bluuebunny/crossref_metadata_2025 huggingface dataset:
Feature Selection - Extraction Methods Based on PCA and Mutual Information to Improve Damage Detection Problem in Offshore Wind Turbines
Authors: Zugasti Ekhi , Mujica Luis Eduardo , Anduaga Javier , Martínez Fernando
Published: July 2013

Damage Detection problem in Structural Health Monitoring (SHM) is widely studied by many researchers, therefore lots of damage detection algorithms can be found in the literature. Feature Selection / Extraction methods are essential in the accuracy of these algorithms, they provide the suitable data to be used. The main goal of this work is to improve the input data to be the most representative for the damage detection problem. This is done using different Feature Selection / Extraction methods (PCA, UmRMR, and a combination of both). After taking the representative features, the results are tested using a damage detection method; the NullSpace in this case. The data has been collected from a Laboratory Offshore tower model. The different results are compared (different preprocessing vs Raw data) and these show how the correct preselection of the data can improve damage detection.
A Simulation-Based Monitoring of a Composite Plate Using an Integrated Vibration Measurement System
Authors: Kostka Pawel , Filippatos Angelos , Höhne Robin , Hufenbach Werner
Published: July 2013

The unique potential to integrate functional elements into fibre-reinforced components combined with the recent progress in the simulation models of composite materials provides new perspectives for reliability improvement of the next generation components. Such combination is presented on the example of a carbon-fibre reinforced composite plate with integrated vibration measurement and excitation systems. The investigated structure was consolidated in an adapted resin transfer moulding process using additional layers for positioning, contacting and isolating of the active elements. The integrated elements enable an online estimation of the structural dynamic behaviour and its damage-dependent changes.The article considers the identification problem of diagnostic models enabling a precise interpretation of the measured vibration responses. An approach based on the generation of classifiers by means of inductive machine learning algorithms is applied. At the baseline phase, modal properties are measured that correspond to the undamaged state of the structure. Using these experimental data, a simulation model of the structure was fitted by means of a mixed numerical experimental technique and used for the generation of multiple vibration patterns resulting from different mass distributions. The unique combination of experimental and numerical results enables a generation of high resolved learning datasets for machine learning algorithms using a minimum amount of experimental data. The verification of the estimated classifiers by means of the achievable diagnostic performance is firstly conducted theoretically using standardised validation techniques and a high performance is identified. Then, at the inspection phase, the performance of the whole diagnostic system is additionally experimentally confirmed based on the dynamic response resulting from different unseen structural disturbances.
Offshore and Onshore Wind Energy Conversion: The Potential of a Novel Multiple-Generator Drivetrain
Authors: Goudarzi Navid , Zhu Wei Dong
Published: July 2013

A multiple generator drivetrain (MGD), where a single large generator in a wind turbine is replaced by multiple generators with the same or different rated powers, is proposed along with an automatic switch as an alternative to an existing MGD configuration. Qualitative and quantitative comparisons of a MGD with a conventional drivetrain are provided to better understand the advantages and disadvantages of having a MGD in wind turbines. New approaches for improving the efficiency and the reliability, expanding the operational range, and reducing the cost of a wind turbine are mentioned. A simple mathematical model for a MGD with electromagnetic clutches is developed, a novel prototype of a MGD is designed and fabricated, and experiments are conducted on the prototype. It is concluded that a multiple-generator drivetrain with generators operating individually or in parallel has a better potential of improving the efficiency and the reliability, expanding the operational range, and reducing the cost of offshore and onshore wind turbines than the existing MGD configuration.
Low-Cost Tower Root Fatigue Load Estimation for Structural Health Monitoring of Grouted Connections in Offshore Wind Turbines
Authors: Perišić Nevena , Kirkegaard Poul Henning
Published: July 2013

The sinking of wind turbines (WTs) with monopile foundations is one of the major issues in

the offshore wind industry nowadays. Dynamic wind and wave loads act on the WTs causing vibrations

of the structure. However, grouted connections in the monopiled WTs are not designed well enough to

transfer bending moments from the wind loading. When the load capacity of the grouted connection

is reached, stress cracks appear in the grout causing transition piece to slide down. Direct measuring

of the fatigue load, called the tower bending moment, causing fatigue failures and sinking of the WTs

is expensive and practically unfeasible. This paper suggests a low-cost, model-based algorithm for

indirect measuring of the tower bending moments from the WT dynamic response measurements.

The bending moment is estimated recursively using well-known Kalman filter theory. The method is

validated using WT simulated data, assuming different measurement noise levels.
Damage Detection Using Electromechanical Impedance Technique Combined with Scanning Laser Vibrometry
Authors: Opoka Szymon , Malinowski Pawel , Wandowski Tomasz , Skarbek L. , Ostachowicz Wieslaw
Published: July 2013

The paper consists of two parts. First, Electromechanical Impedance (EMI) method is proven to be able to determine some vibrational characteristics of the investigated structure. In order to verify this statement, Scannig Laser Vibrometry (SLV) is used to correlate frequency peaks of velocity (or displacement) operational deflection shapes with corresponding ones obtained by EMI method. Finally, the influence of moisture content in CFRP sample on resonance peaks is investigated using EMI method. Damage detection indicator in this case is based on shifts of resonant peaks.
Damage Detection in Composite Materials Using Airborne Acoustics
Authors: Pearson Matthew R. , Eaton Mark J. , Szigeti Eszter , Pullin Rhys , Clarke Alastair , Burguete Richard , Featherston Carol A.
Published: July 2013

