bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Effects of Heat Flux Levels on Heat Release Rate of Wood
Authors: Ji Jingwei , Yang Liz-Hong , Chen Xiaojun , Fan Weicheng
Published: July 2003

The average heat release rate (AHRR) of some kinds of wood were measured using cone calorimeter under different heat flux intensities in this paper. The different heat release characteristics of these wood samples were analyzed theoretically. The temperature field of samples at the ignition time was also calculated. The complex structure, the chemical composition of wood (interior factors) and the external heat flux (exterior factor) are the main factors, which affect the heat release of wood. Both types of factors combine to give the heat release rate of wood distinct characteristics.
Evidence for Petrographic Variation between Small Samples of an Anthracite Coal
Authors: Godefroy J. , Jones J. C.
Published: July 2003

Results in a microcalorimeter for a UK anthracite coal at temperatures of 60 and 70°C are found to display a considerable spread which is tentatively attributed to petrographic variations between the samples. Results are compared with previously reported ones for a low-rank coal in the same instrument at lower temperatures.
Fire Model Analysis and Experimental Validation on Smoke Compartments
Authors: Kee-Chiang Chung , Yu-Lieh Wu , Hsien-Sheng Tung
Published: July 2003

Referring to fire accidental data, more than half the deaths from accidental fires are due to smoke rather than fire. In addition to using smoke curtain to accumulate smoke, it is necessary to consider appropriate smoke compartmentation effects for practical smoke control design. Otherwise evacuation and extinguishing systems would not be operated adequately. However, under the existing fire code of Taiwan, there are many constraints applied to construct smoke compartments inside buildings. Sometimes, it cannot work out for practical design purposes, such as the area of smoke compartments were limited without exception of performance consideration. Therefore, the purpose of this paper is to investigate the phenomena related to fire, heat, and smoke during some postulated fire scenarios occurring in a multicompartment enclosure and the distribution of smoke flow field.

Two different fundamental fire models, CFAST and SMARTFIRE, are used for analyzing and predicting the experimental results from a full-scale test. The comparison results show quite reasonable variations between numerical simulation and experimental data. Although the temperature data are higher than experimental data, the predicted smoke layer heights are lower than experimental data. However, the fire models present correct trend of accumulated smoke layer height and temperature distributions in a multi-compartment structure.
Influence of Surface Chemistry of Poly(Amidoamine) Dendrimers on Caco-2 Cell Monolayers
Authors: El-Sayed Mohamed , Ginski Mark , Rhodes Christopher A. , Ghandehari Hamidreza
Published: July 2003

The objective of this research was to investigate the effect of surface charge of poly(amidoamine), PAMAM, dendrimers on the integrity, paracellular permeability, and viability of Caco-2 cell monolayers by monitoring the transepithelial electrical resistance (TEER), mannitol permeability, and leakage of lactate dehydrogenase (LDH) enzyme, respectively. Neutral PAMAMOH, generations 2-4 (G2-G4), and anionic PAMAM-COOH (G-0.5-G4.5) dendrimers were incubated with Caco-2 cell monolayers at donor concentrations of 0.1, 1.0, and 10.0 mM for 90, 150, and 210 min. Neutral G2-G4 and anionic G-0.5, G0.5, G1.5 and G4.5 dendrimers did not cause any significant change in TEER or mannitol permeability across Caco-2 cell monolayers. Anionic G2.5 and G3.5 dendrimers, however, caused an incubation time-dependant decline in TEER values and up to a 6-fold increase in mannitol permeability. All anionic PAMAM-COOH dendrimers caused an incubation time-, concentration-, and generation-dependant LDH leakage that was not observed with neutral PAMAM-OH dendrimers. These studies suggest a size and/or charge “window” where anionic dendrimers may enhance paracellular transport across Caco-2 cell monolayers further confirming their potential as drug carriers and permeation enhancers for oral drug delivery.
Ceramic Drug Delivery: A Perspective
Authors: Paul Willi , Sharma Chandra P.
Published: July 2003

Different ceramic substances are offered in the market as bone substitute materials. These include monophasic calcium phosphate ceramics of tricalciumphosphate (TCP) or hydroxyapatite (HA), biphasic calcium phosphate ceramics and multiphasic bio-glasses synthetic calcium phosphate cements. Ceramics with appropriate three-dimensional geometry are able to bind and concentrate bone morphogenetic proteins in circulation and may become osteoinductive (capable of osteogenesis) and can be effective carriers of bioactive peptide or bone cell seeds and are therefore potentially useful in tissue engineering and drug delivery. An attempt has been made to review various drug delivery applications of ceramics.
Biological Reactions to a Poly(l-lactide)—Hydroxyapatite Composite: A Study in Canine Mandible
Authors: Cehreli Murat Cavit , Sahin Saime , Kesenci Kemal , Tuzlakoglu Kadriye , Piskin Erhan , Özturk Savas , Ruacan Sevket , Caner Biray , Bozkurt Murat Fani
Published: July 2003

