bluuebunny/crossref_metadata_2025 huggingface dataset:
Hashed Data Transfer in SHM Distributed Systems with the Use of Power Line Communication Technology
Authors: Gołaś Andrzej , Iwaniec Marek , Szopa Krystian
Published: July 2012

Structural Health Monitoring of distributed systems is closely connected with data transmission from measurement points to the main server, where measurement data is processed and subjected to expert assessment. Power Line Communication (PLC) technology allows data transmission through existing power network. The greatest advantage of the PLC technology is the possibility of using ubiquitous, electric infrastructure, wherever there is no access to dedicated wired transmission links. However, it should be stressed that the main application of power lines is transmission of electricity while data transmission is a secondary issue. In monitoring systems and distributed measurement systems it is of vital importance that information from measurement points reaches the receiver in the unchanged form. Hash functions rise possibility of proper recognition if transmitted data is an exact mapping of information sent from measurement point. The paper concerns the method of polynomial hash function implementation for PLC systems in the LabVIEW environment.
Analysis of Experimental Data in the Context of Safety against Derailment of a Railway Vehicle, Using the Energy Method
Authors: Opala Michał
Published: July 2012

This article describes an example analysis of safety against derailment of a railway vehicle. The analysis is based on the experimental data recorded during measurement of the wheel-rail interaction forces and lateral accelerations. The data is used for the calculation of two safety against derailment indicators and then the indicators are compared to each other. The first indicator is the ratio of the lateral to vertical wheel-rail forces Y/Q, based on the Nadal criteria. The second indicator is given in the energy description. In this description, the derailment of a railway vehicle depends on the amount of the work that has been done by the total lateral force acting on the single wheelset. The second indicator can be particularly convenient for a railway vehicle condition monitoring system, because it does not require the measurement of the contact forces.
Impact Damage Detection in Composite Chiral Sandwich Panels
Authors: Klepka Andrzej , Staszewski Wieslaw Jerzy , Uhl T. , di Maio Dario , Scarpa Fabrizio , Tee K.F.
Published: July 2012

This paper demonstrates impact damage detection in a composite sandwich panel. The panel is built from a chiral honeycomb and two composite skins. Chiral structures are a subset of auxetic solids exhibiting counterintuitive deformation mechanism and rotative but not reflective symmetry. Damage detection is performed using nonlinear acoustics,involves combined vibro-acoustic interaction of high-frequency ultrasonic wave and low-frequency vibration excitation. High-and low-frequency excitations are introduced to the panel using a low-profile piezoceramic transducer and an electromagnetic shaker, respectively. Vibro-acoustic modulated responses are measured using laser vibrometry. The methods used for impact damage detection clearly reveal de-bonding in the composite panel. The high-frequency weak ultrasonic wave is also modulated by the low-frequency strong vibration wave when nonlinear acoustics is used for damage detection. As a result frequency sidebands can be observed around the main acoustic harmonic in the spectrum of the ultrasonic signal.
Instantaneous Circular Pitch Cyclic Power (ICPCP) – A Tool for Diagnosis of Planetary Gearboxes
Authors: Jablonski Adam , Barszcz Tomasz
Published: July 2012

The process of monitoring and diagnosis of planetary gearboxes is currently one of the most significant topics for vibroanalysis. The reason for ubiquitous research activities on the topic arises form a shortage of efficient method for a non-destructive thorough vibration analysis of planetary gearboxes, especially working under low speeds. On the other hand, the number of high-value planetary gearboxes working in industry rises rapidly, mainly due to expansion of wind farms. In the paper, the authors present a novel method for the assessment of the technical state of planetary gearboxes with a vibration sensor mounted on the casing, and without a planets position sensor. The method is based on the calculation of cyclic energy of gearbox teeth contact within consecutive carrier revolutions. The methods performance is illustrated on a real data from a wind turbine.
Investigation of Sensor Placement in Lamb Wave-Based SHM Method
Authors: Malinowski Pawel , Wandowski Tomasz , Ostachowicz Wiesław M.
Published: July 2012

In this paper the investigation of a structural health monitoring method for thin-walled parts of structures is presented. The concept is based on the guided elastic wave propagation phenomena. This type of waves can be used in order to obtain information about structure condition and possibly damaged areas. Guided elastic waves can travel in the medium with relatively low attenuation, therefore they enable monitoring of extensive parts of structures. In this way it is possible to detect small defects in their early stage of growth. It is essential because undetected damage can endanger integrity of a structure. In reported investigation piezoelectric transducer was used to excite guided waves in chosen specimens. Dispersion of guided waves results in changes of velocity with the wave frequency, therefore a narrowband signal was used. Measurement of the wave field was realized using laser scanning vibrometer that registered the velocity responses at points belonging to a defined mesh. An artificial discontinuity was introduced to the specimen. The goals of the investigation was to detect it and find optimal sensor placement for this task. Determination of the optimal placement of sensors is a very challenging mission. In conducted investigation laser vibrometer was used to facilitate the task. The chosen mesh of measuring points was the basis for the investigation. The purpose was to consider various configuration of piezoelectric sensors. Instead of using vast amount of piezoelectric sensors the earlier mentioned laser vibrometer was used to gather the necessary data from wave propagation. The signals gather by this non-contact method for the considered network were input to the damage detection algorithm. Damage detection algorithm was based on a procedure that seeks in the signals the damage-reflected waves. Knowing the wave velocity in considered material the damage position can be estimated.
Investigations into the Vibrational Response of an Aero-Engine Turbine Blade under Thermosonic Excitation
Authors: Bolu Gabriel , Pierce Gareth , Gachagan Anthony , Barden Tim , Harvey Gerald
Published: July 2012