Composite materials are increasingly being used in a wide range of structural applications in place of metallic materials. This presents a new range of challenges when considering the monitoring of damage and failure in complex components. This paper explores these challenges and presents a potential monitoring method using airborne acoustics which is both non-contact and easily implemented. A carbon composite panel was manufactured and statically loaded in tension until failure. During the test, Digital Image Correlation (DIC) was used to measure full field surface strain in the panel. An array of microphones, placed adjacent to the panel, was used to capture airborne acoustic signals between 400Hz and 20kHz during the test. The captured sound waves potentially contain signals originating from a range of sources, such as fibre failures and matrix cracking, but also contain background noise. A range of techniques have been used to examine the signals and determine the onset of failure, including Short-Time Fourier Transforms (STFT). The detection of failure using the airborne acoustic system has been validated using the strain data from the DIC measurements. The results presented demonstrate the applicability of the airborne system to monitoring of composite components.
The Status of Research on Self-Sensing Properties of CNT-Cement Based Composites and Prospective Applications to SHM
Authors: Rainieri Carlo , Pannunzio Carmen , Song Yi , Fabbrocino Giovanni , Schulz Mark J. , Shanov Vesselin
Published: July 2013

Degradation phenomenacan affect civil structures over their lifespan. The recent advances innanotechnology and sensing allow to monitor the behaviour of a structure,assess its performance and identify damage at an early stage. Thus, maintenanceactions can be carried out in a timely manner, improving structural reliabilityand safety. Structural Health Monitoring (SHM) is traditionally performed at aglobal level, with a limited number of sensors distributed over a relativelylarge area of a structure. Thus, only major damage conditions are detectable. Densesensor networks and innovative structural neural systems, reproducing thestructure and the function of the human nervous system, may overcome thisdrawback of current SHM systems. Miniaturization and embedment are keyrequirements for successful implementation of structural neural systems. Carbonnanotubes (CNT) can play an attractive role in the development of embeddedsensors and smart structural materials, since they provide to traditionalmaterials like cement both structural capability and measurable response toapplied stresses, strains, cracks and other flaws. In this paper the mainresults of an extensive literature review about CNT/cement composites and theirself-sensing capabilities are summarized and critically revised. The analysisof experimental results and theoretical developments provides useful designcriteria for the fabrication of CNT/cement composites optimized for SHM applicationsin civil engineering.
Automated Damage Detection in Composite Components Using Acoustic Emission
Authors: Pullin Rhys , Pearson Matthew R. , Eaton Mark J. , Featherston Carol A. , Holford Karen M. , Clarke Alastair
Published: July 2013

The ability of a Structural Health Monitoring (SHM) system to automatically identify damage in a composite structure is a vital requirement demanded by end-users of such systems. This paper presents the demonstration of a potential method. A composite fatigue specimen was manufactured and initially tested at 1Hz for 1000 cycles. Acoustic emission (AE) signals were recorded for complete fatigue cycles periodically in order to establish a base-line associated with undamaged specimens. The specimen was then subjected to impact damage to create barely-visible impact damage (BVID) and subjected to further fatigue cycles with acoustic emission recorded until failure. The data was subsequently analysed using a range of techniques including basic RMS signal levels and frequency-based analysis. At various stages during the test, C-scanning was used to validate the results obtained. Results demonstrated that AE is capable of detecting BVID in composite materials under fatigue loading. The proposed method has wide applicability to composite structures which are subjected to cyclic loading, such as wind turbine blades.
Damage Detection of a Substructure Based on Response Reconstruction in Frequency Domain
Authors: Li Jun , Law Siu Seong , Ding Yong
Published: July 2013

A substructural damage identification approach based on structural response reconstruction in frequency domain is presented. The response reconstruction is based on transforming the measured responses into responses at other locations with the transmissibility matrix and then the relationship between two sets of response vectors is formulated. The damage identification is conducted by minimizing the difference between a measured response vector and the reconstructed response vector. Measured acceleration responses from the damaged substructure and the finite element model of the intact substructure only are required in the identification algorithm. A dynamic response sensitivity-based method with the adaptive Tikhonov regularization technique is adopted for the damage identification with improved results from noisy measurements. A seven-storey frame structure is taken as an example to illustrate the effectiveness and performance of the proposed approach.
Integrating Singular Spectrum Analysis with Damage Detection of Structure
Authors: Law Siu Seong , Liu Kun
Published: July 2013

The response sensitivity-based method for damage detection is integrated with the singular spectrum analysis (SSA) technique for an improvement of the identification results. The measured response of the structure is SSA decomposed, and the response sensitivity matrix as well as the computed response vectors are projected into the corresponding decomposition subspace to form the identification equations, and components containing the least measurement noise and most damage information can be selected to detect local damages in the structure. The proposed integrated approach is illustrated with a planar truss structure with discussions on the effectiveness of a single and multiple decomposed component of the measured response in the damage detection.
A Two-Stage Scheme for Plate Damage Identification Based on Lock-in Thermography and Dynamic Analysis
Authors: Gao Hai Yang , Guo Xing Lin , Hou Pei Jun , Wu Cheng Wei , Ouyang Hua Jiang
Published: July 2013

