bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Shear Deformable Shell Elements for Adaptive Laminated Structures
Authors: Iozzi Riccardo , Gaudenzi Paolo
Published: July 2008

An effective mixed interpolation approach for shell elements is here extended to the analysis of adaptive shells consisting of a sequence of active and passive layers. An active layer – made by a piezoelectric material or a similar active medium – is assumed to be included in the stacking sequence of a laminated shell. The actuation capability of the layer is represented by a given inplane strain field that can be thought of as being produced by the converse piezoelectric effect or other induced strain actuation mechanism. In this way, the actuation mechanism is included in the formulation of shear deformable shell element that has been demonstrated not to suffer of shear locking effects. A four node element was developed. Several comparisons have been performed to verify the accuracy of the formulation and to check the predicting capability of the element in comparison with both numerical and experimental results of the recent available literature. Also an application to a real composite structure is illustrated in order to demonstrate the possible use of the proposed element in the engineering practice.
Integration of Smart Materials into Dynamics and Control of Inflatable Space Structures
Authors: Park Gyuhae , Kim Myung-Hyun , Inman Daniel J.
Published: July 2008

An experimental investigation of vibration testing and control of an inflated thin-film torus is presented. Lightweight inflatable structures are a viable alternative in aerospace structure design. These structures, however, pose special problems in testing and in controlling vibrations due to their extremely lightweight, flexible, and high-damping properties. In this study, we show that smart materials, which can be fully integrated into an inflatable space system, could be used as sensors/actuators in order to find modal parameters and to reduce vibrations. The results indicate the potential smart materials for use in the dynamics and control of inflated structures.
New Microscopic Polishing with Magnetic Compound Fluid (MCF)
Authors: Shimada Kunio , Akagami Yoichi , Kamiyama Shinichi , Fujita Toyohisa , Miyazaki Toshio , Shibayama Astushi
Published: July 2008

We propose a magnetic compound fluid (MCF) as a new smart fluid. This fluid includes nm size magnetite and mm size iron particles in a solvent. The magnetic effect can be expected to demonstrate between the magnetic fluid (MF) and magneto-rheological fluid (MRF). Moreover, the magnitude of the shear stress to the shear rate under steady magnetic field can be larger than MRF by varying the compound rate of the MF and MRF. This report shows an experimental application of microscopic polishing with the MCF. We examined the surface roughness of flat titanium material to the attached rotating plate with 15 rpm under magnetic field. By comparing the roughness between the MCF and the MR, the polished plate is more uniformly over the plate with the MCF than the MR. Further the roughness of Ry and Ra are larger under fluctuating magnetic field than steady magnetic field. The more effective polishing can be explained with the cluster model of particles.
A Study on the Vibration Attenuation of a Driver Seat Using an MR Fluid Damper
Authors: Lee Yeongrok , Jeon Doyoung
Published: July 2008

A seat suspension system with a controlled magneto rheological (MR) fluid damper is introduced to improve the ride quality and prevent the health risk of a driver compared to conventional seats. The system locates between a seat cushion and base, and is composed of a spring, MR fluid damper and controller. The MR fluid damper designed in valve mode is capable of producing a wide range of damping force according to applied currents. In experiments, a person was sitting on the controlled seat excited by a hydraulic system. The skyhook control, continuous skyhook control and relative displacement control were applied and the continuous skyhook control improved the vibration suppression by 36.6%.
Electrorheological Semi-Active Damper: Polyaniline Based ER System
Authors: Kim J. W. , Cho Y. H. , Choi H. J. , Lee H. G. , Choi S. B.
Published: July 2008

