.17-web sc, dywidag systems.com/emea. DYWIDAG multistrand stay cable systems, 2017. DYWIDAG-SYSTEMS International, 04 178-1/07.17 -web sc, dywidag-systems.com/emea. FIB bulletin 30, 2005. Acceptance of stay cable systems using prestressing steels. The International Federation for Structural Concrete – FIB, ISSN 1562-3610. Iordachescu, M., De Abreu, M., Valiente, A., 2015. Effect of cold-drawn induced anisotropy on the failure of high strength eutectoid and duplex steel wires. Engineering Failure Analysis 56, 412-421. Maupetit, P., Olivie, F., Raharinaivo, A., Francois, D., 1977. Shear fracture of prestressing plain carbon steel wires under complex loading, International Journal of Fracture 13, 725-727. UNE-EN ISO 15630-3:2010, Aceros para el armado y el pretensado del hormigon. Métodos de ensayo. Parte 3: Aceros para pretensar. Valiente, A., Iordachescu, M., 2012. Damage tolerance of cold drawn ferritic-austenitic stainless steels wires for prestressed concrete. Construction and Building Materials 36, 874-880.