In this study, bone response, possible use and ultimate fate of a chemically-synthesized poly (L-lactide)-hydroxyapatite (PLLA-HA) composite was experimented in canine mandible. Bilateral mandibular second premolars were extracted in four dogs. The PLLA-HA composite was placed into left surgical sites, and right extraction sites were used as controls. After three months of healing, bone specimens were harvested from each animal and processed for histological evaluation. Bone uptake of methylene diphosphonate (99mTc-MDP) was calculated as indicators of osteoblastic activity in the surgical sites. Histological evaluation and the amount of 99mTc-MDP uptake showed that all surgical sites had similar levels of cellular activity and the material was biocompatible. The experimental PLLA-HA composite studied is safe to be used as a small-defect filler in applications such as repair of alveolar defects, ridge augmentations, and sinus lift procedures.
The Effect of Fiber Reinforcement Type and Water Storage on Strength Properties of a Provisional Fixed Partial Denture Resin
Authors: Uzun Gülay , Keyf Filiz
Published: July 2003

Fracture resistance of provisional restorations is an important clinical concern. This property is directly related to transverse strength. Strengthening of provisional fixed partial dentures may result from reinforcement with various fiber types. This study evaluated the effect of fiber type and water storage on the transverse strength of a commercially available provisional resin under two different conditions. The denture resin was reinforced with either glass or aramid fiber or no reinforcement was used. Uniform samples were made from a commercially available autopolymerizing provisional fixed partial denture resin. Sixteen bar-shaped specimens (60 × 10 × 4 mm) were reinforced with pre-treated epoxy resin-coated glass fibers, with aramid fibers, or with no fibers. Eight specimens of each group, with and without fibers, were tested after 24 h of fabrication (immediate group), and after 30-day water storage. A three-point loading test was used to measure the transverse strength, the maximal deflection, and the modulus of elasticity. The Kruskal-Wallis Analysis of Variance was used to examine differences among the three groups, and then the Mann-Whitney U Test and Wilcoxon Signed Ranks Test were applied to determine pair-wise differences. The transverse strength and the maximal deflection values in the immediate group and in the 30-day water storage group were not statistically significant. In the group tested immediately, the elasticity modulus was found to be significant ( P = 0.042). In the 30-day water storage group, all the values were statistically insignificant. The highest transverse strength was displayed by the glass-reinforced resin (66.25 MPa) in the immediate group. The transverse strength value was 62.04 MPa for the unreinforced samples in the immediate group. All the specimens exhibited lower transverse strength with an increase in water immersion time. The transverse strength value was 61.13 MPa for the glass-reinforced resin and was 61.24 MPa for the unreinforced resin. The aramid-reinforced resin decreased from 62.29 to 58.77 MPa. The addition of fiber reinforcement enhanced the physical properties (the transverse strength, the maximal deflection, the modulus of elasticity) of the processed material over that seen with no addition of fiber. Water storage did not statistically affect the transverse strength of the provisional denture resin compared to that of the unreinforced resin. The transverse strength was lowered at water storage but it was not statistically significant. The transverse strength was enhanced by fiber addition compared to the unreinforced resin. The glass fiber was superior to the other fiber. Also the modulus of elasticity was enhanced by fiber addition compared to the unreinforced resin.
The Development of Porous Alginate/Elastin/PEG Composite Matrix for Cardiovascular Engineering
Authors: Chandy Thomas , Rao Gundu H. R. , Wilson Robert F. , Das Gladwin S.
Published: July 2003

The development of suitable three-dimensional matrices for the maintenance of cellular viability and differentiation is critical for applications in tissue engineering and cell biology. To this end, gel matrices of different proportions of alginate/elastin/polythylene glycol (Alg/Ela/PEG) were prepared and examined. The composite matrix membranes were evaluated for their porous scaffold using SEM, enzymatic degradation and water content. An equal blend of Alg/Ela with a ratio of Alg/Ela: PEG (7: 3) was selected for fabricating Alg/Ela/PEG scaffolds for this study. The Alg/Ela/PEG membranes fabricated at 20°C and -20°C had a mean surface pore size of 35-45 μm. However, their ultrastructures had shown bigger pore structures (60-75 μm) compared to their surface. It is interesting to note that the membranes of Alg/Ela/PEG prepared at 20°C had larger ultrastructural pores than that of membranes prepared at -20°C. Further, the SEM studies revealed that in the absence of PEG the composite membranes of Alg/Ela formed with less porous structures.

The water content of membranes prepared at 20°C was higher with Alg/Ela/PEG (61.6 ± 4.8%), compared to Alg/Ela (49.9 ± 0.3%). The enzymatic degradation and water content studies also revealed that the membranes fabricated at -20°C had high water uptake and low enzymatic degradation, as that of the membranes prepared at 20°C. In other words the larger pore structured membranes had less water content and high degradation profile. This study proposes that this novel composite matrix produces a hierarchical structure that is useful for generating tissue scaffolds for repairing the failing cardiac muscles. However, more detailed investigations with cytocompatibility studies are needed to find applications.
Water Sorption, Solubility and Dimensional Changes of Denture Base Polymers Reinforced with Short Glass Fibers
Authors: Polat Tülin N. , Karacaer Özgül , Tezvergil Arzu , Lassila Lippo V. J. , Vallittu Pekka K.
Published: July 2003

The aim of this study was to determine water sorption, solubility and dimensional stability of injection and compression-molded polymethyl methacrylate based denture base polymer that was reinforced with various concentrations and lengths of E-glass fibers. For water sorption and solubility, 20 test groups with different fiber contents and lengths of fibers were prepared. Test specimens without fibers were used as a control. The water sorption and solubility was measured after 90 days water storage. For dimensional stability, rhombic test specimens were prepared and the dimensional changes were measured after processing, drying and storing in water for 4 days and 30 days and were compared with those on the brass model.

