Necking Phenomena in Thin Metallic Sheets: Experimental Tests and Computational Analysis

Nondestructive testing in the field of defects identification in metallic elements plays a remarkable role with special regard to those sectors where the integrity of the mterial is strictly required. As a consequence, the detection ofdefets and discontinuous deformations in metallic plates and bars (inverse proble), together with the relevant shape classification, provides the operator with useful information on the actual mechanical integrity of the specimen. In the study of solid-solid-phase transformations, theloss of uniqueness in the solution together with the relevant fragmenttion ofthe strain fields inside thesolid the equilibrium comes out as a solution represented from a fine mixture among phases. The first prt of this work is dvoted to a partial theoretical characterization of a monodimensional model with respect to the computational aspects. A comparison is then carried out with an experimental consideration of a nondestructive investigation technique based on the eddy current principle. Finally, a novel approach to solve the inverse problem by mens of fuzzy inferenc systems is proposed. In particular, Sugeno's inferences have been taken into ccount to investigate the local discontinuities of the metllic specimen subject to plastic deformations due to phase transformations by application to experimental mono-axial traction. Having acquired this result, we can calculate the stress field by applying the relevant constitutive law, which is not otherwise directly measurable.