An experimental study of NiTi alloy under shear loading over a large range of strain rates. (October 2017)

• Record Type: Journal Article
• Authors: Huang, H.; Durand, B.; Sun, Q.P.; Zhao, H.
• Is Part Of: International journal of impact engineering. Volume 108(2017)
• Page Start: 402
• Page End: 413
• Publication Date: 2017-10
• Subjects: NiTi alloy -- In-plane impact shear test -- Strain rate -- Strain field measurement -- Split Hopkinson pressure bars; Impact -- Periodicals; Shock (Mechanics) -- Periodicals; Impact -- Périodiques; Choc (Mécanique) -- Périodiques; Impact; Shock (Mechanics); Periodicals; 620.1125
• DOI: 10.1016/j.ijimpeng.2017.03.007
• Languages: English
• ISSNs: 0734-743X

Abstract

Highlights: Plane shear testing of Ni-Ti plate over a large strain rate range (10 −4 s -1 to 10 3 s -1 ). Observation of martensitic transformation band during test. Regular rise of transformation stress with the increase of the strain rates. Two transformation bands at 10 2 s -1 instead of one band at lower strain rates. Important stress jump at the strain rate of 10 3 s -1 . Abstract: This paper describes a complete experimental study on a NiTi SMA alloy at the ambient temperature (Pseudoelastic behavior) under a double in-plane shear loading over a large range of strain rates from 10 −4 to 10 3 s -1 . Under the quasi-static loading (10 −4 –10 −2 s -1 ), the optical full-field measurement revealed to be necessary because of the very small total displacement of 0.3 mm. The intermediate loading rate (10 −1 –10 1 s -1 ) is realized with a modified MTS machine able to load at the speed of 300 mm/s. A high-speed camera is needed to follow such test. Finally, the Split Hopkinson bars are used to perform tests at impact loading rates (10 2 –10 3 s -1 ). The tests are continually performed over 7 decades of the strain rate. Not only the nominal stress-strain curves, but also the detailed observation of transformation band evolution are measured. The main findings are as follows: (i) A regular stress increase with the strain rate is observed over 7 decades of the strain rates; (ii) the strain field is not homogeneous under in-plane shear conditions, even at the very low strain rate of 10 −4 s -1 . One band at 10° from the shear direction is visible under the lower strain rate. (iii) At the impact strain rate of 10 2 s -1, two separated bands are observed.