This paper presents a two-stage scheme of damage identification for plate-type structure. In the first stage, probable damaged regions and their relative severities can be detected based on lock-in thermography technique. In the second stage, the relation between the damage level and its corresponding natural frequencies of the plate is constructed by means of Kriging surrogate model based on dynamic analysis. The inverse problem of damage quantification over the surrogate model is then solved by using a robust stochastic particle swarm optimization algorithm. Experimental study on a double-damaged plate demonstrates the feasibility and effectiveness of the proposed scheme.
Damage Detection in a Glass Plate Using Outlier Analysis
Authors: Yang Kai , Worden Keith , Rongong Jem A.
Published: July 2013

This work constitutes a damage detection study of a glass plate using the statistical approach of outlier analysis, which is also referred to here as novelty detection. A glass plate instrumented with low-profile, surface-bonded transducers is used in the investigation. Ultrasonic Lamb waves are applied for detecting various crack length on the same plate. The study reveals a distinction between the damage and undamaged plate, and also assesses the severity of damage.
Two Dimensional Damage Localization Using the Interpolation Method
Authors: Limongelli Maria Pina
Published: July 2013

This paper presents a vibration based procedure for locating reductions of stiffness in two-dimensional structures that can be modeled as plates. This procedure is a generalization to the two-dimensional case of the previously published Interpolation Damage Detection Method (IDDM). The method is based on the definition of a damage sensitive feature in terms of the accuracy of a spline function in interpolating the operational displacement shapes of the structure. These latter are recovered from frequency response functions (FRFs) measured at different locations of the structure during vibrations. At the i-th location, the FRF is calculated through spline interpolation using the FRF’s recorded at the all the instrumented locations but the i-th. For two-dimensional structures a spline surface is defined to interpolate the operational shapes. The accuracy of the spline interpolation is measured by an error function defined as the difference between the measured and interpolated operational mode shapes. At a certain location an increase (statistically meaningful) of the interpolation error, with respect to a reference configuration, points out a localized variation of the operational shapes thus revealing the existence of damage. The two dimensional IDDM algorithm is checked herein through numerical simulations, using the FE model of a plate and modeling local reductions of stiffness through a reduction of the elastic modulus of the material of one or more elements of the model.
Consumed Fatigue Life Assessment of Composite Material Structures by Optical Surface Roughness Inspection
Authors: Zuluaga-Ramírez Pablo , Frövel Malte , Restrepo René , Trallero Rafael , Atienza Ricardo , Pintado José María , Belenguer Tomás , Salazar Félix
Published: July 2013

A strong knowledge of the fatigue state of highly advanced carbon fiber reinforced polymer composite (CFRP) structures is essential to predict the residual life and optimize intervals of structural inspection, repairs, and/or replacements. Current techniques are based mostly in measurement of structural loads throughout the service life by electric strain gauge sensors. These sensors are affected by extreme environmental conditions and by fatigue loads in such a way that the sensors and their systems require exhaustive maintenance throughout system life.This work is focused on providing a new technique to evaluate the fatigue state of CFRP structures by means of evaluating the surface roughness variation due to fatigue damage. The surface roughness is a property that can be measured in the field by optical techniques such as speckle and could be a useful tool for structural health monitoring.
The relation between surface roughness and fatigue life has been assessed on CFRP test specimens. A tensile fatigue load with an R=0.1 (T-T) and a maximum load of 60% of the material ultimate strength has been applied. The surface roughness of the specimens has been determined from the surface topography measured by a high precision confocal microscope. Results show that the surface roughness of the specimens increases with the accumulation of fatigue cycles in such a way that the roughness could be taken into account as a fatigue damage metrics for CFRP.
Use of LU Decomposition of Modal Flexibility in Structural Damage Detection: Numerical Validation
Authors: An Yong Hui , Ou Jin Ping
Published: July 2013

The flexibility can be approximately synthesized with the first several measured modal parameters, i.e. the so called modal flexibility. The modal flexibility matrix will change with damage in a structure, and the change of modal flexibility should contain the information of damage. It is important to find a damage index that can pick up damage from the change of modal flexibility. To address this issue, the mathematical tool LU decomposition is introduced to deal with the modal flexibility matrix in order to find damage clearly. After decomposition, the modal flexibility is decomposed into a lower triangular matrix L and an upper triangular matrix U. Numerical results of both single and multiple damage cases under white noise excitation indicate that the matrix U has enough information of damage; and the proposed new technique can be utilized to locate the damage accurately. The present numerical study will lay a foundation for the application of real-time structural health monitoring in experiments and engineering.
The Layered Silicate, Montmorillonite (MMT) as a Drug Delivery Carrier
Authors: Kevadiya Bhavesh D. , Bajaj Hari C.
Published: July 2013

