scholarly journals Investigation on Non-Linear Vibration Response of Cantilevered Thin Plates with Crack Using Electronic Speckle Pattern Interferometry

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 539
Author(s):  
Nan Tao ◽  
Yinhang Ma ◽  
Hanyang Jiang ◽  
Meiling Dai ◽  
Fujun Yang
Keyword(s):  
Mode Shape ◽  
Speckle Pattern ◽  
Experimental Studies ◽  
Forced Response ◽  
Thin Plates ◽  
Mode Shapes ◽  
Electronic Speckle Pattern Interferometry ◽  
Intact Specimen ◽  
Harmonic Resonance ◽  
Super Harmonic Resonance

The time-averaged electronic speckle pattern interferometry (ESPI) is employed to measure the frequencies and mode shapes of thin, cantilevered plates with root-slit. The first 12 order linear resonance frequency and mode shape of an intact cantilevered plate is determined by using FEM calculation. The dynamic response of the intact specimen forced by a PZT actuator is measured and its super-harmonic resonance of forced response is investigated experimentally. The results show that the principal mode shape of super-harmonic vibration is similar to its natural modal. In contrast to linear forcing vibration, the threshold of force for super-harmonic resonance is much higher than that of the former. In addition, linear free response of four cantilevered root-slit plates with variation length of slit are analyzed by applying the FEM calculation, and their responses of forcing vibration were measured by using the ESPI method. The validity and accuracy of the numerical prediction are confirmed through experimental studies. The present work shows that the ESPI technique can provide whole-field and real-time measurement for vibration analysis and can also be employed for validation of the FEM calculation.

Effect of plasticity at out-of-plane electronic speckle pattern interferometry diagnostics of axisymmetric stresses by the hole-drilling method

2017 ◽  
Vol 53 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Alexander L Popov ◽  
Sergei E Alexandrov ◽  
Victor M Kozintsev ◽  
Alexander L Levitin ◽  
Dmitri A Chelyubeev
Keyword(s):  
Plastic Material ◽  
Speckle Pattern ◽  
Finite Thickness ◽  
Experimental Studies ◽  
Median Plane ◽  
Element Model ◽  
Electronic Speckle Pattern Interferometry ◽  
Hole Drilling ◽  
Disk Model ◽  
Blind Hole

Theoretical, calculated, and experimental results of studies on the registration of the accounting effect of plasticity in the diagnosis of axisymmetric stresses by the hole method and speckle-interferometric detection of the field of normal displacements in its vicinity are presented. Theoretical and computational studies were carried out on a disk model of finite thickness from an ideally elastic–plastic material. The theoretical model considers the formation of elastoplastic deformations in the vicinity of the through hole; the calculated finite element model considers in the vicinity of both through and blind holes of different depths. It was noted that at the blind hole, the most informative are the movements of the axisymmetric bend caused by the violation by the blind hole of symmetry of the disk with respect to its median plane. At the same time, an approximate analytical method has been developed to calculate the stresses that cause only elastic deformations. Experimental studies were carried out on a series of samples in the form of steel disks with axisymmetric stresses near the yield point. These stresses were induced by the hot fit of grinded rings from hardened high-strength steel onto disks made of steel with a low yield strength. Examples are given which show that the stress values determined from normal displacements in the vicinity of the probe holes from the calculated–theoretical and experimental are similar.

scholarly journals Experimental and Numerical Investigation of Resonance Characteristics of Novel Pumping Element Driven by Two Piezoelectric Bimorphs

2019 ◽  
Vol 9 (6) ◽  
pp. 1234 ◽  
Author(s):  
Yu-Chih Lin ◽  
Yu-Hsi Huang ◽  
Kwen-Wei Chu
Keyword(s):  
Speckle Pattern ◽  
Laser Doppler Vibrometer ◽  
Impedance Analysis ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Electronic Speckle Pattern Interferometry ◽  
Element Analysis ◽  
Visible Displacement ◽  
Piezoelectric Bimorphs ◽  
Phase Motion

