Shape Memory Alloys

Shape memory alloys are metal alloys that are able to regain their original shape after undergoing external stimulation. In this case, external stimulation is due to Temperature. There are points of Transition for SMA’s Martensitic start(Ms) and Martensitic finish(Mf)  and Austenite start(As) and Austenite finish(Af). As the SMA material undergoes external stimulation from heat and the cycle repeats continuously the material gets high strain which can be recovered when the Temperature crosses Ms.

Shows how Ms Mf and As Af system works

SMA can withstand high load and can last longer than many materials. It even has an ability to withstand huge strain effect without getting into deformation.

Shows how SMA  principle works

Since SMA’s have high flexibility and elasticity and very good recovery state from huge strains and high controllability they can be used as actuators. It has already been used in the Aviation industry in Commercial aircraft in order to reduce noise and vibration.

SMA material was used in the Boeing 777-300ER with GE-115B engines in order to reduce noise and lower the vibration productively enhancing the overall performance of the Engine.

SMA-actuated variable-geometry chevrons on a Boeing 777-300ER with GE-115B engines

SMA stress-strain behavior

Reference: https://www.researchgate.net/publication/328655295_Review_of_Morphing_Wing