Controlled drug delivery system is a protocol to develop nanostructures and materials that can efficiently encapsulate drugs at high concentration, cross the cell membrane, and release the drug at the target site in a controlled manner for a prescribed period of time. This system can reduces the patient expenses, and risks of toxicity, while it can increase the drug efficacy, specificity, tolerability and therapeutic index of corresponding drugs. Therefore, construction of stimuli-responsive controlled-release systems is of crucial importance for the development of both fundamental science and clinical medicine. Both natural and synthetic materials have been tested and proposed as components of controlled drug delivery. Clay minerals, synthetic or natural, are an important, widely abundant, and low-cost class of materials with unique swelling, intercalation, adsorption, and ion-exchange properties. The safety proof data of clay minerals clearly suggest them to be non-toxic for transdermal application and oral administration. To accomplish controlled-release systems based on layered clay minerals, one of the best ways is to intercalate organic molecules into the interlayer gallery of clay minerals. Intercalation of organic molecules within the gallery of layered silicates offers a novel route to prepare organic and inorganic hybrids that contain properties of both the inorganic host and organic guest in a single material. In this article we will highlight the applications of clay in pharmaceutics as controlled drug delivery carrier.
Adsorption of Acid Dyes on Hydrotalcite-Like Anionic Clays
Authors: Mandal Sujata , Natarajan S. , Raja S. , Vijayalakshmi N. , Muralidharan C. , Mandal Asit Baran
Published: July 2013

Hydrotalcite-like anionic clays have attracted considerable attention in last few decades for their capacity to remove wide range of pollutants from aqueous systems. In this chapter, we discuss our recent studies on synthesis of anionic clays with various compositions (Mg/Al, Zn/Al and Ni/Al) and concentrations and their application for the removal of acid dyes from water. Adsorption efficiencies of the synthesized clays were investigated for the dyes, Acid Blue 113 and Orange II, in aqueous medium. Very high dye uptake capacities were recorded for both the above dyes by using Mg/Al clay (M2+: M3+molar ratios 2 and 3) having NO3-interstitial ion. Adsorption equilibria data were explained using Langmuir and Freundlich isotherm models, however, Langmuir model fitted better than the Freundlich model. Lagergren first order and pseudo-second order kinetic models were used to explain the dye adsorption kinetics of the pristine clay materials. X-ray diffraction studies of the pristine clays and dye loaded clays indicate both anion exchange and physical adsorption were involved in the Orange II uptake process however, uptake of Acid Blue 113 was solely due to physical adsorption. Influence of solution pH on dye uptake by the clay adsorbents and on equilibrium pH of the solution after adsorption was investigated.
Recent Development in Clay Based Functional Coating for Corrosion Protection
Authors: Mishra T. , Mohanty A.K. , Tiwari S.K.
Published: July 2013

There is a large variety of techniques available to protect metals from various types of corrosion. Till date chromate containing metal coatings is one of the most commonly used methods. Layered clays are basically of two types depending on the type of ion exchange capacity. In the recent years different researchers demonstrated the use of such cation/ anionic clays as potential nanocontainers for the inhibitors. These nanocontainers can be used in the coating to induce self-repairing capacity when the coating surface is damaged. Due to the disturbance in the pH and availability of chloride ions clay based nanocontainers can release the inhibitor to protect the surface. In the recent year use of anionic clay like hydrotalcites or layered double hydroxides are much studied in comparison to cationic clay like montmorillonite. This review critically analysed the potential of these clay in the future development of self-healing coating.
Photocatalytic Hydrogen Production
Authors: Chaturvedi Shalini , Dave Pragnesh N.
Published: July 2013

Hydrogen is the efficient storage of solar energy in chemical fuels. It is essential for the large-scale utilization of solar energy systems. The production of clean and renewable hydrogen via photocatalysis has received much attention due to the increasing global energy need. In the chapter we are mainly discussed about photocatalytic method for hydrogen production. All other reported method and mechanism of hydrogen production are also summarized here.
Chemically Deposited Cd1-xPbxSe Thin Films for Photoelectrochemical Studies
Authors: Delekar S.D. , Hankare P.P.
Published: July 2013

Optimum composition of Cd1xPbxSe thin films (0.1 x 0.9) were deposited using single precursor bath containing cadmium sulfate octahydrate, lead nitrate, tartaric acid, potassium hydroxide, ammonia and sodium selenosulfate onto fluorinedoped tin oxide (FTO) glass substrates. The photoelectrochemical (PEC) cells were fabricated using Cd1xPbxSe as an active photoelectrode with sulphide/polysulphide redox couple as an electrolyte and sensitized graphite rod as a counter electrode. The various characteristics of the cells namely currentvoltage (IV), capacitancevoltage (CV) in dark, power output, builtinpotential, photoresponse, spectral response measurements were investigated. The cell performance parameters such as opencircuit voltage (Voc), shortcircuit current (Isc), series resistance (Rs), shunt resistance (Rsh), conversion efficiency (η), fill factor (FF), junction ideality factor (nd), builtinpotential (ΦB), flatband potential (Vfb) were evaluated. PEC characteristics reveal ntype semiconducting nature for Cd1xPbxSe thin films with lead composition x < 0.5, while ptype nature for remaining Cd1xPbxSe thin films. Among the various cells, the maximum PEC efficiency (η = 1.401 %) was found to Cd0.7Pb0.3Se thin films; due to its increase in opencircuit voltage (225 mV) as well as shortcircuit current (3.983 mA/cm2),decrease in resistance (Rs= 0.75 kΩ and Rsh= 331 Ω), and increase in photoelectrode absorption as compared to other thin film materials.
Effect of Si Content on the Size of Fe-Rich Intermetallic Particles in Al-xSi-0.8Fe Alloys
Authors: Sivarupan Tharmalingam , Caceres Carlos H. , Taylor John A.
Published: July 2013

