Analysis of Wave Height in Front of a Wave Absorbing Structure with Rubble Foundation

Wave absorbing structures have been widely applied in many countries. In the present paper, the wave heights in front of a vertical wave absorbing structure with rubble foundation as well as in the wave chamber of the structure are analysed using an approximative calculation method, and the dissipating effect of the structure is verified. On the basis of the results of regular waves, the relative wave heights of irregular waves in front of the wave absorbing structure as well as in the chamber have also been analysed.

Inverse Calculation of Wave-Absorbing Structure Dimensions Based on Extended ANFIS Model

A new wave energy dissipation structure is proposed, aiming to optimize the dimensions of the structure and make the reflection of the structure maintain a low level within the scope of the known frequency band. An optimal extended ANFIS model combined with the wave reflection coefficient analysis for the estimation of the structure dimensions is established. In the premise of lower wave reflection coefficient, the specific sizes of the structure are obtained inversely, and the contribution of each related parameter on the structural reflection performance is analyzed. The main influencing factors are determined. It is found that the optimal dimensions of the proposed structure exist, which make the wave absorbing performance of the structure reach a perfect status under a wide wave frequency band.

3D printed modular Bouligand dissipative structures with adjustable mechanical properties for gradient energy absorbing

Three-dimensional(3D)printing allows for the creation of complex,layered structures with precise micro and macro architectures that are not achievable through traditional methods.By designing 3D structures with geometric precision,it is possible to achieve selective regulation of mechanical properties,enabling efficient dissipation of mechanical energy.In this study,a series of modular samples inspired by the Bouligand structure were designed and produced using a direct ink writing system,along with a classical printable polydimethylsiloxane ink.By altering the angles of filaments in adjacent layers(from 30◦to 90◦)and the filament spacing during printing(from 0.8 mm to 2.4 mm),the mechanical properties of these modular samples can be adjusted.Compression mechanical testing revealed that the 3D printed modular Bouligand structures exhibit stress-strain responses that enable multiple adjustments of the elastic modulus from 0.06 MPa to over 0.8 MPa.The mechanical properties were adjusted more than 10 times in printed samples prepared using uniform materials.The gradient control mechanism of mechanical properties during this process was analyzed using finite element analysis.Finally,3D printed customized modular Bouligand structures can be assembled to create an array with Bouligand structures displaying various orientations and interlayer details tailored to specific requirements.By decomposing the original Bouligand structure and then assembling the modular samples into a specialized array,this research aims to provide parameters for achieving gradient energy absorption structures through modular 3D printing.

Micro-perforated structures as stand-alone sound absorbers

1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was outlined in Ref. [1]. 30 years ago, D. Y. MAA[2] was first in proposing a practicable design concept and calculation model for Micro-Perforated Absorber （MPA） prototypes which still forms the basis for various applications. During the past 12 years the Fraunhofer IBP developed a whole family of MPA products in close cooperation with 8 or more industrial partners operating in a variety of widely differing market segments. Meanwhile a large number of MPA modules and surface elements have evolved from MAA＇s creative pioneer work. More and more ambitious acousticians have, more recently, caught on this attractive idea of employing absorbers made of non-fibrous, non-abrasive materials with non-polluting, almost closed and optically attractive surfaces. MPA structures have played an important part in a long-standing and on-going effort at IBP to establish novel Alternative Fibreless Absorber （ALFA） tools for a better noise control and acoustic comfort.

A low-cost infrared absorbing structure for an uncooled infrared detector in a standard CMOS process

This paper introduces a low-cost infrared absorbing structure for an uncooled infrared detector in a standard 0.5 m CMOS technology and post-CMOS process. The infrared absorbing structure can be created by etching the surface sacrificial layer after the CMOS fabrication, without any additional lithography and deposition procedures. An uncooled infrared microbolometer is fabricated with the proposed infrared absorbing structure.The microbolometer has a size of 6565 m2and a fill factor of 37.8%. The thermal conductance of the microbolometer is calculated as 1.3310 5W/K from the measured response to different heating currents. The fabricated microbolometer is irradiated by an infrared laser, which is modulated by a mechanical chopper in a frequency range of 10–800 Hz. Measurements show that the thermal time constant is 0.995 ms and the thermal mass is 1.3210 8J/K. The responsivity of the microbolometer is about 3.03104V/W at 10 Hz and the calculated detectivity is 1.4108cm Hz1=2/W.

Simulation of crooked plate energy absorption structure under impact

Due to their simple structure,crooked plates are widely processed into energy absorption structures.There are obvious differences in the final deformation of crooked plates with different materials and dynamic conditions under the impact of constant-input kinetic energy.To better understand this phenomenon,we solved the Zhang-Yu equation with Maple software,obtained the law of generalized coordinates(rotation angle)of the energy absorber changing with time,and compared the energy absorption capacity of a crooked plate energy absorber under different parameters.To better understand how the motion of the energy absorber is affected by the change of parameters,we calculated the phase diagram of the energy absorber dynamics.After many numerical simulations,we found that the four-crooked plate energy absorber should have a mass-sensitive structure.We established the finite element model of dynamic buckling of mild steel and 6061-T6 aluminum alloy,and compared it with the Calladine-English dynamic experiment and Zhang-Yu rigid viscoplastic model.The results show that:(1)the Zhang-Yu rigid viscoplastic model has more guiding significance for mild steel(strain rate-sensitive material),and has greater error for 6061-T6 aluminum alloy(strain rate-insensitive material),and the prediction error further increases with the initial angle;and(2)by modifying the equivalent plastic length A of a plastic hinge according to the finite element model,the prediction accuracy of the Zhang-Yu rigid viscoplastic model can be improved.Our research results certain guiding significance for the design and manufacture of energy-absorbing structures of crooked plates.

Influence of Unidirectional Tensile External-loading on Electromagnetic Property of the Perforated Frequency Selective Surface Illuminated by Electromagnetic Wave Incident at Arbitrary Angles

That whether unidirectional tension changes the influence of incident angle on FSS's(frequency selective surface) electromagnetic(EM) property and whether incident angle changes the effect of unidirectional intension on FSS's EM property is researched.The pattern and magnitude of these changes are revealed.Firstly,the analyses for the mechanism of unidirectional tension's influence and the mechanism of the coupling between the influences of unidirectional tension and incident angle are conducted.Then,according to the mechanism of these influences,Mechanics-Electromagnetics co-analysis is conducted based on mechanics finite element method and electromagnetics finite element method.The frequency responses of the FSS which is under different unidirectional tensions and illuminated by EM wave incident at different angles are gained.The concept"unidirectional tensile sensitivity of FSS"is put forward along with two unidirectional tensile sensitivity factors.By using angular sensitivity-factor and unidirectional tensile sensitivity-factor,the influences of unidirectional tension and incident angle,which are coupled with each other,are expatiated respectively.Research results show that these influences have two sides.Meanwhile,basing on Mode Matching Method and according to the results of numerical investigation,one principle for the layout of FSS with apertures is gained.Several suggestions for further research are given.