bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Use of Low and High Cycle Fatigue Damage Models
Authors: Abdel Wahab Magd , Hilmy Irfan , Hojjati-Talemi Reza
Published: July 2013

In this paper, Continuum Damage Mechanics (CDM) theory is applied to low cycle and high cycle fatigue problems. Damage evolution laws are derived from thermodynamic principles and the fatigue number of cycles to crack initiation is expressed in terms of the range of applied stresses, triaxiality function and material constants termed as damage parameters. Low cycle fatigue damage evolution law is applied to adhesively bonded single lap joint. Damage parameters as function of stress are extracted from the fatigue tests and the damage model. High cycle fatigue damage model is applied to fretting fatigue test specimens and is integrated within a Finite Element Analysis (FEA) code in order to predict the number of cycles to crack initiation. Fretting fatigue problems involve two types of analyses; namely contact mechanics and damage/fracture mechanics. The high cycle fatigue damage evolution law takes into account the effect of different parameters such as contact geometry, axial stress, normal load and tangential load.
Synthetic Aperture Focusing Technique for Detecting Transverse Cracks in Austenitic and Dissimilar Welds
Authors: Prager Jens , Höhne Christian , Rahman Mehbub Ur
Published: July 2013

The inspection of austenitic and dissimilar welds using ultrasound demands for sophisticated testing techniques. The application of reconstruction methods like the Synthetic Aperture Focusing Technique (SAFT) on the measurement results provides an appropriate approach for defect characterization and sizing. Nevertheless, the reconstruction algorithm has to consider the aniso-tropic wave propagation inside the inhomogeneous weld material. In recent years the detection of transverse cracks has become increasingly important for ensuring the structural integrity of pipes in the primary circuit of nuclear power plants or longitudinally welded, cladded pipes. However, relia-ble inspection techniques are hardly available. In this particular case, it is expected that the compar-atively long propagation path of the ultrasonic wave field inside the inhomogeneous weld material enhances the effect of anisotropy and influences the accuracy and the signal-to-noise-ratio of the reconstruction result. In this contribution we suggest an advanced ultrasonic testing technique for detecting and sizing of transversal cracks in austenitic and dissimilar welds. The method applies a SAFT reconstruction algorithm considering the anisotropy and the inhomogeneity. A V-arrangement of the transducers in pitch-catch technique is chosen to avoid a direct coupling on the weld face. The reconstruction algo-rithm is based on an extended 3-dimensional weld model and uses a ray-tracing approach for de-termining the wave propagation paths. Along with the reconstruction algorithm the transducer set-up and experimental results of different specimens with artificial transverse flaws are presented. The availability of the proposed method for crack sizing is assessed in comparison to conventional testing techniques.
On the Integration of Real-Time Diagnosis and Prognosis for Scheduled Maintenance Optimization
Authors: Sbarufatti Claudio , Manes Andrea , Giglio Marco
Published: July 2013

Helicopters are very critical aircrafts from the point of view of fatigue loads. A structural damage could grow fast to critical size because of the wide range of manoeuvre loads. As a consequence, scheduled maintenance is a major cost during the operative life of the aircraft. The most advanced methodologies for Structural Health Monitoring and Prognostic Health Management available today are aimed to provide a real-time structural diagnosis, thus maximizing the availability of the helicopter and reducing the maintenance costs. However, on-board diagnostic systems might be gradually introduced in the current maintenance procedures, trying to minimize the risk associated to these newly developed technologies. The work presented inside this paper is about the simulation of the integration of real-time diagnosis and prognosis into a typical scheduled maintenance procedure. A diagnostic unit is capable for anomaly detection and damage quantification (in terms of crack length). It is trained with Finite Element simulated damages and tested with real experimental data. The diagnostic output is then processed in a particle filter algorithm, based on sequential importance sampling technique, aimed at refining the estimation of the structural condition as well as to update the inference on the residual useful life distribution. The coupling of real-time diagnosis with off-line measures (taken during scheduled maintenance stops) is analyzed and applied to a damage tolerant structure, trying to outline the advantages and drawbacks of the proposed approach.
Influence of Physical Parameters and Operating Conditions for Structural Integrity of Mechanical System Subjected to Squeal Noise
Authors: Soobbarayen Kevin , Besset Sébastien , Sinou Jean Jacques
Published: July 2013

This work proposes to study the effects of physical parameters and loading conditions on both dynamic and acoustic responses of a brake system subjected to squeal. A simplified brake system model composed of a disc and a pad is investigated. The friction interface is modeled by introducing linear and non-linear stiffnesses at several local nodes to model contact. The classical Coulomb law is applied to model friction and the friction coefficient is assumed to be constant. A stability analysis of this system is performed with respect to the friction coefficient and the hydraulic brake pressure. Then self-excited vibrations are investigated for two cases of loading conditions: static loading and ramp loading. Time responses for these cases are significantly different: the case with ramp loading presents higher amplitude of velocity than the static loading case. For the case with ramp loading, the spectrum analysis performed by the Continuous Wavelet Transform, shows the appearance of the fundamental frequencies of unstable modes but also their harmonics and combinations frequencies. Sound pressures radiated during squeal event present different peculiar patterns of directivity for both cases and for a progressive load, the levels are significantly higher.
Multi-Technique Approach for the Assessment of Historical Masonry Constructions
Authors: Fernandes Francisco M. , Ramos Luís F. , Manning Elizabeth , Ferreira João , Mendes Paulo
Published: July 2013