Thermosonics is a rapid and potentially cost-saving non-destructive testing (NDT) screening technique that can be applied to the identification of cracks in high pressure compressor turbine blades in turbofan engines. The reliability of the thermosonic technique is not well established for inspecting these complex components; in particular the vibrational energy generated within a component during a thermosonic test is often highly non-uniform, leading to the possibility of missing critical defects. The aim of this study was to develop a methodology, using a combination of vibration measurements and finite element analysis (FEA), to model the vibrational energy within a turbine blade in a typical thermosonic inspection scenario. Using a laser vibrometer, the steady-state vibration response (i.e. frequency response) at several locations on a blade was measured and used to identify the prominent peaks in the frequency spectra. These were then used to generate an excitation function for the finite element modelling approach. Acceptable correlation between the measured and simulated vibration response at a number of specific locations on the blade allowed the forcing function to simulate the vibration response across the whole blade. Finally, the predicted displacement field was used to determine the vibrational energy at every point on the blade which was mapped onto a CAD representation of the blade, thereby highlighting areas on the blade that were below the defect detection threshold.
Low Cost Laser Triangulation System for Rail and Guide Wear Evaluation
Authors: Błaszczyk Paweł M. , Kujawińska Małgorzata
Published: July 2012

Periodic rail and guide wear evaluation is essential for their reliability and safety. By regular measurement it is possible to determine whether certain rail or guide fragments need urgent replacement reducing the risk of accidents. In the paper at first we present the measurement system, which is intended to operate in small rail systems such as trams, light rail, narrow gauge rail, mine rail. It can be adopted to operate in two modes: manual pulled along the rail or guide or automatic attached to a measurement car. The measuring system is flexible enabling the measurement of different features of rail or guide geometry depending on the needs. By simplifying the design, the system can be operated by an unqualified personnel, however final wear evaluation has to be done by a qualified engineer. Finally we present the exemplary results of measurements performed on a selected rail section and the full data processing path. The method of relative calibration and synchronizing data from several measurement modules is also reported.
Monimost - Integrated SHM System for Railway Truss Bridges
Authors: Sala Damian , Pawłowski P. , Kołakowski Przemysław , Świercz Andrzej , Sekuła Krzysztof
Published: July 2012

A railway bridge has been the object of investigation since mid 2007 as a response to increasing interest in structural health monitoring (SHM) from Polish Railways. It is a typical 40 m long, steel truss structure spanning a channel in Nieporet near Warsaw. There is over 1500 similar bridges in the railway network in Poland. The integrated system consists of two components weigh in motion (WIM) part for identification of train load and SHM part for assessing the state of the bridge. Two aspects of wireless transmission are considered short range (in the vicinity of the bridge, 2.4GHz) and far range (from the bridge to the data analysis center, GSM). The system is designed to be energetically self-sufficient, batteries are recharged by solar panels. Both the subsystems use piezoelectric strain sensors. Numerical model of the bridge corresponds well to the experimental data and provides a good starting point for considering different scenarios of simulated damage in the structure.
Non-Invasive Methods of Delamination Monitoring in Multi-Layer Structures
Authors: Iwaniec Joanna , Iwaniec Marek
Published: July 2012

In the paper there are discussed the most interesting methods dedicated to frescos structural health monitoring. In the further part two methods and devices for fresco delamination detection developed by authors are presented. In order to enable future automation of developed measurement techniques and autonomic detection of fresco structural defects, the novel measures quantifying the probability of critical condition appearance (the lack of adhesive force) were introduced. Finally, the results of measurements of dynamic characteristics of healthy and delaminated structures are presented.
Application of Image Based Methods for Monitoring and Measurements of Structures in Power Stations
Authors: Kujawińska Małgorzata , Malesa Marcin , Malowany Krzysztof , Błaszczyk Paweł M.
Published: July 2012

