33 research outputs found
Experimental evaluation of the true intrinsic nonlinearity of rail steel using Rayleigh waves and a new nonlinearity parameter
No full textThe paper presents the experimental evaluation of the true intrinsic nonlinearity of a macroscopically pristine rail
specimen using non-dispersive Rayleigh waves. A second harmonic is produced in the wave as a result of lattice anharmonicity that is sensed at different locations on the specimen surface. The spectral amplitudes of the fundamental
and generated second harmonics are then used to calculate the intrinsic nonlinearity of rail material using a new amplitude based nonlinearity parameter. The material nonlinearity of the rail steel evaluated using the experimental measurements
and amplitude-based parameter are further compared with that obtained using the nonlinear elasticity equations. It is found
that the experimentally obtained nonlinearities are in close agreement with that of the nonlinear elasticity equations that
show the effectiveness of the proposed method in measuring the intrinsic nonlinearity of the rail steel. Furthermore, the
effect of excitation frequency, number of cycles in tone burst, and selection of the windowing functions in evaluating the
intrinsic nonlinearity of rail steel are also investigated. The estimation of intrinsic material nonlinearity may help diagnose
the health status of the macroscopically pristine rail specimens in terms of the level of dissolved impurities and their
microstructural consistency, before fixing them on a track
Laser-Based Guided Wave Propagation and Mode Decomposition in Detecting the Integrity of Structural I-Beams
No full textAnalyzing the features of material nonlinearity evaluation in a rectangular aluminum beam using Rayleigh waves: theoretical and experimental study
No full textThis study proposes a new parameter to evaluate the material nonlinearity in a thick Aluminum (Al)
beam having rectangular cross section using Rayleigh waves. This parameter yields a true value of
material nonlinearity using the amplitudes of Rayleigh wave harmonics, in contrast to the relative
value yielded by the conventional nonlinearity parameter β′. The Rayleigh wave harmonics are
generated in a thick Al 1100 specimen through experiments to estimate its inherent material
nonlinearity. This inherent nonlinearity is embedded in the material via lattice elasticity and reckoned
using the higher order elastic coefficients. With this experimental investigation, it is found that the
accurate evaluation of material nonlinearity is highly dependent on the tone burst cycles in the
excitation signal. It is also found that there is a small amount of contribution to the material
nonlinearity parameter from the imaginary part of the shear wave component. Furthermore, the
relationship between material nonlinearity evaluated using the proposed parameter, excitation
frequency, propagation distance, and tone burst cycles in the excitation signal have been unveiled.
After knowing these relationships, the material nonlinearity evaluated using the proposed parameter
is compared with that obtained from a physics-based nonlinearity parameter containing higher order
elastic coefficients. The deviation between the results is minimal. Thus, with the use of amplitudes of
harmonics of the Rayleigh wave generated through the experiments, the proposed parameter can
evaluate the true material nonlinearity of thick Al beams with fair accuracy
A Fully Optical Laser Based System for Damage Detection and Localization in Rail Tracks Using Ultrasonic Rayleigh Waves: A Numerical and Experimental Study
No full textThe present study focuses on investigating the structural integrity of rail track sections of the high-speed railways using the
Rayleigh waves generated and sensed using a fully non-contact optical Laser system. The raw broadband beam of the
excitation laser was converted to a narrowband beam using a customized optical system, whereas the propagating Rayleigh
waves were sensed using a three-dimensional (3D) scanning laser Doppler vibrometer (3D-SLDV) system. All the
experiments were conducted using the pitch-catch method in presence of surface damages on head of the Rail track. Several
issues were observed during the experiments, which are noted as follows. First, the noise and unwanted wave packets
increase with the increase in the time window and the inspection length. Second, with larger inspection lengths, it is
relatively difficult to interpret the response as the reflection of the incident wave packet may arise from any edge of the rail
specimen, and shall be difficult to precisely identify the source. Third, as a result of lower Signal-to-Noise ratio (SNR), there
may be smaller wave packets that shall be likely deceiving as a reflection of the defect. Fourth, it is observed that a small
change in the location of the sensing point may significantly alter the overall signal. Fifth, it is also observed that the
actuation and sensing position plays a crucial role in receiving the time-domain data with a sufficient SNR and the one that
is easy to analyze and interpret. Based on the numerous experiments, an optimum distance of inspection is estimated which
yields damage detection and localization with high accuracy thereby solving all the aforementioned issues. Further, As the