The water sorption and solubility of injection-molded denture base polymer was lower compared to compression-molded specimens ( p<0.05). The dimensional accuracy of denture base polymer was not affected with fiber reinforcement ( p>0.05).
Immunological Study of a Chitosan Prosthesis in the Sciatic Nerve Regeneration of the Axotomized Dog
Authors: Rosales-Cortés M. , Peregrina-Sandoval J. , Bañuelos-Pineda J. , Sarabia-Estrada R. , Gómez-Rodiles C. C. , Albarrán-Rodríguez E. , Zaitseva G. P. , Pita-López M. L.
Published: July 2003

This study demonstrated that when the regeneration of the axotomized sciatic nerve is induced through tubulization with chitosan, this biomaterial does not induce immunostimulation or immunodepression in the dog. Canine females were distributed among three groups: an intact control group which was only isolated, an axotomized control group, and an axotomized group which was tubulized with 3% chitosan prostheses. In vitro culture and phagocytosis tests, as well as IgG and IgM serum concentrations, were determined in peripheral blood on days 0, 15, 30 and 60. The results showed that chitosan implants did not importantly affect the immune response.
Surface Reactivity of Calcium Phosphate Based Ceramics in a Cell Culture System
Authors: John Annie , Varma H. K. , Kumari T. V.
Published: July 2003

Surface reactivity of Calcium Phosphate materials - Hydroxyapatite (HA), Tricalcium Phosphate (β-TCP), Hydroxyapatite-Tricalcium Phosphate (HA-TCP) were elucidated in a cell culture system. MG-63 osteoblast-like cells were seeded onto the ceramic discs to evaluate changes in the cell morphology and functionality with respect to the different substrates.

The dissolution and re-precipitation of calcium phosphate phases on the surface of the discs in the culture medium was found to be prominent on β-TCP when compared with HA. Low calcium (Ca), magnesium (Mg) and alkaline phosphatase (ALP) levels and high phosphorous (P) levels in the medium of β-TCP were observed. This indicated that P must have leached out into the medium from β-TCP and Ca in turn deposited from the medium onto β-TCP resulting in the apatite phase transformation. The low ALP activity in β-TCP medium is however an indication of low osteoblastic activity.

Under the phase contrast microscope, the osteoblast cells around HA material were found to be confluent and viable, while in the vicinity of β-TCP only cellular debris was observed. In the case of HA-TCP, only a few viable cells surrounded the material amidst the debris. Scanning electron microscopy revealed numerous cells on the surface of HA showing different cell behaviour like anchorage, attachment, adhesion and spreading in the early time period as the surface was only slightly disturbed with re-crystallisation. But with time the entire surface of HA had changed due to precipitation and re-crystallization which did not support cell behaviour while the cells surrounding the material showed normal growth. On the contrary, cells were scarcely observed on the entirely changed surface of β-TCP and HA-TCP even from the earlier days of the culture and the morphology of cells surrounding the material too started changing.

These results establish that HA promoted the activity of osteoblast cells. HA surface remained unaltered for some time, while the surface of β-TCP underwent dissolution of surface ions and resulted in the re-crystallization of apatite over the surface. The resulting changes in the surrounding milieu of β-TCP with high phosphate and low Ca levels probably was responsible for the death of the cells.
Vibration Welding Nylon 66 — Part II Finite Element Analysis
Authors: Bates P. J. , MacDonald J. J. , Wang C. Y. , Liang H.
Published: July 2003

The stress fields of vibration welded joints under different loading and boundary conditions were obtained using an elastic-plastic finite element model with a weld zone. The stress analysis focused on the effect of material and geometry on the joint strength. T-welded and cup-plaque welded joints were chosen to study the effect of geometry on joint strength. The results of the analysis were compared with the experimental data of unreinforced and 33% glass reinforced nylon 66. The numerical FEA results successfully explain the experimental strength and failure mode observed on complex joint geometries.
Effect of Ageing on the Mechanical Properties of Short Sisal Fibre Reinforced Polystyrene Composites
Authors: Nair K. C. Manikandan , Thomas Sabu
Published: July 2003

