bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Wavelet Packet-Based Crack Detection for a Beam under the Moving Load
Authors: Zhang Wei Wei , Wang Zhi Hua , Ma Hong Wei
Published: September 2009

The objective of this study is to show the potential of the crack detection method based on Wavelet Packet Transform (WPT), which is depending on the response at a single point on a beam subject to moving load. In this paper, an ANSYS model of a cracked beam is established. The moving load is transient analyzed by shifting the point of the concentrated force. The response at mid-span of the beam is calculated and wavelet packet transformed. The crack on the beam can be found by the abnormal signal in WPT branches. The size is also estimated by a defined damage index (Dindex) which relates to the energy of the abnormal signal. Finally, the effects of both crack location and wavelet selection on Dindex are discussed in detail.
Fault Damage Power and Self-Recovery System of Machinery
Authors: Gao Jin Ji , Wang Wei Min , He Li Dong , Xu Hong
Published: September 2009

Animals possess the function of self-recovery for adapting the change in their living conditions. Can machinery, by bionic design, just like animals, also possess the function of self-recovery for making itself free of fault, or for eliminating fault automatically during operation In this paper, a new theory of Engineering Self-recovery is discussed, which could provide theoretical basis and new methodology for creating a new generation of machinery with fault self-recovery function. The engineering self-recovery theory is different from engineering cybernetics. Engineering cybernetics endows machinery with purposive behavior which originally is one of animal’s common characteristics, while engineering self-recovery theory endows machinery with the new function of fault self-recovery which originally is another one of animal’s common characteristics. Under the guidance of engineering cybernetics, the automation of machinery has come true. While under the guidance of engineering self-recovery theory, a new generation of machinery with the new function of fault self-recovery could also be realized.
The self-recovery system, which can provide fault self-recovery force to restrain fault force, is investigated in detail. Based on fault mechanism and risk analysis, and by bionic design, a fault self-recovery system, which is a dynamic system to store, supplement and transfer the self-recovery force, is endowed to a machine with the ability to maintain the machine in a health state.
Also, the research in engineering application of the new concept, fault self-recovery, is on the way. As an example, the new concept centrifugal compressor with fault self-recovery function is discussed here with axial displacement and flow induced vibration fault self-recovery as examples to show the steps of fault self-recovery system construction such as fault mechanism, necessity, determination, possibility, fault tolerance, limitation and execution.
Crack Size Estimation Using a Combination of Cross Correlation and Phase Shift Correction in Ultrasonic Time-of-Flight Diffraction Method
Authors: Zhang Yong Hong , Zuo Ming J. , Wang Xiao Dong
Published: September 2009

The ultrasonic time-of-flight-diffraction (TOFD) detection method has been widely used in crack size assessment. The key issue in TOFD is to determine the arrival time of crack tip diffracted signal. In the traditional cross correlation method, the resulting maximum peak of cross correlation function between two signals indicates the time of flight between them. In practical ultrasonic measurement, the transmission wave may be distorted and phase shift may be introduced. This paper presents a method using cross correlation and phase shift correction to improve the accuracy of crack sizing in the TOFD framework. The resulting maximum peak of the cross correlation function between two signals combining with time delay introduced by phase shift determine the arrival time of diffracted signal. Experimental results are used to demonstrate the advantage of the proposed method.
Estimation of Crack Parameters through WFEM and Neural Network
Authors: Li Bing , Zhuo Jie , He Zheng Jia
Published: September 2009

This paper presents the application of the wavelet finite element methods (WFEM) and neural network to crack parameters estimation and discusses the accuracy and efficiency of this method. The crack is presented by a rotational massless spring, and the natural frequencies for various crack parameters (location and depth) are obtained through WFEM. The neural network is then applied to establish the mapping relationship between the natural frequencies and the crack parameters, which uses feed-forward multiplayer neural networks trained by back-propagation, error-driven supervised training. With this trained neural network, the crack location and depth is estimated through using the measured natural frequencies as the input. The results of a cantilever beam experiment indicate that the estimating error of crack location is less than 3%, and the error of crack depth is less than 2%.
The Effects of Blockage on the Propagation of Acoustic Waves in the Liquid-Shell Coupled System
Authors: Duan Wen Bo , Gu Feng Shou , Dupère Iain , Zhong Shan , Ball Andrew
Published: September 2009

The free vibration of a fluid/structure system consisting of a cylindrical blockage submerged in a liquid enclosed by a cylindrical shell is investigated for the purpose of pipe line transportation monitoring. The wavenumbers are obtained and the reflection and transmission characteristics of these waves at the blockage interfaces are investigated theoretically. Reflection and transmission ratios are obtained in the axisymmetric mode, as functions of frequency. High order modes play an important role in the near field of the discontinuity and are taken into account.
Results of Nondestructive Inspection of Layered Composites Using IR Thermography and Ultrasonics
Authors: Constantin Nicolae , Mihai Alexandrina , Anghel Viorel , Găvan Mircea , Sorohan Ştefan , Hillger Wolfgang , Sheerer Michael
Published: September 2009

