Analysis of natural frequencies of delaminated composite beams based on finite element method

Krawczuk, M.,Ostachowicz, W.,Zak, A. Techno-Press 1996 Structural Engineering and Mechanics, An Int'l Jou Vol.4 No.3

This paper presents a model of a layered, delaminated composite beam. The beam is modelled by beam finite elements, and the delamination is modelled by additional boundary conditions. In the present study, the laminated beam contains only one delaminated region through the thickness direction which extends to the full width of the beam. It is also assumed that the delamination is open. The influence of the delamination length and position upon changes in the bending natural frequencies of the composite laminated cantilever beam is investigated.

Localisation of embedded water drop in glass composite using THz spectroscopy

Mieloszyk, Magdalena,Majewska, Katarzyna,Ostachowicz, Wieslaw Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.6

Glass fibre reinforced polymers (GFRP) are widely exploited in many industrial branches. Due to this Structural Health Monitoring systems containing embedded fibre optics sensors are applied. One of the problems that can influence on composite element durability is water contamination that can be introduced into material structure during manufacturing. Such inclusion can be a damage origin significantly decreasing mechanical properties of an element. A non-destructive method that can be applied for inspection of an internal structure of elements is THz spectroscopy. It can be used for identifications of material discontinuities that results in changes of absorption, refractive index or scattering of propagating THz waves. The limitations of THz propagation through water makes this technique a promising solution for detection of a water inclusion. The paper presents an application of THz spectroscopy for detection and localisation of a water drop inclusion embedded in a GFRP material between two fibre optics with fibre Bragg grating sensors. The proposed filtering method allowed to determine a 3D shape of the water drop.

Delamination localization in wind turbine blades based on adaptive time-of-flight analysis of noncontact laser ultrasonic signals

Park, Byeongjin,Sohn, Hoon,Malinowski, Pawel,Ostachowicz, Wieslaw Taylor Francis 2017 Nondestructive testing and evaluation Vol.32 No.1

<P>In this study, a two-level scanning strategy for a noncontact laser ultrasonic measurement system is proposed to expedite the inspection of a wind turbine blade. First, coarse scanning of the entire blade is performed with a low spatial resolution for initial delamination localisation. Then, dense scanning with a high spatial resolution is performed only within the identified delaminated region for delamination visualization. This study especially focuses on the initial delamination localisation using adaptive coarse scanning. Laser ultrasonic responses from two pitch-catch paths, names inspection pairs, are obtained within a specified coarse scanning grid. Then, potential delamination locations within the given grid are estimated through time-of-flight analysis of delamination reflected waves. Once potential delamination locations are estimated, new inspection pairs are placed near the potential locations for precise localisation. These steps are repeated for every coarse scanning grids on the target wind turbine blade. The feasibility of the proposed technique for rapid delamination detection is demonstrated with a 10 kW glass fibre reinforced plastic wind turbine blade.</P>

Crack location in beams by data fusion of fractal dimension features of laser-measured operating deflection shapes

Bai, R.B.,Song, X.G.,Radzienski, M.,Cao, M.S.,Ostachowicz, W.,Wang, S.S. Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.13 No.6

The objective of this study is to develop a reliable method for locating cracks in a beam using data fusion of fractal dimension features of operating deflection shapes. The Katz's fractal dimension curve of an operating deflection shape is used as a basic feature of damage. Like most available damage features, the Katz's fractal dimension curve has a notable limitation in characterizing damage: it is unresponsive to damage near the nodes of structural deformation responses, e.g., operating deflection shapes. To address this limitation, data fusion of Katz's fractal dimension curves of various operating deflection shapes is used to create a sophisticated fractal damage feature, the 'overall Katz's fractal dimension curve'. This overall Katz's fractal dimension curve has the distinctive capability of overcoming the nodal effect of operating deflection shapes so that it maximizes responsiveness to damage and reliability of damage localization. The method is applied to the detection of damage in numerical and experimental cases of cantilever beams with single/multiple cracks, with high-resolution operating deflection shapes acquired by a scanning laser vibrometer. Results show that the overall Katz's fractal dimension curve can locate single/multiple cracks in beams with significantly improved accuracy and reliability in comparison to the existing method. Data fusion of fractal dimension features of operating deflection shapes provides a viable strategy for identifying damage in beam-type structures, with robustness against node effects.