The water absorption behaviour and the effects of ageing on the mechanical properties of short sisal fibre reinforced polystyrene composites have been studied with special reference to fibre loading and fibre-matrix interface modification. The composites were subjected to different ageing conditions viz., immersion in boiling water for 24 h, immersion in cold water for 15 days and exposure to hot air at 80°C for five days. The interface modifications were performed by benzoylation, polystyrene maleic anhydride (PSMA) treatment, toluene diisocyanate treatment and silane treatment. The tensile properties and dimensions of the aged samples were measured and compared with unaged samples. The water uptake was found to increase with fibre loading and decrease with fibre modifications. However, PSMA treatment and silane treatment do not produce much variation in water uptake. The mechanical properties and dimensional stability of the treated fibre composites were found to be superior to those of untreated composites under identical ageing conditions. However, it is interesting to note that on water ageing, untreated fibre composites show minimum decrease in tensile strength compared to treated fibre composites and can be explained based on the thermal shrinkage of the polystyrene matrix. The superior properties of the treated composites were associated with the better interfacial interactions in treated fibre composites.
A Study on the Physical Properties of Rock Wool Fiber—Polystyrene Composite
Authors: Zihlif A. M. , Ragosta G.
Published: July 2003

The physical properties of rock wool fiber-polystyrene composites have been studied as a function of temperature, frequency, filler content and morphological aspects. The glass transition temperature, mechanical properties, dielectric constant and morphology showed dependence on the rock fibers' concentration. The physical properties of the prepared composite were correlated with the morphology and its glass transition temperature.
Performance Evaluation of ER Shock Damper Subjected to Impulse Excitation
Authors: Song H. J. , Choi S. B. , Kim J. H. , Kim K. S.
Published: July 2003

This paper presents shock responses of a cylindrical shock damper featuring an electrorheological (ER) fluid. An appropriate size of the ER shock damper is designed and manufactured on the basis of the field-dependent Bingham model of the ER fluid. The damping force of the ER shock damper is evaluated with respect to the excitation frequency at various electric fields. Subsequently, the ER shock damper is incorporated with a 1 degree-of-freedom (DOF) dynamic system in order to investigate shock responses. A skyhook controller is formulated to attenuate acceleration level due to impulse excitation and empirically realized. Controlled acceleration magnitudes are evaluated and compared with uncontrolled ones at various excitation frequencies.
An Experimental Investigation on Mechanical Fatigue Property of Chemical Starch-Based ER Fluids
Authors: Lee H. G. , Choi S. B. , Kim J. H. , Lee K. J.
Published: July 2003

In this work, mechanical fatigue properties of a chemical starch-based ER fluid are empirically investigated. To do this, a flow-mode type electroviscometer, which has the same working mode as the cylindrical ER damper, is constructed. The linear reciprocating motion is obtained by driving a hydraulic power unit, and the number of fatigue cycle is measured by the limit switch. The field-dependent yield stress and response time to step input are evaluated as a function of the operating cycle. In addition, the vibration control performance of ER suspension for a passenger car is analyzed by incorporating the full-vehicle model with the yield stresses evaluated at different operating cycles.
Numerical Simulation of MR Fluid Damping Characteristics Using a Modified Bingham Model
Authors: Nishiyama Hideya , Fushimi Shigemi , Nakano Masami
Published: July 2003

A numerical simulation is conducted to clarify the unsteady flow behavior and drag force around the oscillating flat plate immersed in MR fluids under the applied magnetic field. A modified Bingham model is adopted to take continuous viscous flow behavior at the very small shear rate and also magnetically variable yield stress into account. The measured yield stress is given to the model as a function of magnetic field intensity. The governing equations for the oscillating flat plate and unsteady MR fluids flow are derived by a modified Bingham model taking magnetic body force, yield stress and viscous force into account. The effects of magnetic field intensity, oscillation frequency and amplitude and further plate thickness on the fluid flow and damping characteristics around the oscillating flat plate are clarified by the numerical simulation.
The Rheological Characteristics of Electrorheological Fluids in Dynamic Squeeze
Authors: El Wahed Ali K. , Sproston John L. , Stanway Roger
Published: July 2003

This paper is concerned with an experimental and theoretical determination of the rheological performance of an electrorheological (ER) fluid when subjected to time-dependent applied loads. The experimental facility was built as a squeeze cell in which the fluid is sandwiched between two electrodes, one fixed and the other moving, which permits the instantaneous measurement of the mechanical and electrical responses of the fluid. The transient rheological characteristics of the fluid were assessed for various mechanical force levels and for constant voltage excitation of the fluid. Input and output stress levels across the fluid were monitored enabling the dynamic response of the fluid to be determined using a combination of displacement, force, velocity and acceleration transducers. The experimental results were compared with the results from a modified theoretical analysis, which employs a bi-viscous shear stress/shear strain characteristic of the electrically stressed fluid together with a fluid yield stress, which has a strain-direction dependence on the electric field.
MR Inserts for Shock Wave Reduction in Warship Structures
Authors: Kim J. H. , Kang B. W. , Park K. M. , Choi S. B. , Kim K. S.
Published: July 2003

The underwater explosion that has high energy brings about the shock wave and the pulsating gas bubble. In general, structural vibration from the shock wave is more serious than the pulsating gas bubble. This shock wave may damage the important fragile structures and equipment in the ship. This paper demonstrates the possibility of shock wave reduction in magneto-rheological (MR) inserts. The wave transmission of MR insert beam is experimentally investigated. A MR insert in an aluminum plate is made and two piezoelectric disks are used as transmitter and receiver. The transmission ratio between the transmitter and receiver is tested with and without magnetic field on the MR insert. The MR insert of the structure shows the capability of shock wave reduction. Details of the experiment are addressed.
Adhesive Layer Effects in Surface-Mounted Piezoelectric Actuators
Authors: Rabinovitch Oded , Vinson Jack R.
Published: July 2003

