Guochang Lin, Chaonan Hu, Lin Cong and Yongtao Yao
The purpose of this paper is to developing a kind of acoustic metamaterial with wide frequency band especially in low frequency region. At the same time, its the tunability of…
Abstract
Purpose
The purpose of this paper is to developing a kind of acoustic metamaterial with wide frequency band especially in low frequency region. At the same time, its the tunability of sound insulation frequency is achieved.
Design/methodology/approach
A three-dimensional (3D) acoustic metamaterial consisting of rigid frame, spherical attachment and thin film is proposed. The material parameters and the effect of the attachment hole on the forbidden band are investigated by finite element simulation. The sound insulation effect of the structure is validated by the combination of simulation and experiment.
Findings
The results show that the elastic modulus of the structural material determines the initial frequency of the forbidden band of the proposed 3D acoustic metamaterials. The lower the elastic modulus of the structural material, the lower the initial frequency of the forbidden band. The material parameters of the frame mainly affect the initial frequency of the first forbidden band, and the material parameters of the attachment will affect both the initial and termination frequency of the first forbidden band. Holes in the attachments reduce the band gap width. The characteristic curve moves down with the increase of subtracted mass.
Research limitations/implications
The findings may greatly benefit the application of the acoustic metamaterials in the fields of sound insulation and noise reduction.
Originality/value
This acoustic metamaterial structure has excellent sound insulation performance. At the same time, the single cell structure can be assembled into any shape. The structure can achieve sound selective filtering and combination control.
Details
Keywords
Yan Liu, Yanzhen Liu and Guochang Lin
This study aims to investigate the basic mechanical properties of inflatable antenna reflector material under high-low temperatures.
Abstract
Purpose
This study aims to investigate the basic mechanical properties of inflatable antenna reflector material under high-low temperatures.
Design/methodology/approach
Uniaxial tensile tests of Kapton (polyimide) foils were conducted in this paper. Kapton foils with a thickness of 25 µm were used and the strip specimens were manufactured according to the machine direction and the transverse direction of the foils.
Findings
The stress–strain curves of the foils were obtained under ten temperature conditions (−70°C, −40°C, −10°C, 0°C, 20°C, 50°C, 80°C, 110°C, 140°C, 170°C) after uniaxial tensile tests. Generally speaking, such stress–strain curves are highly nonlinear, and Kapton can be classified into some kind of ductile material without obvious yielding point.
Practical implications
The tests results provide a basis for partial coefficients of Kapton foils strength design value, and meanwhile provide basic material data for the extreme temperature field test in orbit for the inflatable antenna structure in the future.
Originality/value
Based on the curve itself and strain energy theory, for the first time the equivalent yielding point was determined and the mechanism of constitutive curve changing with temperature was explained. Based on curves above, tensile strength, elongation at break, equivalent yielding stress, yielding strain and elastic modulus were analyzed and calculated. By analyzing the mechanical parameters above, the fitting formulas with temperature as the variable were given.
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Keywords
Xiangkai Zhang, Renxin Wang, Wenping Cao, Guochang Liu, Haoyu Tan, Haoxuan Li, Jiaxing Wu, Guojun Zhang and Wendong Zhang
Human-induced marine environmental noise, such as commercial shipping and seismic exploration, is concentrated in the low-frequency range. Meanwhile, low-frequency sound signals…
Abstract
Purpose
Human-induced marine environmental noise, such as commercial shipping and seismic exploration, is concentrated in the low-frequency range. Meanwhile, low-frequency sound signals can achieve long-distance propagation in water. To meet the requirements of long-distance underwater detection and communication, this paper aims to propose an micro-electro-mechanical system (MEMS) flexible conformal hydrophone for low-frequency underwater acoustic signals. The substrate of the proposed hydrophone is polyimide, with silicon as the piezoresistive unit.
Design/methodology/approach
This paper proposes a MEMS heterojunction integration process for preparing flexible conformal hydrophones. In addition, sensors prepared based on this process are non-contact flexible sensors that can detect weak signals or small deformations.
Findings
The experimental results indicate that making devices with this process cannot only achieve heterogeneous integration of silicon film, metal wire and polyimide, but also allow for customized positions of the silicon film as needed. The success rate of silicon film transfer printing is over 95%. When a stress of 1 Pa is applied on the x-axis or y-axis, the maximum stress on Si as a pie-zoresistive material is above, and the average stress on the Si film is around.
Originality/value
The flexible conformal vector hydrophone prepared by heterogeneous integration technology provides ideas for underwater acoustic communication and signal acquisition of biomimetic flexible robotic fish.
Details
Keywords
Yong Huang, Guangyou Song and Guochang Li
The purpose of this study is to explore the seismic damage mechanism of the Dayemaling Bridge during the Maduo earthquake and discuss the seismic damage characteristics of the…
Abstract
Purpose
The purpose of this study is to explore the seismic damage mechanism of the Dayemaling Bridge during the Maduo earthquake and discuss the seismic damage characteristics of the high-pier curved girder bridge.
Design/methodology/approach
In this study, the numerical simulation method is used to analyze the seismic response using synthetic near-field ground motion records.
Findings
The near-field ground motion of the Maduo earthquake has an obvious directional effect, it is more likely to cause bridge seismic damage. Considering the longitudinal slope of the bridge and adopting the continuous girder bridge form, the beam end displacement of the curved bridge can be effectively reduced, and the collision force of the block and the bending moment of the pier bottom are reduced, so the curved bridge with longitudinal slope is adopted.
Originality/value
Combined with the seismic damage phenomenon of bridges in real earthquakes, the seismic damage mechanism and vulnerability characteristics of high-pier curved girder bridges are discussed by the numerical simulation method, which provides technical support for the application of such bridges in high seismic intensity areas.