- 标题
- 摘要
- 关键词
- 实验方案
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Band gap analysis of periodic structures based on cell experimental frequency response functions (FRFs)
摘要： An approach is proposed to estimate the transfer function of the periodic structure, which is known as an absorber due to its repetitive cells leading to the band gap phenomenon. The band gap is a frequency range in which vibration will be inhibited. A transfer function is usually performed to gain band gap. Previous scholars regard estimation of the transfer function as a forward problem assuming known cell mass and stiffness matrices. However, the estimation of band gap for irregular or complicated cells is hardly accurate because it is difficult to model the cell exactly. Therefore, we treat the estimation as an inverse problem by employing modal identification and curve fitting. A transfer matrix is then established by parameters identified through modal analysis. Both simulations and experiments have been performed. Some interesting conclusions about the relationship between modal parameters and band gap have been achieved.
关键词： Band gap,Periodic structure,Transfer matrix,Parameter identification,Modal analysis
更新于2025-09-23 15:23:52
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Static and dynamic effective thickness in five-layered glass plates
摘要： In the last years, the effective thickness concept has been used to calculate deflections, stresses and modal parameters in laminated glass beams and plates, which consists of using a monolithic element with equivalent bending properties to a laminated element, i.e. the thickness of the equivalent monolithic model is time and temperature dependent because the interlayers show a viscoelastic behavior. Multi-layered laminated glass panels are those with at least three monolithic glass layers and two viscoelastic interlayers which are commonly used in floors, roofs and other applications where a high level of security is required. In this paper, a static deflection effective stiffness for a laminated glass plate consisting of three glass layers and two polymeric interlayers is derived. This static effective thickness is then extended to the frequency domain using the correspondence principle. The models are validated by static experimental tests and operational modal tests carried out on a rectangular multi-layered laminated glass plate pinned supported at the four corners.
关键词： B. Operational Modal Analysis,A. Laminated glass,C. Effective Thickness,D. Viscoelasticity
更新于2025-09-23 15:22:29
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The contribution to the modal analysis using an infrared camera
摘要： The paper deals with modal analysis using an infrared camera. The test objects were excited by the modal exciter with narrowband noise and the response was registered as a frame sequence by the high speed infrared camera FLIR SC7500. The resonant frequencies and the modal shapes were determined from the infrared spectrum recordings. Lock-in technology has also been used. The experimental results were compared with calculated natural frequencies and modal shapes.
关键词： resonance,infrared camera,modal analysis,vibration,modal shape
更新于2025-09-23 15:21:01
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[IEEE 2020 International Workshop on Antenna Technology (iWAT) - Bucharest, Romania (2020.2.25-2020.2.28)] 2020 International Workshop on Antenna Technology (iWAT) - Numerical Analysis of Dielectric Post-Wall Waveguides
摘要： Functional post-wall waveguides that are formed by periodically distributed dielectric posts are numerically analyzed. The propagation constant and attenuation constant of the dielectric post-wall waveguide is rigorously calculated using our originally developed numerical method. The developed formulation is accurate and numerically very fast. Structural parameters of the dielectric post-wall waveguide are properly chosen in order to achieve the confinement of the field in the guiding region as strong as possible even in case of one-layered dielectric structure. The final goal of our investigations is to realize the functional dielectric post-wall waveguide-based filters, which are expected to have a practical application in THz region, where the metallic (PEC) rods are losing their properties.
关键词： dielectric post-wall waveguide,complex waves,modal analysis,periodic structure
更新于2025-09-23 15:21:01
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Resonant modal analysis and dual-mode tailoring in high refractive index contrast two-dimensional nanorod arrays
摘要： Resonant modal analysis and dual-mode tailoring in high refractive index contrast two-dimensional (2-D) nanorod arrays are proposed. The specific modes of the guided mode resonances (GMRs) excited by the 2-D nanorod arrays can be distinguished based on the equivalent medium theory (EMT) and the analysis of the electric/magnetic fields. The broadband reflection and enhanced transmission can be obtained by the tailoring between the resonant dual-mode of the 2-D nanorod arrays. It is shown that the 2-D nanorod arrays can support the excitation of the resonant dual-mode with low-quality factor (low-Q) TM0 and high quality factor (high-Q) TE0 modes on a reflection broadband. The coupling of the edges of the resonant dual-mode can be tailored to create the resonant transmission with polarization independence near 1.31 μm. By merely changing the angle of incidence, one can achieve triple transmission channels due to the interaction of the nondegenerate resonant dual-modes.
关键词： Dual-mode tailoring,Modal analysis,Two-dimensional nanorod arrays,Guided mode resonance
更新于2025-09-23 15:19:57
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Clamp looseness detection using modal strain estimated from FBG based operational modal analysis
摘要： Clamps are widely used to fix and support the pipe in engineering community. Clamps looseness may further lead to the fatigue damage of the pipe, therefore the early detection of clamps looseness is very crucial. The robustness and the accuracy of damages detection have already been the greatest challenges in traditional methods in Structural Health Monitoring (SHM). Due to the higher sensitivity of Strain Mode Shape (SMS) to local damages and more effective performance of fiber Bragg grating (FBG) sensing technology for industrial and mechanical devices, present works focus on a new method to detect clamp looseness based on Strain Mode Shape Differences (SMSD) and FBG sensing technology. In order to estimate the SMSs online, a novel diagram of Operational Strain Modal Analysis (OSMA) with FBG sensing technology is also presented, in which a rational fraction composed by Forsythe Complex Orthogonal Polynomials (FCOP) is employed to fit the 'Positive' Strain Power Spectral Density (PSPSD) of a single output. Traditionally, the fitting of the all the outputs need to be conducted to obtain the SMSs, which increases the calculation cost. To further address this issue, an improved OSMA integrated with strain response transmissibility (SRT) is also proposed to calculate the SMSs by just fitting a single output. Firstly, the identified modal parameters based on the presented method is validated with simulation results. And then, the ability of the SMSD index is further investigated analytically and experimentally for clamp looseness detection under different locations and degrees , the results indicate that the clamp looseness can be detected by the SMSD index.
