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Arkadiusz Żak

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University College Cork

UERJ - Universidade do Estado do Rio de Janeiro / Rio de Janeiro State University

University of Washington

Denis A. Coelho

Universidade da Beira Interior

Narahari Nuggenahalli

R. V. College of Engineering

Imperial College London

Dr. François-Xavier LICARI

Université de Lorraine

University of Trento

Dr Seán McCartan

Coventry University

David Grembowski

University of Washington

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Papers by Arkadiusz Żak

A Survey of Scrutinizing Delaminated Composites via Various Categories of Sensing Apparatus

Journal of composites science, Oct 30, 2019

Scrutinizing delaminated composites is extensively conducted based on measurements of various typ... more Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed during 2000-2017. Not only does the substantial corresponding literature strongly indicates numerous increasing industrial demand for composites, including carbon fiber-reinforced polymer, glass fiber-reinforced polymer, and fiber-reinforced metal laminate, but also the significant potential of composites to delaminate when subjected particularly to impact, machining operation or manufacturing imperfections. Conducting a study on the corresponding literature, the subject of delamination inspection within composites is found to be a dynamic, mature field, while lacking a thorough literature review. Therefore, the present study addresses the mentioned gap regarding various sensation systems utilized so as to detect internal anomalies in composites for the review arrangement. To that end, the literature inclusion in terms of citation times is electronically adopted associated with an appropriate combination of keywords. The study may be considered as a comprehensive, up-to-date review covering all delamination inspection techniques founded on sensation systems, thus benefiting the readers with information in an organized configuration.

Materiały o sterowalnych własnościach fizycznych i ich zastosowania

Wavelet Transform Analysis of Heart Rate to Assess Recovery Time for Long Distance Runners

Electronics, 2020

The diagnostics of the condition of athletes has become a field of special scientific interest an... more The diagnostics of the condition of athletes has become a field of special scientific interest and activity. The aim of this study was to verify the effect of a long (100 km) run on a group of runners, as well as to assess the recovery time that is required for them to return to the pre-run state. The heart rate (HR) data presented were collected the day before the extreme physical effort, on the same day as, but after, the physical effort, as well as 24 and 48 h after. The Wavelet Transform (WT) and the Wavelet-based Fractal Analysis (WBFA) were implemented in the analysis. A tool was constructed that, based on quantitative data, enables one to confirm the completion of the recovery process that is related to the extreme physical effort. Indirectly, a tool was constructed that enables one to confirm the completion of the recovery process. The obtained information proves that the return to the resting state of the body after a significant physical effort can be observed after two da...

Statics and dynamics of composite structures with embedded shape memory alloys

A new class of modern smart materials such as piezoelectric polymers and ceramics, electrorheolog... more A new class of modern smart materials such as piezoelectric polymers and ceramics, electrorheological fluids, optical fibers and shape memory alloys have a great number of possible applications in many industrial and engineering fields. This number grows constantly encouraging scientists and engineers to study and analyze the behavior of the materials, range and ways of their best use. Shape memory alloy reinforced composites are an extremely versatile class of materials. Shape memory alloys are characterized by: large internal forces, unique ability of changing its material properties, wide range of operational temperature, excellent damping properties and high durability. Mechanical and physical properties of SMA strongly depend on temperature and initial stresses. Changes in temperature and initial stresses involve changes in the volume fraction of martensite in the alloys. During the martensite transformation recovery stresses appear. These recovery stresses are not only a funct...

Finite Element Approaches to Model Electromechanical, Periodic Beams

Applied Sciences, 2020

Periodic structures have some interesting properties, of which the most evident is the presence o... more Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active periodic structures of desired dynamic properties. It can be considered that this may extend the scope of application of such structures. Therefore, numerical research on a beam element built of periodically arranged elementary cells, with active piezoelectric elements, has been performed. The control of parameters of this structure enables one for active damping of vibrations in a specific band in the beam spectrum. For this analysis the authors propose numerical models based on the finite element method (FEM) and the spectral finite element methods defined in the frequency domain (FDSFEM) and the time domain (TDSFEM).