In this paper the NDTs research project is briefly described. This project aims at developing and improving several nondestructive techniques typically used in masonry diagnosis. So far, a new acquisition system based on sonic measurements, a geoelectric prototype to perform tomographic measurements of the cross-section of masonry elements and a new type of flat-jack test, the tube-jack, were developed. Finally, the project aims at merging the data of these improved techniques with existing ones in order to produce a better diagnosis of these structures. The initial results of the case study of S. Torcatos church is illustrated here to show the potential of these methods and the quality of the information that can be derived from the merging of the data obtained through different methodologies.
Non-Destructive Investigation of Glass Fiber Reinforced Composites via Magnetic Resonance Imaging
Authors: Wetterling Friedrich , Mok Kenneth Hun , McGoldrick Ciaran , Basu Biswajit
Published: July 2013

Glass fibre reinforced composites (GFRC), used in the manufacture of wind turbine blades, can suffer unpredictable, post-manufacturing, in-situ structural failure. The economic cost of remediation of such blade failures is extremely high, both on land and offshore. We suggest using zero-time-to-echo (ZTE) magnetic resonance imaging (MRI) as a method for characterising glass fibre reinforced composites. Initially, we demonstrate that carbon-13 Nuclear Magnetic Resonance (NMR) spectra acquired at 800MHz provide finger-print like information and that there is sufficient hydrogen-1 NMR signal available to conduct MRI. This work explores the efficacy of using zero timetoecho (ZTE) magnetic resonance imaging (MRI) to detect the rapidly decaying Hydrogen-1 (1H) NMR signal from a representative sample. A 400MHz surface resonator was developed made of a 20mm diameter loop formed with 1.5mm thick silver wire and designed with variable tuning and matching in order to investigate the 1H-MRI signal at 9.4T static magnetic field strength. The thickness of the GFRC was determined from the MRI data to be 3.51±0.28mm while the physical measurement using a caliper device resulted in a measurement of 3.45mm. Hence, a high spatial resolution accuracy is provided by ZTE MRI. Very short T2* (<20μs) of the material led to stronger blurring artefacts for the blade material compared to heat shrink used for insulating the silver wire of the detector. 1H images of the blade material were acquired demonstrating that ZTE is a suitable technique for acquiring image data from glass fibre materials. Work is on-going in studying the relaxation time parameters and chemical frequency shifts for materials with and without structural weaknesses in order to improve the predictive power of the technique. In conclusion, ZTE-MRI can provide useful information about the mechanical properties of glass fibre reinforced composites.
A Compensation Method for Environmental Influences on Passive Lamb Wave Based Impact Evaluation for CFRP
Authors: Schubert Konstantin Jonas , Herrmann Axel Siegfried
Published: July 2013

One of the largest issues remaining on the way to in situ Structural Health Monitoring of composite structures using Lamb waves is the impact that non-damaging factors like temperature changes and humidity absorption have on most measurement strategies. While some of these tasks have been successfully conquered, others, especially related to slowly developing influences like humidity absorption or mechanical ageing, remain challenging. In this paper, a method to approach this problem for a Lamb-wave based passive impact detection system is presented. Passive approaches use the waves generated by the impact event itself to both localize said event and evaluate whether it was large enough to damage the structure. For this, the impacts energy has to be estimated from sensors detecting the Lamb waves. The problem provided by changing conditions within the material is that the locally measurable wave amplitude due to an impact event of a certain energy is altered if the material properties change. This might happen due to temperature changes, mechanical loads, humidity absorption, fluid loads and other factors. The main idea of the presented approach is to mix a passive and an active system. Piezoelectric elements are used to generate Lamb waves to obtain the attenuation coefficients of the material before and after hot/wet-conditioning. These coefficients are then used to estimate the impact energy from passive sensor responses. Both the approach and experimental validation performed with low velocity impacts from an impact hammer are presented to show the ability to correctly calculate impact forces after conditioning.
Monitoring of Changes in Bridge Response Using Weigh-In-Motion Systems
Authors: Cantero Daniel , González Arturo , Basu Biswajit
Published: July 2013