Al-Si-Fe plates with Si contents of 4.5, 9 and 11 mass %, unmodified and Sr-modified, were quasi-directionally solidified in sand moulds with chills at one end. The size and nature of the Fe-rich intermetallics were determined along the plates. Two forms of the intermetallic were observed, α-Al8FeSi and β-Al5FeSi, in proportions and scale dependent on the cooling rate and the Si concentration. The size of the β-phase increased with the concentration of Si at low cooling rates. At high cooling rates the tendency to form α-Al8FeSi phase increased with increasing Si content reducing the size of the β-plates. Modification generally increased the size of the pre-eutectically formed plates while reducing the post eutectically formed ones.
Effect of Ca Level on the Formation of Silicon Phases during Solidification of Hypereutectic Al-Si Alloys
Authors: Al-Helal Kawther , Wang Yun , Stone Ian , Fan Zhong Yun
Published: July 2013

In this paper the effect of Ca on the formation of Si phases during solidification of commercial purity Al-15Si alloy was studied. The Ca impurity level of the commercial purity alloy was 200 ppm which was sufficient to lead to a modified Al-Si eutectic. After the addition of K2SiF6 flux the Ca impurity level was 20 ppm which was insufficient to modify the eutectic Si, but primary Si was refined from 48 µm to 20 µm. The refinement of primary Si in Al-15Si alloy fluxed with K2SiF6, suggests that when Ca level is reduced to less than 20 ppm the impurity level of P (≈20 ppm) in commercial purity hypereutectic Al-Si alloys is sufficient to refine the primary Si without any deliberate addition of P. In the case of adding 0.5 wt.% Ca to the Al-15Si alloy, the eutectic Si was highly modified and the primary Si was coarse and irregular in morphology (unrefined). The addition of such a high level of Ca led to enhanced quantities of entrained oxide inclusions/bifilms. The first phase to solidify was Al2CaSi­2 which nucleated on the oxide bifilms. Primary Si then formed by nucleation and growth on the Al2­CaSi2 particles.
Microstructural Modeling of Mg Alloys and Experimental Validation
Authors: Paliwal Manas , Kang Youn Bae , Essadiqi Elhachmi , Jung In Ho
Published: July 2013

A systematic investigation was carried out in the present study to study the impact of solidification variables like thermal gradient (G), solidification velocity (V) and cooling rate on the second phase fraction and microsegregration in Mg-Al (3, 6 , 9 wt.%) binary alloys. Solidification experiments such as directional solidification and gravity castings were conducted to obtain a cooling rate in the range of 0.05-700 K/s. The experimental results were tested against the microstructural modeling data and a reasonable agreement was obtained between them.
Effect of Ti Addition on Mechanical Properties of High Pressure Die Cast Al-Mg-Si Alloys
Authors: Ji Shou Xun , Watson Douglas , Wang Yun , White Mark , Fan Zhong Yun
Published: July 2013

Titanium significantly improves the mechanical properties, especially the ductility of a diecast Al5Mg1.5Si0.6Mn alloy. When a titanium addition of 0.20 wt.% is made the elongation in the as-cast condition is increased from 11% to 18% and the yield strength is increased from 136 MPa to 157 MPa and the ultimate tensile strength from 296 MPa to 308 MPa. The improved mechanical performance can be attributed to the reduced tendency for hot tearing due to Ti addition.
Study of Mechanical Properties of an LM24 Composite Alloy Reinforced with Cu-CNT Nanofillers, Processed Using Ultrasonic Cavitation
Authors: Miranda Alberto , Alba-Baena Noe , McKay Brian J. , Eskin Dmitry G. , Ko Se Hyun , Shin J.S.
Published: July 2013

This study investigates the effect of Cu-Carbon Nanotube (Cu-CNT´s) composite powders on the mechanical properties of an Al-Si9.5-Cu4-Fe1.3 wt.% (LM24) aluminium matrix composite (AMC). Carbon nanotubes (CNT’s) can exhibit exceptional mechanical properties, e.g. stiffness up to 1000 GPa and strength in the order of 100 GPa. In recent years there has been significant scientific interest in improving properties in conventional alloys, via fabricating CNT metal matrix composites in order to attempt to harness their extraordinary attributes. In this study mechanically alloyed Cu-CNTS powders were added to molten LM24. The melt was processed using ultrasonic cavitation and subsequently high pressure die casting to form as-cast tensile specimens. SEM results indicate that CNT’s can be successfully introduced into the melt using this method. Compared to the unreinforced alloy, the CNT additions resulted in an increment (~20±10 MPa) to both ultimate tensile strength and yield strength, with a corresponding decline (~1±0.5l %) in elongation. This observed increase in strengthening may be attributed to the CNT’s pinning and hindering both grain boundary and dislocation migration during applied loading. Interestingly, no significant difference in properties were found with an increase in the CNT content (from 0.05 to 0.1 wt.%) potentially indicating a saturation limit.
A Study of the Behaviour of Double Oxide Films in Al Alloy Melts
Authors: El-Sayed Mahmoud , Salem Hanadi G. , Kandeil Abdel-Razik , Griffiths William D.
Published: July 2013