Among various materials suitable for an electrorheological (ER) fluid, polyaniline and its many derivatives based upon modification of oxidation state, dopant and polymerization conditions are of technological interest for their adaptation into ER fluids. This is because they have better thermal stability and smaller density than other potential ER materials. Furthermore, polyaniline is easy to polymerize by oxidation polymerization at relatively low temperature and can be doped from a conducting emeraldine hydrochloride form to an insulating state using simple protonic acids. In this study, we adapted the polyaniline based ER fluids for semi-active cylindrical flow-mode type ER damper. A cylindrical flow-mode type ER damper was chosen in this study because it has similar geometrical configuration to the conventional damper normally used for passenger vehicle. The damping forces measured using a semi-active ER damper with polyaniline based ER fluids were found to be controlled by tuning an applied electric field for different piston velocity.
Dynamics of Magnetic Fluid-Permanent Magnet System Subjected to Vertical Vibration
Authors: Sudo Seiichi , Ise Kazutaka , Ikohagi Toshiaki
Published: July 2008

This paper is concerned with the dynamic behavior of a magnetic fluid-permanent magnet system subjected to the vertical vibration. The surface response of magnetic fluid adsorbed to a disc permanent magnet is investigated experimentally. Experiment is performed on a vibration-testing system. The electrodynamic shaker is operated at a given frequency, displacement, and acceleration. The dynamic behavior of magnetic fluid surface is analyzed by a three-dimensional motion analysis system. The displacement of the permanent magnet is also measured with an optical displacement detector system. It is shown that the response amplitude depends on the excitation frequency at the constant excitation amplitude. The 1=2-sub harmonic response on the surface of magnetic fluid is observed at higher frequencies. This response is observed as polygonal modes with large amplitude azimuthal waves. The response of the system such as jumping motion is also shown at the resonance frequency of the system.
Impedance Control of a Single Shaft-Type Clutch Using Homogeneous Electrorheological Fluid
Authors: Nakamura Taro , Saga Norihiko , Nakazawa Masaru
Published: July 2008

This study demonstrates the application of a precise and variable impedance control to the homogeneous electrorheological (ER) clutch. The viscous coefficient of a homogeneous ER fluid can be changed by the application of an electric field. However, the ER effect of the fluid is easily changed by shear rate variation or temperature variation. Therefore, some feedback compensations are necessary for these systems to maintain a more precise viscosity.

In this paper, we apply a force-based impedance control to the homogeneous ER clutch in order to use ER fluid more effectively. First, we study the fundamental characteristics of the homogeneous ER clutch. Next, we apply the viscous control based on the force control in order to maintain a more precise viscosity. The results of our experiment clearly show that the viscosity of the clutch has been accurately and stably controlled by the proposed control method.
Electrorheological Rotating Disk Clutch Mechanism Under AC Electric Field: Part II - Efficiency Metrics
Authors: Shimada Kunio , Nishida Hitoshi , Akagami Yoichi
Published: July 2008

Electric power and efficiency on a rotating disk under AC electric field with suspension-type electrorheological fluid (ERF) were investigated. This report also dealt with the time lags of torque and current density from the applied eloctric field. Especially, the time lag of the current density was arranged by the power factor. The time lag of the torque is changed larger than the one of the current density. On the other hand, the data of the torque and the current density have steady and varying characteristics as amplitude components. Therefore, we need to investigate four electric powers: apparent power, effective power, steady power from the steady component of the current density and total power. From the three electric powers, we can deal with three efficiency of the electric power to the torque. They depend on the angular velocity of the disk, frequency and intensity of the electric field. The results were explained with the particles aggregation model.
Electrorheological Rotating Disk Clutch Mechanism Under AC Electric Field: Part I - Torque and Current Density
Authors: Shimada Kunio , Nishida Hitoshi
Published: July 2008

Torque and current density on a rotating disk immersed in suspension-type electrorheological fluid (ERF) under AC electric field were measured. They have steady and varying amplitude components which depend on the angular velocity of the disk, and the frequency and intensity of the electric field. The results were demonstrated by means of a particle aggregation model. The constant torque and current density under DC electric field were compared to those under AC field. The magnitudes of the differences strongly depend on the angular velocity of the disk and the frequency of the electric field. When an AC electric field is used, a smaller frequency should be applied for the sake of greater efficiency.
Sensing Shear Strains with Electrostriction Effect in Solid Electrorheological Composites
Authors: Kim G. H. , Shkel Y. M.
Published: July 2008

