Visualization Of Mode Shapes Research Articles

Fusing infrastructure health monitoring data in point cloud

This paper presents a unique approach to data fusion in the condition assessment of civil infrastructure systems. The approach fuses dynamic monitoring sensor data with the visual data collected from a bridge structure. Such a data fusion method, named ModeShapeFuser, enables the visualization of mode shapes of engineering structures in their point cloud, offering a higher spatial resolution model of the dynamic behaviors of existing structures. A bridge case study shows that utilizing this immersive data visualization technique can potentially provide a more intuitive and holistic understanding of the dynamic behavior characteristics of engineering structures. The outputs of ModeShapeFuser, the high spatial resolution models of the bridge, are also presented in a Virtual Reality (VR) environment through a head-mounted display and a VRTable, providing a virtual tour of the bridge in its real environment. The study presented herein is critical for an informed decision-making process in assessing infrastructure systems.

Single-Shot Time-Averaged Shearography for Vibration Strain Mode Shape Visualization

Single-Shot Time-Averaged Shearography for Vibration Strain Mode Shape Visualization

An update on techniques to assess normal-mode behavior of rock arches by ambient vibrations

Abstract. Natural rock arches are rare and beautiful geologic landforms with important cultural value. As such, their management requires periodic assessment of structural integrity to understand environmental and anthropogenic influences on arch stability. Measurements of passive seismic vibrations represent a rapid and non-invasive technique to describe the dynamic properties of natural arches, including resonant frequencies, modal damping ratios, and mode shapes, which can be monitored over time for structural health assessment. However, commonly applied spectral analysis tools are often limited in their ability to resolve characteristics of closely spaced or complex higher-order modes. Therefore, we investigate two techniques well-established in the field of civil engineering through application to a set of natural arches previously characterized using polarization analysis and spectral peak-picking techniques. Results from enhanced frequency domain decomposition and parametric covariance-driven stochastic subspace identification modal analyses showed generally good agreement with spectral peak-picking and frequency-dependent polarization analyses. However, we show that these advanced techniques offer the capability to resolve closely spaced modes including their corresponding modal damping ratios. In addition, due to preservation of phase information, enhanced frequency domain decomposition allows for direct and convenient three-dimensional visualization of mode shapes. These techniques provide detailed characterization of dynamic parameters, which can be monitored to detect structural changes indicating damage and failure, and in addition have the potential to improve numerical models used for arch stability assessment. Results of our study encourage broad adoption and application of these advanced modal analysis techniques for dynamic analysis of a wide range of geological features.

Experimental Modal Analysis of an In-situ Clavicle.

Clavicle fractures are widespread, and the understanding of their mechanism of occurrence via dynamic loading is important for prevention and design of protection systems. The proposed work will find the natural frequencies and mode shapes of the human clavicles in-situ, by employing experimental modal analysis (EMA) techniques on cadaver clavicles. The clavicle response to impact depends on mechanical energy transmission to the bone and requires an understanding of bone modal characteristics (natural frequencies and mode shapes), as well as the frequency content of the impact force. These dynamic forces include blunt trauma (sport injury or gun stock impact) or falls (i.e. motorcycle accidents) and exhibit a wide frequency spectrum. Clavicle modes are not well understood, and while researchers performed whole body or individual clavicle EMA, no in-situ EMA has been reported. Since an in-situ clavicle features its natural boundary conditions, mode estimation via EMA was more accurate than one performed for an isolated clavicle.The clavicle EMA used instrumented excitation sources (i.e. impact hammer) and sensors (i.e. triaxial accelerometers). The accelerometer responses gathered at several locations along the cadaver clavicle bone and the exciting force was recorded and through time-frequency transformations, the natural frequencies and mode shapes were identified. Mode shape visualization was performed in ModalView software. While material properties of cadaver clavicles may be influenced by embalming, the results, which include natural frequencies, modes and damping constants, would be more relevant than those obtained for isolated clavicles. These results would be used to design protection systems, define global material properties, and calibrate existing analytical models.

An efficient two-stage method for optimal sensor placement using graph-theoretical partitioning and evolutionary algorithms

This paper presents a two-stage optimal sensor placement method for modal identification of structures. At the first stage, using a graph theoretical technique, the structure is partitioned into equal substructures. At the second stage, a preset number of triaxial sensors are proportionately allocated to the substructures. The location of sensors is determined using an evolutionary optimization algorithm, which optimizes the triaxial modal assurance criterion of the structure. The first stage leads to the even distribution of the sensors. This stage not only improves the mode shape visualization as the secondary criterion but also accelerates the optimization process by space reduction. Here, various graph-theoretical methods including k-means, k-means++, and spectral partitioning are examined as the partitioning techniques. In addition, a dynamic version for quantum-inspired evolutionary optimization algorithm (DQEA) is proposed and applied to find the placement of triaxial sensors, along with the standard version of quantum-inspired evolutionary algorithm and genetic algorithm. In order to examine the efficiency of the methods, the bridge model of the University of Central Florida, USA, is considered as the benchmark structure. The results show that the proposed method efficiently satisfies both criteria. Moreover, the introduced optimization algorithm (DQEA) outperforms other algorithms.

