Three high manganese TWIP steels were produced with stacking fault energies γ SFE ranging from 20.5 to 42 mJ/m 2 . The materials were mechanically tested in tension at temperatures and strain rates varying in the ranges of -50°C…80°C and 10 -3 s -1 …1250 s -1 , respectively. Due to the temperature dependence of γ SFE , also the mechanical behavior of TWIP steels reveals clear temperature dependence, determined by the prevailing deformation mechanism, i.e., dislocation slip, deformation twinning, or ε-martensite transformation. In addition to the 'ordinary' strain rate sensitivity, an increase in temperature due to adiabatic deformation heating contributes to the stacking fault energy (SFE) at high strain rates, shifting γ SFE towards the dislocation slip regime and this way strongly affecting also the mechanical behavior. At stacking fault energies close to the transition between twinning and ε-martensite transformation, lowering the temperature can ultimately result in entering the ε-martensite transformation regime that may bring about further ductility.
The intraoperative in-vivo mechanical function of the left ventricle has been studied thoroughly using echocardiography in the past. However, due to technical and anatomical issues, the ultrasound technology cannot easily be focused on the right side of the heart during open-heart surgery, and the function of the right ventricle during the intervention remains largely unexplored. We used optical imaging and digital image correlation for the characterization of the right ventricle motion and deformation during open-heart surgery. This work is a pilot study focusing on one patient only with the aim of establishing the framework for long term research. These experiments show that optical imaging and the analysis of the images can be used to obtain similar parameters, and partly at higher accuracy, for describing the mechanical functioning of the heart as the ultrasound technology. This work describes the optical imaging based method to characterize the mechanical response of the heart in-vivo, and offers new insight into the mechanical function of the right ventricle.
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