PSI - Issue 81

Jesús Toribio et al. / Procedia Structural Integrity 81 (2026) 455–457

457

4. Discussion The cold drawing process generates a marked microstructural orientation in the progressively drawn material that induces a clear anisotropy in the matter of elastic, plastic and fracture behaviour. In a transverse section of the cold drawn steel, a random orientation of both pearlitic colonies and lamellae is observed, together with an increasing packing closeness with cold drawing (i.e. the pearlite interlamellar spacing decreases with the drawing degree). On the other hand, in a longitudinal section of the same heavily drawn steel, the microstructural units evolve towards an oriented arrangement, becoming almost parallel to the wires axis or drawing direction. Such an orientation is associated with a longitudinal enlargement (with pearlite colonies slenderizing) and a transverse shortening (and the afore-said increase of packing closeness and decrease of interlamellar spacing), as explained by Toribio and Ovejero (1997, 1998a, 1998b, 1998c). The hardness differences between the two analyzed sections can be attributed to the microstructural variations during drawing, because the great number of interfaces (cementite layers) act as barriers to dislocational movement, and the number of interfaces (barriers) depends on the specific glide direction, thereby being a function of the directional hardening and therefore of the drawing degree. Thus in the cold drawn steel, plastic deformation exhibits directional dependence and shows privileged axes, so that the slip bands are parallel to the wire axis or drawing direction. 5. Conclusions During cold drawing of eutectoid steel, an increase of dislocational density takes place, thus producing an increase of Vickers hardness of the prestressing steel in both longitudinal and transverse directions, together with radial variations associated with the presence of residual stresses in the material after cold drawing. In progressively drawn steels, the hardness in the transverse section is higher than that in the longitudinal cut, the difference increasing with the degree of cold drawing. Such a phenomenon is related to the number of interfaces (cementite lamellae blocking dislocational movement), which modifies the shape and distribution of slip bands. 6. Epilogue: A Dalinian Approach The anisotropic plastic behaviour of cold drawn pearlitic steel wires as a consequence of their oriented microstructure reminds one the Spanish painter Salvador Dalí and his melting watches , e.g., in the painting “La persistencia de la memoria”. References Bocciarelli, M.; Bolzon, G.; Maier, G., 2005. Parameter identification in anisotropic elastoplasticity by indentation and imprint mapping. Mechanics of Materials 37, 855-868. Giannakopoulos, A.E.; Suresh, S.,1999.Determination of elastoplastic properties by instrumented sharp indentation.Scripta Materialia 40, 1191-1198. Hill, R., 1998. The mathematical theory of plasticity. Clarendon Press, Oxford, 1998. Jayaraman, S.; Hahn, G.T.; Oliver, W.C.; Rubin, C.A.; Bastian, P.C., 1998. Determination of monotonic stress-strain curve of hard materials from ultra-low-load indentation tests. International Journal of Solids and Structures 35, 365-381. Murakami, Y.; Itokazu, M., 1996. Elastic-plastic analysis of triangular pyramidal indentation. International Journal of Solids and Structures 34, 4005-4018. Pelletier, H., 2006. Predictive model to estimate the stress-strain curves of bulk metals using nanoindentation. Tribology International 39, 593-606. Toribio, J.; Ayaso, FJ.; González, B.; Matos, JC.; Vergara, D.; Lorenzo, M., 2016. Tensile fracture behavior of progressively-drawn pearlitic steels. Metals 6, paper 114. 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. 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.