Comparative Study of Instantaneous Frequency Extraction in Nonlinear Acoustics Used for Structural Damage Detection

2013 ◽  
Vol 588 ◽  
pp. 33-42
Author(s):  
Dorota Włodarska ◽  
Andrzej Klepka ◽  
Wieslaw Jerzy Staszewski ◽  
Tadeusz Uhl
Keyword(s):  
Ultrasonic Wave ◽  
Instantaneous Frequency ◽  
Structural Damage ◽  
Nonlinear Effects ◽  
Nonlinear Acoustics ◽  
Time Domain Analysis ◽  
Nonlinear Phenomena ◽  
Frequency Calculation ◽  
The Time Domain ◽  
Cracked Solids

Nonlinear acoustics deals with various nonlinear effects that occur in ultrasonic wave propagation. The method is suitable for material characterisation, as it uses different nonlinear phenomena associated with material imperfections. The method has been used for detecting nonlinearities in cracked solids by: measuring distortions of acoustic signals, estimating resonance frequency shifts or assessing nonlinear vibro-acosutic modulations. The latter is the most widely used non-classical approach to probe material nonlinearities. The method involves vibro-acoustic interactions of ultrasonic wave and modal vibration in damaged specimens. Modulation intensity that strongly relates to damage severity - is usually assessed in the frequency domain and often leads to confusing results when large modulations are involved. The paper investigates the time domain analysis of vibro-acoustic modulated signals. Several methods for instantaneous frequency calculation used to assess the intensity of modulation - are compared. Simulated and experimental data are used in these investigations.

Nonlinear Acoustics in Non-Destructive Testing - From Theory to Experimental Application

2013 ◽  
Vol 588 ◽  
pp. 192-201 ◽  
Author(s):  
Dariusz Broda ◽  
Andrzej Klepka ◽  
Wieslaw Jerzy Staszewski ◽  
Fabrizio Scarpa
Keyword(s):  
Elastic Wave ◽  
Wave Interaction ◽  
Nonlinear Effects ◽  
Nonlinear Acoustics ◽  
Nonlinear Phenomena ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Contact Acoustic Nonlinearity ◽  
Non Destructive ◽  
Damaged Materials

A growing interest in non-destructive testing methods based on nonlinear acoustics have been observed for the last ten fifteen years. The majority of methods in this area take their origin from the observation that fatigue damaged materials often behave like mesoscopic nonlinear materials (e.g. rocks) in which nonlinear phenomena have been observed for years. The most important phenomena include: higher harmonics generation, vibro-acoustic wave modulations, amplitude dependent resonance frequency shift and slow dynamic effects. All these phenomena result mainly from elastic wave interactions with contact-type defects. There is enough experimental evidence in the literature showing that these nonlinear effects are much more distinct in damaged materials than in intact ones. Despite the fact that many experimental techniques - based on nonlinear acoustic phenomena - have been developed for the last ten years, the physical mechanism of elastic wave interaction with damage materials still not clear. The main reason is the variety of possible nonlinear mechanisms involved. This includes: nonlinear elasticity and dissipation, contact acoustic nonlinearity based on herztian and rough surfaces contact theories and other effects such us adhesion, friction and thermoelasticity. This paper provides a short summary of various theoretical developments and examples of applications to damage detection in different materials.

Experimental Study on the Performance of Constrained Damped Rail Vibration Reduction

2011 ◽  
Vol 42 (10) ◽  
pp. 9-14
Author(s):  
L.Y. Liu ◽  
J.Y. Li ◽  
X.J. Yin
Keyword(s):  
Experimental Study ◽  
Time Domain ◽  
Vibration Amplitude ◽  
Impact Load ◽  
Vibration Reduction ◽  
Time Domain Analysis ◽  
Experimental Basis ◽  
Vibration Acceleration ◽  
The Time Domain ◽  
Vibration Performance

To study the vibration reduction performance of damped rail, we take the standard rail and labyrinth constrained damped rail as the study target. By testing the vibration performance of both standard rail and labyrinth constrained damped rail in an anechoic room, we use the time-domain analysis to study the vibration changes with time passing. The results showed that: the labyrinth constrained damped rail vibration can effectively reduce the vibration amplitude and duration. Under the radial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 5% −19%, time of vibration and attenuation greater than 94%; under the axial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 9% −21%, time of vibration and attenuation greater than 92%. The results have provided an experimental basis for the design of new constrained damped rail.