Crack location in beams by data fusion of fractal dimension features of laser-measured operating deflection shapes

R.B. Bai,X.G. Song,M. Radzieński,W. Ostachowicz,S.S. Wang,M.S. Cao 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.13 No.6

The objective of this study is to develop a reliable method for locating cracks in a beam usingdata fusion of fractal dimension features of operating deflection shapes. The Katz’s fractal dimension curveof an operating deflection shape is used as a basic feature of damage. Like most available damage features,the Katz’s fractal dimension curve has a notable limitation in characterizing damage: it is unresponsive todamage near the nodes of structural deformation responses, e.g., operating deflection shapes. To address thislimitation, data fusion of Katz’s fractal dimension curves of various operating deflection shapes is used tocreate a sophisticated fractal damage feature, the ‘overall Katz’s fractal dimension curve’. This overallKatz’s fractal dimension curve has the distinctive capability of overcoming the nodal effect of operatingdeflection shapes so that it maximizes responsiveness to damage and reliability of damage localization. Themethod is applied to the detection of damage in numerical and experimental cases of cantilever beams withsingle/multiple cracks, with high-resolution operating deflection shapes acquired by a scanning laservibrometer. Results show that the overall Katz’s fractal dimension curve can locate single/multiple cracks inbeams with significantly improved accuracy and reliability in comparison to the existing method. Datafusion of fractal dimension features of operating deflection shapes provides a viable strategy for identifyingdamage in beam-type structures, with robustness against node effects.

Vibration-based structural health monitoring using large sensor networks

A. Deraemaeker,A. Preumont,E. Reynders,G. De Roeck,J. Kullaa,V. Lämsä,K. Worden,G. Manson,R. Barthorpe,E. Papatheou,P. Kudela,P. Malinowski,W. Ostachowicz,T. Wandowski 국제구조공학회 2010 Smart Structures and Systems, An International Jou Vol.6 No.3

Recent advances in hardware and instrumentation technology have allowed the possibility of deploying very large sensor arrays on structures. Exploiting the huge amount of data that can result in order to perform vibration-based structural health monitoring (SHM) is not a trivial task and requires research into a number of specific problems. In terms of pressing problems of interest, this paper discusses: the design and optimisation of appropriate sensor networks, efficient data reduction techniques, efficient and automated feature extraction methods, reliable methods to deal with environmental and operational variability, efficient training of machine learning techniques and multi-scale approaches for dealing with very local damage. The paper is a result of the ESF-S3T Eurocores project Smart Sensing For Structural Health Monitoring(S3HM) in which a consortium of academic partners from across Europe are attempting to address issues in the design of automated vibration-based SHM systems for structures.

Vibration-based structural health monitoring using large sensor networks

Deraemaeker, A.,Preumont, A.,Reynders, E.,De Roeck, G.,Kullaa, J.,Lamsa, V.,Worden, K.,Manson, G.,Barthorpe, R.,Papatheou, E.,Kudela, P.,Malinowski, P.,Ostachowicz, W.,Wandowski, T. Techno-Press 2010 Smart Structures and Systems, An International Jou Vol.6 No.3

Recent advances in hardware and instrumentation technology have allowed the possibility of deploying very large sensor arrays on structures. Exploiting the huge amount of data that can result in order to perform vibration-based structural health monitoring (SHM) is not a trivial task and requires research into a number of specific problems. In terms of pressing problems of interest, this paper discusses: the design and optimisation of appropriate sensor networks, efficient data reduction techniques, efficient and automated feature extraction methods, reliable methods to deal with environmental and operational variability, efficient training of machine learning techniques and multi-scale approaches for dealing with very local damage. The paper is a result of the ESF-S3T Eurocores project "Smart Sensing For Structural Health Monitoring" (S3HM) in which a consortium of academic partners from across Europe are attempting to address issues in the design of automated vibration-based SHM systems for structures.