Weigh-In-Motion (WIM) and Bridge Weigh-In-Motion (B-WIM) are systems that allow obtaining the axle weights of road vehicles in motion, at normal traffic speeds. While WIM employs sensors embedded in the road pavement, B-WIM use the strain recordings of a bridge to infer the traversing vehicle axle weights. Both systems have been heavily improved over the past decades, and commercial versions are currently in operation. The two main applications of these systems are: (1) to assess the traffic loading on the infrastructure, and (2) to enforce the maximum weight limits. This paper suggests a novel application of these two systems to identify changes in bridge stiffness. It requires the bridge to be instrumented with a B-WIM system and a WIM system nearby. The principle is to use both systems to evaluate the gross weight of vehicles passing over the bridge and correlate their predictions. Changes in correlation of the predicted axle weights over time will indicate either structural damage or faulty sensor. A finite element model of a coupled vehicle-bridge system with different damage scenarios is used to test the approach numerically. Vehicle mechanical properties and speeds are randomly sampled within a Monte Carlo simulation. Results show how correlation changes as damage increases and how this correlation can be employed as a damage indicator.
Probabilistic Modelling of the Deterioration of Reinforced Concrete Port Infrastructure
Authors: Molyneaux Thomas C.K. , Law David W. , Collins Frank , Blin Frederic , Zou Roger , Siamphukdee Kanjana
Published: July 2013

Port infrastructure is vulnerable to the corrosive marine environment leading to deterioration, loss of functionality, delays in shipping, major maintenance, remediation and, in the worst cases, loss of structural integrity and consequent replacement of the asset. Despite this, asset managers are unable to adequately plan for the prevention and minimisation of maintenance due to a lack of reliable predictive tools, that simulate the deterioration and a lack of a lifecycle model incorporating protection/maintenance options. This paper reports on a project to develop such a tool to facilitate the probabilistic modelling of the deterioration of reinforced concrete elements from construction through onset of corrosion to subsequent cracking and spalling. The Australian government funded project is in collaboration with several port authorities. The study has narrowed the key factors that have the most impact on the estimation of corrosion initiation and damage propagation allowing better definition of what data should be collected, how much and levels of accuracy required to ensure that predictive outputs obtained are as ‘robust’ as possible.
A Parametric Study of a Drive by Bridge Inspection System Based on the Morlet Wavelet
Authors: McGetrick Patrick J. , Kim Chul Woo
Published: July 2013

Many of the bridges currently in use worldwide are approaching the end of their design lives. However, rehabilitating and extending the lives of these structures raises important safety issues. There is also a need for increased monitoring which has considerable cost implications for bridge management systems. Existing structural health monitoring (SHM) techniques include vibration-based approaches which typically involve direct instrumentation of the bridge and are important as they can indicate the deterioration of the bridge condition. However, they can be labour intensive and expensive. In the past decade, alternative indirect vibration-based approaches which utilise the response of a vehicle passing over a bridge have been developed. This paper investigates such an approach; a low-cost approach for the monitoring of bridge structures which consists of the use of a vehicle fitted with accelerometers on its axles. The approach aims to detect damage in the bridge while obviating the need for direct instrumentation of the bridge. Here, the effectiveness of the approach in detecting damage in a bridge is investigated using a simplified vehicle-bridge interaction (VBI) model in theoretical simulations and a scaled VBI model in a laboratory experiment.
In order to identify the existence and location of damage, the vehicle accelerations are recorded and processed using a continuous Morlet wavelet transform and a damage index is established. A parametric study is carried out to investigate the effect of parameters such as the bridge span length, vehicle speed, vehicle mass, damage level and road surface roughness on the accuracy of results.
Concordia Transform-Based Current Analysis for Induction Motor Diagnosis
Authors: Wang Jin Jiang , Gao Robert X. , Yan Ru Qiang
Published: July 2013

This paper presents a new approach for bearing defect diagnosis in induction motor by taking advantage of three-phase stator current analysis based on Concordia transform. The current signature caused by bearing defect is firstly analyzed using an analytic model. Concordia transform is performed to extract the instantaneous frequency based on phase demodulation. The bearing defect feature is then identified via spectrum analysis of the variation of current instantaneous frequency. Both simulation and experimental studies are performed to demonstrate the effectiveness of proposed method in identifying bearing defects. The method is inherently low cost, non-invasive, and computational efficient, making it a good candidate for various applications.
The Fault Characteristics of Planetary Gear System with Tooth Breakage
Authors: Gui Yong , Han Qin Kai , Li Zheng , Peng Zhi Ke , Chu Fu Lei
Published: July 2013

Tooth breakage is a typical failure form of wind-turbine planetary gear transmission system, it is important to study the influence of tooth breakage on vibration characteristics of planetary gear transmission system. In this paper, considering the tooth breakage defect, a lumped parameter vibration model of a planetary gear system with time-periodic mesh stiffness is established. Effects of the length and width of tooth breakage on meshing stiffness and dynamic response are discussed in detail. The relation between characteristic frequency of the tooth breakage fault and rotating speeds is pointed out. Several statistical indicators are utilized to show the influence of two parameters (length of planet tooth breakage and input speed) on the dynamic response of the system. Experiments are carried out to verify the simulation results. These results would be useful for fault diagnosis of wind turbine transmission system at different operation conditions.
Ultrasonically Assisted Drilling: Machining towards Improved Structural Integrity in Carbon/Epoxy Composites
Authors: Phadnis Vaibhav A. , Makhdum Farrukh , Roy Anish , Silberschmidt Vadim V.
Published: July 2013

