Effect of repeated compressive dynamic loading on the stress-induced martensitic transformation in niti shape memory alloys.

Miller, D. ; Thissell, W.

Technical Information Center Oak Ridge Tennessee

关键词: Nickel alloys;    Titanium alloys;    Phase transformations;    Shape memory effect;    Dynamic loads;   

RP-ID  :  DE2001768250

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

It has been shown that quasi-static, cyclic, isothermal mechanical loading influences the mechanical response of the stress-induced martensitic transformation in fully annealed NiTi Shape Memory Alloys (SMAs). As the cycle number increases, hardening of the stress-strain response during the martensitic phase transformation is seen along with a decrease in the threshold stress for initiation of stress-induced martensite. Also, the amount of plastic strain and detwinned martensitic strain decreases as the cycle number increases. However, NiTi SMAs have not been experimentally explored under high compressive strain rates. This research explores the cyclic near-adiabatic stress-induced martensitic loading using a Split Hopkinskin Pressure Bar (SHPB). The results of the dynamic loading tests are presented with emphasis on the loading rate, stress-strain response, specimen temperature and post-test microstructural evaluation. The results from the high strain rate tests show similarities with the quasi-static results in the hardening of the stress-strain response and shifting of the threshold stress for initiation of stress-induced martensite.