A Survey of Scrutinizing Delaminated Composites via Various Categories of Sensing Apparatus

Journal of Composites Science, 2019

Scrutinizing delaminated composites is extensively conducted based on measurements of various typ... more Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed during 2000–2017. Not only does the substantial corresponding literature strongly indicates numerous increasing industrial demand for composites, including carbon fiber-reinforced polymer, glass fiber-reinforced polymer, and fiber-reinforced metal laminate, but also the significant potential of composites to delaminate when subjected particularly to impact, machining operation or manufacturing imperfections. Conducting a study on the corresponding literature, the subject of delamination inspection within composites is found to be a dynamic, mature field, while lacking a thorough literature review. Therefore, the presen...

Periodic Properties of 1D FE Discrete Models in High Frequency Dynamics

Mathematical Problems in Engineering, 2016

Finite element discrete models of various engineering 1D structures may be considered as structur... more Finite element discrete models of various engineering 1D structures may be considered as structures of certain periodic characteristics. The source of this periodicity comes from the discontinuity of stress/strain field between the elements. This behaviour remains unnoticeable, when low frequency dynamics of these structures is investigated. At high frequency regimes, however, its influence may be strong enough to dominate calculated structural responses distorting or even falsifying them completely. In this paper, certain computational aspects of structural periodicity of 1D FE discrete models are discussed by the authors. In this discussion, the authors focus their attention on an exemplary problem of 1D rod modelled according to the elementary theory.

Comparison of Infinite Element Models

The main objective of this paper is to show the comparison of two models of infinite absorbing la... more The main objective of this paper is to show the comparison of two models of infinite absorbing layer with increasing damping in numerical investigations of elastic wave propagation in unbounded structures. This has been achieved by the Authors by a careful investigation of two different engineering structures characterised by gradually increasing geometrical and mathematical description complexities. The analysis included propagation of longitudinal elastic waves in a 1-D half-infinite isotropic rod, modelled according to the classical 1-mode theory of rods as well as propagation of coupled shear and flexural elastic waves in a 1-D half-infinite isotropic beam modelled according to the Timoshenko beam theory. The comparison of both models has been not only presented by the Authors, but also advantages and disadvantages of both of them have been discussed.

On the Problem for Damage Detection of Vibrating Cracked Plates

Applied Mechanics and Materials, 2006

This work was motivated by the recent NATO funded research on preventing disasters from collapse ... more This work was motivated by the recent NATO funded research on preventing disasters from collapse and improving the safety of aircraft structures. It considers the problem for vibrationbased damage detection in aircraft panels modelled as isotropic plates. The explored method does not use any assumptions of model or linearity, it is simply based on pure signal analysis of the vibration response of plates. FE modelling is used to model the plate’s dynamic response in its intact and in its damaged state. The signals obtained are analysed using multivariate analysis applied in the measured frequency domain. This reduces the data dimensionality and is expected to have a clustering effect. At this stage the measured data is transformed into features – new variables- which have smaller dimension than the initial ones and make the categories more distinguishable. Then a very simple pattern recognition (PR) method is applied to discriminate between the two categories of data -data coming fro...

A spline-based FE approach to modelling of high frequency dynamics of 1-D structures

Computers & Mathematics with Applications, 2021

In this paper a computational methodology leading to the development of a new class of FEs, based... more In this paper a computational methodology leading to the development of a new class of FEs, based on the application of continuous and smooth approximation polynomials, being splines, has been presented. Application of the splines as appropriately defined piecewise elemental shape functions led the authors to the formulation of a new approach for FEM, named as spFEM, where contrary to the well-known NURBS approach, the boundaries of spFEs are well-defined, exactly as it is in the case of the traditional FEM. The current approach has been computationally verified by the authors it terms of high frequency dynamics including such problems as: spectra of natural frequencies, modes of natural vibrations as well as wave propagation problems, especially in the aspect of high frequency responses, all in the case of selected problems involving one-and two-mode theories of 1-D structural elements. The applicability of the proposed approach has been evaluated and compared, in terms of calculated dynamic responses, with the results obtained by the use of well-established FEM approaches: classical FEM as well as TD-SFEM. In all cases investigated by the authors the proposed spFEM approach turned out to be the most accurate approach, free from the main drawback of the other tested FEM approaches thanks to the class of differentiability of approximation polynomials, which guarantees the absence of frequency band gaps in calculated spectra of natural frequencies. A direct consequence of this feature of the proposed approach is that a larger part of the calculated spectra of natural frequency, the same as modes of natural vibrations, can effectively be used for more accurate calculations of dynamic reposes even in the case of multi-mode theories. This in contrast to the other tested FEM approaches.