Solid electrorheological (ER) composites are created by applying an electric field to a liquid suspension of isotropic, homogeneously distributed inclusions and cross-linking the obtained transverse isotropic structure. Electrostriction phenomenon in ER composites can be defined as change in dielectric properties with deformation. Solid dielectric material, which consists of inclusions arranged in a chain-like structure and embedded in a matrix phase, demonstrates strong electrostriction response to normal and shear deformations. Such high sensitivity of ER composites to shear electrostriction can be utilized for sensing shear stresses and strains in active damping of vibrations. In this article, we model an electrostriction response and measure electromechanical properties of solid ER composites.
A Study on the Performance Estimation of Semi-Active Suspension System Considering the Response Time of Electro-Rheological Fluid
Authors: Yeo M. S. , Lee H. G. , Kim M. C.
Published: July 2008

This paper deals with the performance estimation of the semi-active suspension system considering the response time of electro-rheological fluid (ERF)-based damper. The Bingham characteristics and response time of ERFs are obtained experimentally. Then the ER damper is applied to the quarter car model and its performance using sky-hook control algorithm is compared to the system using conventional damper through computer simulation. As simulation results, the gain is improved above 50% but it is deteriorated rapidly with the increase of response time. So it is proved that the response time as well as the yield stress of ERFs is the dominant factor to design the semi-active suspension system using the ER damper.
Smart System for Distant Measurement of the Conditions on Sea Surface
Authors: Andriesh Ion S. , Panasiuk Lev M. , Petrushca Dumitru V.
Published: July 2008

A system for automatic distant measurement of the conditions on sea surface is proposed. The measured parameters are height and length of waves and their direction of motion. The system is placed on an air- or spacecraft board and consists of the optic image recording apparatus and of the programmed hardware, automatically performing the image processing in real-time scale. The photothermoplastic recording method ensures registration of selected sea sections on a photothermoplastic film. The reproducing system consecutively forms images, keeps their samples in memory and ensures their entrance in a special processor. The processor performs the mathematical processing under elaborated algorithm and carries out the searching parameters. These functions of processor are simulated on the computer, performing numerical analysis of the gray scale intensity distribution. The mathematical processing includes 2D smoothing of sample data, forming waves one-dimensional profile and calculating its Fourier transform. Introducing the scale factors, resulting from the optical system space situation relatively to sea surface, it makes possible to obtain certain data on the mentioned waves characteristics. These data demonstrate the possibility of proposed smart system of remote measurements to compress the bidimensional information to some numerical values, characterizing the rough sea instead and to transmit these values through the communication channels.
Some Remarks on the Damage Unilateral Effect Modelling for Microcracked Materials
Authors: Welemane Hélène , Cormery Fabrice
Published: July 2008

This study deals with the macroscopic modelling of the mechanical behaviour of microcracked materials and particularly with the unilateral aspect of such damage which leads, at the closure of microcracks, to a partial damage deactivation. By means of a micromechanical analysis, the aim of this article is first to point out the influence of the opening–closure of microdefects on the effective elastic properties of a microcracked medium. According to these considerations,a new elastic moduli recovery condition at damage deactivation is proposed. The introduction of this condition within the anisotropic damage model proposed by Halm and Dragon, 1996 allows its micromechanical background to be extended while preserving its main advantages, in particular the continuity of the stress–strain response and the symmetry of the stiffness tensor.
Damage Mechanisms in Unidirectional SiC/Ti Composites under Transverse Creep Loading: Experiments and Modeling
Authors: Carrère N. , Kruch S. , Vassel A. , Chaboche J.–L.
Published: July 2008

The damage mechanisms under transverse creep of two unidirectionalmetal matrix composites are investigated. This paper is based on a two-scale approach, and on experimental and numerical studies. On the macroscopic scale, the global response of the composite subjected to aconstant transverse load is analyzed. On the microscopic scale, the influence of each component (matrix, fibre and interface) on the global behavior is investigated.

In the experimental part of the study, creep tests have been performed at different temperatures under vacuum, and scanning electron microscope (SEM) observations have allowed the investigation of the damageevolution under different applied loads.