This paper describes the vibration characteristics of a dual-bimorph piezoelectric pumping element under fluid–structure coupling. Unlike the single bimorph used in most previous studies, the proposed device comprises two piezoelectric bimorphs within an acrylic housing. Amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) was used to examine the visible displacement fringes in order to elucidate the anti-phase as well as in-phase motions associated with vibration. Analysis was also conducted using impedance analysis and laser Doppler vibrometer (LDV) based on the measurement of point-wise displacement. The experimental results of resonant frequencies and the corresponding mode shapes are in good agreement with those obtained using finite element analysis. The gain of flow rate obtained by the anti-phase motion of the dual-bimorph pumping element is larger than both those obtained by in-phase motion and the single bimorph pumping element. This work greatly enhances our understanding of the vibration characteristics of piezoelectric pumping elements with two bimorphs, and provides a valuable reference for the further development of bionic pump designs.

Dynamic Characteristics and Finite Element Model Updating of Micromachined Torsion Structures

2013 ◽  
Vol 284-287 ◽  
pp. 1831-1835
Author(s):  
Wei Hsin Gau ◽  
Kun Nan Chen ◽  
Yunn Lin Hwang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Speckle Pattern ◽  
Element Model ◽  
Mode Shapes ◽  
Electronic Speckle Pattern Interferometry ◽  
Finite Element Model Updating ◽  
Element Analysis

In this paper, two experimental techniques, Electronic Speckle Pattern Interferometry and Stroboscopic Interferometry, and two different finite element analysis packages are used to measure or to analyze the frequencies and mode shapes of a micromachined, cross-shaped torsion structure. Four sets of modal data are compared and shown having a significant discrepancy in their frequency values, although their mode shapes are quite consistent. Inconsistency in the frequency results due to erroneous inputs of geometrical and material parameters to the finite element analysis can be salvaged by applying the finite element model updating procedure. Two updating cases show that the optimization sequences converge quickly and significant improvements in frequency prediction are achieved. With the inclusion of the thickness parameter, the second case yields a maximum of under 0.4% in frequency difference, and all parameters attain more reliable updated values.

scholarly journals Robust Baseline-Free Damage Localization by Using Locally Perturbed Dynamic Equilibrium and Data Fusion Technique

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5964
Author(s):  
Shancheng Cao ◽  
Huajiang Ouyang ◽  
Chao Xu
Keyword(s):  
Data Fusion ◽  
Mode Shape ◽  
Structural Damage ◽  
Dynamic Equilibrium ◽  
Experimental Studies ◽  
Measurement Noise ◽  
Mode Shapes ◽  
Damage Localization ◽  
Shape Estimation ◽  
Fusion Approach

Mode shape-based structural damage identification methods have been widely investigated due to their good performances in damage localization. Nevertheless, the evaluation of mode shapes is severely affected by the measurement noise. Moreover, the conventional mode shape-based damage localization methods are normally proposed based on a certain mode and not effective for multi-damage localization. To tackle these problems, a novel damage localization approach is proposed based on locally perturbed dynamic equilibrium and data fusion approach. The main contributions cover three aspects. Firstly, a joint singular value decomposition technique is proposed to simultaneously decompose several power spectral density transmissibility matrices for robust mode shape estimation, which statistically deals better with the measurement noise than the traditional transmissibility-based methods. Secondly, with the identified mode shapes, an improved pseudo-excitation method is proposed to construct a baseline-free damage localization index by quantifying the locally damage perturbed dynamic equilibrium without the knowledge of material/structural properties. Thirdly, to circumvent the conflicting damage information in different modes and integrate it for robust damage localization, a data fusion scheme is developed, which performs better than the Bayesian fusion approach. Both numerical and experimental studies of cantilever beams with two cracks were conducted to validate the feasibility and effectiveness of the proposed damage localization method. It was found that the proposed method outperforms the traditional transmissibility-based methods in terms of localization accuracy and robustness.