A higher order transversely deformable shell-type spectral finite element for dynamic analysis of isotropic structures

Finite Elements in Analysis and Design, 2018

This paper deals with certain aspects related to the dynamic behaviour of isotropic shell-like st... more This paper deals with certain aspects related to the dynamic behaviour of isotropic shell-like structures analysed by the use of a higher order transversely deformable shell-type spectral finite element newly formulated and the approach known as the Time-domain Spectral Finite Element Method (TD-SFEM). Although recently this spectral approach is reported in the literature as a very powerful numerical tool used to solve various wave propagation problems, its properties make it also very well suited to solve static and dynamic modal problems. The robustness and effectiveness of the current spectral approach has been successfully demonstrated by the authors in the case of thin-walled spherical shell structures through a series of numerical tests comprising the analysis of natural frequencies and modes of vibration of an isotropic spherical shell as well as the wave propagation analysis in the case of the same spherical shell and a half-pipe shell-like structure.

Modelling of high frequency dynamic responses of engineering structures

Smart Acoustic Band Structures

Lecture Notes in Mechanical Engineering, 2019

Smart acoustic band structures exhibit very interesting and non-standard physical properties due ... more Smart acoustic band structures exhibit very interesting and non-standard physical properties due to the periodic nature of their certain characteristic on different scale levels. They manifest mostly in their frequency spectra as so-called frequency band-gaps or stop-bands, what has a great impact on the behaviour of these structures in relation to the propagation of vibro-acoustic signals that can be transmitted through the structures in some precisely defined frequency bands. Properties of acoustic band structures are directly linked to their geometry on the level of the unit cell, which parameters determine structural dynamics of such structures on the macroscopic scale. Here the piezoelectric transducers play a significant role. The combined exploitation of active properties of acoustic band structures equipped with active piezoelectric elements, in order to filter or damp transmitted vibro-acoustic signals, allows for very effective their applications. In their paper, the autho...

Damage Detection in the Wind Turbine Blade Using Root Mean Square and Experimental Modal Parameters

Lecture Notes in Mechanical Engineering, 2019

The paper presents results of an experimental study related to a non-destructive diagnostic techn... more The paper presents results of an experimental study related to a non-destructive diagnostic technique used for preliminary determination the location and size of delamination in composite coatings of wind turbine blades. The proposed method of damage detection is based on the analysis of the ten first mode shapes of bending vibrations, which correspond to displacements of rotor blades perpendicular to the rotor plane. Modal parameters depend on the physical properties of the structure. On the other hand, failures can affect these properties (e.g. locally reduce the stiffness of the structure). Monitoring of selected modal parameter can allow determination the technical condition of the structure. The main assumption of the presented method is a comprehensive analysis of the measured data by determination the root mean square value (RMS) for each measurement point from all forms of free vibration obtained from the experiment. As a result, information contained in all modes of vibrati...

