- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Design and development of in-situ temperature dependent diffuse reflectance spectroscopy setup
摘要： Recent advancements in the commercialization of In-situ temperature dependent optical spectrophotometer have shown potential not only for the recording of optical absorption spectra but also towards the exploration of physical insights and the understanding of instrument handling. Measurement on the effect of the variation of temperature onto optical properties mainly for semi-conducting oxides helps to explore the functioning and play a crucial role towards the development of optoelectronic devices. Being a non-contact, non-destructive technique temperature dependent DRS Setup can be used as a primary tool for the in-situ characterization of optical properties. This appreciation prompts us to design and develop an instrument that can add the ability of in-situ temperature dependent DRS above room temperature. The setup, developed and reported here, is able to accurately characterize the samples from room temperature to 500 K, which is most suitable range for the characterization of semiconducting materials, which is in the heard of current materials’ research. The present study provides the economical alternatives to the existing designs used for this purpose without compromising on the reliability of the obtained data. The in-house developed set up is found to be efficiently used for the analysis of various properties of the samples and will open up the instrumental development and commercialization of the temperature dependent DRS technique.
关键词： Detection of defects,Photon detectors for UV, visible and IR photons (solid-state),Overall mechanics design (support structures and materials, vibration analysis etc),Spectrometers
更新于2025-09-09 09:28:46
-
Total-internal-reflection elastic metasurfaces: Design and application to structural vibration isolation
摘要： This letter presents the concept of the Total Internal Reflection metasurface (TIR-MS) which supports the realization of structure-embedded subwavelength acoustic shields for elastic waves propagating in thin waveguides. The proposed metasurface design exploits extreme phase gradients, implemented via locally resonant elements, in order to achieve operating conditions that are largely beyond the critical angle. Such artificial discontinuity is capable of producing complete reflection of the incoming waves regardless of the specific angle of incidence. From a practical perspective, the TIR-MS behaves as a sound hard barrier that is impenetrable to long-wavelength modes at a selected frequency. The TIR metasurface concept is first conceived for a flat interface embedded in a rectangular waveguide and designed to block longitudinal S0-type guided modes. Then, it is extended to circular plates in order to show how enclosed areas can be effectively shielded by incoming waves. Given the same underlying physics, an equivalent dynamic behavior was also numerically and experimentally illustrated for flexural A0-type guided modes. This study shows numerical and experimental evidence that, when the metasurface is excited at the target frequency, significant vibration isolation can be achieved in the presence of waves having any arbitrary angle of incidence. These results open interesting paths to achieve vibration isolation and energy filtering in certain prototypical structures of interest for practical engineering applications.
关键词： elastic waves,TIR-MS,vibration isolation,Total Internal Reflection metasurface,subwavelength acoustic shields
更新于2025-09-09 09:28:46
-
[IEEE 2018 Condition Monitoring and Diagnosis (CMD) - Perth, WA (2018.9.23-2018.9.26)] 2018 Condition Monitoring and Diagnosis (CMD) - Usability of fiber Bragg grating sensors for the fatigue life monitoring of overhead transmission lines
摘要： Fretting fatigue of transmission lines, caused by Aeolian vibration, always leads to catastrophic failure of conductors. The fatigue life monitoring of overhead transmission lines is an effective method to foresee strands broken of the conductor. Fatigue severity is usually expressed by alternating bending stress which occurs in the vicinity of suspension clamps during vibration. Given that it is hard to measure the fatigue stress directly, according to IEEE, alternating bending amplitude is recommended as a substitute measured parameter for fatigue life. In this paper, an on-line monitoring system based on a fiber- optic acceleration sensor is designed to analyze the fatigue life of overhead transmission lines in Aeolian vibration surveillance. Considering its superior performance of anti-electromagnetic interference, Fiber Bragg Grating (FBG) sensor is used to measure alternating bending amplitude of overhead transmission lines. And a Cumulative Fatigue Damage (CFD) method, which is based on alternating bending amplitude for vibration and the Stress-Cycle (S-N) curves, is proposed to calculate the fatigue life of overhead transmission lines. A case study of the one-month measurement data of Aeolian vibration for 1000kV Ultra-High Voltage (UHV) transmission lines is presented. Then an on-line monitoring system based on a fiber-optic acceleration sensor is designed to analyze the fatigue life of overhead transmission lines in Aeolian vibration surveillance.
