The underwater anechoic coating with local resonant units is an effective method to achieve low-frequency sound absorption. However, the structure obtained in this way is not satisfactory in the sound absorption effect of mid-high frequency bands. Capitalizing on the impedance gradient characteristics of functionally graded materials (FGMs) can improve the impedance matching between the structure and the medium, and enhance the dissipation of sound waves inside the structure. Based on these, we propose an underwater acoustic structure, which can improve and obtain low-frequency and broadband sound absorption performance by embedding local resonators into FGMs. To reveal the sound-absorbing mechanism and further optimize the low-frequency absorption performance of the structure, we conduct quantitative analyses on the parameters of FGMs, the materials and forms of resonators. The results indicate that by appropriately adjusting the studied parameters, different low-frequency sound-absorbing peak can be obtained and the absorption effects are also further improved.
Rail corrugation is a very common phenomenon in high-speed railways. Rail corrugation can cause increased vibration of trains and tracks, and may even affect the safety of train operation. Therefore, this paper will analyze the vibration of the wheel-rail system caused by the rail corrugation. The actual transient rolling contact model is established by using explicit and implicit finite element methods. Through the calculation of the wheel-rail contact force and the wheel-rail mode, the vibration relationship between the rail corrugation and the wheel-rail system is obtained. It can provide some references for further analysis of the cause of rail corrugation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.