Polymeric layered composites exhibit a variety of damages following in service loading conditions, like delamination, matrix cracking or even fibre breaking. Detection of such damages and assessing their extension and severity is vital during maintenance cycle, in view of keeping the normal operational reliability. For local inspections, IR thermography and ultrasonic scanning are among the best valued NDT methods. The paper describes the inspections performed by IR active thermography, in different variants, and pulse-echo ultrasonic scanning on GFRP. A variety of layered composites and defects/damages were inspected and the results are evaluated independently, in some cases being compared each other, with valuable conclusions for the users of the mentioned NDI techniques.
Bayesian Logic Applied to Damage Assessment of a Smart Precast Concrete Element
Authors: Zonta Daniele , Pozzi Matteo , Wu Hua Yong , Inaudi Daniele
Published: September 2009

This paper presents the laboratory validation of a prototype optic-fiber instrumented structural element. The element is a reduced-scale reinforced concrete beam, of dimensions 3.8×0.3×0.5m that can be pre-stressed by an internal Dywidag bar. The sensing technology is based on a multiplexed version of the SOFO strain sensor, prepared in the form of a 3-field smart composite bar; in-line multiplexing is obtained by separating each measurement field through broadband FBGs. The experiment aims to identify the response of the sensors to differing damage conditions artificially produced in the element, including cracking and loss of prestressing. A numerical algo-rithm, based on Bayesian logic, is applied to real-time diagnosis: by processing the sensor meas-urements and prior information, the method assigns a posterior probability to each assumed damage scenario, as well as the updated probability distributions for each relevant structural parameter. With respect to classical damage detection approaches, the merit of those based on Bayesian logic is to provide not only information on the damage, but also the degree of confidence in this informa-tion. The paper discusses the ability of the system to identify the differing damage conditions. The reported test clearly shows that an occurrence such as a loss of prestressing can be recognized early with a high degree of reliability based on the strain data acquired.
Assessment, Strengthening and Validation of Prestressed Damaged Beams
Authors: Della Sala Lucio , Cerone Rosario , Gennari Santori Alberto , Tommasini Mauro
Published: September 2009

The paper describes the evaluation of the actual conditions, the repairing design criteria and procedures, and the final validation tests carried out on a severely damaged prestressed bridge in southern Italy.
In the first phases several release tests have been performed on damaged and, for comparison, on sound beams, with the aim of evaluating the residual prestressing stress acting both on concrete and on tendons. In particular, the tests on concrete have been carried out by extracting cores which have been previously instrumented with strain-gages; in a similar way, the strands were tested by gluing a micro strain-gage on a singular wire of a strand and the cutting the wire itself.
The test results were used for optimising the design of an adjunctive prestressing system, consisting in 6 external unbounded cables and in a continuous FRC reinforcing of the bottom wing. The tensioning procedure of the external cables of each beam was then monitored by means of 12 strain-gages installed on concrete at mid span and at the two support sections, and by measuring the vertical deflection using laser optical levels.
The validation of the repairing works was finally performed by a static load acceptance test, performed using the same apparatus previously adopted for the tensioning monitoring.
Modal Approach for Forced Vibration of Beams with a Breathing Crack
Authors: Baeza Luis , Ouyang Hua Jiang
Published: September 2009

This paper presents a method for the vibration of a beam with a breathing crack under harmonic excitation. The infinitely thin crack is characterised by a parameter that takes into account the shape and the depth of the crack. The closed- and open-crack states are both modelled by a modal approach: two sets of equations of motion cast in the modal coordinates of their individual mode shapes. The state change (from closed to open or vice versa) involves the calculation of the modal coordinates associated with the new state from the modal coordinates of the previous state. By imposing the continuity of displacement and velocity the beam at the instant of the state change, the matrix that transforms the modal coordinates from one state to the other is determined and proved to be the Modal Scale Factor matrix. This analytical approach takes advantage of exact nature and mathematical convenience of beam modes and is time-efficient. Forced vibration at various values of crack parameter is determined. It is found that as decreases (crack length increases) the vibration becomes increasingly erratic and finally chaotic.
FE Model Updating for Damage Detection – Application to a Welded Structure
Authors: Husain Nurulakmar Abu , Snaylam Andy , Khodaparast Hamed Haddad , James S. , Dearden Geoff , Ouyang Hua Jiang
Published: September 2009

Finite Element (FE) model updating is initially developed to update numerical models of structures to match their experimentally measured modal properties (i.e., natural frequencies and modes). In FE model updating, uncertain physical parameters of a structure are modified so that the discrepancies between the numerically estimated and experimentally measured modal properties are minimized. The process of updating is employed not only in parameter identification; it can also be developed for structural damage identification.
In this work, a welded structure that is intended to represent a common configuration used in automotive body construction is investigated. It is known that presence of any damage in the welds of such a structure could affect its dynamic behavior. So, in theory modal test data can allow damage to be assessed accurately. As a typical automotive body contains thousands of welds, the effects of damage in the welds could be influential.
The FE model updating process using experimental data is presented. It is carried out using NASTRAN optimization code. The procedure aims to adjust the uncertain properties of the FE model (from the weld joints) by minimizing the differences between the measured modal properties and the corresponding numerical predictions. The initial parameter values used in the numerical model are the nominal values. The procedure brings the numerical results of the structure as close as possible to the experimental ones, according to an objective function, therefore altering some of the FE model parameters of the structure. It may be concluded that when the identified values of certain parameters deviates from the nominal values to certain extent, there is a fault or damage at that particular joint.
Particle Impact Damping in Two Dimensions
Authors: Bhatti Riaz Ahmad , Wang Yan Rong , Wang Zhou Cheng
Published: September 2009