关键词： Fretting fatigue,Aeolian vibration,life prediction,fiber Bragg grating
更新于2025-09-09 09:28:46
-
Vibration and modal analysis of a rotating disc using high-speed 3D digital image correlation
摘要： Rotating structures are of interest in many engineering fields, where knowing their dynamic behaviour is important to prevent undesired operating states. However, the experimental measurement of vibrations in rotating structures is still a relatively demanding task that requires the use of special measurement technique or method. The paper deals with the application of high-speed digital image correlation in vibration analysis of rotating structures. The method introduced in this research is based on the elimination of rigid body motion components contained in the primary responses measured by cameras. The process of separation and subsequent elimination of these components is given by numerical post-processing of three-dimensional displacement fields. The basis is to determine rotation matrix and translation vector that optimally describe rigid transformation between two positions of an analysed object. The proposed method is applicable for measuring under both constant and variable speed of rotation. Practical application is presented by three experiments in which vibrations of a flat rotating disc were analysed. The first experiment is focused on determine the operating deflection shapes of the disc rotating at 4700 rpm. The second one is a run-up analysis under variable rotational speed that ranges from 0 to 4700 rpm. The aim of the third measurement is to obtain natural frequencies and modal shapes of the disc rotating at 4800 rpm. The results of the experiments show that the elimination of rigid body motions leads to a higher accuracy of measurement and provides more pronounced frequency response spectra.
关键词： Vibration analysis,Rotating disc,Rigid body motion elimination,Digital image correlation,Modal analysis
更新于2025-09-09 09:28:46
-
A Feasibility Study of Controllable Gas Foil Bearings With Piezoelectric Materials Via Rotordynamic Model Predictions
摘要： This study presents a new concept of controllable gas foil bearings (C-GFBs) with piezoelectric actuators. The C-GFB consists of a laminated top foil, bump foil, and piezo stacks and can simply change the bearing shape or film thickness locally and globally by varying the thickness of the piezo stacks with input voltages. The control schemes are (1) clearance control: the bearing clearance adjusted by changing overall piezo stack thickness, and (2) preload control: the mechanical preload modulated by the thickness expansion of several piezo stacks. Bearing lubrication performance is predicted for four cases of C-GFBs with different bearing clearances and preloads. The piezo stack control generates meaningful differences in the fluid-film thickness and pressure. Clearance control has a great effect on the dynamic force coefficients, but preload control slightly increases. Furthermore, the rotordynamic prediction of a rotor supported on two journal C-GFBs is conducted. As a result, both control modes for C-GFB are found to have a positive effect on rotordynamic amplitudes. Finally, using the orbit simulations, the C-GFB is controlled to have a small bearing clearance and large preload at critical speeds to make it possible to stably pass through the critical speeds. Consequently, it turns out that the C-GFB can improve bearing lubrication and rotordynamic performances by controlling only the input voltage of the piezo stacks. In addition, the C-GFB can be used to form various shapes to meet the operation conditions of an applied system.
关键词： active gas bearing,rotordynamic instability,piezoelectric actuator,vibration control,gas foil bearing
更新于2025-09-09 09:28:46
-
[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Assessment of Damage Progression in Automotive Electronics Assemblies Subjected to Temperature and Vibration
摘要： Electronics in automotive underhood environments is used for a number of safety critical functions. Reliable continued operation of electronic safety systems without catastrophic failure is important for safe operation of the vehicle. There is need for prognostication methods, which can be integrated, with on-board sensors for assessment of accrued damage and impending failure. In this paper, leadfree electronic assemblies consisting of daisy-chained parts have been subjected to high temperature vibration at 5g and 155°C. Spectrogram has been used to identify the emergence of new low frequency components with damage progression in electronic assemblies. Principal component analysis has been used to reduce the dimensionality of large data-sets and identify patterns without the loss of features that signify damage progression and impending failure. Variance of the principal components of the instantaneous frequency has been shown to exhibit an initial damage progression, increasing trend during the attaining a maximum value and decreasing prior to failure. The unique behavior of the instantaneous frequency over the period of vibration can be used as a health-monitoring feature for identifying the impending failures in automotive electronics. Further, damage progression has been studied using Empirical Mode Decomposition (EMD) technique in order to decompose the signals into Independent Mode Functions (IMF). The IMF’s were investigated based on their kurtosis values and a reconstructed strain signal was formulated with all IMF’s greater than a kurtosis value of three. PCA analysis on the reconstructed strain signal gave better patterns that can be used for prognostication of the life of the components.
