Superelastic shape-memory alloys model - se_sma

This is a uniaxial model for superelastic shape-memory alloys (SMAs), programmed by Fugazza [2003], and that follows the constitutive relationship proposed by Auricchio and Sacco [1997]. The model assumes a constant stiffness for both the fully austenitic and fully martensitic behaviour, and is also rate-independent.

Seven model calibrating parameters, the values of which can be obtained from simple uniaxial tests performed on SMA elements (wires or bars, typically), must be defined in order to fully describe the mechanical characteristics of the material:

Modulus of elasticity - E
This value represents the modulus of elasticity both for austenite and martensite response phases. Its value usually oscillates between 10000 and 80000 MPa. The default value is 10000 MPa.

Austenite-to-martensite starting stress - s-AS
This value represents the level of stress at which the austenite-to-martensite phase transformation starts. Its value typically varies between 200 and 600 MPa. The default value is 200 MPa.

Austenite-to-martensite finishing stress - f-AS
This value represents the level of stress at which the austenite-to-martensite phase transformation finishes. Its value typically varies between 300 and 700 MPa. The default value is 300 MPa.

Martensite-to-austenite starting stress - s-SA
This value represents the level of stress at which the martensite-to-austenite phase transformation starts. Its value typically varies between 600 and 200 MPa. The default value is 200 MPa.

Martensite-to-austenite finishing stress - f-SA
This value represents the level of stress at which the martensite-to-austenite phase transformation finishes. Its value typically varies between 500 and 100 MPa. The default value is 100 MPa.

Superelastic plateau strain length - L
This value represents the length of the superelastic plateau, which may vary between 4 and 8%. The default value is 5%.

Specific weight -
This is the specific weight of the material. The default value is 65 kN/m3.