Spectral Element Methods for Damage Detection and Condition Monitoring

Spectral Finite Element Method in Condition Monitoring and Damage Detection

It is well known that the dynamic behaviour of engineering structures may carry very important an... more It is well known that the dynamic behaviour of engineering structures may carry very important and crucial information that can be further used for the assessment of their condition as well as detection of any damage induced. The current interest in monitoring techniques based on the propagation of guided elastic waves requires that numerical techniques used for modelling the phenomena associated must shift into the realm of high frequency dynamics in contrast to traditional low frequency dynamic modal analysis. However, high frequency dynamics may present serious difficulties, which may have their origin in the numerical approach used. In that light the aim of the current work is to present certain results obtained by the authors related to two different spectral finite element approaches (frequency-domain and time-domain) for condition monitoring and damage detection of various engineering structures including simple 1-D and 2-D structures as well as complex 3-D structures. Also a...

Detection of damages in a riveted plate

A higher order shell element for wave propagation in isotropic shell structures

Shell Structures: Theory and Application, 2013

Predicting Failure in Multi-Bolt Composite Joints Using Finite Element Analysis and Bearing-Bypass Diagrams

Key Engineering Materials, 2005

A three-dimensional finite element model of a three-bolt, single-lap composite joint is construct... more A three-dimensional finite element model of a three-bolt, single-lap composite joint is constructed using the non-linear finite element code MSC.Marc. The model is validated against an experiment where the load distribution in the joint is measured using instrumented bolts. Two different joint configurations are examined, one with neat-fit clearances at each bolt-hole and another with a 240 µm clearance at one hole with neat-fits at the others. Bearing and by-pass stresses are extracted from the model and used in conjunction with published bearing/by-pass diagrams to predict the failure load, mode and location for the joints. It is shown that the proposed model accurately predicts the failure behaviour of the joints, as determined from experiments on three-bolt joints loaded to failure. It is also shown that introducing a clearance into one hole significantly changes the failure sequence, but does not affect the ultimate failure load, mode or location. The proposed method demonstrat...

Spectral finite element method for propagation of guided elastic waves in wind turbine blades for shm purposes

Certain results of numerical simulations obtained by the use of the spectral finite element metho... more Certain results of numerical simulations obtained by the use of the spectral finite element method in time domain are presented by the authors. They were selected in order to show the effectiveness of the spectral finite element method for investigation of problems associated with propagation of guided elastic waves in a wind turbine laminated composite blade. Results of these simulations were subsequently evaluated in order to detect and localise simulated damage in the form of cracks or delaminations.

A Survey of Scrutinizing Delaminated Composites via Various Categories of Sensing Apparatus

Journal of composites science, Oct 30, 2019

Scrutinizing delaminated composites is extensively conducted based on measurements of various typ... more Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed during 2000-2017. Not only does the substantial corresponding literature strongly indicates numerous increasing industrial demand for composites, including carbon fiber-reinforced polymer, glass fiber-reinforced polymer, and fiber-reinforced metal laminate, but also the significant potential of composites to delaminate when subjected particularly to impact, machining operation or manufacturing imperfections. Conducting a study on the corresponding literature, the subject of delamination inspection within composites is found to be a dynamic, mature field, while lacking a thorough literature review. Therefore, the present study addresses the mentioned gap regarding various sensation systems utilized so as to detect internal anomalies in composites for the review arrangement. To that end, the literature inclusion in terms of citation times is electronically adopted associated with an appropriate combination of keywords. The study may be considered as a comprehensive, up-to-date review covering all delamination inspection techniques founded on sensation systems, thus benefiting the readers with information in an organized configuration.

Materiały o sterowalnych własnościach fizycznych i ich zastosowania

Wavelet Transform Analysis of Heart Rate to Assess Recovery Time for Long Distance Runners

Electronics, 2020

The diagnostics of the condition of athletes has become a field of special scientific interest an... more The diagnostics of the condition of athletes has become a field of special scientific interest and activity. The aim of this study was to verify the effect of a long (100 km) run on a group of runners, as well as to assess the recovery time that is required for them to return to the pre-run state. The heart rate (HR) data presented were collected the day before the extreme physical effort, on the same day as, but after, the physical effort, as well as 24 and 48 h after. The Wavelet Transform (WT) and the Wavelet-based Fractal Analysis (WBFA) were implemented in the analysis. A tool was constructed that, based on quantitative data, enables one to confirm the completion of the recovery process that is related to the extreme physical effort. Indirectly, a tool was constructed that enables one to confirm the completion of the recovery process. The obtained information proves that the return to the resting state of the body after a significant physical effort can be observed after two da...

