80 research outputs found
Performance of Vibration Based Damage Detection Algorithms for Detection of Disbond in Stiffened Metallic Plates
No full textAbstractThough vibration based health monitoring has been the focus of attention for quite some time, there exist a strong requirement for an extensive and comprehensive study on the relative performance of different damage detection algorithms under different damage scenarios. To fulfill this objective, a stiffened aluminium plate has been selected to make a comparative study on the performance of several vibration based damage detection techniques, namely, Modal Curvature, Gapped Smoothing Method/Modal Curvature, Generalized Fractal Dimension and Uniform Load Surface Curvature based on four different criteria: variation of damage intensity (i.e., disbond length), position of stiffener and disbond, the effect of noise and capability to detect multiple damage. In addition to this, a new approach, based on the curvature of wavelet coefficients, has been presented. It is found that this novel approach is extremely effective in determining the presence and location of damage under different situations. The entire numerical modelling is done in ANSYS 14.0 and the damage detection algorithms written in MATLAB codes have been used to generate the required damage indices using the modal data retrieved from ANSYS. The study ultimately enlightens inherent characteristics of the various damage detection algorithms under different damage conditions
Dynamic Characterization of Connections in Plane Frames Using SFFEM
No full textAbstractIn the construction of civil engineering structures, two or more members are often rigidly connected to increase the structural integrity. These rigid joints are often designed with bolts, rivets and welding. The actions of in-service loading and environmental effects, or fabrication errors make these joints semirigid, which ultimately reduces the structural reliability. Realistic dynamic analysis of these structures requires accurate modelling of rigidity of joints. Dynamic analysis of plane frames can be accomplished by combining spectrally formulated Rod and Euler-Bernoulli Beam element. In this study, a six parameter spectral plane frame joint element is formulated using linear and rotational springs to account for semi-rigidity of joints. Methodology and experimental set up for evaluation of dynamic characteristics of connections is discussed in this paper
Quantitative Investigation of Acoustic Emission Waveform Parameters from Crack Opening in a Rail Section Using Clustering Algorithms and Advanced Signal Processing
No full textAcoustic emission (AE) is an emerging technology for real-time non-destructive testing of structures. While research on a simulated AE source in rail and testing on rail material using small beam samples have been conducted, a study is required in lab environment to investigate AE waveform characteristics generated by crack in rail. In this paper, a three-point bending test is conducted on an actual rail section of 1500 mm with transverse damage of 38% head area to simulate AE source due to crack opening in the rail. AE signals are recorded for three different loads. For data analysis, unsupervised machine learning algorithms such as k-means, fuzzy-C mean and gaussian mixture model are used to cluster and filter out usable signals from the whole dataset corrupted by noisy signals from various sources. k-mean with principal component was observed to be best technique based on silhouette score. The frequency and amplitude of waveform have been discussed in relation to load and crack opening displacement. This study establishes a baseline for linking load, crack opening, and AE wave characteristics. This work can ultimately aid in the development of robust denoising, and damage analysis algorithms based on the frequency content and dispersion of the AE waveform
Guided wave based nondestructive analysis of localized inhomogeneity effects in an advanced sandwich composite structure
No full textIn this paper, we present a nondestructive analysis of localized inhomogeneity effects on guided wave propagation in an advanced sandwich composite structure. In the process, guided wave dispersion curves were semi-analytically determined for the structure to accurately identify different wave modes in experimental and numerical analysis signals. Finite element simulation of wave propagation in the target structure was then carried out in ABAQUS and validated with the experiment. Significant influences on the wave mode amplitudes were observed due to the presence of a localized inhomogeneity in the structure. An inhomogeneity identification strategy was prepared based on the amplitude changes in the registered guided wave signals from a predefined piezoelectric transducer network. The influence of varying elastic modulus and mass-density of the inhomogeneous region on the wave mode amplitudes and the corresponding inhomogeneity-index magnitudes were also studied
Wave Propagation in a Honeycomb Composite Sandwich Structure in the Presence of High-Density Core Using Bonded PZT-Sensors
No full textHoneycomb Composite Sandwich Structure (HCSS), is one of the novel materials that has been adopted universally to form major structural components of aerospace, marine and automotive vehicles due to its high strength to weight ratio and high energy-absorption capabilities. In this research paper, the scope to study the general characteristics of guided wave (GW) propagation in an HCSS plate with the presence of a high-density (HD) core subjected to timedependent transient surface excitations is presented numerically and experimentally. Significant effects are detected due to the presence of HD core in terms of decay in amplitude and reduction in group velocity of the output GW signals. A two-dimensional (2D) numerical model is made in ABAQUS. An effective non-reflecting boundary condition (NRBC) is modeled in ABAQUS in order to mitigate the undesirable boundary reflections during numerical simulation. Good agreements between the numerical and experimental results are noticed for all the cases studied
Ultrasonic guided wave propagation and detection of high density core region in a honeycomb composite sandwich structure using embedded piezoelectric transducers
No full textAn organized numerical and experimental study is carried out in order to understand ultrasonic guided wave (GW) propagation and interaction with a high density (HD) core region in a honeycomb composite sandwich structure (HCSS). Also the location of HD core region in a HCSS using embedded piezoelectric wafer transducer (PWTs) is investigated in this study. Due to complex structural characteristics, the study of guided wave (GW) propagation in HCSS with HD-core region inherently carries many challenges. Therefore, a three-dimensional (3D) numerical simulation of GW propagation in the HCSS with and without HD core region is carried out using embedded PWT network. It is observed that the presence of HD core significantly reduces the amplitude of the propagating GW modes. In order to verify the numerical results, experiments are conducted in the laboratory. A good agreement between the numerical and experimental results is observed, in all the cases studied. Finally, based on the change in amplitude of the received GW modes, the location of an unknown HD core region, within the PWT array is determined by applying a probability based signal difference coefficient (SDC) algorithm
Identification of Semi-rigid Joints in Steel Frame Structures Using Vibration-Based Technique
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