The role of the adhesive layers in active panels with surface-mounted (bonded) piezoelectric layers is studied. The investigation focuses on the strain transfer mechanism between the active layers and the host structure, the stress concentrations involved, and the influence of the geometrical and mechanical properties of the adhesive layers on the static response of the panel. The analysis is based on the High-Order approach and uses 2D elasticity to model the adhesive layers. The mathematical formulation is derived using variational principles, compatibility requirements, and the piezoelectric constitutive equations. Confirmation of the analytical model is achieved through an experimental study that reveals good agreement between the theoretical predictions and the behavior of the active structure. Numerical results are presented for a typical piezoelectric active panel and compared to detailed 2D finite element analysis. The results reveal the high-order effects and the stress concentrations in the transition zone near the edge of the panel and indicate that a careful selection of the adhesive's properties can improve the behavior of the structure and reduce the severity of the stress concentrations involved. The paper concludes with a summary and recommendations for the analysis, design, and use of smart structures with bonded actuators.
Design and Control Considerations for a High-Speed Electro-Rheological Traversing Mechanism
Authors: Johnson Andrew R. , Bullough William A. , Makin John
Published: July 2003

A high-speed traversing mechanism using two electro-rheological clutches is described. An application of the traversing mechanism is in winding textile filaments onto spinning or weaving bobbins. The design specifications are a traverse speed of 5m/s; a turn round period of 10-20 ms and a traverse length of 250 mm. The turn round position must be controllable and repeatable within ± 1 mm and the traverse length requires to be periodically varied in order to shape the ends of the resulting bobbin. These combined criteria of high speed and controllability makes the use of electro-rheological fluids an attractive proposition. The paper considers the effects of the main geometric and fluid parameters on the performance of the mechanism and uses this to outline the limiting performance of the mechanism, together with the effects on the precision of the mechanism. The paper also outlines control aspects of the mechanism and uses this to indicate important areas for consideration in the future development of electro-rheological fluids.
Application of the Relaxed Free Energy of Mixing to Problems in Shape Memory Alloy Simulation
Authors: Hall Garrett J. , Govindjee Sanjay
Published: July 2003

Recent theoretical advances in the development of functional representations for the free energy of mixing associated with solid-solid phase transformations has made possible the development of a new class of constitutive models based directly on bounds to the relaxed free energy. The present work, which continues that of Govindjee et al. (2002) and Hall and Govindjee (2002), demonstrates the application of the theory to the simulation of the complex behavior exhibited by shape memory alloys. The first three case studies undertaken herein support the validity of the theoretical approach by analyzing subtle aspects of the physics associated with such phase transformations. The final simulation, a torsion tube under combined loading, provides impetus for future experimental and theoretical advancements.
Transformation Surfaces of a Textured Pseudoelastic Polycrystalline Cu-Zn-Al Shape Memory Alloy
Authors: Aleong Douglas , Dumont Cyril , Chirani Shabnam Arbab , Patoor Etienne , McDowell David L.
Published: July 2003

Pseudoelasticity is a useful regime of behavior for industrial applications of shape memory alloys. The complexity of the physical phenomena of pseudoelastic shape memory behavior requires micromechanical methods of scale transition to model at higher length scales using crystallographic information. Using a self-consistent model to transition from single crystal to polycrystal behavior, we present results for computed surfaces of constant effective transformation strain for random, drawn, tension, compression and rolled textures of a polycrystalline Cu-Zn-Al shape memory alloy in the pseudoelastic regime. These results are relevant to the development of macroscopic transformation surfaces in stress space. A feature of the results is that normality of transformation strain rate to surfaces of constant macroscopic transformation strain is observed for the most part, apart from regions of high curvature that bridge different segments of the transformation surface.
Simulation of the Damping of a Shape Memory Alloy Rod by Using the Likhachev Model
Authors: Pushtshaenko O. , Oberaigner E. R. , Antretter T. , Fischer F. D. , Tanaka K.
Published: July 2003

In this paper vibration damping of a shape memory alloy rod is studied. The mathematical model includes the heat conduction equation, the stress wave equation, a kinetic law and a constitutive law. As kinetic law the Likhachev model is used, which describes the one-way effect, pseudoelasticity properties and thermal loading cycles. It is observed that the vibration amplitude of the rod decreases in this model very quickly. Results are in good agreement with earlier investigations, where other kinetic laws have been used.
Application of Fiber-Optic Distributed Sensors to Health Monitoring for Full-Scale Composite Structures
Authors: Murayama Hideaki , Kageyama Kazuro , Naruse Hiroshi , Shimada Akiyoshi , Uzawa Kiyoshi
Published: July 2003

