Topic: Field measurement of Ni-tisheartests over a large range of strain rates
Reporter: Prof. Han Zhao, Université Pierreet Marie Curie
Time: 10:00a.m. July 15th, 2016(Friday)
Venue: Room 211---Lecture Hall, Building ofArchitecture
Audience: Teachers and graduates in thisfield
Tips: For teachers and students who willattend the lecture, please find your seats 10 minutes earlier and switch yourcommunication tools into silent mode. Please keep quite.
Brief introduction of the reporter
(1)Main research fields:
The mechanical property of porous material;granular material compression; rate-sensitive materials (transformation inducedplasticity steel, polymer, laminated plate); rate-sensitive shape memory alloy;impact test; impact dynamics of thin-wall structure; the impact resistance ofriveted structure; the high velocity penetration of sandwich plate.
(2)Learningand working experiences
1992, Ph.D in solid mechanics, ENPC(EcoleNationale des Ponts et Chaussées)
1992-1993, researcher, École Polytechnique
1993-1995, R&D engineer, French Scienceand Technology Foundation
1995-1998, R&D engineer, French ARMINES
1998-now, professor, Université Pierre etMarie Curie
(3)Titles and Awards
Jean Mandel Prize, 1999
Overseas member of EPSRC(2003-2006)
Member of the peer review committee of EU,France, Switzerland, the UK and China
Review expert for more than 40international journals
Vice Chairman of LMT Cachan, head of“Mechanics & Materials”
Editorial member for journals includingInt. J. Impact Engineering，Int. J.Aerospace &lightweight Struct, Journal of defense technology, Shock wave& Explosion, Open journal of transportation
He organized the porous Material seminar inthe IUTAM (International Union of Theoretical and Applied Mechanics) and theImpact Test seminar in the 10th European Mechanics and Material Conference
He served as presidents for seminars inseveral international conferences
2 Monographs, 2 works with others, 2special editions with others
Over 150 articles published in academicjournals and meetings
Google Scholar, index H, citation rate:2306
The report presents a complete experimentalstudy of the pseudoelastic behavior of Ni-Ti shape memory alloys under shearload on a flat surface at ambient temperature under a wide range of strain rates(10-4-103/s). For Quasi-static loading (loading rate 10-4-10-2/s), opticalfull-field measurement is necessary, because at this time the totaldisplacement is very small, only 0.3mm. The experiment at an intermediateloading rate (10-1-101/s) can be done by using modified MTS machine which canload at a speed of 300mm/s. High-speed cameras are needed in the experiment. Atlast, the impact load rate (102-103/ s) was achieved by the split Hopkinsonrod. The experiment focuses on the use of methodology to explore the question:how to complete the experiment with today’s technology? From a mechanical perspective,a fixture system has been designed that can handle the correspondingexperimental requirements; from testing, a large number of optical cameras witha sampling rate of 500FPS have been massively adopted. Experts started toanalyze problems including unit size, uncertainty in texture, picture,luminance and DIC. In addition, infrared cameras are often used in low loadingrate experiment to prove the optical full field measured by DIC.
The nominal stress-strain curve and thedevelopment of transformed band through experiment over strain rates of 7orders of magnitude were obtained. The major results are: 1, stress increaseswith the increase of strain rate (strain rates of 7 orders of magnitude in thisexperiment) 2, the stress field is not balanced under a low strain rate (like10-4/s) in the in-plane shear; there is an obvious transformed band in30-degree shear direction. 3, two decoupled bands are observed at an impactstrain rate of 102/s, which indicates that local transformed band also hasrate-dependence.
All teachers and students are welcome!
College of Architectural Engineering andMechanics
July 12, 2016