scholarly journals Effect of strain rate on strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy

2021 ◽  
Vol 250 ◽  
pp. 05012
Author(s):  
Sebastian Henschel ◽  
Lutz Krüger
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Image Correlation ◽  
Coarse Grained ◽  
Strain Rates ◽  
Localized Deformation ◽  
Strength And Deformation

The strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy at different strain rates was studied. Furthermore, the effect of grain size was investigated. To this end, a batch with bamboo-like grain arrangement and a batch with smaller, nevertheless coarse, grains were analyzed. Tensile tests at quasi-static, intermediate, and dynamic loading rates were performed. Digital image correlation and microstructural analysis revealed the localized deformation and phase transformation in favorable oriented grains. At higher strain rates, a increased number of orientations was activated for the phase transformation. A higher strain rate resulted in an increased strength for the coarse-grained material while the bamboo-like material did not show this effect. The analysis of fracture surfaces revealed ductile fracture and cleavage fracture for all strain rates.

A Study on Tensile Deformation Behavior in Fe-Based Shape Memory Alloy by Rate Sensitive Transformation Kinetics Model

2016 ◽  
Vol 725 ◽  
pp. 77-81
Author(s):  
Anthony Budiaman ◽  
Kazuki Fujita ◽  
Takeshi Iwamoto
Keyword(s):  
Numerical Simulation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Rate Sensitivity ◽  
Kinetics Model ◽  
Strain Rates ◽  
Transformation Kinetics ◽  
Tensile Deformation Behavior

Fe-based shape memory alloy (Fe-SMA) shows a shape memory effect (SME) governed by forward and reverse stress-induced martensitic transformation (SIMT). Fe-SMA has been applied to joints and dampers utilized at various strain rates. To utilize Fe-SMA better, it is necessary to understand the mechanical properties in a wide range of strain rate. In previous study, the results of a tensile test at various strain rates show a rate-sensitivity, however, the mechanism of rate-sensitive tensile deformation behavior is still unclear. Thus, a numerical simulation using a transformation kinetics model is needed to clarify the mechanism. Some transformation kinetics models have been proposed, however, the rate sensitivity cannot be included. In this study, the rate sensitivity of volume fraction martensite is considered into the transformation kinetics model as an improvement of the past-proposed model. The numerical simulation of the uniaxial tensile test at various strain rates is performed to reproduce transformation behavior of the martensite phase. Then, the model is validated by comparing to the experimental results. Afterwards, the mechanism of rate-sensitive tensile deformation behavior of Fe-SMA is discussed.

Bending of Superelastic Shape Memory Alloy Tubes

2011 ◽  
Author(s):  
Benjamin Reedlunn ◽  
Christopher Churchill ◽  
Emily Nelson ◽  
Samantha Daly ◽  
John Shaw
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Response ◽  
Surface Displacement ◽  
Beam Theory ◽  
Image Correlation ◽  
Reasonable Assumption ◽  
Significant Shift ◽  
Localized Deformation ◽  
Tension And Compression

Many shape memory alloy (SMA) applications exploit superelasticity in a bending mode, yet the large displacements and rotations associated with bending of slender structures make controlled experiments difficult. A custom pure bending fixture was built to perform experiments on superelastic NiTi tubes. To understand the bending results, the tubes were also characterized in uniaxial tension and compression, where a custom fixture was utilized to avoid buckling. In addition to measuring the global mechanical response, stereo digital image correlation (DIC) was used in all the experiments to capture the local surface displacement and strain fields. Consistent with the tension/compression data, our bending experiments showed a significant shift of the neutral axis towards the compression side. Also, the tube had strain localization on the tension side, but no such localization on the compression side. Detailed analysis of the strain distribution across the tube diameter revealed that the usual assumption of beam theory, that plane sections remain plane, did not hold along the tension side. Averaged over a few diameters of gage length, plane sections remain plane is a reasonable assumption and can be used to predict the global moment–curvature response. However, this assumption should be used with caution since it can under/over predict local strains by as much as 2× due to the localized deformation morphology.

Effect of Phase Transformation on Localized Deformation in Ti-Ni Shape Memory Alloy.

1996 ◽  
Vol 45 (4) ◽  
pp. 411-416 ◽  
Author(s):  
Xiaoping JIANG ◽  
Moritaka HIDA ◽  
Yoshito TAKEMOTO ◽  
Akira SAKAKIBARA ◽  
Shuzo FUJII
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Localized Deformation

Mechanical Behavior of an Ni-Ti Shape Memory Alloy Under Axial-Torsional Proportional and Nonproportional Loading

1999 ◽  
Vol 121 (1) ◽  
pp. 9-18 ◽  
Author(s):  
T. Jesse Lim ◽  
David L. McDowell
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Micromechanical Model ◽  
Numerical Differentiation ◽  
Thin Wall ◽  
Proportional Loading ◽  
Nonproportional Loading

Several biaxial proportional and nonproportional loading experiments are reported for thin-wall tubes of a pseudoelastic Ni-Ti shape memory alloy (SMA). In addition to the mechanical behavior, temperature was measured during the experiments. It is shown that the phase transformation exhibits asymmetrical behavior in the case of tension-compression cycling. The transformation strain rate is determined for selected histories by numerical differentiation of data. Under nonproportional loading, the rate of phase transformation does not follow a generalized J2-J3 criteria based on results of micromechanical simulations for proportional loading. The role of simultaneous forward and reverse transformations on the nonproportional transformation response is examined using a simple micromechanical model, and the direction of the inelastic strain rate is adequately predicted. Load- and strain-controlled experiments at different strain rates, with and without hold times, are reported and coupled thermomechanical effects are studied.

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