The mechanical properties of Al castings are reduced by inclusions, particularly double oxide films, or bifilms, which are formed due to surface turbulence of the liquid metal during handling and/or pouring. These defects have been reported not only to decrease the tensile and fatigue properties of Al alloy castings, but also to increase their scatter. Recent research has suggested that the nature of oxide film defects may change with time, as the air inside the bifilm would react with the surrounding melt leading to its consumption, which may enhance the mechanical properties of Al alloy castings. In order to follow changes in the composition of the internal atmosphere of a double oxide film defect within an Al melt, a series of analogue experiments were carried out to determine the changes in gas composition of an air bubble trapped in a melt of commercial purity Al, subjected to stirring. The bubble contents were analysed using a mass spectrometer to determine their change in composition with time. Also, the solid species inside the bubbles solidified in the melt were analysed. The results suggested that first oxygen and then nitrogen inside the bubble were consumed, with consumption rates of 2.5x10-6 and 1.3x10-6 mol m-2s-1, respectively. Also, hydrogen diffused into the bubble from the melt at an average rate of 3.4x10-7 mol m-2s-1, although the rate of H diffusion increased significantly after the consumption of most of the oxygen inside the bubble. Based upon these reaction rates the time required for a typical alumina bifilm to lose all its oxygen and nitrogen was determined to be just under 10 minutes.
Assessment of Quality when Delivering Molten Aluminium Alloys Instead of Ingots
Authors: Bjurenstedt Anton , Seifeddine Salem , Liljenfors Tomas
Published: July 2013

Recycled aluminium alloys manufactured at Stena Aluminium, in Älmhult, Sweden, are delivered in special designed transport containers, called thermoses. Thermoses are best described as an insulating layer protected by a steel cover with a heat loss of about 5 degrees/h. Three thermoses are transported by a truck, giving the possibility for a total capacity of about 24 tonnes delivered aluminium just-in-time to the foundry. By delivering a full load of liquid aluminium, about 2 tonnes of carbon dioxide emissions are saved, compared with delivering ingots.
The aim of the paper is to assess the quality benefits, in terms of inclusions sedimentation and mechanical properties, assured by delivering aluminium melts instead of ingots. The results indicate that materials produced by just-in-time melt delivery have slightly improved quality compared to ingots. The trends are explained in terms of quality, density and bifilm indexes, based on microstructural observations as well as tensile test data analysis.
Determination of the Magnitude of Interfacial Air-Gap and Heat Transfer during Ingot Casting into Permanent Metal Moulds by Numerical and Experimental Techniques
Authors: Swan Jason , Ward Mark , Reed Roger C.
Published: July 2013

Numerically and experimentally the size of the casting–mould air-gap was investigated for the aluminium alloy LM25 cast into a cylindrical H13 steel mould. The air-gap significantly affects the magnitude of heat transfer. A numerical model has been developed to predict the size of the air-gap and the temperature distribution along the metal-mould interface given an initial Interfacial Heat Transfer Coefficient (IHTC), dependent on the mould surface roughness, and sufficient knowledge of the radiative and thermomechanical properties of the casting and mould materials. The model is then able to predict the development of the air-gap and the resulting IHTC values over time. Validation was conducted experimentally by measuring the thickness of the air-gap using optical techniques to measure displacements of the mould and the casting surface during solidification. Temperatures of the mould and casting were also measured and allowed the time-varying IHTC to be calculated. A fair agreement between the numerical and experimental results was found, giving confidence in the numerical model’s ability to predict the magnitude of the air-gap and temperature distribution. This can be extended to regions where destructive measurement techniques were not used. The air-gap width for this casting process reached 0.6 mm, for which heat transfer by conduction was found to be dominant over radiative heat transfer.
Microstructural and Mechanical Characterization of AM60B Alloy Cast by RSF Process
Authors: Bassan Fabio , Timelli Giulio
Published: July 2013

The effects of different microstructural features on the mechanical properties of a conventional and semi-solid gravity sand cast AM60B alloy are investigated. The Rapid Slurry Forming (RSFTM) technology and a step casting geometry, with a range of thickness from 5 to 20 mm, have been used. Tensile specimens have been drawn from the middle and external regions of the casting. The results show that the microstructure of conventionally gravity cast step castings consist of primary α-Mg dendrites, while those cast from the semi-solid state show the presence of globular and rosette-like α-Mg phase. Partially divorced Mg-Mg17Al12 eutectic and fine intermetallic AlxMny compounds, distributed among the interdendritic channels and along grain boundaries, are also revealed. Due to low solidification rate, discontinuous precipitation of Mg17Al12 also takes place. The presence of primary blocky α-Mg phase and lower eutectic fraction tend to increase the mechanical properties of semi-solid cast Mg alloy.
Effect of A-EMS Melt Treatment Process on Microstructure and Property of Squeeze Casting Al-Zn-Mg-Cu-Sc Alloys
Authors: Zhang Zhi Feng , Wang Zhi Gang , Li Bao , Xu Jun , Wang Rui
Published: July 2013

