Mechanical behaviour and phase transition mechanisms of a shape memory alloy by means of a novel analytical model

The aim of the present paper is to examine both the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy through cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine and the contents of both austenite and martensite phase are experimentally measured by means of X-Ray diffraction (XRD) analyses. On the basis of such experimental results in terms of martensite content, an analytical model is here formulated to correlate the stress-strain relationship to the phase transition mechanisms. Finally, a validation of the present model by means of experimental data pertaining the stress-strain relationship is performed

Numerical Simulation of Traditional and Technological Zinc-Based Coatings: Part I

Herein, the bending behavior of a hot-rolled hyper-sandelin steel subjected to hot-dip galvanizing (HDG) is numerically simulated. Two coating types are analyzed, that is, a pure zinc coating and a zinc-based coating with 3% Sn addition by weight. It is experimentally observed that the tin addition influences the thickness of each intermetallic phase and increases the ductility of the intermetallic phases. Therefore, the key of the numerical simulation is to assume suitable constitutive laws to phase layers, by considering that only few mechanical parameters are available in the literature. Such an approach has shown quite satisfactory results and it can be promising as a numerical tool to be used by HDG industry, being quite simple but quite accurate to estimate flexural strength and damage of Zn-based coated steels

FATIGUE BEHAVIOUR OF A SHAPE MEMORY ALLOY

In the present paper, the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy are examined by means of tensile cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine, which allows in situ X-Ray diffraction (XRD) analyses in order to measure the contents of both austenite and martensite phase. On the basis of such experimental results in terms of martensite content, an analytical model is here proposed to correlate the stress-strain relationship to the phase transition mechanisms. Finally, analytical and experimental results are compared in terms of stress-strain relationship

FATIGUE BEHAVIOUR OF A SHAPE MEMORY ALLOY

In the present paper, the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy are examined by means of tensile cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine, which allows in situ X-Ray diffraction (XRD) analyses in order to measure the contents of both austenite and martensite phase. On the basis of such experimental results in terms of martensite content, an analytical model is here proposed to correlate the stress-strain relationship to the phase transition mechanisms. Finally, analytical and experimental results are compared in terms of stress-strain relationship

Novel zinc-based alloys used to improve the corrosion protection of metallic substrates

The protection of metallic structural components against corrosion is fundamental to preserve their mechanical properties in aggressive environments. Zn-based coating represents one of the most used techniques to make protective coatings for metallic substrates. In the present paper, two types of novel zinc-based coating are proposed, by employing either a tin addition or an aluminium-tin-copper addition to the traditional zinc bath. The behaviour of steel-coated specimens under bending is experimentally and numerically investigated by considering different bath dipping times. A quite satisfactory agreement between experimental and numerical results is observed, especially under plastic behaviour regime