title: Modeling Permanent Deformations of Superelastic and Shape Memory Materials.
abstract: In this paper we propose a modification of the polycrystalline shape memory alloy constitutive model originally proposed by Souza. By introducing a transformation strain energy with two different hardening coefficients, we are able to take into account the effect of the martensitic transformation of unfavorably oriented grains occurring after the main plateau. By choosing a proper second hardening coefficient, it is possible to reproduce the correct stress strain behavior of the material after the plateau without the need of introducing a much smaller Young modulus for martensite. The proposed modification is introduced in the model comprising permanent deformation effects. Model results for uniaxial stress tests are compared to experimental results showing good agreement.
authors.affiliation: SAES Getters S.p.A., v.le Italia, 77, 20020 Lainate (MI), Italy. marco_urbano@saes-group.com.
authors.forename: Marco Fabrizio
authors.initials: MF
authors.lastname: Urbano
authors.affiliation: Università di Pavia, Via Ferrata 9, 27100 Pavia, Italy. ferdinando.auricchio@unipv.it.
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Auricchio
keywords: constitutive modeling; elastic modulus; functional fatigue; shape memory alloys; superelasticity