The implementation of selected full-field optical methods for monitoring and measurements of displacements, strains and shape of structures in power plants are reported. Digital Image Correlation, Fringe Projection and integrated thermovision-DIC method have been utilized for monitoring and control of repair processes of selected elements during general overhauls in power plants, including control of welds annealing process in boiler drum and steam pipes and measurements of geometry changes of steam pipes in “hot” and “cold” states. The experience gathered during the measurement sessions in power plants has been used for enhancement and adaptation of typical architecture of measurement systems to demanding and difficult industrial environment conditions. The measurements had been carried out in different power plants located in Poland. The possible future application of full-field optical measurement methods as the alternative to standard techniques (ultrasound, X-ray, strain gauges) and their advantages and disadvantages are discussed.
Optimised Vibration Energy Harvesting for Aerospace Applications
Authors: Wood O.J. , Featherston C.A. , Kennedy D. , Eaton Mark J. , Pullin Rhys
Published: July 2012

Accurate knowledge regarding the ongoing condition of an aircraft’s structural condition together with future life predictions enable optimal use of material, hence reducing mass, cost and environmental effects. Previous work by the authors has demonstrated the potential for using energy harvested from vibrating aircraft panels to power a self contained health monitoring system based on the use of wireless sensor nodes for an aircraft structure. However the system proposed was far from optimal. Research is being undertaken to investigate the various factors affecting the power output of such a system, including the design of the harvesters used (length, width, number of layers), their positioning and their orientation. The work presented in this paper enables the determination of the optimised positions for a series of harvesters on a representative aircraft panel, based on the use of shape functions for the various modes of vibration over the expected frequency range, to derive a function related to power output which is then optimised. A series of recommendations are made.
Practical Application of Monitoring System Based on Optical Sensors for Marine Constructions
Authors: Murawski Lech , Ostachowicz Wieslaw , Opoka Szymon , Mieloszyk Magdalena , Majewska Katarzyna
Published: July 2012

The paper presents structural health monitoring (SHM) system, dedicated to marine structures. The considered system is based on the fibre optic technique with Fibre Bragg Grating (FBG) sensors. The aim of this research is recognition of possible practical applications of the fibre optic techniques in selected elements of marine structures. SHM and damage detection techniques have a great importance (economical, human safety and environment protection) in the wide range of marine structures, especially for ships and offshore platforms. In the paper monitoring system of the Horyzont II and Dar Młodzieży ships and offshore oil platform is presented. Practical implementation of safety system based on optical sensors meets several difficulties. There has been installed the FBG system and its measurement results have been compared with classical techniques, e.g. piezoelectric accelerometers. The investigations have been performed for undamaged and damaged structure. Different types of failures have been modelled and tested. Damage detection ability has been specifying on the base of static and dynamic structural characteristics.
Practical Solution of Rail Vehicle and Track Dynamics Monitoring System
Authors: Chudzikiewicz Andrzej , Drozdziel Jozef , Sowinski Bogdan
Published: July 2012

The improvement of traveller comfort and safety, in parallel to an increase of passenger train speed, is a reason to implement monitoring systems. These systems are more often used to monitor components of railway infrastructure and vehicles. Studies in this area must be preceded by identification and a complex analysis of the railway vehicle - track system. This allows us to recognise the dynamic properties of the system and then select the appropriate place to install sensors on board the vehicle. This paper presents the results of model studies and a prototype monitoring system which is installed on a passenger electric traction unit. This system is aimed, inter alia, at monitoring the state of train suspension and the detection of some particular track geometric irregularities.
SHM System Based on Modal Filtration
Authors: Mendrok Krzysztof , Uhl Tadeusz , Maj Wojciech , Paćko Paweł
Published: July 2012

The modal filter has various applications, among the others for damage detection. It was shown, that a structural modification (e.g. drop of stiffness due to a crack) causes an appearance of peaks on the output of the modal filter. This peaks result from not perfect modal filtration due to system local structural changes. That makes it a great indicator for damage detection, which has fallowing advantages: low computational afford due to the data reduction, the structural health monitoring system based on it, is easy to automate. Furthermore the system is theoretically insensitive to environmental changes as temperature or humidity variation (global structural changes do not cause a drop of modal filtration accuracy). In the paper the practical implementation of the presented technique is shown. The developed structural health monitoring (SHM) system is described as well as results of its extensive simulation and laboratory testing. Finally the application of the system for the structural changes detection on the airplane parts is presented..
Structural Health Monitoring of Composite Material Typical of Wind Turbine Blades by Novelty Detection on Vibration Response
Authors: Dervilis Nikolaos , Barthorpe R. , Staszewski Wieslaw Jerzy , Worden Keith
Published: July 2012

New generations of offshore wind turbines are playing a leading role in the energy arena. One of the target challenges is to achieve reliable Structural Health Monitoring (SHM) of the blades. Fault detection at the early stage is a vital issue for the structural and economical success of the large wind turbines. In this study, experimental measurements of Frequency Response Functions (FRFs) are used and identification of mode shapes and natural frequencies is accomplished via an LMS system. Novelty detection is introduced as a robust statistical method for low-level damage detection which has not yet been widely used in SHM of composite blades. Fault diagnosis of wind turbine blades is a challenge due to their composite material, dimensions, aerodynamic nature and environmental conditions. The novelty approach combined with vibration measurements introduces an online condition monitoring method. This paper presents the outcomes of a scheme for damage detection of carbon fibre material in which novelty detection approaches are applied to FRF measurements. The approach is demonstrated for a stiffened composite plate subject to incremental levels of impact damage.
Structure's Condition Monitoring Based on Optical Measurements
Authors: Kohut Piotr , Holak Krzysztof , Uhl Tadeusz , Krupiński Krzysztof , Owerko Tomasz , Kuraś Przemysław
Published: July 2012

