scholarly journals Determination of phase transformation surfaces around crack tip in shape memory alloys

2015 ◽  
Vol 33 ◽  
pp. 02010
Author(s):  
Mohamed Rachid Laydi ◽  
Christian Lexcellent
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Crack Tip

Experimental and FEM Analysis of the Fracture Behavior in NiTi Shape Memory Alloys

2006 ◽  
Vol 324-325 ◽  
pp. 919-922 ◽  
Author(s):  
Xin Mei Wang ◽  
Zhu Feng Yue
Keyword(s):  
Fracture Toughness ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Fracture Behavior ◽  
Micromechanical Model ◽  
Crack Tip ◽  
Fem Analysis ◽  
Transformation Behavior ◽  
Niti Shape Memory Alloys

In the present work, the fracture toughness of a NiTi pseudoelastic alloy has been obtained by experiments on CT specimens, which is KIC =39.38MPa·m1/2. Then the stress induced phase transformation behavior in front of the crack tip of the CT specimen is simulated by a micromechanical model considering the different elastic properties between martensite and austenite. The results show that the pre-crack promotes phase transformation at the crack tip. And the phase transformation is localised near the crack tip. It is also shown that phase transformation reduces the Mises stress around the crack tip.

scholarly journals Phase transformation surfaces around a crack tip for a shape memory alloys

2017 ◽  
Vol 39 (4) ◽  
pp. 375-386
Author(s):  
Christian Lexcellent
Keyword(s):  
Phase Transformation ◽  
Stress Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Elastic Stress ◽  
Crack Tip ◽  
Mechanical Theory ◽  
Compression Behavior ◽  
Linear Elastic ◽  
Tension And Compression

Depending of the shape of the crack tip e.g. with or without curvature, the size of the phase transformation surface between a mother phase A (austenite) and a producted phase M (martensite) is different. The presentation is focussed to the modes I and II (opening and shearing modes). The elastic stress field around the crack tip without curvature is known in the litterature and the use of Linear Elastic Mechanical Theory is consistent with the deformations amplitude associated the beginning of the phase transformation (A \(\Rightarrow\) M). In order to take into account the curvature at the crack tip, one uses the approximated expressions of Creager and Paris (1967). A special attention is devoted to take into account the asymmetry between tension and compression behavior in the surfaces prediction.

On the Fracture Toughness of Pseudoelastic Shape Memory Alloys

2013 ◽  
Vol 81 (4) ◽  
Author(s):  
Theocharis Baxevanis ◽  
Chad M. Landis ◽  
Dimitris C. Lagoudas
Keyword(s):  
Fracture Toughness ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Energy Release Rate ◽  
Shape Memory ◽  
Energy Release ◽  
Release Rate ◽  
Crack Tip ◽  
Reverse Phase ◽  
Element Analysis

A finite element analysis of quasi-static, steady-state crack growth in pseudoelastic shape memory alloys is carried out for plane strain, mode I loading. The crack is assumed to propagate at a critical level of the crack-tip energy release rate. Results pertaining to the influence of forward and reverse phase transformation on the near-tip mechanical fields and fracture toughness are presented for a range of thermomechanical parameters and temperature. The fracture toughness is obtained as the ratio of the far-field applied energy release rate to the crack-tip energy release rate. A substantial fracture toughening is observed, in accordance with experimental observations, associated with the energy dissipated by the transformed material in the wake of the growing crack. Reverse phase transformation, being a dissipative process itself, is found to increase the levels of toughness enhancement. However, higher nominal temperatures tend to reduce the toughening of an SMA alloy—although the material's tendency to reverse transform in the wake of the advancing crack tip increases—due to the higher stress levels required for initiation of forward transformation.

On the Energy Release Rate During Global Thermo-Mechanically-Induced Phase Transformation in Shape Memory Alloys

2013 ◽  
Author(s):  
Antonino Parrinello ◽  
Theocharis Baxevanis ◽  
Dimitris Lagoudas
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Energy Release Rate ◽  
Shape Memory ◽  
Energy Release ◽  
Release Rate ◽  
Crack Tip ◽  
Crack Driving Force ◽  
Order Of Magnitude ◽  
Specific Material

In this work, the effect of thermo-mechanically-induced global phase transformation (actuation) on the crack driving force in Shape Memory Alloys (SMAs) is investigated by means of the finite element method. The prototype problem of an infinite center-cracked SMA plate is analyzed during a thermal cycle in isobaric, plane strain loading conditions. The temperature variation is sufficient to induce global phase transformation. The Virtual Crack Closure Technique (VCCT) is employed to measure the crack tip energy release rate during the entire actuation cycle. Results show that the energy release rate can increase drastically during actuation, an order of magnitude for specific material systems. This in turn implies that crack growth may be triggered as a result of thermo-mechanically-induced phase transformation. The sensitivity of the crack tip energy release rate during actuation on key thermo-mechanical parameters is studied.

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