TiNi AEROSPACE, INC.
AS9100 Rev B and ISO 9001:2008 Registered
Shape Memory Alloys
SMAs do not operate based on volumetric expansion as in paraffin or wax type actuators. Rather Shape Memory Alloys are able to recover from “deformation” by heating from one state to another. The mode of deformation and subsequent recovery can be in all directions (i.e. tensions, compression, bending, twisting, or any combination thereof). Recoverable strains for binary Nitinol is in the order of 4% where single crystal derivatives can exceed 10%.
Titanium Nickel based alloys can generally go up to 100C. Copper based alloys (such as our SCSMA) can go up to 200C.
Yes, the transition temperature can be raised with load or stress. The value is typically in the order of 1°C/ksi. As an example, an element that has a free recovery transition temperature of 70C will exhibit an In-Situ actuation temperature of 100C if under a load of 30ksi.
Super-Elasticity refers to the ability of Shape Memory Alloys to spring back after exposure to significant deformation. For SCSMAs this can be 9% strain (or more) which is approximately 20 times greater than normal metals.
No. The Frangibolt Actuator has adequate stroke to function even if the bolt or Fastener is not preloaded. Joint preload is generally an application requirement to “hold down” the item being secured to avoid “rattle” under high G conditions such as launch. It is important however that the Frangibolt joint does not have, or develop, any gaps or compliancy which can rob the Actuator of stroke needed to fracture the bolt.
Load feedback is offered by installing calibrated strain gages directly in the ERM enclosure. This offers very accurate measurement of preload during torque up. This option is readily introduced into the bottom mount configuration where the Actuator enclosure is in the load path. It has also been incorporated into the Top Mount configuration where the enclosure is not in the load path by use of a “transfer tube”.