The purpose of structural health monitoring (SHM) is to lead a structure to be safer at lower cost. SHM systems capable of assessing structural integrity during manufacture and in-service operation would allow timely maintenance actions to increase safety and lifetime of structures. In such systems, it is important to evaluate the actual state of a structure. Recently, fiber-optic sensors have been actively developed, and one can measure many kinds of the physical measurands by them. Since they also have excellent characteristic, such as immunity of electromagnetic interference, durability and capability to realize distributed sensing, they are supposed to be suitable sensors for SHM systems. We installed fiber-optic sensors into full-scale composite structures to monitor strain or temperature during manufacture or to monitor in-service structural performance, i.e., stiffness. The structures applied with the sensors are International America's Cup Class (IACC) yachts and a Japanese experimental reentry vehicle, namely, HOPE-X, that are made of carbon fiber reinforced plastic. The fiber-optic sensors used in this study are two kinds of distributed sensors using Brillouin scattering and Raman scattering, respectively. The former can measure strain or temperature and the latter can measure temperature at an arbitrary region along an optical fiber. We could successfully measure strain or temperature of the full-scale composite structures in field and access the structural state. The results of this study demonstrate the great potential of fiber-optic distributed sensors for practical applications to large composite structures.
Control of Shape Memory Alloy Actuators Using Pulse-Width Pulse-Frequency (PWPF) Modulation
Authors: Song G. , Ma N.
Published: July 2003

This paper presents the design and experimental results of control of a Shape Memory Alloy (SMA) actuator using Pulse-Width Pulse-Frequency (PWPF) modulation to reduce the energy consumption of the SMA actuator. An SMA wire test stand is used in this research. Based on results of open-loop testing of the SMA wire actuator and parameter analysis of the PWPF modulator, a PWPF modulator is designed to modulate a Proportional plus Derivative (PD) controller. Experiments demonstrate that control of the SMA actuator using PWPF modulation effectively save actuation energy while maintaining same control accuracy as compared to continuous PD control.
A Remote Electromechanical Vibration Absorber
Authors: Nichols Todd S. , Ghoneim H.
Published: July 2003

A remote energy-absorbing technique for the vibration suppression of beams is introduced. The technique is based on the idea of coupling the primary beam to a remote dynamic absorber (RDA) beam electromechanically via piezoelectric elements. A thorough experimental/analytical investigation of the concept, using a RDA beam identical to the primary beam as had been suggested previously, has been conducted. In addition to elucidating the limitations of the concept, the investigation demonstrated that using identical RDA would not work. Instead, a tuned RDA, where the electromechanical coupling stiffness is incorporated in the RDA, is proposed and analytically studied. The study suggests that this tuned RDA concept is valid and may even be practical.
Intelligent Bi-State Control for the Structure with Magnetorheological Dampers
Authors: Xu Zhao-Dong , Shen Ya-Peng
Published: July 2003

Magnetorheological (MR) damper is a kind of intelligent control device, which can be used to reduce earthquake responses of building structures. In this paper, a mathematical model of MR dampers is introduced, and the relation between the yielding shear stress and the control current of MR dampers is formulated. Then the bi-state control strategy of the structure with MR dampers is studied. Results show that the control strategy easily leads to overrun of the parameters and the control force of MR dampers under the minor earthquake, which results in amplification of acceleration responses of the structure. For this reason, a modified bi-state control strategy is proposed. In this method, the neural network technique is used to predict the seismic responses of the structure, whilst the intelligent bi-state control strategy on the smart structure with MR dampers is applied to solve the time-delay problem of semiactive control. Numerical simulation of a three-story reinforced concrete frame structure with MR dampers and without MR dampers are performed using the bi-state control method, the modified bi-state control method and the intelligent bi-state control method. Results show that the intelligent control strategy solves the time-delay problem of semiactive control and overrun of control forces under the minor earthquake, and the control force is most veritable and the earthquake mitigation effect is the best.
Hybrid Multidamped Composite Plates with Viscoelastic Composite Plies and Shunted Piezoelectric Layers
Authors: Plagianakos Theofanis S. , Saravanos Dimitris A.
Published: July 2003

A laminate mechanics formulation and a finite element method are presented for predicting the overall damping of composite laminates with shunted piezoelectric layers. The mechanics encompass both damping contributions of the viscoelastic composite plies and the resistively shunted piezoelectric layers. A novel plate finite element is formulated for analyzing the total damping capacity of laminated piezocomposite plate structures. The modal damping of composite beams with a shunted piezoceramic patch is measured for variable shunting resistance and correlated with predicted values. Numerical results for beams and plates illustrate the strong dependence of each damping mechanism on the laminate configuration, and their beneficial interaction in producing a more uniform overall damping capacity in composite structures.
Study of the Behavior of MR Fluids in Squeeze, Torsional and Valve Modes
Authors: Kulkarni P. , Ciocanel C. , Vieira S. L. , Naganathan N.
Published: July 2003

