The performance of magnetorheological (MR) elastomers can be controlled by an applied field, so we can design intelligent isolators with adjustable and controllable parameters. All isolators more or less suffer from creep deformation, and the intensity will directly affect the service life of the equipment to be isolated. In this paper, NDI polyurethane-based MR elastomers were prepared and their creep properties were tested. The results show that as the filling mass fraction of carbonyl iron powder was increasing, the creep intensity in MR elastomers was first increased and then reduced; when the mass fraction was 70%, the creep intensity was less than that of the base material. Therefore, the creep property of MR elastomers can be improved by designing an appropriate content of carbonyl iron powder according to use requirement.

The dynamic magnetorheological (MR) effects of 1,5-Naphthalene diisocyanate (NDI) polyurethane-based MR elastomers were tested by changing excitation frequency, excitation amplitude, magnetic strength, or preload. NDI polyurethane-based elastomers show high dynamic mechanical property, and were used as base material to prepare MR elastomers, whose mechanical performance and dynamic MR effect were tested. The results show that: (1) the prepared NDI polyurethane-based MR elastomers have high mechanical performance and MR effect; (2) their MR effect was reduced with the increase in excitation amplitude or preload, but did not change obviously with the increase in excitation frequency. Therefore, MR elastomer devices should be reasonably designed to maximize MR effect.

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Slippery liquid-infused surfaces (SLISs) are developed as a potential alternative to superhydrophobic surfaces (SHSs) to resolve the issues of poor durability in corrosion protection and wear resistance. In this work, we used a simple laser processing technology to prepare a SLIS on the aluminum alloy (7075) surface. The superhydrophobicities of the modified surface and the oil film formed by liquid injection make the corrosive medium difficult to directly contact the surface and thus have a significant effect on corrosion resistance. The water and oil repellent SLIS exhibits durable corrosion resistance and excellent tribological properties compared with the SHS. The anticorrosion and wear resistance performances provided by the composite film have been assessed by multiple methods including the electrochemical test, immersion test, and friction wear test. The results indicate that compared to the bare surface, laser-ablated surface (LAS), and fluoroalkyl silane-modified SHS, the SLIS composite coating has better corrosion resistance and wear resistance, which is of great significance to expand the potential applications of 7075 aluminum alloys. The work provides a research basis for expanding the practical application of SLISs in complex environments.

This paper describes an improved extended transfer matrix method to evaluate the acoustic absorption coefficient of multi-layered structure with viscoelactic materials for perpendicular incidence plane acoustic. Here, the dynamic behavior of viscoelastic materials is taken into account. By comparing the calculated and measured results, it is shown that the results calculated by the improved extended transfer matrix method are in good agreement with the results measured. This improved extended transfer matrix method can accurately estimate the sound properties of multilayered structures with viscoelastic materials.

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