Particle impact damping (PID) is a technique of achieving high structural damping with small metallic particles embedded within a cavity that is attached to vibrating structure. This is a highly non-linear damping mechanism in which energy dissipation is primarily related to friction and impact phenomena. In this work a simple yet detailed analytical model is presented to study PID in two dimensions under transient vibrations. Normal as well as oblique impacts are considered. The effect of cavity size and acceleration amplitude on PID is studied and the results are supported by experiments. Fairly good agreement is found between the theory and the experiment.
GA-SVR Based Bearing Condition Degradation Prediction
Authors: Feng Fu Zhou , Zhu Dong Dong , Jiang Peng Cheng , Jiang Hao
Published: September 2009

A genetic algorithm-support vector regression model (GA-SVR) is proposed for machine performance degradation prediction. The main idea of the method is firstly to select the condition-sensitive features extracted from rolling bearing vibration signals using Genetic Algorithm to form a condition vector. Then prediction model is established for each feature time series. And the third step is to establish support vector regression models to obtain prediction result in each series. Finally, the condition prognosis can be obtained through combing all components to form a condition vector. Vibration data from a rolling bearing bench test process are used to verify accuracy of the proposed method. The results show that the model is an effective prediction method with a higher speed and a better accuracy.
Harvesting Vibration Energy for Structural Health Monitoring in Aircraft
Authors: Featherston C.A. , Holford Karen M. , Greaves Bea
Published: September 2009

The concept of harvesting energy is not a new one: there has been an interest in this area for around 10 years. Devices typically use either vibration (rigid body motion) or thermal gradients and can harvest sufficient energy to power telemetry, small devices or to charge a battery or capacitance device. However, for the new generation of aircraft, (both fixed wing and rotating) there is now an urgent need to develop energy harvesting systems in order to provide localised power for sensors in structural health monitoring systems (SHM). By implementing SHM, aircraft manufacturers can benefit from improved safety, reduced maintenance and extended aircraft life.
The work presented examines the feasibility of designing an energy harvesting system powered by the vibrations of aircraft panels generated in flight. PZT (lead zirconate titanate) harvesters are bonded to an aluminium alloy panel, representative of an aircraft wing panel which is vibrated across a range of amplitudes (up to + 0.2mm) and frequencies (up to 300Hz). By recording voltage and current outputs from each harvester, generated power is calculated which when normalised for area and mass indicates values of up to 7.0 Wm-2 and 2.5Wkg-1 respectively, representing mechanical to electrical energy conversion efficiencies of up to 35% dependant on frequency of vibration. From these values it is estimated that a harvester area of down to 71cm2 or mass of as little as 20g is necessary to meet the current minimum power requirements of SHM systems of 50mW.
With predicted reductions in sensor power consumption indicating system power requirements in the order of 0.1-1mW, this work shows that piezoelectric energy harvesting has future potential for powering aerospace SHM systems.
Application of Compressive Sampling for Accelerometer Signals Used in Structural Health Monitoring
Authors: Bao Yue Quan , Beck James L. , Li Hui
Published: September 2009

In structural health monitoring (SHM) of civil structures, data compression is often needed for saving the cost of data transfer and storage because of the large volumes of sensor data generated from the monitoring system. The traditional framework for data compression is to first sample the full signal, then to compress it. Recently, a new data compression method named compressive sampling (CS) has been presented, that can acquire the data directly in compressed form by using special sensors. In this paper, the potential of CS for data compression of vibration data is investigated using simulation of the CS sensor algorithm. The acceleration data collected from the SHM system of Shandong Binzhou Yellow River Highway Bridge is used to analyse the data compression ability of CS. For comparison, the wavelet transform based and Huffman coding methods are also employed to compress the data. The results show that CS is useful for compression of vibration data in SHM of civil structures.
Gearbox Condition Estimation Using Cyclo-Stationary Properties of Vibration Signal
Authors: Zimroz Radoslaw , Bartelmus Walter
Published: September 2009

