DTA

Corso Ordinario Secondo Livello

BELARDINI, CARLO MARIA

etd-11122021-182500

Strength estimation of notched sheet metal in presence of hydrogen

Cl. Sc. Sperimentali - Ingegneria

INGEGNERIA - INGEGNERIA

Tutor Prof. BERGAMASCO, MASSIMO
Relatore Prof. BEGHINI, MARCO
Relatore Prof. MONELLI, BERNARDO DISMA
Presidente Prof. FRISOLI, ANTONIO
Membro Prof. RICOTTI, LEONARDO
Membro Prof. ODDO, CALOGERO MARIA
Membro Prof. CUCINOTTA, TOMMASO
Membro Prof. CIARAMELLA, ERNESTO
Membro Prof. CASTOLDI, PIERO

• High Strength Steel Hydrogen Embrittlement

16/12/2021;

completa

Because of their excellent strength along with relatively high ductility, high strength steels are commonly used in the automotive industry, for example for impact safety components. A major setback of this family of materials is their high susceptibility to Hydrogen Embrittlement, which can be defined as a sharp ductility and strength reduction in presence of diffusible hydrogen inside the metal matrix. Prior results in the literature show that hydrogen mostly influences the post-necking behaviour of standard tensile specimen, significantly reducing the measured elongation at fracture. This weakening is amplified in presence of strain localisation phenomena, such as stress concentration effects caused by notches, which also are typical features present in automotive sheet metal components. The aim of this work is to estimate the strength of hydrogenated sheet metal from tensile tests performed on V-notched specimen. Because of the significant stress concentration effect, strain at fracture is the driving parameter for the specimen failure in those conditions. Nevertheless, estimating the fracture strain from V-notched tensile force/elongation curves is not straightforward.
Using an array of bilinear hypothetical materials, Finite Element simulations are conducted in order to find suitable correlations that allow for a simple estimation of strain at fracture.

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