Conventional-drilling (CD) methods often initiate discrete damage phenomena such as micro-cracking, matrix burning; delamination and fibre pull-out in difficult-to-machine heterogeneous materials such as carbon fibre-reinforced polymer (CFRP) composites. Ultrasonically assisted drilling (UAD) is a promising machining technique suitable for drilling holes in CFRP composites. UAD has been shown to possess several advantages over CD, including reduction in a thrust force and torque, diminished burr formation at drill exit in ductile materials and an overall improvement in roundness and surface finish of the drilled hole. Recently, our in-house experiments of UAD in CFRP composites demonstrated remarkable reductions in levels of thrust force and torque (average force reductions in excess of 60%) when compared to CD with the same machining parameters. 3D Finite Element (FE) models of CD and UAD techniques for a CFRP laminate were developed using a general-purpose FE software ABAQUS/Explicit and validated using experimental results. The magnitudes of thrust force and torque obtained with FE analysis of UAD are compared with those for CD. The numerical results obtained with the developed FE model were found to be in a good agreement with the experimental data.
Spalling Size Evaluation of Rolling Element Bearing Using Acoustic Emission
Authors: Ming An Bo , Qin Zhao Ye , Zhang Wei , Chu Fu Lei
Published: July 2013

Spalling of the races or rolling elements is one of the most common faults in rolling element bearings. Exact estimation of the spall size is helpful to the life prediction for rolling element bearings. In this paper, the dual-impulsive phenomenon in the response of a spalled rolling element bearing is investigated experimentally, where the acoustic emission signals are utilized. A new method is proposed to estimate the spall size by extracting the envelope of harmonics of the ball passing frequency on the outer race from the squared envelope spectrum. Compared with the cepstrum analysis, the proposed procedure shows more powerful anti-noise ability in the fault size evaluation.
Fatigue Analysis of Offshore Wind Turbines on Fixed Support Structures
Authors: Alati Natale , Nava Vincenzo , Failla Giuseppe , Arena Felice , Santini Adolfo
Published: July 2013

A stochastic time domain fatigue analysis is pursued on steel tripod and jacket support structures for offshore wind turbines, following the basic concepts of recently validated simplified linear analyses. A set of environmental lumped load cases with corresponding probabilities of occurrence is considered. Results are compared in terms of a lifetime damage equivalent load.
Changes in the Dynamic Behaviour of Carbon Fibre Reinforced Polymer Elements with Increasing Damage
Authors: Capozucca Roberto , Maccioni Vanessa
Published: July 2013

This paper deals with effects of damage on Carbon FRP (CFRP) elements subjected both to defects and micro-cracking due to static tensile loading through an investigation of CFRP elements under natural vibration tests. The correlation between the response and frequency decrease due to damage for cross section reduction of CFRP cantilever beam elements has been analysed. Successively, the response of CFRP subjected to different values of tensile force has been investigated; experimental frequency values are compared with theoretical values and discussed.
On Structural Health Monitoring of Wind Turbine Blades
Authors: Skov Jonas Falk , Ulriksen Martin Dalgaard , Dickow Kristoffer Ahrens , Kirkegaard Poul Henning , Damkilde Lars
Published: July 2013

The aim of the present paper is to provide a state-of-the-art outline of structural health monitoring (SHM) techniques, utilizing temperature, noise and vibration, for wind turbine blades, and subsequently perform a typology on the basis of the typical 4 damage identification levels in SHM. Before presenting the state-of-the-art outline, descriptions of structural damages typically occurring in wind turbine blades are provided along with a brief description of the 4 damage identification levels.
Active Blade Pitch Control for Straight Bladed Darrieus Vertical Axis Wind Turbine of New Design
Authors: Chougule P.D. , Nielsen S.R.K. , Basu Biswajit
Published: July 2013

As Development of smallvertical axis wind turbines (VAWT) for urban use is becoming an interestingtopic both within industry and academia. However, there are few new designs ofvertical axis turbines which are customized for building integration. These aregetting importance because they operate at low rotational speed producing veryless noise during operation, although these are less efficient than HorizontalAxis Wind Turbines (HAWT). The efficiency of a VAWT has been significantlyimproved by H-Darrieus VAWT design based on double airfoil technology asdemonstrated by the authors in a previous publication. Further, it is well knowthat the variation of the blade pitch angle during the rotation improves thepower efficiency. A blade pitch variation is implemented by active blade pitchcontrol, which operates as per wind speed and position of the blade withrespect to the rotor. A double multiple stream tube method is used to determinethe performance of the H-Darrieus VAWT. The power coefficient is compared withthat of a fixed pitch and a variable pitch double airfoil blade VAWT. It isdemonstrated that an improvement in power coefficient by 20% is achieved andthe turbine could start at low wind speed
An Analysis of the Effectiveness of Application of Rotation Rate Sensors in Non Destructive Damage Evaluation
Authors: Kokot Seweryn , Zembaty Zbigniew , Bobra Piotr
Published: July 2013