The paper explores the cyclo-stationary properties of vibration signals for estimation of gearbox condition. The advantage of such approach may be clearly seen especially for so called multi-faults problem, i.e. for more than one faults that occurred in the system. In complex mechanical systems like multistage gearboxes, such situation may be often seen. Although this approach becomes more and more popular, it has been noticed that there is difficult to find examples highlighting its potential, especially for real industrial situations. In order to fill partially the gap, the paper deals with the multi fault detection in complex mechanical systems like multi-stage gearboxes: fixed axis and planetary. It has been discussed that during the operation in such machines many faults may appear simultaneously and the classical method like envelope analysis is difficult to use. The paper presents the use of cyclo-stationary properties of signals to identify and characterize sources of modulation. From Spectral Correlation Density Map or more precisely Spectral Coherence Map have been observed the number of sources with different properties of modulation. It is shown that the number of harmonics is important for a kind of fault extraction and interpretation. This approach has been applied to two, three and five stage gearboxes used in mining industry. Vibration signals received in industrial environment during normal operation of objects are considered. It has been also proposed the simple diagnostic feature to estimate the changes of condition with application to a planetary stage in a 5-stage gearbox.
Thermoelectric Energy Harvesting for Wireless Sensor Systems in Aircraft
Authors: Featherston C.A. , Holford Karen M. , Waring Greg
Published: September 2009

The use of structural health monitoring in the aerospace industry has many benefits including improved safety, reduced maintenance and extended aircraft lifecycles. A major focus of current research in this area is the development of wireless sensor 'nodes‘ which rely on batteries as a power source, severely limiting the product lifespan. This paper presents the results of work carried out to examine the feasibility of replacing or supplementing existing battery power supplies using thermoelectric energy conversion from ambient temperature differences in aircraft.
An average power demand of 1mW over a typical sensor duty cycle is identified for current wireless sensor hardware. Temperature differentials between the wing fuel tanks and external air are determined and a theoretical model for thermoelectric energy harvesting potential is developed. Results indicate that average power outputs sufficient for the intended application of 6.6-22mW could be achieved during flight, based on a commercially available thermoelectric module of 30×30×4.1mm.
An experimental investigation of the performance of this module when subjected to appropriate temperature conditions, using a Ranque-Hilshe vortex tube to generate easily controlled temperatures to -25°C is described. Excellent consistency is demonstrated between theoretical predictions and experimental results, confirming the accuracy of the theoretical model.
Condition Monitoring of CI Engine Running on Biodiesel Using Transient Process
Authors: Tesfa B. , Mishra R. , Gu Feng Shou , Ball Andrew
Published: September 2009

Various research groups across the globe have developed models for engine condition monitoring and fault diagnosis based on the data from steady state performance measurements over the last two decade. However, these performance data are not amenable for easy collection in some situations and some of the data may show little performance deviation at the steady state conditions of operation. The aim of this study is to identify engine operating conditions and parameters that can be used to develop a diagnostic tool for internal combustion (CI) engine running on biodiesel blends fuel. Ricardo Wave Software was used to stimulate healthy and degraded engine. The degraded condition of operation was created by forcing one injector to work with 90%, 80% and 70% of the normal fuel flow efficiency. The measurable performance parameters such as brake power, brake torque and exhaust temperature and CO emission have been used to compare the deviations during steady and transient condition. From the comparison of the data obtained from transient and steady state simulation of the engine with and without injector fault, it can be concluded that the transient parameters show higher deviations and hence are better suited for condition monitoring and diagnostic modelling in engine working speed.
Bispectrum Analysis of Motor Current Signals for Fault Diagnosis of Reciprocating Compressors
Authors: Naid Abdelhamid , Gu Feng Shou , Shao Yi Min , Al-Arbi Salem , Ball Andrew
Published: September 2009

The induction motor is the most common driver in industry and has been previously proposed as a means of inferring the condition of an entire equipment train, predominantly through the measurement and processing of power supply parameters. This has obvious advantages in terms of being non-intrusive or remote, less costly to apply and improved safety. This paper describes the use of the induction motor current to identify and quantify a number of common faults seeded on a two-stage reciprocating compressor. An analysis of the compressor working cycle leads to current signal the components that are sensitive to the common faults seeded to compressor system, and second- and third-order signal processing tools are used to analyse the current signals. It is shown that the developed diagnostic features: the bispectral peak value from the amplitude modulation bispectrum and the kurtosis from the current gives rise to reliable fault classification results. The low feature values can differentiate the belt looseness from other fault cases and valve leakage and inter-cooler leakage can be separated easily using two linear classifiers. This work provides a novel approach to the analysis stator current data for the diagnosis of motor drive faults.
Experimental Study on Rubbing Acoustic Emission for Rotor-Bearing System Based on Parameter Analysis
Authors: He Yong Yong , Yin Xin Yun
Published: September 2009

Rubbing between the rotor and the stator is the frequent fault and will cause very serious accident, even catastrophe, to rotating machinery. Therefore, timely detection of such rubbing is very important avoid severe consequences. Vibration based methods are very mature and traditional methods but not effective to detect incipient rubbing in rotating machinery. Rubbing between the rotor and the stator will cause elastic strain in the rubbing location and thus can produce acoustic emission (AE). Apparently, such AE contains direct and abundant information about the rubbing and can be used to detect and diagnose such fault effectively. In this paper, the AE based method is proposed for detecting and identifying the rubbing of the rotor-bearing system. An experimental study is presented to investigate the characteristics and features of rubbing AE using parameter analysis method. The results show that AE is very sensitive to the rubbing and AE parameters can reveal the characteristics and features of rubbing AE. Parameter analysis demonstrates that rubbing AE contains multiple modals, which will attenuate with propagation by negative exponent manner.
Research on the Fault Diagnosis Technology of Diesel Engine Based on the Instantaneous Speed
Authors: Hu Yi , Zhou Rui Ping , Yang Jian Guo
Published: September 2009