Deflection Measurements of Laminated Thin Plates Using Electronic Speckle Pattern Interferometry

2002 ◽  
Vol 24 (4) ◽  
pp. 215 ◽  
Author(s):  
EA Armanios ◽  
RB Bucinell ◽  
DW Wilson ◽  
D Golda ◽  
D Kedlaya ◽  
...  
Keyword(s):  
Speckle Pattern ◽  
Thin Plates ◽  
Electronic Speckle Pattern Interferometry

Interpretation of Experimental and Theoretical Data for Prediction of Mode Shapes of Vibrating Turbocharger Blades

1988 ◽  
Vol 110 (1) ◽  
pp. 53-58 ◽  
Author(s):  
G. M. Chapman ◽  
X. Wang
Keyword(s):  
Natural Frequencies ◽  
Speckle Pattern ◽  
Theoretical Data ◽  
Mode Shapes ◽  
Electronic Speckle Pattern Interferometry ◽  
Experimental Investigations ◽  
Exhaust Gas ◽  
Element Analysis ◽  
Design Engineers ◽  
Vibration Excitation

The blading in large turbochargers is subjected to vibration excitation originating from pulsations in the exhaust gas stream coupled with the blade pass frequencies. The amplitude of vibrations induced are a source of concern to design engineers as they can seriously affect the operation of the turbocharger. This paper discusses theoretical and experimental investigations aimed at identifying the natural frequencies and the associated mode shapes for a single turbocharger blade. Modal Analysis, Electronic Speckle Pattern Interferometry (ESPI), and Finite Element Analysis are all used in an attempt to categorize the modal patterns.

Characterization of the Modal Characteristics of Structures Operating in Dense Liquid Turbopumps

2017 ◽  
Author(s):  
Joseph Chiu ◽  
Andrew M. Brown
Keyword(s):  
Natural Frequency ◽  
Mode Shape ◽  
Numerical Solutions ◽  
Forced Response ◽  
Modal Testing ◽  
Liquid Oxygen ◽  
Mode Shapes ◽  
Annular Disk ◽  
Modal Characteristics ◽  
Modal Test

It is well-known that the natural frequencies of structures immersed in heavy liquids will decrease due to the fluid “added-mass” effect. This reduction has not been precisely determined, though, with indications that it is in the 20–40% range for water. In contrast, the mode shapes of these structures have always been assumed to be invariant in liquids. Recent modal testing at NASA/Marshall Space Flight Center of turbomachinery inducer blades in liquid oxygen, which has a density slightly greater than water, indicates that the mode shapes change appreciably, though. This paper presents a study that examines and quantifies the change in mode shapes as well as more accurately defines the natural frequency reduction. A literature survey was initially conducted and test-verified analytical solutions for the natural frequency reductions were found for simple geometries, including a rectangular plate and an annular disk. The ANSYS© fluid/structure coupling methodology was then applied to obtain numerical solutions, which compared favorably with the published results. This initial study indicated that mode shape changes only occur for non-symmetric boundary conditions. Techniques learned from this analysis were then applied to the more complex inducer model. ANSYS numerical results for both natural frequency and mode shape compared well with modal test in air and water. A number of parametric studies were also performed to examine the effect of fluid density on the structural modes, reflecting the differing propellants used in rocket engine turbomachinery. Some important findings were that the numerical order of mode shapes changes with density initially, and then with higher densities the mode shapes themselves warp as well. Valuable results from this study include observations on the causes and types of mode shape alteration and an improved prediction for natural frequency reduction in the range of 30–41% for preliminary design. Increased understanding and accurate prediction of these modal characteristics is critical for assessing resonant response, correlating finite element models to modal test, and performing forced response in turbomachinery.

Analytical and Experimental Studies of Orthotropic Corner-Supported Plates With Segmented In-Plane Actuators

2005 ◽  
Author(s):  
Hartono Sumali ◽  
Jordan E. Massad ◽  
Philip L. Reu ◽  
Pavel M. Chaplya ◽  
Jeffrey W. Martin
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Speckle Pattern ◽  
Experimental Studies ◽  
Electronic Speckle Pattern Interferometry ◽  
Two Dimensional ◽  
Dimensional Array ◽  
Laboratory Setup

This paper outlines a model for a corner-supported, thin, rectangular bimorph actuated by a two-dimensional array of segmented, orthotropic PVDF laminates; it investigates the realization and measurement of such a bimorph. First, a model is derived to determine the deflected shape of an orthotropic laminate for a given distribution of voltages over the actuator array. Then, boundary conditions are realized in a laboratory setup to approach the theoretical corner-supported boundary condition. Finally, deflection measurements of actuated orthotropic PVDF laminates are performed with Electronic Speckle Pattern Interferometry and are compared to the model results.

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