An advanced rheo-squeeze casting process, based on the annular electromagnetic stirring (A-EMS) melt treatment technology was developed by GRINM for manufacturing near-net shape Al-alloy components with high integrity. Effects of A-EMS melt treatment process on microstructure and property of squeeze casting Al-Zn-Mg-Cu-Sc alloys were studied. The results revealed that the A-EMS melt treatment process apparently benefited grain refinement and homogeneity, and the hot-cracking of the test alloy for a complicated casting was significantly alleviated, and thus the strength and ductility of the casting were found to be comparable to those of conventionally forged alloys.
Tailoring Microstructure and Mechanical Properties of 6063 Aluminium Alloy for Lightweight Structural Parts
Authors: Chrominski Witold , Kulczyk Mariusz , Siwek Marcin , Lewandowska Małgorzata
Published: July 2013

In this work, an attempt has been made to improve the mechanical strength of 6063 aluminium alloy and thus its lightness via combination of severe plastic deformation (grain size refinement) and heat treatment (precipitation hardening). 6063 aluminium alloy was chosen as the best material for lightweight structures, where mass reduction is important, because of its high extrudability. Samples were hydrostatically extruded (HE) in supersaturated condition and subsequently subjected to an aging process. HE brings about significant grain size refinement well below 1 micron. The influence of aging parameters such as time and temperature on mechanical properties evolution of extruded material was determined. The microstructure of ultrafine grained (UFG) alloy was investigated using transmission electron microscopy. The average grain diameter and grain boundary misorientation angles (using Kikuchi lines) were measured. Mechanical properties were examined in microhardness and tensile tests. The results have shown that it is possible to combine grain boundary and precipitation strengthening and obtain ultrahigh strength in 6xxx series alloys. Additionally, heat treatment of UFG samples causes an increase in ductility measured in tensile tests, which is rather poor in severely deformed materials. To prove advantages of UFG aged samples for lightweight applications, finite element modelling was performed to compare the mass of chair elements made of coarse and ultrafine grained material. Simulations were made for the same stresses applied. It has been shown that if the chair was made of UFG aluminium alloy the mass reduction would be approximately 30 %.
Effect of Selected Alloying Elements on Aluminium Physical Properties and its Effect on Homogenization after Casting
Authors: Knych Tadeusz , Mamala Andrzej , Ściężor Wojciech
Published: July 2013

Modern technology for near net shape aluminium alloy flat rolled products includes twin roll casting, cold rolling and heat treatment. The technology is most common for 1XXX, 3XXX and 8XXX aluminium alloys. In fact, this technology of cold forming is applied to materials with as cast structure which may in some cases limit formability during rolling. As a consequence, the fundamental operation for high quality products is a well chosen homogenization process of material after casting. During the homogenization of 8XXX alloys after twin roll casting, important changes in electrical conductivity of the material have been reported in the literature. Possibly, the observed effects are connected with the migration of alloying element atoms in the microstructure. This study presents the influence of selected alloying elements on the electrical conductivity and mechanical properties of aluminium. On this basis, it is possible to analyse the effect and level of diffusion of alloying elements from particles to matrix and from matrix to particles during homogenization of 8XXX alloys in as cast temper. Additional comparison of experimental results with theoretical considerations via Nordheim’s rule was also analyzed in this study.
Development of a High Strength Cast Aluminium Alloy for Possible Automotive Applications
Authors: Shaji M.C. , Ravikumar Kuriakkattil Kunjayyappan , Ravi M. , Sukumaran K.
Published: July 2013

Al-Si-Cu alloys of the 319 type are age hardenable alloys and offer a good combination of mechanical properties with excellent castability, corrosion resistance and low cost, making these alloys attractive for the automotive industry. The mechanical properties of Al-Si-Cu alloys can be improved by minor alloying additions. The paper describes the attempts to develop a high strength cast aluminium alloy by the addition of Mg to 319 alloy for producing high integrity automobile components. The importance of optimizing the addition of Mg and optimization of the heat treatment parameters, especially the ageing temperature for achieving high strength, are explained. The increase in UTS is accompanied by a decrease in elongation. The elongation is proposed to be increased by the microstructural refinement that can be achieved by squeeze casting.
Relating Grain Misorientation to the Corrosion Behaviour of Low Copper 7xxx Aluminium Alloys
Authors: Cassell Alexander , Thompson George E. , Zhou Xiao Rong , Hashimoto Teruo , Scamans Geoff
Published: July 2013