In the numerical work, the creep tests were simulated on a representative unit cell using the finite element method and taking into account the various nonlinearities (matrix viscoplasticity coupled with interface damage).

The experimental and numerical results show that the global behavior of the composite depends on the local interfacial behavior. Two domains are evidenced as a function of the applied stress, a critical stress being thus determined. Below the critical stress, the interfaces remain undamaged, leading to a low creep rate and a long duration test. Above the critical stress, the interfaces are totally debonded, thereby increasing the secondary creep rate and leading to a possible specimen failure.
Thermal Elasto-Viscoplastic Damage Behavior of Structural Members in Hot-Dip Galvanization
Authors: Toi Yutaka , Lee Jae-Myung
Published: July 2008

Continuum damage mechanics is applied to the prediction of the initiation of cracks on structural members in hot-dip galvanization. The elastoviscoplastic constitutive equation considering damage, in which most material parameters are temperature-dependent, is employed in the three-dimensional finite element analysis of the structural behavior in hot-dip galvanization. The material constants concerning damage are determined by the comparison of the finite element solutions with the bending test results for the stiffened plates in molten zinc in order to consider the effect of zinc-embrittlement of the material. Numerical study is conducted for the possibility of cracking near the holes for bolts on pylon members in hot-dip galvanization.
Experimental Characterization of Matrix Cracking Behavior in Thermally Cycled CFRP Laminates
Authors: Ogihara Shinji , Kobayashi Akira , Ishiguro Takamoto , Otani Nobuo
Published: July 2008

The effect of thermal cycling on the mechanical properties of composite materials is an important issue in engineering, especially in their applications to the space environment. The present study concerned with the experimental study of both the thermal cycling induced matrix cracking and the effect of thermal cycling on the matrix cracking behavior under tensile loading in CFRP laminates. Two kinds of carbon/epoxy systems, T800H/3631 and T300/2500, are used for the laminate configurations of (0/90)s and (90/0)s. The specimens are thermally cycled between −196 and 100°C. Thermal cycling tests are performed up to 1000 cycles. The polished edge surfaces of specimens are examined by the replica technique, and then the matrix crack density is measured as a function of the number of thermal cycles. It is found that the first matrix cracking in (0/90)s and (90/0)s laminates occurs at almost the same numbers of thermal cycles. It is also found that the matrix crack density increases more rapidly in (0/90)s laminates than in (90/0)s laminates in both material systems. To investigate the effect of thermal cycling on matrix cracking behavior under tensile loading, a series of tensile tests on thermally cycled specimens are performed. The effect of thermal cycling on matrix cracking under tension is evaluated in terms of the change in the critical energy release rate and the critical stress for matrix cracking.
An Experimental Study of Shear Damage Using In-Situ Single Shear Test
Authors: Tang C. Y. , Lee T. C. , Rao B. , Chow C. L.
Published: July 2008

An experimental study has been performed to investigate the shear damage mechanism of aluminium alloy 2024T3 by an in-situ single shear test using scanning electron microscope (SEM). The observation of microstructural change and measurement of shear strain in mesoscale have been undertaken simultaneously. Hence, the shear damage mechanism and the shear stress–strain curve have been obtained. By measuring the deformed grid of a laser-marked sample, the shear strain distribution has also been found. On the basis of the experimental results, the relation between the shear damage evolution and the corresponding shear stress–strain state have also been obtained. It has been observed that two groups of microshear bands were formed in the shear process. When the shear stress is close to the shear strength of the alloy, slipping within the microshear bands occurs. The causes of macro-shear band formation and the interrelation and interaction among different types of microdefects are also discussed.
Failure Modes of Composite Sandwich Beams
Authors: Daniel I. M. , Gdoutos E. E. , Wang K.–A. , Abot J. L.
Published: July 2008