In the paper the vision-based method of civil engineering constructions in-plane deflection measurement and state monitoring is presented. The displacement field of the analyzed structure resulting from a load was computed by means of the digital image correlation coefficient. The application of homography mapping enabled the deflection curve to be computed from two images of the construction acquired from two distinct points in a space. There developed methodology, created software tool as well as experimental results obtained from tests made on lab set-ups and a civil engineering construction are investigated. The experiments are carried out on the lab setup consisting of SRL high resolution digital cameras and the steel frame loaded by a point force. The vision based method results are compared with other contact and non-contact measurement techniques. The deflection of the tram viaduct is investigated and results are compared with the data obtained by the interferometric radar.
The Active Magnetorheological Support as an Element of Damping of Vibrations Transferred from the Ground to Large-Scale Structure Supports
Authors: Bajkowski Jerzy , Jasiński Marcin , Mączak Jędrzej , Radkowski Stanisław , Zalewski Robert
Published: July 2012

The active support of a large-scale structure, made up of two elements was designed and manufactured. The first of them - piezoelectric actuator, enables the simulations of vibrations transferred from the ground to the structure. In order to minimize vibrations transmitted through the ground to the construction, the second element of the active support - a system based on magnetorheological dampers was used. The active support enables the simulations of vibrations from the ground using a piezoelectric stack controlled in a reverse feedback loop. Control signals of the feedback loop are: the volume of deformation and vibrations in the selected structures node.
The Development of the Non-Parametric Classification Models for the Damage Monitoring on the Example of the ORLIK Aircraft Structure
Authors: Dragan Krzysztof , Dziendzikowski Michal , Uhl Tadeusz
Published: July 2012

This paper presents approach for the damage growth monitoring and early damage detection in the PZL-130 ORLIK TC II turbo propeller military trainer based on the array of the PZT sensors which will be deployed in the structure of the aircraft. Special attention will be paid to the preliminary results of the statistical models which provide an automated tool to infer about the damage presence and its size. In particular the effectiveness of the selected signal characteristics will be assessed using dimensional reduction methods (PCA) and the so called averaged damage indices will be described. Verification of the several classification models based on the emerged damage indices will be presented using cross validation techniques. The preliminary results of the data collected from the subcomponents tests with the model description, as well as approach for the SHM system design will be delivered. The verification of the models results will be presented on the example of the aerospace structures.
The Phenomenon of Continuous Mode Conversion of Lamb Waves in CFRP Plates
Authors: Willberg Christian , Mook G. , Gabbert Ulrich , Pohl J.
Published: July 2012

The effect of mode conversion of Lamb waves is a well known phenomenon. Lamb waves occur in multiple modes, which can transform into each other under special conditions. Typically mode conversion takes place at discrete positions inside a structure, e.g. damages and edges. However, we observed a continuous mode conversion in a multi-layer composite plate. The symmetric S0-mode converts continuously into the A0-mode without passing a macroscopic discontinuity. In the paper this phenomenon of continuous mode conversion is investigated experimentally as well as numerically.
Applications of Self-Organizing Maps in Structural Health Monitoring
Authors: Buethe Inka , Kraemer Peter , Fritzen Claus Peter
Published: July 2012

The Structural Health Monitoring process includes several steps like feature extraction and probabilistic decision making, which need some form of data fusion and information condensation. These take place after data acquisition and before being able to decide, if a monitored structure has faced damage. Although feature selection is an important step, the processing and suitable preparation of these data are significant, influencing the potential of decision making in various ways. With Self-Organizing Maps (SOM) a multi-purpose instrument for these tasks of pattern recognition and data interpretation is presented here. Self-Organizing Maps belong to the group of artificial neural networks and by using the special map character provide the opportunity of additional visualization. Especially when monitoring a structure over a long period of time, environmental changes often occur, which can mask the effects of damage on the dynamic behavior of the structures. As one potential application of SOM, the possibility of distinguishing between environmental changes and damage of the structure is shown. In this application a self-organizing network is trained with data of the undamaged structure and via calculation of the distance to the map a damage indicator is developed. Moreover, the distinction between different damage modes of piezoelectric sensors is presented using SOM as a tool of pattern recognition and visualization. This application uses data recorded from different damage modes extracted from one specimen of a piezoelectric element. The trained network can be compared with other piezoelectric elements mounted in a similar way to be able to detect possible sensor damage. This helps avoiding false alarms even under changing environmental conditions. Both applications have been successfully used to analyze experimental data on coupon level showing the applicability of the presented concepts.
The Project of Tank Inspection Robot
Authors: Giergiel Mariusz , Buratowski Tomasz , Małka Piotr , Kurc Krzysztof , Kohut Piotr , Majkut Konrad
Published: July 2012