quality of received signals differs at different sensing points as a result of the surface conditions of the specimen, the Self
Adaptive Smart Algorithm (SASA) method was adopted to filter out the noise and accurately pinpoint the defect reflected
wave packet which ultimately aids in better detection and localization. Finally, a 3D Finite Element simulation was
conducted to validate the findings and each observation resulting from the experiments. Based on the obtained accuracy of
the results, the proposed methodology has been found to be capable of inspecting rail track specimens in a completely
non-contact manner with reasonably good accurac
Estimating the probability of detection of cracks in metal plates using lamb waves
No full textThis paper focusses on the development of a data-driven damage detection method to
quantify fatigue crack in metal plates using Lamb waves and its reliability using a probability of
detection (POD) technique. The guided Lamb waves are generated and sensed using an array of
direct-write (DW) polyvinylidene fluoride (PVDF) annular comb shaped transducers designed to
explicitly generate a desired guided wave mode in the test specimen. The annular comb design
helps generate a single desired wave mode in the specimen thereby suppressing the energy of other
wave modes that can be generated simultaneously. The guided wave responses are obtained
through a simulation study and are recorded at different progressions of crack. A damage index
(DI) is constructed as a function of crack size that can effectively track the change in ultrasonic
response variations and for diagnosing fatigue crack in the metallic specimens. This DI is then
further used in the POD model to estimate the crack detection probability. The POD curves can be
helpful to check the reliability of the proposed inspection system as well as identify the critical
experimental parameters that can significantly influence the crack detection results
LOCATING DAMAGES IN THIN ALUMINIUM PLATES USING LAMB WAVES AND AGENETIC OPTIMIZATION APPROACH
No full textA new damage localization method based on Lamb waves is
presented here for thin aluminium (Al) plate specimens using a Genetic
optimization (GO) approach. Two different types of damages are
considered to demonstrate the effectiveness of the proposed method and
its practical applicability. The lamb wave signals for interrogating the
plate structure are obtained using experiments and a sparse array of four
piezoelectric wafer (PW) transducers. The PW transducers are mounted onto the specimen in the form of vertices of a square roughly in the centre
portion of the specimen to record the responses for pristine and damaged
states of the specimen. The time of arrival (TOA) of defect waves to the
sensor are extracted using the continuous wavelet transform (CWT)
applied on all the residual signals and are subsequently used in the astroid
algorithm to locate the damage as an enclosed area. The damage locations
are further optimized within the enclosed area using the GO algorithm.
The optimized results of damage well correspond with the actual ones
and thus manifest the ability of the proposed approach for locating
different types of defects in an Al specimen using a sparse array of
permanently installed PW transducers
Damage detection in hybrid metal-composite plates using ultrasonic guided waves based on outliers estimate
No full textThe present research focusses on the development of a robust data-driven damage
diagnosis technique to detect different types of damages in a hybrid metal-composite (HMC) plate
specimen resulting from manufacturing processes, loading conditions, and ambient environmental
conditions. These defects over a course of time deteriorate the load-bearing capacity of the HMC’s
and in turn, their reliability in terms of safe operation. In this work, ultrasonic guided waves
(UGW) are used for non-destructive evaluation (NDE) of the HMC. The use of UGW for NDE
offers advantages such as long-range inspection and sensitivity to small-sized surface and sub surface damages. The ultrasonic tests are simulated using a pitch-catch active sensing technique at
a typical frequency-mode pair best suited to detect and classify damages in the HMCs. The
damage-sensitive feature is extracted from the received UGW using Hilbert transform-based
feature extraction method. The damage indicator is classified in the damage-sensitive feature space
using the root mean square technique identified as outliers, which is further used to classify the
detected damages. The achieved results manifest the ability of the proposed technique to be a part
of the industrial structural integrity inspection process typically for HMCs in detecting and
classifying embedded damages with high accuracy
Theoretical and Experimental evaluation of the health status of a 1018 steel I Beam using nonlinear Rayleigh waves: Application to evaluating localized plastic damage due to Impact loading
No full textThis study proposes a sensitive and baseline-free method to evaluate the health status of a
1018 steel I-beam by measuring its material nonlinearity using a new nonlinearity parameter defined for
Rayleigh waves. This parameter yields a true value of material nonlinearity using the Rayleigh wave
harmonics obtained from the experiments carried out at the intact and impacted states of the I-beam.