This paper reports the analysis of the effectiveness of the application of rotation rate sensors in structural damage identification problem using harmonic vibrations for plexiglass models of cantilever beams. The two types of sensors are applied: angular rate sensors and conventional translational, piezoelectric accelerometers. The amplitudes of dynamic response under harmonic kinematic excitations were subsequently used in the stiffness reconstruction procedure. Particularly promising results are obtained by using only rotation rate sensors in the reconstruction procedure.
How Many Vibration Response Sensors for Damage Detection & Localization on a Structural Topology? An Experimental Exploratory Study
Authors: Sakaris Christos S. , Sakellariou John S. , Fassois Spilios D.
Published: July 2013

The number of vibration response sensors required for structural damage detection andprecise localization on a continuous structural topology is investigated. For damage detection thestate–of–the–art of vibration based methods need a required number of sensors q that may be “low”compared to the number of structural modes m, that is q << m. Yet, the opposite is generally suggestedfor precise damage localization, that is q > m. In this study the hypothesis that a “low” numberof vibration response sensors, q << m, may, under certain conditions, suffice for precise damage localization,is postulated. This hypothesis is “proven” experimentally by demonstrating that preciselocalization is indeed possible using a single vibration response sensor and an advanced StructuralHealth Monitoring methodology on a laboratory 3D truss structure.
Spatial Filter for Operational Deflection Shape Component Filtration
Authors: Wójcicki Jeremi , Mendrok Krzysztof , Uhl Tadeusz
Published: July 2013

Modal filtration in the field of damage detection has many advantages, including: its autonomous operation (without the interaction of qualified staff), low computational cost and low sensitivity to changes in external conditions. However, the main drawback of this group of damage detection methods is its limited applicability to operational data. The modal filtration of the responses spectra (in place of FRFs), proposed in the literature, often does not give the expected results, working properly only for excitation in the form of white noise, or an ideal impulse. In other cases, for example in rotational machines, when in the response spectrum the rotational velocity harmonics dominate it can give wrong results. For such cases authors propose to use a new type of spatial filter, similar to modal filter with the difference that it has ability to filter the operational deflection shape components from the system response. Its application together with classical modal filter allows for damage detection using operational data with other type of excitation. The main assumption of the new spatial filter is the orthogonality of the filter coefficient vector to the operational deflection shape vector, it is then similar to the classical modal filter.
Cointegration and the Empirical Mode Decomposition for the Analysis of Diagnostic Data
Authors: Antoniadou Ifigeneia , Cross Elizabeth J. , Worden Keith
Published: July 2013

The use of cointegration has been proposed recently as a potentially powerful means of removing confounding influences from structural health monitoring (SHM) data. On the other hand the Empirical Mode Decomposition method is a recent multi-scale decomposition technique with the ability to decompose a signal into meaningful signal components. In this paper the EMD method will be used to highlight the dominant time-scales that have been affected by varying environmental and operational conditions and the time-scales that are related to damage. Then cointegration will be used to remove the nonstationary effects not associated with damage at the time-scales of interest in the data. The final step of the damage detection approach proposed, will be the use of two different amplitude-frequency separation methods, the Hilbert Transform and the more recent Teager Kaiser energy operator approach in order to compare the merits of both, concerning the estimation of the instantaneous characteristics of the signals.
Extension of Lamb Waves Defect Location Techniques to the Case of Low Power Excitation by Compressing Chirped Interrogating Pulses
Authors: de Marchi Luca , Testoni Nicola , Perelli Alessandro , Marzani Alessandro
Published: July 2013

In this work a signal processing algorithm for Lamb waves based defect detection/localization procedures is proposed. In particular, the proposed signal processing allows active-passive networks of piezosensors to use chirp shaped pulses in actuation, instead of classically applied spiky pulses. Thus, defect detection/localization can be achieved by using low power voltages in actuation. Basically, the proposed processing is capable to compensate the acquired time-waveforms from the dispersion due to the traveled distance as well as to compress the additional pulse spreading due to the chirp actuation. A processed time-waveform is thus directly transformed into a distance of propagation. Next, the compensated and compressed signals are exploited to feed an imaging algorithm aimed at providing the position of the defect on the plate. As a result, an automatic detection procedure to locate defect-induced reflections is demonstrated and successfully tested by analyzing experimental Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented in real applications for structural health monitoring.
Real Human Hearing: Damage Detection and Monitoring of the Treatment Effectiveness
Authors: Ovchinnikov Evgeny L. , Ivanov Vladislav V. , Ovchinnikova Yuliya V. , Peskov Pavel V.
Published: July 2013