In order to understand the effectiveness of MR fluids in some applications, such as bearings, this work focuses on the properties of MR fluids under squeeze mode, torsional mode and squeeze combined with torsional mode. A special device was designed and fabricated to perform these experiments, which were carried out on an Instron Multiaxial Testing Machine. The hysteresis loops of the MR fluids were studied for different intensities of electric current, frequency, strain amplitude and angle amplitude. The results showed that the damping force and the area of the hysteresis loop of MR fluids increase with the current and strain amplitude. Changes on the frequency did not influence the stress values significantly, within the range of frequencies used in these experiments. In order to evaluate the performance of a squeeze film damper (SFD), measurements were made using a MR damper manufactured by Lord Corporation (RD1005), which operates in valve mode. The results of the SFD were compared to the ones obtained with the RD1005 damper. The shape of the hysteresis loop curves and the MR effect were found to be different for the squeeze film damper and the RD1005 damper.
Controlling Tube Vibration Using an Electro-Rheological Fluid
Authors: Oyadiji S. O.
Published: July 2003

The vibration transmissibility characteristics of a cantilevered brass tube are controlled by means of an electro-rheological (ER) fluid which is employed as a constrained layer damping medium. The ER fluid, which is a 50 wt.% mixture of silicone oil and starch, was contained in the annular space formed between the outer surface of the tube and the inner surface of a bigger brass tube. It is shown that the modal characteristics of the tube depend on the electric field strength and on the height of the ER fluid. The modal frequencies of the tube increase as the electric field strength is increased and as the height of the ER fluid is increased. Also, the loss factors generally increase as the electric field is increased, but decrease as the height of ER fluid in the annular space is increased. When the annular space is 100% filled with ER fluid, the fluid effectively couples the inner and outer tubes into one vibrating system. Overall, the modal transmissibility of the tube is least when the annular space is filled with the ER fluid to a level of 12.5% of the maximum and an electric field strength of 1 k V/mm is applied.
Heat Transfer from an ESF Radial Plate Clutch Surface
Authors: Ellam D. J. , Bullough W. A. , Oravský V.
Published: July 2003

The aim of this work was to investigate the rate of heat transfer from a radial plate clutch surface. The paper presents experimental results over a range of angular speeds (Ω) and fluid gap widths ( h ), which are then favourably compared to analytical and computational fluid dynamics (CFD) solutions for the same geometry and operating conditions. Verifying the heat transfer capabilities of the latter goes some way towards validating the CFD package as a viable virtual prototyping method. The results allow a procedure to be established for the selection of a good electro-structured fluid (ESF) clutch design.
Design and Development of a High Pumping Frequency Piezoelectric-Hydraulic Hybrid Actuator
Authors: Sirohi Jayant , Chopra Inderjit
Published: July 2003

This paper describes the design and development of a piezoelectric-hydraulic hybrid actuator operating at a high pumping frequency. The actuator is envisaged as a potential actuator for a trailing edge flap on a full scale smart rotor system. While recent research efforts based on the same concept have investigated actuators with large piezoelectric stacks operating at a relatively low pumping frequency, the goal of the present work is to investigate the behavior of the actuator at a low volumetric displacement and high pumping frequency. Preliminary design of the actuator system is carried out, and the dependence of the performance of the actuator on various system parameters is identified. This enables the optimum selection of geometric parameters and piezostack characteristics for a given external load. Challenges to achieving high pumping frequencies were identified and solutions were implemented. The actuator was driven by two piezostacks, of a total length of 36 mm and cross-sectional area 100 mm 2 . The actuator was tested up to a pumping frequency of 1 kHz, developing a maximum no-load velocity of 1.2 in/s and a blocked force of 35 lb in the unidirectional output mode. Bidirectional output performance was also measured, by incorporating a 4-way valve in the hydraulic circuit. At a frequency of 5 Hz, a no-load output displacement with an amplitude 32 mils was measured.
Modeling of Plate Structures Equipped with Current Driven Electrostrictive Actuators for Active Vibration Control
Authors: Pablo F. , Osmont D. , Ohayon R.
Published: July 2003

The study here reported is focused on active vibration control applications performed on plate host structures equipped with electrostrictive patches. In such applications the design of controllers requires to simulate the behavior of the coupled structure. These simulations can then be performed through a Finite Element Method which implies the elaboration of electrostrictive finite elements. The purpose of the present paper is to use the electrostrictive plate finite element elaborated in a previous paper such as to simulate active vibration control of a cantilever beam equipped with current driven or voltage driven electrostrictive actuators. From these numerical results it is shown that a linear controller is as efficient as a nonlinear one in terms of vibration absorption, whatever the driving input used. An experimental implementation of the current driving input is moreover presented. Based on experimental measurements, it is proved that current driving electrostrictive actuators induce a decrease of electric energy consumption compared to a classical voltage driving input.
Development of a PVDF Piezopolymer Sensor for Unconstrained In-Sleep Cardiorespiratory Monitoring
Authors: Wang Feng , Tanaka Mami , Chonan Seiji
Published: July 2003

