TiNi Aerospace
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FAQ  >  Frangibolts
TiNi Aerospace, Inc.

Shape Memory Alloys



How is the Frangibolt retained after actuation? The Actuator is typically housed in an enclosure which keeps it in a confined cavity after actuation. The opposing bolt segment may be automatically secured by threading directly into the deployable or similarly retained by using a retainer.
Does the Frangibolt joint have to be preloaded to work? 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.
How do I know the Frangibolt has been reset correctly? Verification that the Frangibolt has been reset correctly is by measuring its compressed length. This value should be within +0.005" of previously recorded value for the particular Serial Number. Maintaining a log of all firings is therefore very important for critical applications.
Is there any harm (or benefit) in compressing the Frangibolt a 2nd time? No, the Frangibolt Actuator can be exposed to the compression force repeatedly without any effect on performance. Generally, once the Actuator has been reset, the application of the same force will not result in any further compression.
Why is it that I measured the length of my Frangibolt Actuator after a successful firing and do not see the 3% stroke noted? The fully recovered length of the Actuator can only be measured while hot (at approximately 100C). Any other measurement will be less than that due to either incomplete transformation or self-shortening which can occur during cooling.
Why is it that I measure only 80C at actuation when the quoted actuation temperature is supposed to be 100C? This is because the embedded temperature sensor (RTD element) does not read the exact temperature of the TiNi cylinder which governs actuation (i.e. it happens to be at a colder spot within the heater assembly). Note that this also depends on power applied and starting temperature (i.e. the temperature distribution may differ from cycle to cycle depending on these external conditions).
Can I machine my own Frangibolt Bolt or Fastener? No, the Frangibolt Fastener is an integral part of the overall mechanism and must be manufactured by TiNi Aerospace. This is done to very high standards requiring a significant amount of inspection and testing of every Lot produced. Furthermore, the notch profile and material used are key in providing the proper performance.
What are the typical shut off methods used with the Frangibolt? Power is typically shut off based on either a timed pulse, maximum temperature read, or using an inline shut off switch.
What maximum temperature does TiNi recommend for me to base my shut off? Generally, the Frangibolt temperature (as read by the embedded RTD) should not be allowed to exceed 150C. However, it is highly recommended that the customer perform worst case system level testing to quantify both the function time and max temperature for the particular conditions of the application. This is typically enveloped by high voltage/temperature and low voltage/temperature which result in the fastest and slowest function time, respectively.
Can I reset the Frangibolt immediately after actuation? Yes, as long the Actuator is allowed to cool back down to room temperature 23 +/- 5 C.

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