Dynamic Instability in Quartering Seas—Part III: Nonlinear Effects on Periodic Motions

1997 ◽  
Vol 41 (03) ◽  
pp. 210-223 ◽  
Author(s):  
K. J. Spyrou
Keyword(s):  
Periodic Motion ◽  
Horizontal Plane ◽  
Dynamic Instability ◽  
Parametric Instability ◽  
Nonlinear Effects ◽  
Ship Motions ◽  
Nonlinear Phenomena ◽  
Specific Sequence ◽  
The Stability ◽  
Two Stages

The loss of stability of the horizontal-plane periodic motion of a steered ship in waves is investigated. In earlier reports we referred to the possibility of a broaching mechanism that will be intrinsic to the periodic mode, whereby there will exist no need for the ship to go through the surf-riding stage. However, about this point the discussion was essentially conjectural. In order to provide substance we present here a theoretical approach that is organized in two stages: Initially, we demonstrate the existence of a mechanism of parametric instability of yaw on the basis of a rudimentary, single-degree model of maneuvering motion in waves. Then, with a more elaborate model, we identify the underlying nonlinear phenomena that govern the large-amplitude horizontal ship motions, considering the ship as a multi-degree, nonlinear oscillator. Our analysis brings to light a very specific sequence of phenomena leading to cumulative broaching that involves a change in the stability of the ordinary periodic motion on the horizontal plane, a transition towards subharmonic response and, ultimately, a sudden jump to resonance. Possible means for controlling the onset of such undesirable behavior are also investigated.

Some Nonlinear Effects of Magnetic Bearings

1999 ◽  
Author(s):  
Norbert Steinschaden ◽  
Helmut Springer
Keyword(s):  
Equations Of Motion ◽  
Period Doubling ◽  
Path Following ◽  
Nonlinear Effects ◽  
Magnetic Bearing ◽  
Operating Conditions ◽  
Active Magnetic Bearing ◽  
Nonlinear Phenomena ◽  
Amb System ◽  
Large Rotor

Abstract In order to get a better understanding of the dynamics of active magnetic bearing (AMB) systems under extreme operating conditions a simple, nonlinear model for a radial AMB system is investigated. Instead of the common way of linearizing the magnetic forces at the center position of the rotor with respect to rotor displacement and coil current, the fully nonlinear force to displacement and the force to current characteristics are used. The AMB system is excited by unbalance forces of the rotor. Especially for the case of large rotor eccentricities, causing large rotor displacements, the behaviour of the system is discussed. A path-following analysis of the equations of motion shows that for some combinations of parameters well-known nonlinear phenomena may occur, as, for example, symmetry breaking, period doubling and even regions of global instability can be observed.

scholarly journals A Novel Piezoceramic-Based Sensing Technology Combined With Visual Domain Networks for Timber Damage Quantification

2021 ◽  
Vol 8 ◽  
Author(s):  
Haibei Xiong ◽  
Lin Chen ◽  
Cheng Yuan ◽  
Qingzhao Kong
Keyword(s):  
Time Domain ◽  
Damage Assessment ◽  
Structural Damage ◽  
High Efficiency ◽  
Experimental Studies ◽  
Stress Wave Propagation ◽  
Timber Structures ◽  
Sensing Technology ◽  
The Time Domain ◽  
Visual Domain

