Investigation of mechanical behaviors and improved design of V-shaped braid stents

Abstract

V-shaped braid stents (VBSs), as highly retrievable and flexible nitinol stents, are extensively applied in endovascular diseases. They also cause less damage to vessel wall compared to tube-cutting stents. However, poor performance of VBS or suboptimal operation can give rise to unwanted clinical situations such as thrombosis and intimal hyperplasia. Therefore, research on designing factors affecting the performance of these devices is of great significance. Furthermore, simulation of stenting process can help designers understand the interactions of stents and vessel wall to reduce time to market. Thus, finite element analysis (FEA) and bench test are performed taking into account both designing factors and stenting process of VBS, including development of parametric modeling tool, research on the relationships among structural parameters and radial force, exploration of the interactions of VBS and vessel wall and pulsating load effect. This research was performed using a commercial solver Abaqus/standard with a user material subroutine (UMAT/nitinol). Structural parameters of VBS, unit-cell height and wire diameter have significant impacts on radial force, unit-cell number has slight influence on radial force, and arc diameter has almost negligible impact on radial force. Without pulsatile load, maximum stress and strain always occur in arc position; however, in pulsatile load, maximum stress and strain are gradually transformed to strut position. The stress created near vessel wall and VBS interface is higher than interaction stress due to pulsating load. The obtained result provided valuable information on the structural design of stents as well as the effects of stent on vessel wall and that vessel wall on stent deformation. Graphical abstract [Formula: see text]

Influence of Structural Porosity and Martensite Evolution on Mechanical Characteristics of Nitinol via In-Silico Finite Element Approach

“…In a real uniaxial mechanical test, an asymmetry between tension and compression response (discussed earlier) is possible. The different modes are found to exhibit different strain levels [ 94 ]. This concept is proposed using a parameter ∝, which is calculated (Equation (1)) from the initial values of phase transformation in tension and compression mode.…”

Electro-induced tensile deformation of over-braiding composite tube with carbon fiber reinforced shape memory polyurethane filament

“…2D smart braided tube is a smart structure design with a combination of smart filament materials, having been implemented in various applications such as medical stents [1][2][3], artificial muscle [4] and smart robots [5,6] because of large deformation recovery, excellent radial flexibility and bending * Author to whom any correspondence should be addressed. compliance.…”