Abstract
Coronary stents are medical/mechanical micro devices which are used to
open the arteries occluded by the build-up over time of fat,
cholesterol, or other substances. A wide range of studies should be
conducted on coronary stents since they play an important role in the
health of patients who suffer from heart diseases. However, due to micro
scale of these tools, and also their gripping and loading complexity
during a test, it is very difficult to conduct experimental studies to
understand their behavior. Moreover, because of their micro dimensions
and subsequently, existence of only a few grains along their thickness,
J(2) flow theory is not appropriate to be implemented in order to define
the mechanical behavior of such devices. Therefore, in this paper, 3D
crystal plasticity finite element method (3D-CP-FEM) is used to
understand the behavior of these devices. To achieve this goal and to
find the hardening constants of strut, some simulations were designed
and compared with an experimental study. Also, the effect of grain size
in terms of w/d and lid was investigated on the failure strain of struts
under uniaxial tensile test. ``w'' and ``I'' are the width and
length of the strut, respectively, and ``d'' is the average grain
size. The results showed that failure strain increases within creasing
w/d and decreasing lid. Parameter waviness was used to measure the
qualification of stent struts in bending and unbending simulations.
Results revealed that the edges of strut are the critical areas and have
more potential to failure. Additionally, it was found that with the
increase in the w/d ratio, waviness decreases and the struts become
homogeneous in behavior. (C) 2016 Elsevier Ltd. All rights reserved.
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