An investigation was conducted of failure modes and criteria for their occurrence in composite sandwich beams. The initiation of the various failure modes depends on the material properties of the constituents (facings and core), geometric dimensions and type of loading. The beams were made of unidirectional carbon/epoxy facings and aluminum honeycomb and PVC closed-cell foam cores. The constituent materials were fully characterized and in the case of the foam core, failure envelopes were developed for general two-dimensional states of stress. Sandwich beams were loaded under bending moment and shear and failure modes were observed and compared with analytical predictions. The failure modes investigated are face sheet compressive failure, adhesive bond failure, indentation failure, core failure andfacing wrinkling.
Integral Formulation of Coupled Damage and Viscoplastic Constitutive Equations: Formulation and Computational Issues
Authors: Nesnas K. , Saanouni K.
Published: July 2008

In this paper, well-known differential elasto-viscoplastic constitutive equations, accounting for hardening and damage, are reformulated into integral form in order to propose an efficient implicit integration scheme. By working out some examples, it will be shown that the proposed formulation appears to be computationally more appealing in terms of numerical accuracy and CPU time.
Design of Prestressed Skin-Flange Assembly
Authors: Matous Karel , Dvorak George J.
Published: July 2008

A prestressing procedure for reduction of adhesive peel and shear stresses at the leading edge of a skin-flange assembly is analyzed for tensile and bending loads applied to the skin. Both an analytical solution based on the Green’s functions and a finite element solution are presented for specific examples, together with design diagrams. Substantial shear and peel stress reductions are obtained with the proposed procedure.
Effect of Stacking Sequence on the Mechanical Properties of Glass–Carbon Hybrid Composites before and after Impact
Authors: Onal Levent , Adanur Sabit
Published: July 2008

Hybrid composites are susceptible to accidental low energy impacts from hazards such as tools dropping during maintenance, transportation debris and hailstones. These impacts can cause significant strength reduction and localized damage which is potentially a source of mechanical weakness especially for graphite composites. The effect of stacking sequence on mechanical properties of stitched composites is studied for low velocity impact damages. Tests were performed for the same volume fraction (Vf) with different hybrid sequence and ply angle. The incorporation of glass fibers in carbon reinforced structures improved impact properties and increased the strain to failure. The addition of carbon fibers to the surface of glass-reinforced composites increases the flexural modulus for undamaged samples. Tensile failure mechanism of damaged plies seems to be affected by the interaction of reinforcement property, hybrid order and ply angle.
A Novel Technique for Determination of Vapor Transmission Rate through Textiles
Authors: Jena Akshaya , Gupta Krishna
Published: July 2008

A novel technique for precise, accurate and fast determination of vapor transmission rate through textiles is discussed. Vapor at a constant pressure is maintained on one side of the textile and the increase in pressure of the vapor on the other side is measured. The technique was used to investigate two textiles. The vapor permeabilityof the textiles is almost five orders of magnitude lower than their air permeability. The air permeability of the textiles are identical, however, they show strong differences in vapor permeability.
Thermal Insulation Properties of Biodegradable, Cellulosic-Based Nonwoven Composites for Automotive Application
Authors: Yachmenev V. G. , Parikh D. V. , Calamari T. A.
Published: July 2008

Moldable, cellulosic-based nonwoven composites with excellent thermal insulation properties were fabricated from kenaf, jute, flax, and waste cotton using recycled polyester and substandard polypropylene. The composites of these fibers have excellent shape stability and high tensile and flexural properties coupled with economic and environmental benefits. Four different designs incorporating different cellulosic fibers, manufacturing techniques and various ratios of vegetable–synthetic fibers were manufactured on laboratory-scale equipment. A Steady-State Heat Flow meter was used for measurement of thermal conductivity and thermal transmittance of samples of composites. The data show that thermal insulation properties of the cellulosic-based nonwoven composites vary significantly, depending on the type of the cellulosic fibers, the ratio of cellulosic fibers to synthetic fibers, and the resulting density of the composite.
Air Permeability of Multilayer Needle Punched Nonwoven Fabrics: Theoretical Method
Authors: Mohammadi M. , Banks-Lee P. , Ghadimi Parviz
Published: July 2008

