will be held on Tuesday September 8 and Thursday September 10 from 16:00 until 18:00. It will be organised as a special discussion oriented session with the aim to support the activities of European researchers developing modelling tools for smart structures with SMAs in frame of ESF EUROCORES programme S3T.

Within the ESF EUROCORES modelling session results of Roundrobin SMA Modelling will be presented by participants in order to compare the capabilities, power and suitability of particular SMA models.

• Paper & PresentationMaterial inputExperimental conditionsDatasets

Roadmap to Paper & Presentation

Roundrobin modelers are kindly requested to send their contributions before September 20, 2009. In the case that the abstract was regularly submitted through the esomat web page http://esomat.fzu.cz, the paper can be submitted through the Author-submissions menu item appearing in the User Home menu (after logging in). Otherwise the paper can be sent to esomat@fzu.cz. The papers will appear in the electronic proceedings at www.esomat.org.

To ensure that an easy and transparent comparison of models can be done, roundrobin SMA modeling results must be provided in the following form:

• Basic reference to the SMA model used (paper, report if not published etc.)
• 1-2 page text describing the strength and weakness of the SMA model (Ms Word template|LaTeX). This part should also contain the set of used material parameters and their values.
• Numerical solutions of the selected case studies in a form of ASCII data: three columns and five columns – temperature, strain and stress – for tests in tension, recovery strain and recovery stress, and five columns – temperature, strain (in tension), stress, torsional strain, torque – for torsion symmetric test and combine torsion-tension tests.

Experiments to be simulated

• Tensile tests - Stress-strain responses of NiTi wire in tension for three temperatures T = -20 ˚C, T = 10 ˚C and T = 60 ˚C.
• Thermal cycling tests at constant applied stresses - Thermal cycle through transformation interval under three different tensile constant stresses 300 MPa, 400 MPa and 500 MPa.
• Torsion symmetrical tests - Torque-torsion angle symmetrical +/- responses at low prestress (70 MPa) and three temperatures - T = -30 ˚C, T = -10 ˚C and T = 30 ˚C.
• Combined tension-torsion tests - Responses in torsion test at temperature T = 30˚C and at four constant bias axial stresses 70 MPa, 255 MPa, 317 MPa, 379 MPa.
• Thermomechanical recovery stress tests - Tensile stress-temperature wire loaded in tension at room tempeature T = 26 ˚C (>Af ) up to 3.5 % prestrain (both at upper and lower plateau), followed by thermal cycling at constant prestrain and final unloading at room temperature.

Every modeler may determine his own set of material parameters. The choice of material parameters is left on the decision of each modeler but it is obligatory to state clearly which material parameters were used, how they were obtained and what their values are. Since a single NiTi wire has been used in all tests, the same material parameters have to be used in all benchmark tests.

Material input

SMA element: Straight annealed NiTi FWM #1 superelastic wire d=0.1 mm, l0=50 mm, relevant material information can be obtained from the www site of the SMA provider FWM nitinol.
Material parameters: Individual modellers shall determine material parameters from the provided experimental datasets according to their own procedures. Alternatively, they may use material parameters evaluated by IP ASCR group by their procedure summarized in attached file FWM_No1_wire_parameters.pdf.

Experimental conditions

Tensile and Torsion tests were performed at temperature controlled by Peltier furnace
Sample for each tensile dataset a sample was first trained by 100 cycles to stabilize its mechanical response – this sample was then used in experiments within each dataset, for each tension-torsion dataset (one applied axial load within the entire temperature range) a new sample was used that had been trained by 10 cycles at 50 ˚C
Test control mode - position (torsion angle) rate constant
Strain rate - tests were performed at low strain rates (<10-3 s-1 ) so the heat effects are minimized
Temperature rate - tests were performed at low temperature rates ( <10˚C/min) to assure well defined test conditions
History - prior each test, the sample was heated to T=395K>Af and cooled down to test temperature

Datasets

Download the datasets and their description here