Statics and dynamics of composite structures with embedded shape memory alloys

A new class of modern smart materials such as piezoelectric polymers and ceramics, electrorheolog... more A new class of modern smart materials such as piezoelectric polymers and ceramics, electrorheological fluids, optical fibers and shape memory alloys have a great number of possible applications in many industrial and engineering fields. This number grows constantly encouraging scientists and engineers to study and analyze the behavior of the materials, range and ways of their best use. Shape memory alloy reinforced composites are an extremely versatile class of materials. Shape memory alloys are characterized by: large internal forces, unique ability of changing its material properties, wide range of operational temperature, excellent damping properties and high durability. Mechanical and physical properties of SMA strongly depend on temperature and initial stresses. Changes in temperature and initial stresses involve changes in the volume fraction of martensite in the alloys. During the martensite transformation recovery stresses appear. These recovery stresses are not only a funct...

Finite Element Approaches to Model Electromechanical, Periodic Beams

Applied Sciences, 2020

Periodic structures have some interesting properties, of which the most evident is the presence o... more Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active periodic structures of desired dynamic properties. It can be considered that this may extend the scope of application of such structures. Therefore, numerical research on a beam element built of periodically arranged elementary cells, with active piezoelectric elements, has been performed. The control of parameters of this structure enables one for active damping of vibrations in a specific band in the beam spectrum. For this analysis the authors propose numerical models based on the finite element method (FEM) and the spectral finite element methods defined in the frequency domain (FDSFEM) and the time domain (TDSFEM).

A Survey of Scrutinizing Delaminated Composites via Various Categories of Sensing Apparatus

Journal of Composites Science, 2019

Scrutinizing delaminated composites is extensively conducted based on measurements of various typ... more Scrutinizing delaminated composites is extensively conducted based on measurements of various types of nondestructive sensing apparatus, classified herein as systems of thermographic inspection, piezoelectric inspection, optical interferometric inspection, electromagnetic testing, ultrasonic testing, and visual testing. The development of the subject has been reviewed during 2000–2017. Not only does the substantial corresponding literature strongly indicates numerous increasing industrial demand for composites, including carbon fiber-reinforced polymer, glass fiber-reinforced polymer, and fiber-reinforced metal laminate, but also the significant potential of composites to delaminate when subjected particularly to impact, machining operation or manufacturing imperfections. Conducting a study on the corresponding literature, the subject of delamination inspection within composites is found to be a dynamic, mature field, while lacking a thorough literature review. Therefore, the presen...

Periodic Properties of 1D FE Discrete Models in High Frequency Dynamics

Mathematical Problems in Engineering, 2016

Finite element discrete models of various engineering 1D structures may be considered as structur... more Finite element discrete models of various engineering 1D structures may be considered as structures of certain periodic characteristics. The source of this periodicity comes from the discontinuity of stress/strain field between the elements. This behaviour remains unnoticeable, when low frequency dynamics of these structures is investigated. At high frequency regimes, however, its influence may be strong enough to dominate calculated structural responses distorting or even falsifying them completely. In this paper, certain computational aspects of structural periodicity of 1D FE discrete models are discussed by the authors. In this discussion, the authors focus their attention on an exemplary problem of 1D rod modelled according to the elementary theory.

Comparison of Infinite Element Models

The main objective of this paper is to show the comparison of two models of infinite absorbing la... more The main objective of this paper is to show the comparison of two models of infinite absorbing layer with increasing damping in numerical investigations of elastic wave propagation in unbounded structures. This has been achieved by the Authors by a careful investigation of two different engineering structures characterised by gradually increasing geometrical and mathematical description complexities. The analysis included propagation of longitudinal elastic waves in a 1-D half-infinite isotropic rod, modelled according to the classical 1-mode theory of rods as well as propagation of coupled shear and flexural elastic waves in a 1-D half-infinite isotropic beam modelled according to the Timoshenko beam theory. The comparison of both models has been not only presented by the Authors, but also advantages and disadvantages of both of them have been discussed.

