Superelastic shape-memory alloys model 2 - se_sma2

This is a uniaxial model for superelastic shape-memory alloys (SMAs), programmed by Hoult and that follows the constitutive relationship proposed by Abdulridha et al. (2013). In comparison to the SE_SMA model, the model proposed by Abdulridha et al. (2013) includes several improvements, including explicit consideration of permanent (i.e., residual) strains, degradation of the lower plateau stress (reverse transformation), and a trilinear unloading response.

Six model-calibrating parameters must be defined to fully describe the mechanical characteristics of the materials. These six parameters can be obtained from simple uniaxial tests performed on SMA elements (wires or bars, typically).

Modulus of elasticity - E
This value represents the modulus of elasticity for both austenite and martensite response phases. Its value usually oscillates between 10000 and 80000 MPa. The default value is 31000 MPa.

Pseudo-yield stress - y
This value represents the level of stress at the austenite response phase. Its value typically varies between 200 and 600 MPa. The default value is 349 MPa.

Ultimate stress - u
This value represents the level of stress for the ultimate stress plateau. Its value typically varies between 600 and 2000 MPa. The default value is 900 MPa.

Strain at the onset of strain hardening - sh
This value represents the level of strain, at which the austenite-to-martensite phase transformation finishes. It may vary between 1 and 10%. The default value is 4%.

Strain at the onset of ultimate stress plateau- u
This value represents the level of strain at which the ultimate stress plateau starts. It may vary between 5 and 15%. The default value is 10%.

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