The theoretical permeability of multilayered nonwoven fabrics was studied using a modified Kozeny equation. The Kozeny equation is based on the concept of a hydraulic radius, i.e., a characteristic length parameter. It is limited to structures with porosities less than 0.94. The structures used in this research are intended for use as high temperature insulation and all had porosities of greater than 0.96. The Kozeny equation was therefore modified to extend its usefulness to fabrics with higher porosity. Fabric construction parameters, along with fabric and fiber properties were used as inputs to this model and theoretical air permeability was determined. The effect of number of barbs and layering structure on the determination of theoretical air permeability was also considered and discussed. Statistical analysis was performed showing that fabric thickness, number of needle barbs, mean pore size and fabric density are significant factors in predicting theoretical air permeability.
Characteristics of Ultraviolet Cured Glass–Epoxy Composites Part 2: Results and Discussion
Authors: Adanur Sabit , Arumugham Yuvaraj
Published: July 2008

A curingsystem usingultraviolet radiation is proposed for use on a braidingmachine, which can expedite composite manufacturingand eliminate additional secondary processes. This work investigated some of the facts and characterized the processes to suit the design for the braiding machine. The addition of diacrylates and triacrylates was found to reduce the effects of oxygen quenching and increase the curingspeed of acrylated epoxy monomers. Mechanical testingwas performed to study these effects. Epoxies follow the cationic polymerization mechanisms. The preliminary study was carried out on epoxy (Shell Epon 826) with a cationic photoinitiator (Radcure, Uvacure 1590). It was found that on exposure to ultraviolet radiation, gelling takes place in 10 s. The degree of curing attained was found to be appreciable if cross-linkingagents like Imidazole or an anhydride was added to the formulation.
Advantages of Fiber Rope Over Wire Rope
Authors: Foster Gale P.
Published: July 2008

Over the years, fiber ropes have increased in strength to the point where they began to replace wire ropes in some applications. The major factors have been the development of high tenacity fibers and the advancements in fiber rope constructions. This started with high tenacity nylon and polyester fiber ropes, ropes combining both of those fibers, the combining of polyester and polypropylene ropes and ropes combining polypropylene and polyethylene. This was followed by the development of high-tech fibers, with the result that stronger and stronger ropes could be produced to the ultimate where a fiber strength member can provide a 10–1 strength-to-weight ratio advantage over wire rope. At the same time, new finishes for fibers were developed that improved durability and strength retention, new constructions were able to provide increased translation efficiency, and better inspection and testing methods were developed. Application advantages are discussed, each having a number of factors that reduce costs, even though the actual cost of the fiber strength member may be slightly higher than for wire. The result is a rationale that when the cost of a flexible strength member is fully measured there is a strong reason that a fiber strength member, when compared with a wire rope, can save money and improve operations in an increasing range of applications.
Systematic Design of Displacement-Amplifying Mechanisms for Piezoelectric Stacked Actuators Using Topology Optimization
Authors: Lau Gih Keong , Du Hejun , Guo Ningqun , Lim Mong King
Published: July 2008

Displacement-amplifying mechanisms can be systematically designed using topology optimization. Due to the special need for large displacement amplification of piezoelectric stacked actuators, suitable objective functions should be formulated. Among various possible formulations, this work considers maximum output stroke, magnification factor and mechanical efficiency as objective functions. As the formulation of maximum magnification factor performs better numerically than the rest, it is recommended as a suitable design goal for displacement amplifiers undergoing undamped harmonic response. The design problem is solved as a 2D material distribution problem using Method of Moving Asymptotes (MMA). Plane stress solid is assumed for the design domain. Stiffness of the actuator and the workpiece is included in the analysis. To show the viability of this design methodology, two examples of magnification mechanisms for printer heads driven at different excitation frequencies were presented.
Analytical Study on Training Effect of Pseudoelastic Transformation of Shape Memory Alloys in Cyclic Loading
Authors: Naito Hisashi , Sato Junpei , Funami Ken , Matsuzaki Yuji , Ikeda Tadashige
Published: July 2008