The paper presents the project of tank inspection robot. In order to discuss the designing process, algorithm of design has been provided. There are four design stages: the analysis of the construction problem, the synthesis, testing/improving robots construction and finally testing it. First stage of project process is divided into constructive and imitative analysis. Constructive analysis means searching for still not existing solutions of robots and detection methods. In this paper we concentrate only on constructive analysis.
The Reference Signal of Geomagnetic Field for MMM Expert Systems
Authors: Witoś Miroslaw
Published: July 2012

The first step of a methodological approach to the validation of the metal magnetic memory (MMM) method in non-destructive testing (NDT) applications and in systems used for the diagnosis of early stages of material fatigue in mechanical constructions (structural health monitoring, SHM, and prognosis health management, PHM) has been presented in the paper. The study is focused on the properties of the external natural source of magnetisation of the object under MMM examination and the impact of its components. The precise data of the Earth's geomagnetism measurements (from ground stations and satellites) and the revised model of the Earth's magnetism can be applied in order to calibrate high sensitive magnetic field sensors, validate measurement results and extend the functional capacity of the MMM method.
Vibration-Based Symptoms in Condition Monitoring of a Light Rail Vehicle
Authors: Firlik Bartosz , Tabaszewski Maciej , Sowinski Bogdan
Published: July 2012

Light rail systems have now their great return in many European cities carrying an increasing number of people every year. This increasing trend requires suitable operation and maintenance standards for both vehicle and track. Furthermore, in order to make a public transport competitive to private transport, its very important to increase safety and ride comfort for passengers. The aim of the presented work was to determine the suitable vibration-based symptoms for the identification of a light rail vehicle technical state, as well as the development of appropriate methodology to use the information contained therein. Both simulation and experimental phase are described. The present analysis is focused mainly on the suspension state monitoring, but some others failures were also considered.
Weigh-in-Motion System Testing
Authors: Sekuła Krzysztof , Świercz Andrzej
Published: July 2012

The paper presents some results of research on the Weight-in-motion (WIM) system. The device is used for identification of loads on the road surface generated by traveling vehicles. The proposed approach utilizes the piezoelectric measurement techniques to monitor strain development in a deformable body and eventually these measurements are used for tire-pavement load identification. An advantage of the proposed concept is that no additional limitation for a vehicle velocity and direction is required in order to make the measurement feasible. The device allow to identify many parameters which can be stored for statistical and planning purposes. When an overload or an exceed in speed limit is detected the data can be sent for penalization purposes. The research includes a computer simulation of the bending plate detector using the Finite Element Method (FEM). Its objective is to validate the concept as well as to test some factors which are important with respect to the proposed load identification methodology. An experimental research involved field tests on the WIM system using a bending plate detector and inductive loops to detect a vehicle.
Wind Turbine Main Bearing Diagnosis - A Proposal of Data Processing and Decision Making Procedure under Non Stationary Load Condition
Authors: Zimroz Radoslaw , Bartelmus Walter , Barszcz Tomasz , Urbanek Jacek
Published: July 2012

Condition Monitoring of bearings used in Wind Turbines (WT) is an important issue. In general, bearings diagnostics is well-recognized field; however it is not the case for machines working under non-stationary load. An additional difficulty is that the Main Bearing (MB) discussed here, it is used to support low speed shaft, so dynamic response of MB is not clear as for a high-speed shaft. In the case of varying load/speed a vibration signal acquired from bearings is affected by operation and makes the diagnosis difficult. These difficulties come from the variation of diagnostic features caused mostly by load/speed variation, low energy of sought features and high noise levels. In the paper a novel diagnostic approach is proposed for main rotor bearings used in wind turbines. From a commercial diagnostic system two kind of information have been acquired: peak-to-peak vibration acceleration and generator power that is related to the operating conditions. The received data cover the period of several months, when the bearing has been replaced due to its failure and the new one has been installed. Due to serious variability of the mentioned data, a decision-making regarding the condition of bearings is pretty difficult. Application of classical statistical pattern recognition for data from the period A (bad condition) and the period B (after replacement, good condition) is not sufficient because the probability density functions of features overlap each other (pdf of peak-to-peak feature for bad and good conditions). Proposed approach is based on an idea proposed earlier for planetary gearboxes, i.e. to analyse data for bad/good conditions in two-dimensional space,feature - load. It is shown that the final data presentation is a good basis to the very successful classification of data (i.e. recognition of damaged and undamaged bearings).
Wireless Power Transmission Using Ultrasonic Guided Waves – Electric Circuit Measurement and Simulation
Authors: Kural Aleksander , Pullin Rhys , Featherston C.A. , Lees J. , Naylon J. , Paget C. , Holford Karen M.
Published: July 2012