On the Problem for Damage Detection of Vibrating Cracked Plates

Applied Mechanics and Materials, 2006

This work was motivated by the recent NATO funded research on preventing disasters from collapse ... more This work was motivated by the recent NATO funded research on preventing disasters from collapse and improving the safety of aircraft structures. It considers the problem for vibrationbased damage detection in aircraft panels modelled as isotropic plates. The explored method does not use any assumptions of model or linearity, it is simply based on pure signal analysis of the vibration response of plates. FE modelling is used to model the plate’s dynamic response in its intact and in its damaged state. The signals obtained are analysed using multivariate analysis applied in the measured frequency domain. This reduces the data dimensionality and is expected to have a clustering effect. At this stage the measured data is transformed into features – new variables- which have smaller dimension than the initial ones and make the categories more distinguishable. Then a very simple pattern recognition (PR) method is applied to discriminate between the two categories of data -data coming fro...

A spline-based FE approach to modelling of high frequency dynamics of 1-D structures

Computers & Mathematics with Applications, 2021

In this paper a computational methodology leading to the development of a new class of FEs, based... more In this paper a computational methodology leading to the development of a new class of FEs, based on the application of continuous and smooth approximation polynomials, being splines, has been presented. Application of the splines as appropriately defined piecewise elemental shape functions led the authors to the formulation of a new approach for FEM, named as spFEM, where contrary to the well-known NURBS approach, the boundaries of spFEs are well-defined, exactly as it is in the case of the traditional FEM. The current approach has been computationally verified by the authors it terms of high frequency dynamics including such problems as: spectra of natural frequencies, modes of natural vibrations as well as wave propagation problems, especially in the aspect of high frequency responses, all in the case of selected problems involving one-and two-mode theories of 1-D structural elements. The applicability of the proposed approach has been evaluated and compared, in terms of calculated dynamic responses, with the results obtained by the use of well-established FEM approaches: classical FEM as well as TD-SFEM. In all cases investigated by the authors the proposed spFEM approach turned out to be the most accurate approach, free from the main drawback of the other tested FEM approaches thanks to the class of differentiability of approximation polynomials, which guarantees the absence of frequency band gaps in calculated spectra of natural frequencies. A direct consequence of this feature of the proposed approach is that a larger part of the calculated spectra of natural frequency, the same as modes of natural vibrations, can effectively be used for more accurate calculations of dynamic reposes even in the case of multi-mode theories. This in contrast to the other tested FEM approaches.

A higher order transversely deformable shell-type spectral finite element for dynamic analysis of isotropic structures

Finite Elements in Analysis and Design, 2018

This paper deals with certain aspects related to the dynamic behaviour of isotropic shell-like st... more This paper deals with certain aspects related to the dynamic behaviour of isotropic shell-like structures analysed by the use of a higher order transversely deformable shell-type spectral finite element newly formulated and the approach known as the Time-domain Spectral Finite Element Method (TD-SFEM). Although recently this spectral approach is reported in the literature as a very powerful numerical tool used to solve various wave propagation problems, its properties make it also very well suited to solve static and dynamic modal problems. The robustness and effectiveness of the current spectral approach has been successfully demonstrated by the authors in the case of thin-walled spherical shell structures through a series of numerical tests comprising the analysis of natural frequencies and modes of vibration of an isotropic spherical shell as well as the wave propagation analysis in the case of the same spherical shell and a half-pipe shell-like structure.

