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NiTi Springs Exhibiting Pseudoelastic behavior from negative 130 degrees to 90 degrees celsius

Ohio, United States
Government : Federal
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The Mars Spring Tire Project at NASA Glenn Research Center is considering procuring NiTi springs (wire formed in a helical shape) that meet specific material, geometric, and environmental requirements.  The following is a list of specifications that are required in the finished springs.

1.      Springs shall be made from a binary NiTi alloy that is processed to achieve pseudoelastic (otherwise known as superelastic) stress-induced martensite transformation over temperature ranges from 90° down to -130°C.  All springs shall have finished properties such that pseudoelastic performance is achievable through this entire temperature range in both tension and bending.

2.      At all temperatures (-130° to 90°C), the material used to manufacture the springs shall have a fully reversible, strain potential of at least εtran = 6% in tension (where εtran is the transformation strain of the material).

3.      The material used for spring production shall have an onset-stress plateau, stress/temperature sensitivity less than or equal to 2 MPa/°C. (i.e. the slope of the stress plateau shift as a function of temperature shall not exceed 2 MPa/°C).

4.      The material shall have a fully stabilized stress-induced response having a stress required to achieve 2% strain at 90°C of at least 550 MPa and a stress required to achieve 5% strain at 90°C of at least 850 MPa, regardless of final wire diameter sought. This is required to ensure both adequate strength properties as well as the proper non-linear deformation behavior that is required for achieving the correct force/deflection characteristic for the application.

5.      The vendor shall be capable of manufacturing springs with the above properties using wire diameters from 0.010” – 0.100” for coil diameters ranging from 0.090” – 0.500” with pitches ranging from 0.200” – 0.500”.

6.      Springs within the ranges listed above shall be manufacturable in lengths ranging from 8” – 24”.

7.      Pitch in the delivered springs shall be controlled to within +/- 0.002” in order to ensure that the delivered springs can be woven to form a cylindrical mesh.

8.      Vendor must be able to supply quantities between 500 – 1000 springs per batch, within two months from time of order. Vendor must also be able to demonstrate capability to deliver 40 batches of 500 – 1000 springs over a 4-year period.

9.      Vendor shall meet the following requirements of NASA-STD-6016A:

a.       Section 4.1.2a,d,e,f              (M&P Controls)

b.      Section 4.1.7                        (Materials Certification and Traceability)

10.    Vendor shall be AS9100 compliant or equivalent.

Brian M. Evans, Contract Officer, Phone 2164332407, Email

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