A project investigating the possibility to transmit electrical power (several mW) along the structure of an aircraft by using an intermediate medium of ultrasonic Lamb waves is being carried out at Cardiff University in conjunction with Airbus. This power supply method is aimed at wireless, surface-bonded sensor packages, primarily for the aircraft structural health monitoring (SHM) applications. It is expected to replace conventional batteries or energy harvesting devices. This paper presents methods of piezoelectric transducer characterisation, electric power measurement and electric circuit simulation that were developed in support of the ultrasonic power transmission project. The unique combination of low power and a high AC frequency range (up to 200 kHz) precluded the use of conventional power measurement instruments and called for a tailored system and software to be developed. Two approaches were developed: one relying on the measurement of the ultrasonic transducers impedance characteristics and their subsequent use in a circuit simulation; and another relying on the direct measurement of voltage waveforms in the power transmission setup. The two methods were found to be capable of producing closely matching results up to 300 kHz. Results of early power transmission trials are also presented. The optimum approach resulted in 1 mW of power transmission over a distance of 74 cm in a 1.5 mm thick aluminium plate.
Assessment of Bonded Patch Bridge Repairs Using Acoustic Emission and Acousto-Ultrasonics
Authors: Pullin Rhys , Eaton Mark J. , Pearson Matthew R. , Pollard Christopher , Holford Karen M.
Published: July 2012

Composite patch repairs are being increasingly used throughout bridge structures in the UK. These patches offer a convenient and strong repair providing that the bond used to adhere the patch to the structure retains its integrity. Acoustic emission (AE), a passive approach and Acousto-Ultrasonic (AU), an active approach offer two methodologies for monitoring the structural bond and ensuring the patch repair remains effective. An experimental program was developed to assess the suitability of using AE and AU for monitoring the bond. Two concrete beams were manufactured and pre-cracked in three point bending prior to being repaired using a bonded composite patch. Two static tests were then completed to assess the performance of the two techniques for monitoring the bond. Results were compared with strain gauges adhered to the bonded patch and visual observation. For active monitoring a baseline of signals were captured at a known load and post damage a further series was captured at the same load. The signals sets were then compared using a cross correlation function technique. A simple accumulative acoustic energy analysis was then completed for the passive data. Results demonstrated that both techniques can be utilised to monitor the bonded structure. By comparing the results with those recorded by the strain gauges and visual inspection it was possible to demonstrate the successful effectiveness of the techniques for detecting global damage but specific debonding events would require further investigations.
Development of Lamb Waves-Based SHM Systems
Authors: Ambrozinski Lukasz , Stepinski Tadeusz , Uhl Tadeusz , Ochonski Janusz , Klepka Andrzej
Published: July 2012

Guided waves (GW) based methods are a promising tool for structural health monitoring (SHM) of plate-like metallic and composite structures in which high safety standards are required. In this paper we present research with the aim to design and manufacture a prototype of Lamb waves (LW) SHM system. Two approaches can be applied for SHM of plate-like structures. One of them can be based on a sparse array and damage imaging involving incoherent summation of signals envelope. The second approach involves phased arrays with transducers spaced at a distance lower than half wavelength of the excited Lamb-mode. The influence of an arrays parameters on beamforming of Lamb waves is discussed in the case of linear array. It appears that an unequivocal localization of damage on a plate requires a 2D arrays topology; therefore a star-shaped active array was designed and manufactured for the developed SHM system. Two signal processing approaches were applied for that array, the standard one, based on the delay and sum (DAS) synthetic aperture focusing scheme, and the second one, using a self-focusing technique to obtain the separate images for each scatterer existing in the plate.
Defect Propagation in Broad-Area Diode Lasers
Authors: Hempel Martin , Tomm Jens W. , Zeimer Ute , Elsaesser Thomas
Published: July 2012

A simple model is presented for the propagation of macroscopic defects within the quantum well (QW) plane of broad-area high power diode lasers. The catastrophic optical damage (COD) effect is considered the mechanism for creating an initial damage site and further development of defect pattern. The relations between the parameters used in the model and the actual physical properties of the semiconductor materials are discussed. Experimentally observed damage patterns are well described.
Kinetics of Defect Propagation during the Catastrophic Optical Damage (COD) in Broad-Area Diode Lasers
Authors: Tomm Jens W. , Hempel Martin , Elsaesser Thomas
Published: July 2012

The initial phase of defect propagation in broad area diode lasers, which are affected by the catastrophic optical damage (COD) effect, is studied. The decay of laser power within the first several 100 ns is found to be determined by defect propagation. When analyzing different device designs, a correlation is found between defect propagation velocities and thermal resistances of the materials vicinal to the quantum well, being the main heat source. The findings are confirmed by direct inspection of the defect pattern in opened devices.
Nondestructive Measurement of Carrier Density in GaAs Using Relative Reflectivity of Two Terahertz Waves
Authors: Hamano Akihide , Ohno Seigo , Minamide Hiroaki , Ito Hiromasa , Usuki Yoshiyuki
Published: July 2012