This paper reports the development of an unconstrained sensing technique for monitoring the respiration and heartbeats during sleep using a polyvinylidene fluoride (PVDF) piezopolymer film sensor with the aim that the sensor can be used on the ordinary bed together with the condition that the use of the sensor does not interfere the daily sleep of the patient under measurement. A PVDF film is used as the sensory material in the sensor system. The film is placed under the sheet at the location of the thorax to pick up the fluctuation of the pressure on the bed caused by the respiratory movement and heartbeats. Wavelet multiresolution decomposition analysis is used for the detection of respiration and heartbeat from the sensor output. It is shown that the respiration and heartbeats can simultaneously be detected by the sensor with the use of the wavelet multiresolution decomposition analysis.
Cohesive-Shear-Lag Model for Cycling Stress-Strain Behavior of Unidirectional Ceramic Matrix Composites
Authors: Yang B. , Mall S.
Published: July 2003

During fatigue tests of fiber-reinforced ceramic matrix composites (CMCs), the stress-strain hysteresis loops undergo typically through various changes in shape and size before they stabilize after many cycles. These hysteresis loops are a good representation of intrinsic deformation and damage modes occurring in the materials. The present study proposes a cohesive-shear-lag model to analyze the cyclic stress-strain behavior of unidirectional fiber-reinforced CMCs. The model, as a modification to classical shear-lag model, takes into account the effects of spatially distributed fracture of a partial number of fibers as well as matrix cracking and partial interfacial debonding. The effect of the distributed fibers fracture is modeled in an average sense by using a cohesive damage law. The proposed model has been utilized to investigate the stress-strain hysteresis loops of a unidirectional fiber-reinforced ceramic-glass matrix composite, SiC/1723. The results demonstrate its capability not only in characterizing the cycling stress-strain behavior but also in tracking the progressive damage process that occurred during the tension-tension fatigue of the composite. The dominant progressive damage mechanisms in this case were found to be accumulation of fibers breakage, growth of fiber-matrix interfacial debond, and smoothening of frictional debonded interface, following matrix cracking, which presumably occurred in the first few cycles.
Brittle Elastoplastic Damage Constitutive Model for Jointed Rockmasses and Computation Concerning Bolt-Reinforcement
Authors: Zhu Weishen , Zhang Qiangyong , Li Shucai , Lee C. F.
Published: July 2003

The present paper puts forward a 3D brittle elastoplastic damage fracture constitutive model (BEPDFC model) for jointed rockmass, which is established according to the evolution equation for energy damage of rock fissures, the generalized orthogonal flow rule and the conformability conditions of plastic damage. On the basis of this constitutive model, a cylindrical damage rock-bolt element model (CDRBE model) is proposed to simulate the reinforcing effect of bolts. Finally, the proposed models are applied to the stability analysis of the high slopes of ship lock of Three Gorges Project being under construction. The 3D nonlinear FEM analysis on the jointed rockmass of high slopes gives satisfactory results.
Damage Evolution in Elasto-Plastic Materials - Material Response Due to Different Concepts
Authors: Olsson Mattias , Ristinmaa Matti
Published: July 2003

The purpose of this paper is to show that shortcomings exist in the plasticity induced damage theories. Existing phenomenological thermodynamic approaches used for describing elasto-plasticity coupled with damage are therefore evaluated. Within the concept of effective stress both the postulate of strain equivalence and the postulate of (complementary) energy equivalence, as well as extensions of the postulates, are considered.

As a prototype model the von Mises plasticity model coupled with isotropic damage is considered. Simulations of a strain-controlled uniaxial model are also performed. The results reveal that a mapping, similar to that of the stress, of both the kinematic and isotropic hardening variables is to be preferred. More interesting is that, irrespective of the postulate employed, the elastic strain will not equal zero when failure takes place, i.e. the interpretation of elastic strain is lost. From the results it is also concluded that (complementary) energy equivalence have some undesirable properties.
The Mechanical Behavior Analysis of CFCC with Overall Anisotropic Damage by the Micro-Macro Scale Method
Authors: Luo Dongmei , Takezono Shigeo , Tao Katsumi , Minamoto Hirofumi
Published: July 2003

In this paper, a micro-macromechanical approach is used to establish the macroscopic constitutive model with anisotropic damage in continuous fiber reinforced ceramic matrix composites (CFCC). For microlevel analysis of unit cell, the homogenization method based on double-scale asymptotic expansion is used to derive the material properties of composites. The macrolevel analysis is conducted to compute the macrostresses and strains with anisotropic damage. The two analyses are conducted by using Finite Element Method (FEM). An overall anisotropic damage tensor for the whole composite is used to describe all types of damage that composite undergoes, such as matrix cracking, fiber breakage, and interfacial damage between matrix and fiber. The damage evolution equation is obtained by using thermodynamic theory. The numerical calculation is carried out to investigate and to predict the onset and evolution of anisotropic damage for composites with different types of laminate. The damage material parameters are determined by fitting the numerical results to the experimental data, and some results are compared well with experimental results in the literature [Wang, S.W. and Parvizi-Majidi, A. (1992). Experimental Characterization of the Tensile Behavior of Nicalon Fiber-Reinforced Calcium Aluminosilicate Composites, Journal of Materials Science, 27: 5483-5496.]. By using the proposed model, the stiffness and nonlinear stress-strain response of brittle composite materials are predicted, and the macroscopic elastic brittle anisotropic damage behavior is also described