An Investigation of Ultrasonic Transducer Loading on a Workpiece

2018 ◽  
Author(s):  
Marco Zennaro ◽  
Alex Haig ◽  
Dan J. O’Boy ◽  
Stephen J. Walsh
Keyword(s):  
Natural Frequencies ◽  
Ultrasonic Transducer ◽  
Input Voltage ◽  
Guided Wave ◽  
Laser Vibrometer ◽  
Effective Coupling ◽  
Element Analysis ◽  
Dry Coupling ◽  
Natural Frequency Analysis ◽  
Thickness Shear

Arrays of dry-coupled thickness-shear transducers are often employed in the guided wave sector to inspect pipelines and plate-like structure. The dry coupling permits to dismiss any coupling material between the transducer and the waveguide, but as a drawback a preload must be applied on the transducers to guarantee an effective coupling between the two surfaces. Although the influence of the preload on the natural frequencies is studied in the literature, the frequency response function of a transducer relating the input voltage to the displacement output is not present in the literature. Moreover, the distribution of force on the backing mass and the effect of the preload on the uniformity of vibration of the transducers are still missing. A natural frequency analysis and a forced analysis are then computed numerically with finite element analysis to quantify the influence of the preload on a thickness-shear transducer. Furthermore, these results are compared with experimental results obtained with a Laser Vibrometer. It is then shown how the geometrical layout of the transducer coupled with the preload influences the vibration of the transducer.

Ground Excitation and Resonance in Liquid-Filled Tanks

2006 ◽  
Author(s):  
N. Yang ◽  
G. M. Warner ◽  
H. Nayeb-Hashemi ◽  
M. Olia
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Frequency Analysis ◽  
Natural Frequencies ◽  
Water Levels ◽  
Resonance Phenomenon ◽  
Earthquake Excitation ◽  
Element Analysis ◽  
Cylindrical Tanks ◽  
Natural Frequency Analysis

Recent research has demonstrated that natural frequencies associated with some circumferential modes inn fluid filled tanks may be close to the frequency of earthquake excitation. This can lead to a resonance phenomenon, and consequently failure of the tanks. In this paper, we perform natural frequency analysis of fluid-filled tanks, using finite element analysis. The problem is solved for different geometries and water levels of tanks. Results are provided for circular, cylindrical tanks and cylindrical tanks with coaxial walls and a fluid annulus. Combinations of parameters most likely to cause resonance are presented.

Natural Frequency Analysis of Liquid-Filled Tanks

2005 ◽  
Author(s):  
Rouzbeh Amini ◽  
Grant Warner ◽  
Hamid Nayeb-Hashemi
Keyword(s):  
Natural Frequency ◽  
Frequency Analysis ◽  
Natural Frequencies ◽  
Water Levels ◽  
Resonance Phenomenon ◽  
Modal Shape ◽  
Earthquake Excitation ◽  
Element Analysis ◽  
The Difference ◽  
Natural Frequency Analysis

Traditionally, the cantilever modal shape of liquid-filled tanks has been considered as the most critical mode. However, recent research has demonstrated that natural frequencies associated with some circumferential modes might be close to the frequency of earthquake excitation. This can lead to a resonance phenomenon, and consequently failure of the tanks. In this paper, we perform Natural Frequency Analysis of fluid-filled tanks, using finite element analysis. Modeling and solution employ ADINA potential-based flow elements, which require the assumption of inviscid, irrotational and incompressible flow. The problem is solved for different geometries and water levels of tanks; the results are compared with the current results in the literature and the difference is demonstrated.