Modelling of high frequency dynamic responses of engineering structures

Smart Acoustic Band Structures

Lecture Notes in Mechanical Engineering, 2019

Smart acoustic band structures exhibit very interesting and non-standard physical properties due ... more Smart acoustic band structures exhibit very interesting and non-standard physical properties due to the periodic nature of their certain characteristic on different scale levels. They manifest mostly in their frequency spectra as so-called frequency band-gaps or stop-bands, what has a great impact on the behaviour of these structures in relation to the propagation of vibro-acoustic signals that can be transmitted through the structures in some precisely defined frequency bands. Properties of acoustic band structures are directly linked to their geometry on the level of the unit cell, which parameters determine structural dynamics of such structures on the macroscopic scale. Here the piezoelectric transducers play a significant role. The combined exploitation of active properties of acoustic band structures equipped with active piezoelectric elements, in order to filter or damp transmitted vibro-acoustic signals, allows for very effective their applications. In their paper, the autho...

Damage Detection in the Wind Turbine Blade Using Root Mean Square and Experimental Modal Parameters

Lecture Notes in Mechanical Engineering, 2019

The paper presents results of an experimental study related to a non-destructive diagnostic techn... more The paper presents results of an experimental study related to a non-destructive diagnostic technique used for preliminary determination the location and size of delamination in composite coatings of wind turbine blades. The proposed method of damage detection is based on the analysis of the ten first mode shapes of bending vibrations, which correspond to displacements of rotor blades perpendicular to the rotor plane. Modal parameters depend on the physical properties of the structure. On the other hand, failures can affect these properties (e.g. locally reduce the stiffness of the structure). Monitoring of selected modal parameter can allow determination the technical condition of the structure. The main assumption of the presented method is a comprehensive analysis of the measured data by determination the root mean square value (RMS) for each measurement point from all forms of free vibration obtained from the experiment. As a result, information contained in all modes of vibrati...

Spectral Element Methods for Damage Detection and Condition Monitoring

Spectral Finite Element Method in Condition Monitoring and Damage Detection

It is well known that the dynamic behaviour of engineering structures may carry very important an... more It is well known that the dynamic behaviour of engineering structures may carry very important and crucial information that can be further used for the assessment of their condition as well as detection of any damage induced. The current interest in monitoring techniques based on the propagation of guided elastic waves requires that numerical techniques used for modelling the phenomena associated must shift into the realm of high frequency dynamics in contrast to traditional low frequency dynamic modal analysis. However, high frequency dynamics may present serious difficulties, which may have their origin in the numerical approach used. In that light the aim of the current work is to present certain results obtained by the authors related to two different spectral finite element approaches (frequency-domain and time-domain) for condition monitoring and damage detection of various engineering structures including simple 1-D and 2-D structures as well as complex 3-D structures. Also a...

Detection of damages in a riveted plate

A higher order shell element for wave propagation in isotropic shell structures

Shell Structures: Theory and Application, 2013

Predicting Failure in Multi-Bolt Composite Joints Using Finite Element Analysis and Bearing-Bypass Diagrams

Key Engineering Materials, 2005

A three-dimensional finite element model of a three-bolt, single-lap composite joint is construct... more A three-dimensional finite element model of a three-bolt, single-lap composite joint is constructed using the non-linear finite element code MSC.Marc. The model is validated against an experiment where the load distribution in the joint is measured using instrumented bolts. Two different joint configurations are examined, one with neat-fit clearances at each bolt-hole and another with a 240 µm clearance at one hole with neat-fits at the others. Bearing and by-pass stresses are extracted from the model and used in conjunction with published bearing/by-pass diagrams to predict the failure load, mode and location for the joints. It is shown that the proposed model accurately predicts the failure behaviour of the joints, as determined from experiments on three-bolt joints loaded to failure. It is also shown that introducing a clearance into one hole significantly changes the failure sequence, but does not affect the ultimate failure load, mode or location. The proposed method demonstrat...

Spectral finite element method for propagation of guided elastic waves in wind turbine blades for shm purposes

Certain results of numerical simulations obtained by the use of the spectral finite element metho... more Certain results of numerical simulations obtained by the use of the spectral finite element method in time domain are presented by the authors. They were selected in order to show the effectiveness of the spectral finite element method for investigation of problems associated with propagation of guided elastic waves in a wind turbine laminated composite blade. Results of these simulations were subsequently evaluated in order to detect and localise simulated damage in the form of cracks or delaminations.