A macroscopic multi-mechanism based constitutive model for the thermo-mechanical cyclic degeneration of shape memory effect of NiTi shape memory alloy

2017 ◽  
Vol 33 (3) ◽  
pp. 619-634 ◽  
Author(s):  
Chao Yu ◽  
Guozheng Kang ◽  
Qianhua Kan
Keyword(s):  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Niti Shape Memory Alloy

415 Fabrication of fine fibers of NiTi shape memory alloy and its shape memory effect

2007 ◽  
Vol 2007.46 (0) ◽  
pp. 123-124
Author(s):  
Makoto KIMATA ◽  
Kenta HASEGAWA ◽  
Hiroyuki KATO ◽  
Kazuaki SASAKI
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Niti Shape Memory Alloy

scholarly journals Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

2003 ◽  
Vol 791 ◽  
Author(s):  
Gordon A. Shaw ◽  
Wendy C. Crone
Keyword(s):  
Mechanical Properties ◽  
Shape Memory Alloy ◽  
Film Thickness ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Spherical Cavity ◽  
Niti Shape Memory Alloy ◽  
Cavity Model ◽  
Critical Film Thickness

ABSTRACTThe mechanical properties of sputter-deposited NiTi shape memory alloy thin films ranging in thickness from 35 nm to 10 μm were examined using nanoindentation and atomic force microscopy (AFM). Indents made in films as thin as 150 nm showed partial shape recovery upon heating, although film thickness was found to have a marked effect on the results. A modified spherical cavity model is used to describe the findings, which suggest that the substrate tends block the shape memory effect as film thickness decreases below a threshold level which is specific to applied load. This has the net effect of decreasing the indent recovery below the critical film thickness. The fact that the spherical cavity model predicts the critical film thickness at which the shape memory effect is blocked indicates that the increased recovery of nanoscale indentations is due to a suppression of plastic processes rather than an enhancement of shape memory processes.

Conventional Plasticity Constitutive Model for Shape Memory Alloys

2011 ◽  
Vol 216 ◽  
pp. 469-473
Author(s):  
Hai Tao Li ◽  
Xiang He Peng
Keyword(s):  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Numerical Algorithm ◽  
Individual Behavior ◽  
Two Phase ◽  
The Individual

A two-phase constitutive model for shape memory alloys (SMAs) is proposed based on the fact that SMAs is dynamically composed of austenite and martensite. The behavior of SMAs is regarded as the dynamic combination of the individual behavior of each phase. This model can describe the main characteristics of SMAs, such as pseudoelasticity and shape memory effect. The corresponding numerical algorithm was also developed to describe the main features of shape memory alloy Au-47.5at.%Cd.

Thermomechanical Forming of NiTi Shape Memory Alloy Wire

2014 ◽  
Vol 939 ◽  
pp. 430-436 ◽  
Author(s):  
Kuang Jau Fann ◽  
Hau Chi Hsu
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Niti Shape Memory Alloy ◽  
Processing Temperature ◽  
Shape Memory Alloy Wire ◽  
Alloy Wire ◽  
Niti Shape Memory Alloys

Because of their smart characteristics with shape memory effect and superelasticity, NiTi shape memory alloys used in sensors and actuators are regarded as an emerging applied material with high added value by their additional biomedical compatibility for medical devices and implants. It is meaningful to pay more attention to study the production technique of NiTi shape memory alloys. For this reason, this article is aimed to investigate the results of a NiTi shape memory alloy wire in thermomechanical forming process regarding the processing temperature and duration. Thereafter a NiTi shape memory alloy wire of 0.63 mm in diameter is formed in a furnace at 450°C, 500°C, 550°C, and 600°C, respectively, by a semi cylindrical punch of 32 mm in diameter, then held together with the die set in the furnace for 10, 30, and 50 minutes long, respectively, and then quenched in the water. All of the formed wires have shape memory effect. That is, the wires returned their formed geometry once they were straightened below martensite transformation finishing temperature about room temperature and heated again above austenite transformation finishing temperature about 70°C. These thermomechanical forming processes were also investigated by commercial finite element software DEFORM. Both analytical and experimental results showed that the formed wires could not have the geometry precision as wanted because of stress relaxation found in process, which depends on the process temperature and the treatment duration. As a result, the lower the temperature and the shorter the duration is, the larger the springback is. That means that the higher the treatment temperature is and the longer the holding time is, the better the precision of the formed part is.

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