Hearing loss is determined by the diapason change of perceived ear sound frequencies and intensity. Cochlear tonotopicity represents the relationship between stimulation frequency f and place ℓ along the cochlea by the equation of the acoustic-wave hearing model at before-receptors stage ℓ(f) = Lo.22log(f/fmo), where Lo = 32 mm – the cochlear duct length, fmo = 20 kHz – maxima frequency of audible sound. Age-related frequencies standards can be represented by f(t)=fmoe–rt, where r=0.01 year–1 – high-frequency loss factor sound. Using both relations together, we get the length of the cochlear duct for T years LT = Lo.22log(fT/fmo). Destruction of the cochlear duct is exposed apex experiencing cyclical exposure to sound, which represents a decline of frequency fmo. The real length of the cochlear duct LR determined by the same ratio at a frequency fT = fmaxR, established audiometric. Treatment (pharmacological or physical therapy) causes a change in the physical and audiometric properties of inner ear structures. Daily monitoring of the upper frequency sound (fmaxX) determines the effective (useful) the length of the cochlear duct LX. Value LX/LR can be a criterion of treatment effectiveness: LX/LR →1 when the treatment is effective.
Hydrotalcites as Catalysts and Catalysts Precursors for the Synthesis of Biodiesel
Authors: Reyero Inés , Arzamendi Gurutze , Gandía Luis M.
Published: July 2013

This chapter aims at providing an overview of the potential of layered double hydroxides (LDHs) or hydrotalcite-like compounds (HTs) for contributing to the catalysis of the synthesis of biodiesel through the transesterification of triglycerides. First, the main methods of preparation of HTs and the most relevantfeatures of these materials are presented, with emphasis on their basic properties. Afterwards, the literature on the use of HTs as catalysts, catalysts precursors, and supports of transesterification catalysts is reviewed. HTs are promising materials for the synthesis of biodiesel from refined and waste vegetable oils, showing reasonable resistance to water and free fatty acids but an improvement of the chemical stability under the desired reaction conditions is still necessary.
Turning Investigations on Machining of Ti64 Alloy with Different Cutting Tool Inserts
Authors: Ramesh S. , Karunamoorthy L.
Published: July 2013

Turning operation is fundamental in the manufacturing industry to produce cylindrical parts especially for producing near-nett shape, and aesthetic requirements with good dimensional accuracy. This present research chapter, an attempt has been made to investigate the machining characteristics of titanium alloys. The investigation has been carried out to measure the effect of tool flank wear, surface roughness, cutting force and temperature on different cutting tools by adopting Taguchi’s design of experiment concept. This investigation was set to analyse and develop a mathematical model using response surface methodology, fuzzy logic. The observed responses were optimized using grey relational grade algorithm. Except for a few cases, the experimental results have close proximity (95%) to the predicted value. This validates the model developed in this work. Orthogonal array with grey relational analysis has been successfully implemented for the optimization of the machining parameters. The optimized cutting conditions evolved in this research study will help to achieve better machinability of these advanced materials like titanium alloy.
Challenges in Drilling of Multi-Materials
Authors: Krishnaraj Vijayan , Zitoune Redouane , Collombet Francis , Davim J. Paulo
Published: July 2013

Drilling of multimaterails is a challenge to manufacturing engineers. Many combinations of multimaterial stacks are possible, they are CFRP/Ti, CFRP/Al, CFRP/Ti/Al etc. The thrust force and surface roughness measured during drilling using plain carbide drill (K20) with drill parameters in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminium (Grade 2024) stack and CFRP/Ti were experimentally investigated in this study.
Preparation, Characterization and Photocatalytic Application of Carbonate Modified Titania
Authors: Dhodapkar Rita Sandeep , Neti Nageswara Rao
Published: July 2013

Carbonate is a common pollutant in water and wastewater. A study to understand its influence on the photodegradation rates is necessary especially when TiO2/UV technique is emerging as an advanced technology for pollution abatement. In the present investigation, we report surface modification of titanium dioxide using carbonate ions, characterization of carbonate modified titanium dioxide (CMT) and photocatalytic application of carbonate modified TiO2. Titanium dioxide from two different sources namely BDH, Mumbai and Degussa AG, Germany was used as photocatalyst. The CMT catalysts were characterized using potentiometry, FT-IR and XPS. Approximately, 18.9 mg CO3/g CMT(BDH) and 8.13 mg CO3/g CMT(Degussa) was found loaded as determined by potentiometry. The C 1s and O 1s binding energies observed at 289.2 and 531.3 eV, respectively were attributed to surface carbonate species. The adsorption and photodegradation of Acid Blue I dye examined using neat TiO2as well as CMT catalysts revealed that carbonate inhibits catalytic activity for color and Chemical Oxygen Demand (COD) removal. The photo degradation rate constant (k, s-1) decreases gradually with increasing concentration of carbonate. Thus, in the absence of carbonatekdyeis 5.45 × 10-4s-1(R2= 0.97) andkCODis 3.50 × 10-5s-1(R2= 0.97). At 100 mg/L CO32-,kdyeis 0.16 × 10-4s-1(R2= 0.96) andkCODis 2.66 × 10-5s-1(R2= 0.98). In addition, the carbonate spiking studies revealed the onset of inhibition soon after the addition of carbonate into reacting suspensions of TiO2. The results suggest that carbonate inhibits catalytic activity through formation of strong surface complex under suitable pH by displacing OH2+and OH groups from TiO2surface. This results not only in fewer (OH)surfacegroups available for h+trapping for oxidation into OH radicals but also in non-availability of adsorption sites for the dye molecules. A pretreatment to remove carbonate from (waste) water appears necessary prior to application of TiO2/UV technique
Preparation and Applications of Non-Metal Doped Semiconductors as Photocatalysts
Authors: Punjabi Pinki B. , Ameta Rakshit , Sharma Sanyogita , Chauhan N.P.S. , Kalal Sangeeta
Published: July 2013