The instantaneous speed signals of diesel contain lots of information about machine states, which is useful for fault diagnosis of diesel engine. Mixed fault diagnosis method of diesel engine based on the instantaneous speed has been proposed, which combines with the lower order angular vibration amplitude and SOM neural network to diagnose the cylinder pressure fault, then extracts three feature parameters of instantaneous speed to locate the fault cylinder. The method can detect the cylinder pressure fault accurately in diesel engine and locate the fault cylinder. The experimental confirmation shows that it has good effect on fault diagnosis of diesel engine.
Research on Nonlinear Process Monitoring and Fault Diagnosis Based on Kernel Principal Component Analysis
Authors: He Fei , Li Min , Yang Jian Hong , Xu Jin Wu
Published: September 2009

In order to monitor nonlinear production process effectively, multivariate statistical process control based on kernel principal component analysis is applied to process monitoring and diagnosis. Squared prediction error (SPE) statistic of the kernel principal component analysis (KPCA) model is used for process monitoring, and the fault causes of the production process could be tracked by the methods of data reconstruction and the optimal neighbor selection strategy. Simulation data and Tennessee Eastman process data are used for model validation, as a result the proposed method has better performance on abnormality detecting, compared with multivariate statistical process control based on linear principal component analysis. What is more, the causes of the faults are tracked effectively, thus the production process can be adjusted to prevent substandard products.
Fault Diagnostics Based on Pattern Spectrum Entropy and Proximal Support Vector Machine
Authors: Yu Xiang Tao , Lu Wen Xiu , Chu Fu Lei
Published: September 2009

Based on pattern spectrum entropy and proximal support vector machine (PSVM), a motor rolling bearing fault diagnosis method is proposed in this paper. It is very difficult to filter the fault vibration signals from the strong noise background because the roller bearing fault diagnosis is a problem of multi-class classification of inner ring fault, outer ring fault and ball fault. Firstly, vibration signals are processed by the pattern spectrum. Secondly, the morphological pattern spectrum entropy, and pattern spectrum values are utilized to identify the fault features of input parameters of PSVM classifiers. The experiment results demonstrate that the pattern spectrum quantifies various aspects of the shape-size content of a signal, and PSVM costs a little time and has better efficiency than the standard SVM.
Feature Extraction for Damage Detection in Structures Based on Nonlinearity Analysis
Authors: Peng Zhi Ke , Lang Z.Q. , Wolters C. , Billings S.A.
Published: September 2009

In the present study, a nonlinear system identification approach known as NARMAX (Nonlinear Auto-Regressive Moving Average with eXogenous Inputs) modelling method and the NOFRF (Nonlinear Output Frequency Response Function) are introduced to detect damage in plate. A set of NOFRF-based damage features is proposed, and the procedure about how to extract the features from the measured response data is presented in detail. An experimental application to the detection of damages in aluminium plates demonstrates the effectiveness and engineering significance of the new damage detection technique.
Numerical Study of Thickness Distribution of Stretch-Blow Bottles for Defects Prediction
Authors: Pan Ya Yue , Zheng Shui Ying , Pan Xiao Hong
Published: September 2009

Nowadays, polyethylene terephthalate (PET) bottles have been increasingly used as drink containers. They are usually manufactured by a stretch-blow molding process. The improper parameters set in the stretch blow molding process may lead to many defects in the stretch-blow bottle. Finite Element (FE) simulations of the forming process were performed in this paper. The influences of the technological parameters, such as the balance between stretching and blowing rate, the movement of the stretch rod and the inflation pressure, were studied. As a result, the defects, such as over-thin area, cracking and deformation, can be predicted by this method. Especially, it is shown that the cracking in the bottom of products may result from the improper values of the dwell time and the stretch rate. The trends shown by the simulation results are in good agreement with the experimental results. The method can be applied to predict the probable defects, assess the structural properties, and optimize the processing parameters of the stretch blow molding process.
Pseudo Strain Energy Density-Based Structural Damage Identification
Authors: Chen Xiao Qiang , Zhu Hong Ping , Wang Dan Sheng
Published: September 2009

In this paper, a new time-domain method for detecting structural local damage has been developed, which is based on the measured strain signals. The “pseudo strain energy density (PSED)” is defined and used to build two major damage indexes, the “average pseudo strain energy density” (APSED) and the “average pseudo strain energy density changing rate” (APSEDR). A probability and mathematical statistics technique is utilized to derive a standardized damage index. Afterwards, these indexes are used to establish the damage identification strategies for beam structures and plate structures respectively. Furthermore, the wavelet packet transform is used to pre-process the measured dynamic strain signals. Then, the effectivity of the new damage identification method is confirmed by numerical simulations. Finally, a laboratory beam model experiment is conducted to verify this method examine the feasibility and applicability of the new method.
Dynamic Behaviour of Single Lap-Jointed Cantilevered Beams
Authors: He Xiao Cong
Published: September 2009

