Magnetorheological elastomers (MREs) have been developed as a new class of smart materials for such diverse applications as adaptive vibration control of systems and energy dissipation. The linear viscoelastic (LVE) behavior of MREs is expected to play a significant role in determining filler morphology (structure, size, and aspect ratio) and working conditions. The LVE behavior of pre-structures, especially anisotropic structures, has not been clearly explained. To this end, this study aimed to analyze the LVE behavior and dynamic properties according to different pre-structures of magnetic particles. This is based on MRE pre-structures oriented at 0°, 30°, 45°, and 90° using oscillatory shear excitation as a function of frequency and amplitude sweep tests. For the latter, the excitation frequency and magnetic field intensity were analyzed. These analyses were performed for both storage modulus and loss factor corresponding to 10% strain amplitude from the roughly level linear line of the LVE region. The results showed that increasing the frequency or magnetic field intensity to increase anisotropy reduced the LVE limit. For every oriented pre-structure and analyzed frequency tested, the magnetic field decreased the LVE limit. Thus, the orientation of the carbonyl iron particles in the matrix enhanced the viscoelastic properties.

Recently, vibration control has been useful in various engineering fields such as aerospace, adaptive dynamic vibration absorbers, and infrastructure. Magnetorheological elastomer (MRE) is an interesting material for controlling and suppressing undesirable vibrations through the application of a magnetic field. The present study aims at analyzing the pre-structure of the magnetorheological viscoelastic core in the dynamic response of an MRE-sandwich structure. The forced vibration tests were performed under a non-homogenous magnetic field to evaluate the dynamic properties of the MRE-sandwich structure in a frequency bandwidth range of 0-250 Hz. Experimental results show that the proposed MRE-sandwich structures are capable of eliminating unwanted resonances due to induced magnetic field intensity in the activated region, especially at the fundamental mode. Moreover, results highlight that an oriented pre-structure in an MRE-sandwich has an attenuation effect on vibrations in the low frequency range. Additionally, the external magnetic field increased the structural vibrations damping capability by approximately 200%. Oriented pre-structures of the MRE core were also used to dissipate vibration. Consequently, they could potentially be used in vibration attenuation applications such as stop operations in dynamic structures.

Abstract. This research aims to study the effects of experimental design parameters such as the number of wires, the length and braiding angle of stent on mechanical properties of braiding stentriever made from shape memory alloy. Self-expanding stents or stentriever were fabricated by braiding a number of wires together by braiding machine, followed by heat-treatment for shape setting. Superelastic NiTi shape memory alloy wires with diameters of 0.08mm were used while the number of wires was selected to be 12, 24 and 36, respectively. Braiding angle was designed to be 52o±2o and 38o±2o. Diameter of stentriever was set to be 4 mm. On the other hand, this design is focused on stent using in 3 mm to 4 mm intracranial vessel diameter stent, radial resistive test, radial expansion test and three-point bending test under temperature at 37o are carried out. The result shows that the maximum radial resistive force, maximum radial expansion force and maximum bending force which are equaled to 50 mN/mm, 37 mN/mm and 0.423 N, respectively can be confirmed in stent with 36 wires.