Water is one of the most essential commodity for mankind, but we know that only 1% of available water on earth may be used for human consumption. However, due to increasing anthropogenic activities the water is getting polluted. Scientists all over the world are looking for ecofriendly methods to treat polluted water for its reuse. One technique that has been gaining popularity in recent years and it is quite promising also for the treatment of resilient pollutants is the photocatalysis. Numerous studies have been reported in the last decade on the photocatalytic degradation of organic pollutants using semiconductor materials as photocatalysts, but the limited optical absorption due to the relatively wide band gap energies and recombination of photogenerated electron-hole pair results in low activity of photocatalysts. Therefore, improvement of charge separation as well as enhancement of visible light absorption is highly important for the efficient photocatalytic reactions. In this context, doping of semiconductor by non-metals seems a promising strategy to enhance the activity of a photocatalyst. In this chapter; preparation, characterization, mechanism and various applications of non-metal doped semiconductors has been reported and the applications of semiconductors have been focused on waste water treatment. Some other applications include generation of hydrogen by photocatalytic splitting of water, antimicrobial activity etc.
A Brief History of the Grain Refinement of Cast Light Alloys
Authors: St. John David H. , Easton Mark A. , Cao Peng , Bermingham Michael , Qian Ma
Published: July 2013

The development of grain refinement technologies began in the 1930s in response to the need to improve the mechanical properties of as-cast components. Commercial grain refining technologies were developed by industrial and experimental trials often with good success including the production of effective master alloys. In parallel, researchers developed theories to explain the mechanisms of refinement in order to improve the efficiency of refiners and develop new better performing grain refining master alloys. This research continues today. Here we briefly present the history of these developments. It is shown that many developments in our understanding were based on assumptions arising from experimental and industrial observations and the prevailing solidification theories of the time.
Simulation of Cold Shuts and Misruns in Centrifugal Casting of TiAl Low Pressure Turbine Blades
Authors: Jana Santhanu , Jakumeit Juergen , Tiefers Ruedoger , Stoyanov Todor
Published: July 2013

In this work cold shuts and misruns in thin turbine blade test geometries are predicted using a three-phase mold filling and solidification simulation methodology applied to a centrifugal casting process of turbine blades. The methodology is based on a finite-volume method with arbitrary shaped polyhedral control volumes. The Volume-of-Fluid (VOF) approach has been used to capture the phase separation between gas, melt and solid. A High Resolution Interface Capturing (HRIC) scheme has been established to gain sharp interfaces between phases, mandatory for correct calculation of surface tension and wetting angle effects. An additional source term in the momentum equation based on Darcy-law for porous media and Kozeny-Carman relation for the permeability estimation was implemented to model the resistance of the dendrite network to the melt flow. A series of test blades with decreasing thickness has been simulated and cold shuts and misruns predicted at different locations, depending on the blade thickness. Casting trials show an excellent agreement between simulation prediction and experimental findings.
Solidification Mechanisms in Melt Conditioned Direct Chill (MC-DC) Cast AZ31 Billets
Authors: Xia Ming Xu , Prasada Rao A.K. , Fan Zhong Yun
Published: July 2013

The solidification mechanism in the melt conditioned direct chill (MC-DC) casting process was investigated by pouring liquid Pb into the sump during the casting process. This preserved the solidification front for subsequent metallographic examination. The results demonstrated that the solidification in the MC-DC casting process was preceded by the sedimentation of rosettes, which were nucleated in the sump and then grew under intensive melt flow.
Production of High Purity Mg-X Rare Earth Binary Alloys Using Zr
Authors: Prasad Arvind , Uggowitzer Peter J. , Shi Zhi Ming , Atrens Andrej
Published: July 2013

