PSI - Issue 81

Jesús Toribio et al. / Procedia Structural Integrity 81 (2026) 547–551

551

4. Discussion The afore-said locally anisotropic fracture behaviour (increasing with the cold drawing degree) is a clear consequence of the microstructural evolution with cold drawing in the form of elongation and axial orientation of the pearlitic colonies (first microstructural level) and increase of packing closeness (with decrease of interlamellar spacing) of the pearlite (ferrite//cementite) lamellae (second microstructural level), together with orientation in the direction of the wire axis (or cold drawing direction). However, in spite of the microstructural orientation, only local anisotropy is achieved (in the form of micro-deflections). It does not become global because of the uniaxial stress state during the tensile tests on the wires and the corresponding lack of stress triaxiality (constraint) in the samples. Toribio and Ayaso (2020) have demonstrated, by means of fracture tests on notched specimens of progressively cold drawn pearlitic steels, the necessity of both stress triaxiality and microstructural orientation to produce ( global ) fracture path deflection in cold drawn pearlitic steel. 5. Conclusion The progressively cold drawn perlitic steel wires exhibit in their micro-fracture maps (MFM) an increasing trend towards a more anisotropic fracture as the cold drawing degree increases. However, it is only a locally anisotropic fracture behaviour in the form of axial (or longitudinal) micro-cracking, micro-splitting, micro-delamination, micro-deflection or micro-kinking in the fracture surface. This local anisotropy of fracture behaviour (increasing with the cold drawing degree) in the progressively cold drawn pearlitic steel wires does not become a global anisotropy , even in the most heavily drawn steels, due to the lack of stress triaxiality (constraint) in the smooth (unnotched) wires. 6. Epilogue: A Picassian Approach The local anisotropy of fracture behaviour in heavily cold drawn pearlitic steel, with its associated embryos of anisotropic fracture in the form of axial (or longitudinal) micro-cracking, micro-splitting, micro-delamination, micro-deflection or micro-kinking can be associated with the change of viewpoint of the cubist painting by Picasso (Fig. 4).

Fig. 4. Painting by Picasso ( Three musicians )

References

Toribio, J., Ayaso, F.J. 2020. On the Necessity of Triaxiality and Microstructural Orientation to Produce Anisotropic Fracture in Cold Drawn Pearlitic Steel: Resembling John Ford’s Monument Valley . Procedia Structural Integrity 28, 2416-2423. Toribio, J., Ovejero, E., 1997. Microstructure Evolution in a Pearlitic Steel Subjected to Progressive Plastic Deformation. Materials Science and Engineering A234 236, 579-582. Toribio, J., Ovejero, E., 1998a. Microstructure Orientation in a Pearlitic Steel Subjected to Progressive Plastic Deformation. Journal of Materials Science Letters 17, 1037-1040. Toribio, J., Ovejero, E., 1998b. Effect of Cumulative Cold Drawing on the Pearlite Interlamellar Spacing in Eutectoid Steel. Scripta Materialia 39, 323-328. Toribio, J., Ovejero, E., 1998c. Effect of Cold Drawing on Microstructure and Corrosion Performance of High-Strength Steel. Mechanics of Time-Dependent Materials 1, 307-319.