Constitutive Equation Based on Phase Transformations for Shape-Memory Actuators of Reconfigurable Systems

Abstract

The main purpose of this work is to develop a constitutive model for shape-memory devices, according to the phase transformation from austenite to martensite in NiTi Alloys and the relation with the stress-strain curve. First experimental testing is made to determine the mechanical behavior of the NiTi at several temperatures, and then a constitutive model is found according to the phase transformation behavior. The results show the microstructure evolution and its relation with the stress–strain curve. To conclude, a new constitutive model for the NiTi alloy has been developed which permits further analysis or simulation by finite element, which will be used in actuators for reconfigurable machines for flexible manufacture.

Keywords:

• Actuators for reconfigurable machines
• Austenite transition
• Characteristic strain
• Constitutive model
• Flow stress of austenite
• Flow stress of martensite
• Mechanical behavior of NiTi
• NiTi
• Shape memory actuators
• Shape memory devices
• Stress induced phase transformation
• Stress–strain behavior
• Thermo elastic martensitic structural changes
• Volume of austenite
• Volume of martensite