Accordingly, the evaluated nonlinearities are inherent and damaged induced respectively. The results
show that, for an intact state, the nonlinearity obtained using the new parameter and the experimental
results for different propagation distances, consist of several peaks and the first peak reaches the true
material nonlinearity. Whereas, in case of damaged state, the nonlinearity parameter at the impacted
location shows a sudden increase and reaches a value higher than that of the nonlinearity evaluated at the
same location for intact state. Thus, the health status can be easily tracked by comparing the nonlinearity
obtained from the current state of the I-beam at its first peak with that of a physics based nonlinearity
parameter evaluated at the intact state using the higher order elastic coefficients of the material. Therefore,
this method is termed as baseline-free. Lastly, a novel concept of evaluating the population of dislocations
formed in the material as a result of impact loading, using the new nonlinearity parameter is introduced
and an equation for its estimation is given. The trend of the results given by this new equation are in
accordance with those reported in the literature. In contrast, deviation between the linear parameter such
as the wave velocity at the intact and impacted state remains marginal. Thus, by using the new
nonlinearity parameter, it has been proven that the inspected steel specimen can be easily differentiated
whether it is at the intact or damaged state
A SENSITIVE APPROACH TO DETERMINE THE HEALTH STATUS OF I-BEAMS BY MEASURING ITS NONLINEARITY THROUGH THE USE OF RAYLEIGH WAVES
No full textThe present study focusses on evaluating the health
status of a 1018 steel I-beam using a new nonlinearity
parameter defined for Rayleigh waves. This parameter yields
a true value of material nonlinearity using the Rayleigh wave
harmonics obtained from the experiments carried out at the
intact and the impacted state of the I-beam. Accordingly, the
evaluated nonlinearity is the inherent and damaged induced
nonlinearity. The results show that, for an intact state, the
nonlinearity obtained using the new parameter and the
experimental results, consist of several peaks and the first
peak reaches to the true material nonlinearity. Whereas, in
case of damaged state, the nonlinearity parameter at the
impacted location shows a sudden increase and reaches a
value higher than that of the nonlinearity evaluated at the
same location of intact state. Thus, the health status can be
easily tracked by comparing the nonlinearity obtained from
the current state of the I-beam with that of a physics based
nonlinearity parameter obtained at the intact state. In
contrast, the velocity and wave attenuation remains
unaffected. Thus, by using the new nonlinearity parameter, it
has been proven that the inspected I-beam can be easily
differentiated whether it is at the intact or impacted state
EVALUATION OF MATERIAL NONLINEARITY IN FATIGUED SAMPLES USING AN IMPROVED LAMB-WAVE NONLINEAR PARAMETER
No full textThe present study focuses on estimating the material nonlinearity of
thin fatigued plate specimens using an improved amplitude-based Lamb
wave nonlinear parameter. This parameter depends on the spectral
amplitudes of the fundamental and second harmonics of Lamb waves generated because of the material nonlinearity. The cumulative effect
required for an effective propagation of second harmonic is achieved
using the resonant 0 − 0 and 1 − 2 mode pair that works on
approximate phase velocity matching at a low-frequency region and strict
phase and group velocity matching at a high frequency region
respectively. The material nonlinearity is also evaluated using a Physics based nonlinear parameter that depends on the second and third order
nonlinear elastic constants and is independent of the propagation distance
thereby giving the global material nonlinearity. It is found that for a
pristine state, the peak of amplitude-based parameter equals the physics
based one and for a fatigued state, the amplitude-based parameter keeps
increasing with an increase in fatigue damage. In contrast, the
conventional relative nonlinear parameter is found to be useful for
qualitative estimation of material nonlinearity. Thus, for a quantitative
estimation, the improved nonlinear parameter is found to be more useful