The aim of this study is to predict the dynamic behaviour of single lap-jointed cantilevered beams theoretically and to validate the predictions via experimental tests. The ABAQUS finite element analysis (FEA) software was used to predict the natural frequencies, mode shapes and frequency response functions (FRFs) of lap-jointed beams. The LMS (Leuven Measurement System) CADA-X dynamic test software and the LMS-DIFA Scadas II 48 channel data acquisition hardware were used in experimental measurement of the dynamic response of the lap-jointed beams. It is shown that the natural frequencies of the single lap-jointed cantilevered beams from experiment are lower than those predicted using FEA. It is also found that the measued FRFs are close to the predicted FRFs for the first two modes of vibration of the single lap-jointed cantilevered beam. Above the second mode of vibration, there is considerable discrepancy between the measured and predicted FRFs.
Removing the Ambiguity in Lamb Wave-Based Damage Localization
Authors: Malinowski Pawel , Wandowski Tomasz , Ostachowicz Wiesław M.
Published: September 2009

The aim of this work is the investigation and improvement of a Structural Health Monitoring method based on Lamb waves propagation. This research concentrates on ambiguity in damage localization using attached piezoelectric transducers as sources and sensors of the elastic waves. A linear phased array is chosen as a starting point of the investigation. It has a great advantage in damage localization, namely it enables to amplify the wave reflected from damage, increasing the signal to noise ratio, and precisely indicates not only the distance to damage from the array but also the direction on which the damage lies. However it has also a great disadvantage which needs to be handled – the localization results are symmetric in relation to the line on which the transducers of linear phased array are placed. This obviously does not facilitate Structural Health Monitoring process and precise indication of damage placement. Therefore this investigation aims to improve this localization method by removing the ambiguity in results. In this work the placement of transducers forming a linear phased array is modified to achieve this goal. Several array modification are investigated and compared in order to determine the best solution. Presented research is based on theoretical calculations as well as laboratory experiments on prepared specimens. The measurements are conducted with a compact 13–channel SHM system controlled by a MATLAB® script.
A Method for Acoustic Emission Source Identification Based on Optimisation
Authors: Spencer Andrew , Worden Keith , Pierce Gareth
Published: September 2009

When a metal or composite structure begins to fail, for example due to high cycle fatigue, acoustic emissions caused by the propagation of cracks give rise to bursts of ultrasonic waves travelling through the structure. The health of a structure can be monitored by means of sensors which detect these waves. Acoustic emissions are often generated in experiments by breaking a pencil lead against the surface of the structure in a standardised way but the forces that this imparts are not well understood at present. A Local Interaction Simulation Approach (LISA) algorithm has been implemented to simulate the propagation of ultrasonic waves. This code has been validated against experiments in previous work and has been shown to accurately reproduce the propagation of Lamb waves (including reflections and dispersion etc.) within thin-plate like structures. This paper deals with the use of the LISA code to characterise the forces associated with standard pencil lead breaks. The displacement due to waves emanating from a break is measured and a Differential Evolution (DE) optimisation scheme is used to find the optimal profile of forcing to match the simulation with experiment.
Automatic Image Measurement Technology in Endoscopy NDT
Authors: Liu Guan Jun , Zhang Yong , Qiu Jing , Lu Ke Hong
Published: September 2009

Endoscopy is an important non-destructive testing (NDT) method. It plays an important role in damage assessment and fault detection for aeroengine and structure [1,3]. However, the endoscopy usually relies on the operator’s experience to measure the defects manually in the application. Therefore, the current endoscopy method has some shortcomings that the accuracy and the efficiency of its measurement are low. To solve these problems, an automatic image measurement method based on the cubic spline interpolation is proposed in this paper. Firstly, the endoscopy image pre-processing such as gray processing, filtering, sharpening, segmentation and edge extraction are presented. Then, the pixel points in the processed edge image are handled by cubic spline interpolation and the spline function is got. After the starting point, vertex and endpoint of the defect are determined automatically, the width, depth and distance of defects are worked out. Finally, the method is applied in the fault detection for aeroengine’s blade. The experimental results show that this method can detect the width, depth and distance of the aeroengine’s blade defects exactly and quickly.
Acoustic Emission Monitoring of Mechanical Seals Using MUSIC Algorithm Based on Higher Order Statistics
Authors: Fan Yi Bo , Gu Feng Shou , Ball Andrew
Published: September 2009

This paper presents the use of the MUSIC algorithm improved by higher order statistics (HOS) to extract key features from the noisy acoustic emission (AE) signals. The low signal-to-noise ratio of AE signals has been identified as a main barrier to the successful condition monitoring of pump mechanical seals. Since HOS methods can effectively eliminate Gaussian noise, it is possible in theory to identify a change in seal conditions from AE measurements even with low signal-to-noise ratios. Tests conducted on a test rig show that the developed algorithm can successfully detect the AE signal generated from the friction of seal faces under noisy conditions.
Fabrication of BaTiO3-PMMA Polymer Nanocomposite Thin / Thick Films and their Dielectric Properties
Authors: Habib Amir , Stelzer Nils , Haubner Roland
Published: September 2009