With increasing number of loading cycles, stress-strain hysteresis loops of pseudoelasticity of a shape memory alloy vary continuously in experiments. To account for such characteristic variance observed during phase transformations, the effect of residual martensite is taken into account in a thermomechanical model based on the phase interaction energy function which we proposed in our previous studies. A functional form of volume fraction of the residual martensite which monotonically increases with increasing loading cycle has been determined using experimental stress-strain loops. It is shown that a simple function of the volume fraction of the residual martensite may model complicated behavior of the transformations in the cyclic loading.
Use of Piezoelectric Shear Response in Adaptive Sandwich Shells of Revolution - Part 2: Finite Element Implementation
Authors: Benjeddou A. , Gorge V. , Ohayon R.
Published: July 2008

A theoretical model has been presented in Part 1 of this paper for the use of piezoelectric shear response in adaptive sandwich shells of revolution. This second part presents its corresponding finite element implementation. For this, an isoparametric finite element discretization is retained for the cylindrical coordinates and independent mechanical and electric variables. These are interpolated with linear Lagrange polynomials along the meridian, but expanded with Fourier series along the shell circumference. This leads to a simple two-nodes conical finite element with 22 degrees of freedom. Straight meridian has been assumed to reduce eventual membrane locking, whereas the selective reduced integration has been used to avoid eventual shear locking. Therefore, prior to the element assembly, a geometric transformation from local curvilinear to global cylindrical coordinate system was made to take into account the shell meridian curvature and to handle its eventual discontinuities. After its validation, the present finite element has been used for vibration analysis of adaptive sandwich cylindrical shells and circular plates with open-and short-circuited embedded piezoelectric shear actuators. It was found that, contrary to extension actuators, shear ones are insensitive to the electric boundary conditions for axisymmetric modes. For non-axisymmetric ones, it was also found that bending modes dependence varies more than other radial, torsion and extension ones.
Aroma, Oxygen and Moisture Barrier Behavior of Coated and Vacuum Coated OPP Films for Packaging
Authors: Mount Eldridge M. , Wagner John R.
Published: July 2008

Various coated and vacuum coated, biaxially oriented polypropylene film product designs are examined in terms of their moisture, oxygen and aroma barriers. Factors that are thought to control oxygen barrier in these products are discussed and extended to aroma barrier development. The differences between the various vacuum coated and uncoated films with three organic permeants are evaluated and discussed in relationship to the impact on the polymer/coating interface and the development of aroma barrier in coated films. It is demonstrated that the existence of an evaporated barrier layer does not guarantee the existence of a chemical barrier. New combinations of film technology are described that permit the development of excellent aroma, oxygen and moisture barrier films.
Synthesis, Characterization and Biodegradability of Acid-Functionalized Copolyamidoamines
Authors: Mokoena Alice M. , Bariyanga Joseph
Published: July 2008

Acid-functionalized copolyamidoamines containing main-chain poly(ethylene oxide) were prepared and characterized by elemental analysis and nuclear magnetic resonance (NMR). Different feed ratios have been used in preparation and all of the obtained polymers, with one exception, were soluble for a short time (around one month) and become insoluble afterwards. There was an increase in the uptake of 0,0'-bis(2-aminopropyl)poly(ethylene oxide) (ED 600) into the polymer with increases in the molar fraction of starting materials. The most soluble polymer was characterized by gel permeation chromatography (GPC) and electrospray mass spectrometry. The absolute molecular mass was estimated at 5500. Degradation by papain and leucine aminopeptidase in a buffer at pH 7.81 and at 370C was investigated using GPC molecular weight distributions. For both enzymes, the polymer was found very stable up to 74 h under the working conditions.
Two-Way Shape Memory Behavior Obtained by Combined Loading Training
Authors: Tokuda Masataka , Sugino Souichi , Inaba Tadashi
Published: July 2008

The two-way shape memory effect obtained by combined loading training is investigated experimentally by applying the combined loads of axial force and torque to the thin-walled tubular specimen of Cu-based shape memory alloy. In this paper, some unique two-way behaviors are shown and discussed.
Surface Characterization of LLDPE Film Containing Glycerol Monostearate
Authors: Sakhalkar Sachin S. , Walters Keisha B. , Hirt Douglas E. , Miranda Nathanael R. , Roberts William P.
Published: July 2008