Bionic design of the tower for wind turbine

2021 ◽  
pp. 095440622110046
Author(s):  
Yuqiao Zheng ◽  
Fugang Dong ◽  
Huquan Guo ◽  
Bingxi Lu ◽  
Zhengwen He
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Maximum Stress ◽  
Natural Frequencies ◽  
Bionic Design ◽  
Analytic Hierarchy ◽  
Element Analysis ◽  
Maximum Deformation ◽  
Overall Stability ◽  
Biological Selection

The study obtains a methodology for the bionic design of the tower for wind turbines. To verify the rationality of the biological selection, the Analytic Hierarchy Procedure (AHP) is applied to calculate the similarity between the bamboo and the tower. Creatively, a bionic bamboo tower (BBT) is presented, which is equipped with four reinforcement ribs and five flanges. Further, finite element analysis is employed to comparatively investigate the performance of the BBT and the original tower (OT) in the static and dynamic. Through the investigation, it is suggested that the maximum deformation and maximum stress can be reduced by 5.93 and 13.75% of the BBT. Moreover, this approach results in 3% and 1.1% increase respectively in the First two natural frequencies and overall stability.

scholarly journals An Investigation of Silica Aerogel to Reduce Acoustic Crosstalk in CMUT Arrays

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1459
Author(s):  
Varshitha Yashvanth ◽  
Sazzadur Chowdhury
Keyword(s):  
Silica Aerogel ◽  
Ultrasonic Transducer ◽  
Fluid Interface ◽  
Fractional Bandwidth ◽  
Neighboring Element ◽  
Element Analysis ◽  
Average Improvement ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Scholte Wave ◽  
Fea Simulation

This paper presents a novel technique to reduce acoustic crosstalk in capacitive micromachined ultrasonic transducer (CMUT) arrays. The technique involves fabricating a thin layer of diisocyanate enhanced silica aerogel on the top surface of a CMUT array. The silica aerogel layer introduces a highly nanoporous permeable layer to reduce the intensity of the Scholte wave at the CMUT-fluid interface. 3D finite element analysis (FEA) simulation in COMSOL shows that the developed technique can provide a 31.5% improvement in crosstalk reduction for the first neighboring element in a 7.5 MHz CMUT array. The average improvement of crosstalk level over the −6 dB fractional bandwidth was 22.1%, which is approximately 5 dB lower than that without an aerogel layer. The results are in excellent agreement with published experimental results to validate the efficacy of the new technique.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

Research on the Piezoelectric Ultrasonic Actuator Applied to SFSS

2015 ◽  
Author(s):  
Y. J. Tang ◽  
Z. Yang ◽  
X. J. Wang ◽  
J. Wang
Keyword(s):  
Natural Vibration ◽  
Structural Parameters ◽  
Laser Vibrometer ◽  
Vibration Modes ◽  
Element Analysis ◽  
Linear Type ◽  
Frequency Sweep ◽  
The Finite Element Analysis ◽  
Frequency Sweep Test ◽  
Overall Performance

This paper presents an investigation of a novel linear-type piezoelectric ultrasonic actuator for application in a Smart Fuze Safety System (SFSS). Based on the requirements of SFSS, the structural parameters of the proposed piezoelectric ultrasonic actuator are determined by fuze arming mode. Moreover, sensitivity analysis of the structural parameters to the frequency consistency is conducted using FEM software, after which the optimal dimensions are obtained with two close natural vibration frequencies. To validate the results of FEM, the frequency sweep tests of the piezoelectric ultrasonic actuator are performed to determine the motor’s actual working mode frequencies with PSV-300-B Doppler laser vibrometer system. Furthermore, the results of frequency sweep test are compared with that of the finite element analysis, and further verified by impedance analyzer. To investigate the overall performance of the piezoelectric ultrasonic actuator, vibration modes of actuator’s stator, output speed and force of the piezoelectric ultrasonic actuator are tested. The experimental results show that the output speed and force of the actuator can reach 88.2 mm/s and 2.3N respectively, which means that piezoelectric ultrasonic actuator designed in this paper can meet the demands of the SFSS.