Thin and thick BaTiO3-polymer nanocomposite dielectric films were prepared using BaTiO3 nanoparticles and poly (methyl methacrylate) (PMMA). The cubic BaTiO3 (~ 30-60 nm) and tetragonal BaTiO3 (~ 120 nm) synthesized via hydrothermal/solvothermal route were used as nanofillers. The dielectric constant of 9 was achieved for the films of thicknesses in the 150-300 nm range, which corresponds to a capacitance density of 32 nF/cm2. The dissipation factor of the composite film was of a value of 0.04 at 10 kHz. Thick films (~ 16.3 µm) were prepared by doctor blade method and tested for their capacitance and dielectric properties in the 10-100 kHz frequency range for cubic and tetragonal BaTiO3. The BaTiO3 particles were dispersed homogeneously in the films at lower filler loading. The homogenous distribution of BaTiO3 achieved by surface functionalization of BaTiO3 nanoparticles and use of tetragonal BaTiO3 resulted in the improvement of electric properties of thick and thin films.
Characterization of PET Nanocomposites with Different Nanofillers
Authors: Todorov Lyudmil V. , Martins Carla I. , Viana Júlio C.
Published: September 2009

This study investigates the influence of various nanofillers of different shapes and sizes on the properties of PET nanocomposites. PET was reinforced with 0.3 wt.% of different nanoreinforcements, namely: (i) 1D platelet-like shape of organo-modified layered silicates (montmorillonite) (platelet size approx. 1 x 200 nm) with average agglomerate size of: (a) 30 μm and (b) 8 μm; (ii) 3D spherical shape particles of titanium oxide with an average size of 21 nm and (iii) 3D spherical shape silica with an average particle size of 12 nm. PET nanocomposites were prepared by melt blending in an asymmetric batch minimixer followed by compression moulding process. The effect of nanofillers upon thermal, mechanical and structural properties in comparison to the neat PET are discussed.
From Nanocomposite to Blend Hybrid pHEMA/SiO2 Hydrogels: The Effect of Chemical Coupling on Thermal Stability, Swelling and Bioactivity
Authors: Costantini A. , Luciani Giuseppina , Silvestri Brigida , Tescione Fabiana , Branda Francesco
Published: September 2009

Hybrids of poly(2-hydroxyethylmethacrylate) (pHEMA), a polymer widely employed for biomedical applications, and silica gel, exhibiting a well-known bioactivity, were produced by in- situ sol-gel synthesis using two different procedures. Only Tetraethylortosilicate (TEOS) was used as inorganic precursor in the former, whereas both TEOS and methacrylate monomers bearing an alkoxysilyl unit, prepared by Michael addition of 2-hydroxyethylmethacrylate (HEMA) to 3-Aminopropyltriethoxysilane (APTS), were employed in the latter. A final concentration of 30% w/w of silica gel to the mass of polymer was obtained in both procedures. The samples prepared through the former route will be referred as T03, those obtained the latter route will be named as AT03.
AT03 hybrids are optically transparent, whereas T03 samples show phase separation between the polymer and the silica gel. Synthesis procedure strongly affects hybrids structure: the silica phase mean diameter changes from 500 nm (T03) to about 50 nm when the coupling hybrid monomer is employed (AT03). Both hybrids keep swelling properties and show improved thermal stability than the as-prepared polymer, indeed AT03 exhibits the highest decomposition temperature and T03 show the highest swelling ratio. Moreover, silica gel has hydroxyapatite formed on both hybrids surface, when soaked in SBF.
Characterisation of the Chitosan/Layered Silicate Nanocomposites
Authors: Cheaburu Catalina Natalia , Vasile Cornelia , Duraccio Donatella , Cimmino Sossio
Published: September 2009

Characterization of chitosan / layered silicate nanocomposites obtained by solution-mixing technique, having different compositions including treated and untreated montmorilonite (MMT) has been performed. The optimum amount of MMT and also the effect of nanoparticles type on nanocomposite properties by DSC, X-ray diffraction and TG measurements have been established. The chitosan chains were inserted into silicate layers to form the intercalated nanocomposites. The interlayer distance of the silicates in the nanocomposites enlarged as their amount increased. The stiffness and thermal stability enhanced.
Nanocomposites Based on Montmorillonite/Acrylic Copolymer for Aqueous Coating of Soft Surfaces
Authors: Yılmaz Onur , Chiriac Aurica P. , Cheaburu Catalina Natalia , Nita Loredana E. , Gülümser Gürbüz , Duraccio Donatella , Cimmino Sossio , Vasile Cornelia
Published: September 2009

Nanocomposites based on layered silicate organically modified montmorillonite (Cloisite 20A) and acrylic comonomers (butyl acrylate and methyl methacrylate) were prepared by simple “in situ” batch emulsion polymerization method. The particle size and zeta potential of the emulsions were analyzed. The structural characterizations of the nanocomposites were performed by FTIR, thermal behaviors of the films were investigated by DSC, mechanical properties of the films were tested by DMA and intercalation success was viewed by XRD. The mechanical properties of the nanocomposites were improved significantly especially at the temperatures above Tg. The ultrasonication process was found to be useful for increasing the homogeneity of the emulsions and intercalation success. The obtained nanocomposite emulsions were applied on garment leathers in a finishing formulation as aqueous binders sharing good film forming ability and elasticity.
The Influence of Nano-Silica on the Wear Resistance of Ceramic – Polymer Composites Intended for Dental Fillings
Authors: Siejka-Kulczyk Joanna , Mystkowska Joanna , Lewandowska Małgorzata , Dabrowski Jan R. , Kurzydlowski Krzysztof Jan
Published: September 2009