Mode Shape Expansion for Lively Pedestrian Bridges through Kriging

AbstractThis paper investigates the use of kriging as a powerful tool for mode shape interpolation in flexible pedestrian bridges. Kriging can be used to interpolate a set of sparse mode shape coordinates obtained through experimental modal identification techniques onto a dense structure geometry, leading to better mode shape visualization and efficient model updating. Kriging does not require a finite-element (FE) model (analytical modes) to be available a priori, as it is purely statistical in nature. Despite this key advantage, kriging has not been adopted for mode shape interpolation due in part to the relative lack of exposure within the modal analysis community and the arbitrariness of the parameter defining the spatial correlation between discrete geometry points. The first objective of this paper is to describe kriging in detail, especially focusing on pedestrian bridges. Second, modifications to the computational procedure for kriging are presented with a new metric to automatically tune the cor...

Vibration analysis of CNT-reinforced functionally graded rotating cylindrical panels using the element-free kp-Ritz method

In this paper, analysis of free vibration of carbon nanotube (CNT) reinforced functionally graded rotating cylindrical panels is presented. The analysis is performed by using the element-free kernel particle Ritz method or in short the kp-Ritz method. The rotating cylindrical panels are reinforced by single-walled carbon nanotubes (SWCNTs) with different types of distributions along thickness direction of the panels. Extended rule of mixture is selected to estimate the effective material properties of the resulting nanocomposite rotating panels. Two-dimensional displacement fields of the plates are approximated by a set of mesh-free kernel particle functions. The discretized governing eigen-equations are developed via the Ritz procedure. This kp-Ritz method enforces essential boundary conditions through the full transformation method. Detailed parametric studies have been carried out to reveal the influences of volume fraction of carbon nanotubes, edge-to-radius ratio and rotation speed on the frequency characteristics, with mode shape visualization provided. In addition, effects of different boundary conditions and types of distributions of carbon nanotubes are examined in detail.

Mode shape visualization system for high-stability quartz resonators in high and continuously changing temperature

Mode shape visualization system for high-stability quartz resonators in high and continuously changing temperature

1Pb-27 3D mode shape visualization system based on laser(Poster Session)

1Pb-27 3D mode shape visualization system based on laser(Poster Session)

회전 디스크 브레이크의 스퀼소음에 대한 선형안정성 연구

The squeal propensity of an automotive disc brake system is studied in the theoretical and computational manner. The rotating disc is in contact with two stationary pads and the nonlinear friction is engaged on the contact surface. The friction-coupled equations of motion are derived in the finite element(FE) of the actual brake disc and pad. From the general definition of friction force, the rotation and in-plane mode effects can be included properly in the brake squeal model. The eigenvalue sensitivity analysis and the mode shape visualization at squeal frequencies are also conducted for the detailed investigation. It is found that the squeal propensity is strongly influenced by rotation effect and the in-plane mode can be involved in squeal generation.

Time-average TV holography for vibration fringe analysis

Time-average TV holography is widely used method for vibration measurement. The method generates speckle correlation time-averaged J0 fringes that can be used for full-field qualitative visualization of mode shapes at resonant frequencies of an object under harmonic excitation. In order to map the amplitudes of vibration, quantitative evaluation of the time-averaged fringe pattern is desired. A quantitative evaluation procedure based on the phase-shifting technique used in two beam interferometry has also been adopted for this application with some modification. The existing procedure requires a large number of frames to be recorded for implementation. We propose a procedure that will reduce the number of frames required for the analysis. The TV holographic system used and the experimental results obtained with it on an edge-clamped, sinusoidally excited square aluminium plate sample are discussed.

Laboratory, computational and field studies of snowboard dynamics

While many studies have documented the dynamic behaviour of skis, similar studies for snowboards have been rare. Characteristics such as board stiffness and damping are acknowledged to be linked to performance, but a quantitative determination of corresponding natural frequencies and damping ratios has to date not been published. The present work uses laboratory, computational and field studies to develop and document an in-depth understanding and quantification of snowboard dynamics. In particular, laboratory tests are used to determine the first three bending and first two torsional natural frequencies and modal damping ratios for eight snowboards from two manufacturers. Computer models are developed using the software packages Pro/ENGINEER and Pro/MECHANICA that accurately reproduce the experimentally measured natural frequencies and that facilitate visualization of mode shapes. Field tests are discussed that provide insights into the strains and accelerations experienced by snowboards while subject to turns, stops and jumps. Quantitative results are shown to correlate well with qualitative descriptions offered by manufacturers and riders. Medium-quality boards designed for beginner riders and characterized as ‘soft’ have lower natural frequencies and larger damping ratios than similar boards designed for advanced riders and characterized as ‘stiff.’ Moreover, boards designed for advanced riders and characterized as ‘high-quality’ have natural frequencies higher than ‘medium-quality’ boards while still exhibiting high damping ratios.

Visualization of Mode Patterns of Piezoelectric Resonators Using Correlation Filter

The application of a two-dimensional correlation filter to the mode shape visualization of piezoelectric devices is described. The filter extracts the vibrational patterns from two laser-speckle images of the driven and resting phases. The experimental results demonstrate clearly the feasibility of the proposed technique.

Visualization of mode shapes in unelectroded quartz crystal resonators using a microphone

Visualization of mode shapes in unelectroded quartz crystal resonators using a microphone