Vibration-Based Crack Detection in L-Frames

2014 ◽  
Vol 658 ◽  
pp. 261-268
Author(s):  
Jean Louis Ntakpe ◽  
Gilbert Rainer Gillich ◽  
Florian Muntean ◽  
Zeno Iosif Praisach ◽  
Peter Lorenz
Keyword(s):  
Strain Energy ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Vibration Modes ◽  
Structural Elements ◽  
Element Analysis ◽  
Accurate Localization ◽  
Mathematical Expressions ◽  
Measurement Results ◽  
Non Destructive

This paper presents a novel non-destructive method to locate and size damages in frame structures, performed by examining and interpreting changes in measured vibration response. The method bases on a relation, prior contrived by the authors, between the strain energy distribution in the structure for the transversal vibration modes and the modal changes (in terms of natural frequencies) due to damage. Using this relation a damage location indicator DLI was derived, which permits to locate cracks in spatial structures. In this paper an L-frame is considered for proving the applicability of this method. First the mathematical expressions for the modes shapes and their derivatives were determined and simulation result compared with that obtained by finite element analysis. Afterwards patterns characterizing damage locations were derived and compared with measurement results on the real structure; the DLI permitted accurate localization of any crack placed in the two structural elements.

scholarly journals Fatigue crack detection in pipes with multiple mode nonlinear guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 180-192 ◽  
Author(s):  
Ruiqi Guan ◽  
Ye Lu ◽  
Kai Wang ◽  
Zhongqing Su
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Testing ◽  
Harmonic Wave ◽  
Guided Wave ◽  
Element Analysis ◽  
Fatigue Crack Detection ◽  
Wave Modes

This study elaborates fundamental differences in fatigue crack detection using nonlinear guided waves between plate and pipe structures and provides an effective approach for analysing nonlinearity in pipe structures. For this purpose, guided wave propagation and interaction with microcrack in a pipe structure, which introduced a contact acoustic nonlinearity, was analysed through a finite element analysis in which the material nonlinearity was also included. To validate the simulation results, experimental testing was performed using piezoelectric transducers to generate guided waves in a specimen with a fatigue crack. Both methods revealed that the second harmonic wave generated by the breathing behaviour of the microcrack in a pipe had multiple wave modes, unlike the plate scenario using nonlinear guided waves. Therefore, a proper index which considered all the generated wave modes due to the microcrack was developed to quantify the nonlinearity, facilitating the identification of microscale damage and further assessment of the severity of the damage in pipe structures.

Axial Wave Propagation in Infinitely Long Periodic Curved Panels

2003 ◽  
Vol 125 (1) ◽  
pp. 24-30 ◽  
Author(s):  
C. Pany ◽  
S. Parthan
Keyword(s):  
Wave Propagation ◽  
Natural Frequencies ◽  
Propagation Constant ◽  
Infinite Length ◽  
Approximate Methods ◽  
Bending Vibration ◽  
Element Analysis ◽  
Curved Panel ◽  
Propagation Of Waves ◽  
Curved Panels

Propagation of waves along the axis of the cylindrically curved panels of infinite length, supported at regular intervals is considered in this paper to determine their natural frequencies in bending vibration. Two approximate methods of analysis are presented. In the first, bending deflections in the form of beam functions and sinusoidal modes are used to obtain the propagation constant curves. In the second method high precision triangular finite elements is used combined with a wave approach to determine the natural frequencies. It is shown that by this approach the order of the resulting matrices in the FEM is considerably reduced leading to a significant decrease in computational effect. Curves of propagation constant versus natural frequencies have been obtained for axial wave propagation of a multi supported curved panel of infinite length. From these curves, frequencies of a finite multi supported curved panel of k segments may be obtained by simply reading off the frequencies corresponding to jπ/kj=1,2…k. Bounding frequencies and bounding modes of the multi supported curved panels have been identified. It reveals that the bounding modes are similar to periodic flat panel case. Wherever possible the numerical results have been compared with those obtained independently from finite element analysis and/or results available in the literature.

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