High strength aluminium alloys provide benefits in vehicle efficiency and reduced energy consumption. Weldable, low copper 7xxx aluminium alloys are being developed for body-in-white production. Here, the influences of thermomechanical history on microstructure and, consequently, on the corrosion behaviour of lean 7xxx aluminium alloy sheet have been investigated. Cold worked microstructures in the alloys studied are susceptible to sub-surface cracking after accelerated corrosion testing. High resolution transmission electron microscopy (HAADF) with allied EDX analysis of a warm rolled alloy has revealed significant differences between some grain boundaries, showing differences in grain boundary precipitate distribution, which is influenced by grain misorientation and thermomechanical processing history. Possible relationships between the previously described phenomena are being sought. Electron backscatter diffraction has been employed to provide crystallographic information concerning grain orientation relationships from specific areas surrounding the attacked microstructure.
Electrochemical Corrosion Behaviour of WE54 Magnesium Alloy
Authors: Kazum O. , Kannan Mathan Bobby , Scharnagl Nico , Blawert Carsten , He Ying He
Published: July 2013

The electrochemical corrosion behaviour of WE54 magnesium alloy in 0.5 wt.% NaCl solution was studied using electrochemical techniques. Polarization results suggested that the rare-earths in WE54 alloy enhanced the passivation tendency of the alloy and decreased the corrosion current by ~30% compared to pure magnesium. Pitting corrosion resistance was also higher in WE54 alloy than that in pure magnesium. Long-term electrochemical impedance results showed that the polarization resistance of WE54 alloy was more than two times higher than that of pure magnesium even after initial passivity breakdown.
Microstructure and Microgalvanic Corrosion of an Extruded Mg-10Gd-2Y-0.5Zr Magnesium Alloy
Authors: Li Jian Ping , Wang Ping , Guo Yong Chun , Thompson George E. , Zhou Xiao Rong , Zhong Sheirley , Hashimoto Teruo
Published: July 2013

In the present study, the microstructure and corrosion behaviour of an extruded Mg-10Gd-2Y-0.5Zr alloy (noted as GW102) in 3.5 wt.% NaCl for different times have been investigated using a combination of computed phase diagrams, optical microscopy, high resolution scanning electron microscopy (SEM) and scanning Kelvin probe force microscopy (SKPFM). It was revealed that the extruded alloy is composed of fine recrystallized, equiaxed Mg solid solution grains. Additionally different second phases of varying sizes and shapes are present, including a large square-shaped Mg5(Gd,Y) particles which solidified from the melt and are located within the Mg grains and/or at grain boundaries, fine spherical zirconium-rich particles which are located in the Mg grains and fine needle-like precipitates of Mg5(Gd,Y) and Mg24(Gd,Y)5which are uniformly distributed within the Mg grain interior. The latter was formed during thermal extrusion processing. Further, a number of deformation bands or twins were found existing in the magnesium grains. SKPFM potential maps showed that Zr-rich particles and Gd(Y)-rich particles have positive potentials relative to the Mg matrix and the highest potential was recorded on Zr-rich particles. Immersion testing revealed that microgalvanic corrosion initiated at the periphery of Zr-rich particles due to their strong cathodic activity, thereby forming microgalvanic couples with the adjacent Mg grains.
Preliminary Design and Assessment of a Novel Electromagnetic Edge Dam for Aluminium Twin Roll Casting
Authors: McBrien Martin , Allwood Julian
Published: July 2013

Past work has shown non-contact, electromagnetic (EM) edge dams to be feasible alternatives to conventional refractory mechanical edge dams for containing liquid metal in twin roll casting, particularly in aluminium. However, these EM edge dams have had limited application. A novel EM edge dam geometry is proposed, applicable to a range of horizontal twin roll caster designs without significant modifications to the main caster structure. The design is analysed using finite element modelling. Static experiments using Wood’s metal are used to verify the performance of the proposed novel EM edge dam. The novel edge dam is compared with others in the literature, with particular attention to strength and stiffness constraints that determine the operating window.
Food Processing Trials Using Underwater Shock Wave by Electrical Discharge
Authors: Iwasa Seisaku , Maehara Hironori , Nishi Masatoshi , Tanaka Shigeru , Watanabe Toshiaki , Itoh Shigeru , Hokamoto Kazuyuki
Published: July 2013

We propose a new method for the efficient decompression of frozen food under high dynamic pressure. Two experiments are conducted on an ice block containing peeled shrimp: wire explosion and underwater shock wave. In these experiments, the ice is finely crushed, while the frozen peeled shrimps retain their original shape and can be efficiently extracted. Since ice crushing is performed momentarily, the defrosting time is significantly shorter than that in traditional thawing techniques, such as melting in running water or cold-water soaking. This new method could increase the efficiency of food production processes.
Measurement of Discharged Energy and Pressure of Underwater Shockwave Changing Materials of Contact Switch in High Voltage Power Supply
Authors: Matsui Takumi , Higa K. , Matsubara R. , Hanashiro S. , Higa O. , Itoh S.
Published: July 2013

We have developed the high voltage power-supply unit for ingenerate high pressure due to underwater shockwave by discharging and electrical sparking consists of Cockcroft-Walton circuit. This power supply has the problem of the contact switch operation due to melting of materials of contact switch by electrical spark. We have studied the optimization of materials of contact switch by reducing energy loss and problem of operation. In this research, We changed material of contact switch metal to carbon. And verified that new contact switch made of carbon is effective to reduce energy loss and solve problem of contactor switch operation.