A new nondestructive method using terahertz waves for determining the carrier density of GaAs is proposed. The reflectance around the longitudinal optical (LO) phonon frequency changes with carrier density, whereas the reflectance around the transverse optical (TO) phonon frequency is constant. The relative reflectance, which is evaluated from the reflectance at the two frequencies related to the TO and LO phonon, as a function of the carrier density of GaAs was calculated from the dielectric function. A broadband tunable terahertz source is convenient for producing two waves around these phonon frequencies. Imaging of n-type GaAs wafer using this new terahertz method is described.
Characterization of Dislocation Structures in Hexagonal SiC by Transmission Electron Microscopy
Authors: Sugawara Yoshihiro , Yao Y. , Ishikawa Yukari , Danno Katsunori , Suzuki Hiroshi , Bessho Takeshi , Kawai Yoichiro , Ikuhara Yuichi
Published: July 2012

We developed the transmission electron microscopy (TEM) sample preparation technique for the low dislocation density of 4H-SiC by combining the KOH+Na2O2 (KN) etching and the focused ion beam (FIB) microsampling technique. The dislocation under sea-shell pit was then characterized by large-angle convergent-beam electron diffraction (LACBED). It is demonstrated that this method is powerful for evaluating Burgers vectors of dislocations. Burgers vector of the measured basal plane dislocation (BPD) is determined to be b=1/3[-12-10]. Two-beam bright-field (TBBF) imaging identified the rotating direction of the threading screw dislocation (TSD) is counter-clockwise.
Lock-In Thermography and Related Topics in Photovoltaic Research
Authors: Breitenstein Otwin
Published: July 2012

In this contribution the basic principles of DLIT (dark lock-in thermography) are introduced and typical application examples are shown. These results are compared with that of other solar cell characterization techniques like electroluminescence (EL) and photoluminescence (PL) imaging, which are also very popular in Germany. It will be shown that these techniques are largely complementary to each other. Luminescence techniques are most sensitive for the detection of local recombination centers in the bulk and of series resistance problems of the cells, whereas DLIT is most effective for investigating all problems being connected with the dark current of the cells. A new DLIT technique is introduced which allows a separate imaging of the so-called diffusion current and the recombination current. These two contributions of the dark current are based on different physical mechanisms (recombination in the bulk and in the depletion region, respectively), and their spatial distributions differ significantly. Such investigations are impossible by applying luminescence-based imaging techniques.
EBIC Study on Metal Contamination at Intra Grain Defects in Multicrystalline Silicon for Solar Cells
Authors: Sameshima Takashi , Miyazaki Naoto , Tsuchiya Yuki , Tachibana Tomihisa , Ohshita Yoshio , Arafune Kouji , Ogura Atsushi
Published: July 2012

Interactions between intra-grain defects and metal impurities in multicrystalline silicon (mc-Si) were evaluated. After metal contaminations, EBIC contrasts at > 1.5o SA-GBs were more enhanced than those at Ni/1000 oC > Ni/600 oC. These results might attribute to Fe atoms form deeper energy levels of recombination centers than Ni atoms and the gettering abilities at SA-GBs depend on the misorientation angles. Many dark spots were observed in EBIC images in the Ni/600 oC. Since the dark spots corresponded to the etch pits, the dark spots might be dislocations decorated with Ni. The gettering abilities of SA-GBs depended on the misorientaion angles, and the recombination properties at SA-GBs and dark spots, such as small defects after metal contamination were different by annealing temperatures and the types of metal impurities.
Behaviour of Light Induced Defect Generation and Carrier Lifetime Degradation in Solar Grade Silicon
Authors: Rezgui Béchir Dridi , Mong-The Yen Virginie , Périchaud Isabelle , Barakel Damien , Pasquinelli Marcel , Palais Olivier
Published: July 2012

Light-induced defect generation seriously reduces the minority-carrier lifetime of crystalline silicon (c-Si) wafers which causes a decrease in solar cell efficiency. In this paper we investigate the impact of boron-oxygen complexes and iron impurities on the light induced minority-carrier lifetime degradation in c-Si, comparing electronic grade and upgraded metallurgical grade materials. For the later, the characteristic of the decay process is shown to be composed of a fast initial decay and a subsequent slow asymptotic decay. We conclude that the dissociation of iron-boron pairs must be taken into account to explain the light-induced lifetime reduction.
Considerations on the Effect of Interstitial and Precipitated Fe in Intentionally Fe-Doped mc-Silicon
Authors: Azizi Maral , Meissner Elke , Friedrich Jochen
Published: July 2012