Early detection of timber damage is essential for the safety of timber structures. In recent decades, wave-based approaches have shown great potential for structural damage assessment. Current damage assessment accuracy based on sensing signals in the time domain is highly affected by the varied boundary conditions and environmental factors in practical applications. In this research, a novel piezoceramic-based sensing technology combined with a visual domain network was developed to quantitatively evaluate timber damage conditions. Numerical and experimental studies reveal the stress wave propagation properties in different cases of timber crack depths. Through the spectrogram visualization process, all sensing signals in the time domain were transferred to images which contain both time and frequency features of signals collected from different crack conditions. A deep neural network (DNN) was adopted for image training, testing, and classification. The classification results show high efficiency and accuracy for identifying crack conditions for timber structures. The proposed technology can be further integrated with a fielding sensing system to provide real-time monitoring of timber damage in field applications.

Numerical Simulation on Mooring Performance of LNG-FPSO System in Realistic Seas

2005 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Time Domain ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Time Domain Analysis ◽  
Analysis Tool ◽  
Motion Response ◽  
Non Linear ◽  
Floating System ◽  
Exciting Forces ◽  
The Time Domain

The LNG-FPSO concept is receiving much attention in recent years, due to its active usage to exploit oil and gas resources. The FPSO offloads LNG to an LNG carrier that is located close to the FPSO, and during this transfer process two large vessels are in close proximity to each other for daylong periods of time. Due to the presence of neighboring vessel, the motion response of both the vessels will be affected significantly. Hydrodynamic interactions related to wave effects may result in unfavorable responses or the risk of collisions in a multi-body floating system. Not only the motion behavior but also the second order drift forces are influenced by the neighboring structures due to interactions of the waves among the structures. A study is made on the time domain analysis to assess the behavior and the operational capability of the FPSO system moored in the sea having an LNG carrier alongside under environmental conditions such as waves, wind and currents. This paper presents an analysis tool to predict the dynamic motion response and non-linear connecting and mooring forces on a parallel-connected LNG-FPSO system due to non-linear exciting forces of wave, wind and current. Simulation for the mooring performance is also investigated. The three-dimensional source-sink technique has been applied to obtain the radiation forces and the transfer function of wave exciting forces on floating multi-bodies. The hydrodynamic interaction effect between the FPSO and the LNG carrier is included to calculate the hydrodynamic forces. For the simulation of a random sea and also for the generation of time depended wind velocity, a fully probabilistic simulation technique has been applied. Wind and current loads are estimated according to OCIMF. The effects of variations in wave, wind and current loads and direction on the slowly varying oscillations of the LNG and FPSO are also investigated in this paper. Finally, some conclusions are drawn based on the numerical results obtained from the present time domain simulations.

scholarly journals Time-domain analysis of distortion-product otoacoustic emissions using a hydrodynamic cochlea model

2017 ◽  
Vol 3 (2) ◽  
pp. 453-456
Author(s):  
Dennis Zelle ◽  
Ernst Dalhoff ◽  
Anthony W. Gummer
Keyword(s):  
Time Domain ◽  
Otoacoustic Emissions ◽  
Short Pulse ◽  
Human Subjects ◽  
Time Domain Analysis ◽  
Distortion Product Otoacoustic Emissions ◽  
Sound Waves ◽  
Cochlear Function ◽  
Distortion Product ◽  
The Time Domain

AbstractAs a by-product of nonlinear amplification in the cochlea, the inner ear emits sound waves in response to two tones with different frequencies. These sound waves are measurable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). DPOAEs putatively consist of two components emerging at different locations in the cochlea. Wave interference between the two components limits the accuracy of DPOAEs as a noninvasive measure of cochlear function. Using short stimulus pulses instead of continuous stimuli, the two DPOAE components can be separated in the time domain due to their different latencies. The present work utilizes a nonlinear hydrodynamic cochlea model to simulate short-pulse DPOAEs in the time domain. When adding irregularities to the mechanical parameters of the model, the simulated DPOAE signals show two distinguishable components and long-lasting beat tones, similar to band-pass filtered experimental data from normal-hearing human subjects. The model results suggest that the beat tones can occur solely due to interference of the coherent-reflection component with the fading nonlinear-distortion component.

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