Ceramic – polymer composites based on acrylic (bis–GMA) and urethane – methacrylate (UM) resins with a 60 % total volume fraction of filler consisting of micro particles of glass and nano-particles of silica were fabricated. The nano-silica contents were: 0, 10, 20 vol. %. The composite samples were subjected to wear tests using an occlusion simulator tester which applies reciprocating movement and cyclic loading on the test material. This method of testing provides some similarity to the masticatory pattern occurring in the mouth during eating. The enamel of a human tooth was used as a counter-sample. The coefficient of friction was determined and the wear resistance of the composite samples containing the various nano-silica contents was established. In addition, the relative influence of the composite composition on the rate of wear of the human tooth enamel was estimated. The results of the study indicate that the addition of nano-silica significantly improves the wear resistance of the ceramic – polymer composites and reduces the wear of enamel. It was found that the addition of nano-silica has no influence on the coefficient of friction. It was also established that composites based on UM resin show better wear resistance than those based on a mixture of bis-GMA and TEGDMA resin.
Nanocomposites Based on Acrylic Copolymer, Iron Lignosulfonate and ZnO Nanoparticles Used as Wood Preservatives
Authors: Dumitrescu Lucia , Perniu Dana , Manciulea Ileana
Published: September 2009

The paper presents research concerning the synthesis and characterization of some new nanocomposite used as wood coating nanomaterials, consisting of a hybrid of organic (functionalized acrylic copolymers with iron lignosulfonate) and inorganic nanomaterials (ZnO nanoparticles obtained by sol-gel process). The presence of acrylic copolymers in water emulsion (based on monomers ethyl acrylate, butyl acrylate, acrylonitrile and the lignin derivative iron lignosulfonate) and ZnO nanoparticles enables the formation of a crosslinked nanometric network of inorganic and organic domains, emphasized by AFM analysis. The interphase characterization of the nanostructured materials synthesized was performed using FT-IR analysis.
Considering the biocide activity for the acrylic copolymers, the lignin derivative iron lignosulfonate and ZnO nanoparticles, the obtained nanocomposites were biologically investigated and proposed as wood preservation agents.
Effect of Freezing and Thawing Process on Betamethasone Acetate Release from Polyvinyl Alcohol Nanospheres
Authors: Bonakdar Shahin , Poursamar Seyed Ali , Rafienia Mohammad , Shokrgozar Mohammad A. , Farhadi Afshin , Hosseini Motahhareh
Published: September 2009

Betamethasone acetate (BA) is a glucocorticoid steroid with anti-inflammatory and immunosuppressive properties which can be used in treatment of asthma and itching. In this research, polyvinyl alcohol nanospheres loaded by betamethasone acetate were prepared by oil in water emulsion method after which they were exposed to 1, 2 and 4 cycles of freeze-thawing (F-T) process including 24 hours freezing cycle at -25 °C and 24 hours thawing at ambient temperature. Nanospheres fabrication was confirmed by transmission electron microscopy and betamethasone release was analyzed by UV spectrophotometer at 245 nm. The results revealed that by increasing the number of F-T cycles the rate of drug release decreased. The effect of BA concentration was also investigated on human chondrosarcoma (sw 1353). The MTT assay was utilized to assess the cell proliferation. The results showed that these biocompatible nanospheres can be used for sustained release of such drugs for more than four months and drug release rate can be effectively controlled by implementing F-T cycles.
L10 FePt-Filled Carbon Nanotubes by Wet Chemical Synthesis
Authors: Capobianchi Aldo , Foglia Sabrina , Palange Elia , Arrizza Lorenzo , Veroli C. , Vasquez Mansilla Marcelo , Fiorani Dino
Published: September 2009

This paper reports on the synthesis of iron-platinum (FePt) alloy clusters within Multi Wall Carbon Nanotubes using a novel wet chemical method that allows the filling of the nanotube cavity keeping clear their external wall. In the present case, the procedure permits the filling of the nanotubes with precursor salts of Pt and Fe and, by direct heating at 700°C of the Fe and Pt mixed salts, magnetic hard, face-centred-tetragonal (fct) crystallographic (L10) phase FePt alloy nanoparticles are obtained without the need to pass through the formation of the magnetic soft, face-centred-cubic (fcc) FePt alloy phase. By a suitable choice of the concentration of the starting material solution, we obtained particles of two different sizes into the nanotubes with magnetic blocked and super-paramagnetic states at room temperature. Morphological, structural and magnetic properties of the filled nanotubes have been performed by magnetic measurements, X-ray diffraction and transmission electron microscopy in normal and high resolution mode