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On the recovery stress of a ni50.3ti29.7hf20 high temperature shape memory alloy
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Gaydosh, D. J. Noebe, R. D. Padula II, S. A. Garg, A. Halsmer, T. J. Benafan, O. Bigelow, G. S. |
| Copyright Year | 2015 |
| Description | Recovery stress in shape memory alloys (SMAs), also known as blocking stress, is an important property generally obtained during heating under a dimensional constraint as the material undergoes the martensitic phase transformation. This property has been instinctively utilized in most SMA shape-setting procedures, and has been used in numerous applications such as fastening and joining, rock splitting, safety release mechanisms, reinforced composites, medical devices, and many other applications. The stress generation is also relevant to actuator applications where jamming loads (e.g., in case the actuator gets stuck and is impeded from moving) need to be determined for proper hardware sizing. Recovery stresses in many SMA systems have been shown to reach stresses in the order of 800 MPa, achieved via thermo-mechanical training such as pre-straining, heat treatments or other factors. With the advent of high strength, high temperature SMAs, recovery stress data has been rarely probed, and there is no information pertinent to the magnitudes of these stresses. Thus, the purpose of this work is to investigate the recovery stress capability of a precipitation strengthened, Ni50.3Ti29.7Hf20 (at.) high temperature SMA in uniaxial tension and compression. This material has been shown to exhibit outstanding strength and stability during constant-stress, thermal cycling, but no data exists on constant-strain thermal cycling. Several training routines were implemented as part of this work including isothermal pre-straining, isobaric thermal cycling, and isothermal cyclic training routines. Regardless of the training method used, the recovery stress was characterized using constant-strain (strain-controlled condition) thermal cycling between the upper and lower cycle temperatures. Preliminary results indicate recovery stresses in excess of 1.5 GPa were obtained after a specific training routine. This stress magnitude is significantly higher than conventional NiTi stress generation capability. |
| File Size | 4458773 |
| Page Count | 29 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20150023061 |
| Archival Resource Key | ark:/13960/t4rj9fw15 |
| Language | English |
| Publisher Date | 2015-09-21 |
| Access Restriction | Open |
| Subject Keyword | Recovery Stress High Temperature Shape Memory Alloy Nitihf Stress Analysis Deformation Shape Memory Alloys Hafnium Alloys Nickel Alloys Compression Tests Compression Loads Thermal Cycling Tests High Temperature Recovery Titanium Alloys Tensile Stress Heat Resistant Alloys Tension Thermal Stresses Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Presentation |