关键词： modal strain,Operational Strain Modal Analysis,Clamp looseness detection,FBG sensing.
更新于2025-09-19 17:15:36
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A laser triangulation sensor for vibrational structural analysis and diagnostics
摘要： The industrial progress has reached a level in which it is necessary to understand the behavior of mechanical components and to monitor their conditions without disassembling them. Nowadays, a suitable methodology is based on vibrational analysis usually performed through acceleration signals measured directly on the system to be tested. However, in the last years, the industrial scenario has deeply changed due to the need for time reduction, in particular, for the control operations at the end of the productive line. The genuine methods based on acceleration measurements, for example, through piezoelectric accelerometers, came into conflict with the industrial need as the sensors used for the quality control have to be easily and fastly mounted and unmounted. A valid alternative is represented by the exploitation of laser triangulation sensors that are able to measure the dynamic displacement in a contactless way, strongly reducing the (un)mounting time. The target of this paper is to highlight pros and cons of the contactless displacement analysis through laser triangulation sensors with respect to the contact one through genuine accelerometers by means of a comparison between the results obtained both for experimental modal analysis and vibrational diagnostics of rotating machines.
关键词： displacement analysis,experimental modal analysis,laser triangulation sensor,Vibration,vibrational diagnostics
更新于2025-09-19 17:13:59
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Finite Element Modelling and Analysis for Dynamic Investigation of a Laser Spot Welded Hat-Plate Structure under Initial Stress Influence
摘要： This paper presents the finite element modelling and analysis of the dynamic behaviour of a laser spot welded structure under the influence of initial stress. Modal based updating with a new scheme was used to improve the finite element model of the structure. Element connectors with CWELD ELPAT format were used to represent the laser spot welded in the structure. The modal parameters of the structure were measured using impact hammer testing and roving accelerometers under free-free boundary conditions. NASTRAN SOL 200 was used in updating the finite element model in light of the experimental results. In this study, it was found that modal updating with the new scheme has successfully matched the finite element model of the welded structure with the experimental model. The achievement demonstrates the accuracy and efficiency of the proposed new scheme.
关键词： Finite Element Analysis,Initial Stress,Experimental Modal Analysis,Model Updating
更新于2025-09-16 10:30:52
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Modal analysis for nanoplasmonics with nonlocal material properties
摘要： Plasmonic devices with feature sizes of a few nanometers exhibit effects which can be described by the nonlocal hydrodynamic Drude model. We demonstrate how to exploit contour integral methods for computing eigenfrequencies and resonant states of such systems. We propose an approach for deriving the modal expansion of relevant physical observables. We use the methods to perform a modal analysis for a metal nanowire. All complex eigenfrequencies in a large frequency range and the corresponding resonant states are computed. We identify those resonant states which are relevant for the extinction cross section of the nanowire.
关键词： extinction cross section,nanoplasmonics,hydrodynamic Drude model,modal analysis,nonlocal material properties,metal nanowire
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Assessment of Accelerometer Versus LASER for Board Level Vibration Measurements
摘要： The ongoing trend to deploy ICs in more complex and harsher applications, entails precise evaluation of solder joint reliability of components subjected to vibration loads. For this, a good understanding of the PCB vibrational motion during a board level vibration test is essential. This can only be achieved by a well characterized vibration test setup. The vibration motion can be recorded by using a contact-based measurement approach, using an accelerometer, or a contactless measurement configuration, i.e. using a Laser Doppler Vibrometer (LDV). This paper evaluates both measurement techniques by recording the PCB dynamic response, i.e. the resonance frequency and peak-to-peak displacement, in a board level vibration test set up. Bare and assembled printed circuit boards (PCBs) are investigated using different PCB form factors and package outlines (Wafer Level Chip Scale Package (WLCSP) and Ball Grid Array (BGA)), showing that LDV enables better lateral resolution and a more accurate measurement solution. Especially when the weight of the accelerometer cannot be neglected compared to the weight of the component on the PCB. An accelerometer is shown to perturb the PCB vibration motion. It is found that depending upon the test objectives and PCB electronic system involved, both techniques can be used as complementary to one another. The accelerometer weight may give rise to substantial modification of vibration response which can be used to simulate the presence of a component on a bare PCB. In addition, both methods are expected to recognize the same trends when e.g. studying the environmental impact during vibration tests. Finally, the experimental observations are also confirmed using a Finite Element Model (FEM).
关键词： board level reliability,LASER Doppler Vibrometer,Wafer Level Chip Scale Package,vibration test,modal analysis,PCB dynamic response
更新于2025-09-11 14:15:04