In this work laboratory scale multicrystalline silicon ingots were grown which have been intentionally contaminated with iron in the range between 10 to 400 ppmw by adding FeSi2 to the silicon feedstock. It is shown that an iron contamination at these high levels does not result in a structural breakdown of the columnar grain growth regime because constitutional supercooling could be avoided by strong mixing of the melt in the present crystal growth experiments. The minority carrier lifetime mappings are dominated by the iron contamination and show the distribution of the impurity over the ingot height. The measured values of the specific electrical resistivity show a significant drop from 40 to below 20 Ωcm for a contamination level of 10 ppmw Fe probably due to interactions of iron with thermal donors. At higher contamination levels the specific resistivity increases significantly with increasing iron concentration compared to the 10 ppmw ingot. Above 400 ppmw iron the specific resistivity drops below the initial value for nominally iron free material. These results indicate that interstitial iron shows a donor-like behavior in multicrystalline silicon and precipitated iron decreases the specific resistivity.
High-Speed Deep-Level Luminescence Imaging in Multicrystalline Si Solar Cells
Authors: Okayama Futoshi , Tajima Michio , Toyota Hiroyuki , Ogura Atsushi
Published: July 2012

We demonstrated high-speed imaging of photoluminescence (PL) and electroluminescence (EL) for not only band-to-band but also multiple deep-level emissions in a multicrystalline Si solar cell. We used a cooled InGaAs camera with a photosensitive range of 900 - 1700 nm equipped with band-pass filters for the selective detection of various deep-level emissions. The exposure time for imaging was only 1 - 10 seconds. Comparisons of the present PL images with the microscopic PL mappings confirmed for us that essentially the same luminescence patterns were obtained.
Photoluminescence Imaging and Wavelength Analysis of Basal Plane Frank-Type Defects in 4H-SiC Epilayers
Authors: Kamata Isaho , Zhang Xuan , Tsuchida Hidekazu
Published: July 2012

Frank-type defects on a basal plane have been investigated using photoluminescence (PL) imaging microscopy and wavelength profile measurement. A wide range of emission in the near-infrared wavelength was observed from a Frank partial dislocation at the edge of the defect, while a narrow emission at around the visible light range was obtained from a stacking fault region. The emissions from a stacking fault region of three kinds of basal plane Frank-type defects were confirmed to have different wavelengths depending on their stacking structures.
Structural Study of Small Angle Grain Boundaries in Multicrystalline Si
Authors: Miyamura Yoshiji , Harada Hirofumi , Ito Shun , Chen Jun , Sekiguchi Takashi
Published: July 2012

Small angle grain boundaries (SA-GBs) are known as the most electrically active defects in multicrystalline silicon. These SA-GBs are classified in “general” and “special” by the normal and strong electrical activity at 300K, respectively. In this study, the origins of these electrical activities of SA-GBs were elucidated by using electron beam induced current (EBIC) and transmission electron microscopy (TEM). It was found that both general and special SA-GBs were composed of edge-type and 60 deg / screw dislocations. The fraction of edge dislocation in special SA-GB was higher than that of general one, which suggests that strong electrical activity is mainly originated in edge dislocations.
Combinatorial Synthesis Study of Passivation Layers for Solar Cell Applications
Authors: Ikeno Norihiro , Tachibana Tomihisa , Lee Hyunju , Yoshida Haruhiko , Arafune Koji , Satoh Shinichi , Chikyow Toyohiro , Ogura Atsushi
Published: July 2012

We investigated the new materials applicable for the field effect passivation layer in crystalline Si solar cells, ZrO2-Al2O3 and ZrO2-Y2O3 binary systems, by using combinatorial synthesis method. As-deposited samples indicated hysteresis curves and flat band-voltage (VFB) shifts at capacitance-voltage (C-V) measurements. After oxygen gas annealing (OGA) at 700 oC for 5min, an improvement of the hysteresis and a positive shift of VFB were observed. OGA process influenced defects density related to decreasing oxygen vacancy. OGA processed ZrO2 incorporated with 20 % Al2O3 and 15 % Y2O3 structures showed the maximized negative fixed charge of -5.8 × 1012 cm-2 and -7.8 × 1012 cm-2 in each system, respectively, suggesting that the ZrO2 based alloy systems were revealed to be the promising material for the passivation in the solar cell application.
Change of the Characterization Techniques as Progress of CuInSe2-Based Thin-Film PV Technology
Authors: Kushiya Katsumi , Sugimoto Hiroki , Chiba Yoshiyuki , Tanaka Yoshiaki , Hakuma Hideki
Published: July 2012

In the CuInSe2(CIS)-based thin-film PV technology, various characterization techniques have been applied to measure the composition, crystal structure, depth profile and defect chemistry and so on, since Boeing Aerospace, for the first time, has come to the 10 % milestone in a thin-film form in 1980 by fabricating a very small single cell with top grids. More advanced and comprehensive characterization techniques are being applied after over 18 % total-area efficiency was consistently achieved employing the “three stage method”, which was developed by National Renewable Energy Laboratory (NREL). Comparing to the CIS-based absorber, there are not so many researches to investigate the absorber/buffer interface because the buffer is too thin to analyse separately and precisely and there are quite limited information on reaction pathways and composition of the buffer layer. However, in order to achieve the aperture-area efficiency of over 18 % on over 800cm2-sized large-area integrated circuits, it is remarkably important how to enhance the quality of absorber/buffer interface. Therefore, analytical works to understand how to improve the FF should tend to be more and more important.