An Fe content lower than the tolerance limit is critical in controlling corrosion rates of Mg alloys. The possibility of reducing Fe below the tolerance in Mg melts was studied using Zr as a precipitating agent. The experiments were carried out on Mg-X binary alloys with rare-earths, X = Y, Ce, Gd, Nd, and La. The laboratory scale results show that Zr is effective in reducing the Fe content from the Mg melt for Mg-X binary alloys. Purification occurs by the precipitation from the melt of Fe rich precipitates, and the settling of the precipitates to the bottom of the melt. Any desired Fe content down to one wt ppm can in principle be achieved by appropriate melt treatment. The experimental results are discussed with respect to calculated phase diagrams.
Effect of Intensive Melt Shearing and Zr Content on Grain Refinement of Mg-0.5Ca-xZr Alloys
Authors: Peng Guo Sheng , Wang Yun , Fan Zhong Yun
Published: July 2013

The effect of intensive melt shearing and Zr concentration on grain refinement of Mg‑0.5Ca-xZr alloy has been investigated experimentally. It was found that without intensive melt shearing, the grain size of Mg-0.5Ca alloy decreased from 290 µm to 76 µm when the Zr concentration is varied between 0 and 1 wt.%. However, intensive melt shearing makes the grain size of the same alloys first decrease and then increase with increasing Zr addition. The minimum grain size (85 µm) was achieved at 0.4 wt.% Zr.
Evolution of Near-Surface Deformed Layers on AA3104 Aluminium Alloy
Authors: Li Kai , Zhou Xiao Rong , Thompson George E. , Hunter John A. , Yuan Yu Die
Published: July 2013

The present work studied the microstructure of near-surface deformed layers and their evolution from the transfer slab to the cold rolled final gauge sheet of an AA3104 aluminium alloy. Electron microscopy of ultramicrotomed cross-sections revealed two types of near-surface deformed layers, i.e. type A and type B, both with different microstructures to the underlying bulk alloy. A typical feature of the deformed layers is the nano-sized ultrafine grains, with diameters ≤ 200 nm for the type A and ≤ 500 nm for the type B deformed layer. Electron energy loss spectroscopy (EELS) indicated that oxide particles are present along grain boundaries within the type A deformed layer, while the type B deformed layer is free of oxide particles. The type A deformed layer is mainly generated at elevated temperatures during the early stages of hot rolling. Its thickness is non-uniform across the surface, with a maximum of ~4 µm on the transfer slab, ~1 µm on the re-roll gauge sheet and ~0.8 µm on the final gauge sheet. While the surface of the hot rolled sheet is mainly covered by the type A deformed layer, the surface undergone cold rolling is alternately covered by the type A and the type B deformed layers.
Strengthening of Al 6061 Alloy by High-Pressure Torsion through Grain Refinement and Aging
Authors: Intan Fadhlina Mohamed , Lee Seung Won , Horita Z.
Published: July 2013

The concurrent strengthening process by high-pressure torsion (HPT) and fine precipitation hardening of an Al 6061 alloy has been studied. The HPT was conducted on disks of the alloys at room temperature with an applied pressure of 6 GPa for 1 and 5 turns with a rotation speed of 1 rpm. It is shown that the HPT processing leads to microstructural refinement with an average grain size of ~200 nm and to an increase in hardness up to a saturation after 5 turns. Aging treatment was performed at temperatures of 373 and 423 K for a maximum period up to 256 hours. The hardness at the saturation level remains the same during aging at 373 K. When aged at 423 K, the hardness decreases from the beginning of the aging. This study thus suggests that aging of the HPT-processed sample may not be effective to strengthen the alloy if it is carried out at higher temperatures. It is suggested that simultaneous strengthening may be achieved through reduced straining and aging at reduced temperatures.
Forming Behaviour of Al-TiC In Situ Composites
Authors: Rai Ram Naresh , Rao A.K. Prasada , Dutta G.L. , Chakraborty M.
Published: July 2013

The forming behaviour of in-situ Al-TiC composites was investigated by comparing microstructure and mechanical properties of as-cast, forged and rolled specimens. The microstructures of forged and rolled specimens reveal uniform distribution of the TiC particles, which are responsible for the enhancement of the tensile strength of the composite. The formed samples were found to be crack free. This feature is very likely to be due to good interface bonding of uniformly dispersed sub-micron size TiC particles with the Al matrix.
Integrated Modeling of Strength Evolution in Al-Mg-Si Alloys during Hot Deformation
Authors: Kabliman Evgeniya , Sherstnev Pavel
Published: July 2013

In the present work we develop a physically based model of strength evolution during hot deformation of Al-Mg-Si alloys. The goal is to predict a change of material strength taking into account the impact of microchemistry, i.e. the influence of solutes and precipitates on strengthening and softening mechanisms. The material strengthening is considered in the present work in terms of solid solution strengthening (the Labusch-Naborro model), work hardening (the advanced one-parameter Kocks model), as well as precipitation strengthening due to the stress contribution of non-deformable particles, i.e. dispersoids (the Orowan by-pass). The material softening is described by dynamic recovery through thermal activation of dislocation climb. For the precipitation kinetics the computational thermodynamics code MatCalc (Materials Calculator) was used. The model was validated by comparison with experimental data of compression tests of the 6xxx series aluminium alloys and a reasonable agreement of the simulated and measured flow stress curves was found.