关键词： high temperature vibration,prognostication,Empirical Mode Decomposition,spectrogram,kurtosis,automotive electronics,principal component analysis
更新于2025-09-09 09:28:46
-
[ASME ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems - Colorado Springs, Colorado, USA (Monday 21 September 2015)] Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting - Traveling Wave Phenomenon Through Piezoelectric Actuation of a Free-Free Cylindrical Tube
摘要： Previous work has demonstrated that piezoceramics are capable of generating net wave propagation without reflections in one‐dimensional structures. The investigation into cylindrical traveling waves provides insight into unique dynamics (i.e., symmetric and non-symmetric modes) that have yet to be fully defined for two and three dimensional systems. The work herein will focus on the generation and characterization of traveling waves that propagate along the circumferential direction. The coupled system, given by a free‐free cylinder with multiple piezoelectric actuator (PZT) patches, is used to evaluate several traveling wave modes in the cylinder. The use of structurally integrated piezoelectric patches as actuators has many advantages over the conventional shakers. Apart from the small, low weight, low cost and the size of these ceramic plates, PZTs can also generate waves over a wide frequency range. The use of multiple PZTs can be leveraged to excite the systems at a given frequency with a defined phase difference between them in order to generate highly controlled directional traveling waves in the cylindrical structure without reflections. Finite Element Modeling (FEM), in conjunction with experiments, were conducted to provide a comprehensive understanding of the generation and propagation behavior of the traveling wave modes in a thin walled cylinder.
关键词： 2D,piezoelectric,dynamics,FEA,Traveling waves,vibration
更新于2025-09-09 09:28:46
-
Fiber-optic Fabry-Perot sensor for simultaneous measurement of tilt angle and vibration acceleration
摘要： A fiber-optic Fabry-Perot (F-P) sensor, based on a pendulum structure, for simultaneous measurement of tilt angle and vibration acceleration was proposed, which also has a high tilt angle resolution. The real-time cavity lengths are absolutely measured using a fast demodulation algorithm. The tilt angle is estimated from the mean value of the real-time cavity lengths while the vibration acceleration derives from the alternating quantity of them. A series of experiments are conducted using a micro-tilt platform and a vibration table to simulate tilt angle change and the vibration perturbation, respectively. The experimental results show a tilt angle resolution of 0.023″ in the measurement range from -2.8° to 2.6°. Meanwhile, the vibration acceleration results are obtained by using a spectral analysis to the alternating quantity and basing on a non-linear fitting curve of the frequency response of the acceleration sensibility, within the frequency range of 0~180 Hz.
关键词： vibration acceleration,simultaneous measurement,tilt angle,pendulum,Fabry-Perot interferometer
更新于2025-09-09 09:28:46
-
[ASME ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems - San Antonio, Texas, USA (Monday 10 September 2018)] Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation - Forced Vibration Analysis of FG-Graphene Platelet Reinforced Polymer Composite Shells Bonded With Piezoelectric Layers Considering Electroelastic Nonlinearities
摘要： In the present article, we focus on the forced vibration and control analysis of functionally graded (FG) graphene-polymer composites bonded with piezoelectric layers considering strong electric fields. Different non-uniform gradient distributions of graphene platelets (GPLs) are assumed through the thickness direction. The Modified Halpin-Tsai micromechanics model is used to obtain the effective material properties of GPL/polymer composites. Electromechanical coupling of piezoelectric layers is described by two rotationally invariant non-linear constitutive relations. A four-node shell element considering transverse shear effect based on the Reissner-Mindlins hypothesis has been developed for forced vibration and control analysis of smart FG-GPL/composites using the principle of virtual work considering nonlinear material law for the piezoelectric layers. The developed element is verified and compared with the numerical results those available in the literature. Different configurations of FG-GPL composite shells have been analysed and discussed to compare in terms of settling time, first resonance frequency and absolute amplitude corresponding to first resonant frequency by carrying out time and frequency response analysis, and the effects of weight fraction of GPLs on vibration response of such shell structures are also discussed. The influence of electromechanical nonlinear constitutive relations is also presented and discussed by performing active control analysis on different FG-GPL composite shell structures. Moreover, the results show that the GPL distribution and weight-fraction of GPLs have a significant effect on the vibration and damping characteristics of the FG-GPL composite shell structures.
关键词： graphene platelets,nonlinear electromechanical coupling,piezoelectric layers,functionally graded materials,forced vibration
更新于2025-09-09 09:28:46
-
Competing optical instruments for the estimation of Full Field FRFs
摘要： Thanks to the progress of optical measurement systems, known to use non-contact transducers (with their own peculiarities, application domains and drawbacks), nowadays addressing complex testing problems, especially direct dynamic measurements and modal analyses on lightweight structural components, is becoming even more common than in the recent past. Furthermore, obtaining vibration patterns with optical gears, in broad frequency bands with high spatial resolution, is easier than before, for the advantage of many advanced applications in vibration engineering, testing and product development.
关键词： Full Field Operative Deflection Shapes,Full Field Frequency Response Functions,Dynamic ESPI,Full field vibration measurements,Surface structural dynamics,Optical metrology,Hi-Speed DIC,SLDV
更新于2025-09-09 09:28:46