Glycerol monostearate (GMS) can serve as an anti-fogging agent by increasing the hydrophilic nature of a film surface. In this study, blends of GMS and LLDPE were extruded into film and the GMS was allowed to migrate to the surface over time. The surface was characterized by measuring the static water contact angle, which was then used to calculate the surface free energy of the film. Results showed that the equilibrium wettability of the film deviated dramatically from that of neat LLDPE when the GMS concentrations were greater than about 1900 ppm. Time-dependent studies demonstrated that the rate of surface-energy change was significantly influenced by the GMS concentration.
Effect of MWD on the Amount of Polymer Process AID Required to Suppress Sharkskin Melt Fracture in LLDPE
Authors: Mavridis H. , Fronek K.
Published: July 2008

At TAPPI-2000 it was reported [1] that different types of High-Performance Hexene Linear Low Density Polyethylene (HPH-LLDPE) behaved differently with respect to the onset of sharkskin melt fracture (SSMF), depending on the breadth of the molecular weight distribution (MWD). The MWD differences were small and subtle, but the effect on the onset of melt fracture was significant. The present study is a continuation of that work, through a comparative investigation under shear rate conditions high enough to induce melt fracture in both narrow and broad-MWD LLDPEs. A fluoropolymer process aid (PPA) was then added in stepwise increments until melt fracture was eliminated. It was found that the narrow-MWD resin required more than twice the amount of PPA to eliminate SSMF.
Improved Surface Treatment of SMA Foils and Damage Suppression of SMA-Foil Embedded CFRP Laminates
Authors: Ogisu Toshimichi , Ando Norio , Takaki Junji , Okabe Tomonaga , Takeda Nobuo
Published: July 2008

The authors have been conducting research and development studies on some applications of embedded SMA foil actuators in CFRP laminates for weight reduction and improvement of reliability for next generation aircraft. The goal of this research is to develop a method for the suppression of damage growth in CFRP laminates. It is certified that one of the key technologies is bonding properties between SMA foils and CFRP laminates.

In this paper, improvement of bonding properties between SMA foils and CFRP and confirmation of suppression effects of damage growth are described. Some surface treatments (sol-gel method, anodic-oxidation method and spattering method) were performed on SMA foils. Then, peel resistance and single lap shear strength tests were performed using surface treated SMA foils. It was found that treatment by 10%NaOH is the most effective treatment for improvement of bonding properties. The treated surface was found porous and rough, which is supposed to provide anchoring effects of SMA/CFRP interfaces.

Then, quasi-static load-unload tests were performed using the optimum treatment as mentioned above to investigate the damage behavior of quasi-isotropic CFRP laminates with embedded SMA foils. Micromechanisms of fracture behavior and the correlation between the crack density and the residual strain were discussed. The recovery stress of the SMA foil generated at over Af temperature showed capability of suppression for onset of transverse cracks in quasi-isotropic CFRP laminates with embedded SMA foils.
Damage Detection Testing on a Helicopter Flexbeam
Authors: Ghoshal A. , Harrison J. , Sundaresan M. J. , Hughes D. , Schulz M. J.
Published: July 2008

The main and tail rotor systems of a helicopter must be maintained in a damage-free condition to ensure the safety of the helicopter. The components of the rotor system require regular maintenance and inspection, and some of the components are difficult to inspect. Accordingly, an integrated sensor system that continuously monitors the structural integrity of the rotor system is needed to assure the safety of flight and reduce the cost of maintenance of the rotor system. This smart monitoring system could also provide immediate information on the dynamic loading in the rotor system. This information could define the performance limit of the helicopter based on the condition of the rotor system. The operator will then be able to adjust the flight condition and prevent damage from occurring or propagating. The challenges in designing this monitoring system are related to the operating conditions of the helicopter. These include significant aerodynamic and external damping in bending and torsion modes, moderate nonlinearities in the system, large dynamic loads, and difficulty in actuating pure interrogation signals in the airborne condition. In this paper, piezoceramic sensors and actuators and different techniques for damage detection that use symmetry properties of the structure and no structural model are tested in a static condition for health monitoring of a helicopter flexbeam. Testing under dynamic loading is needed as the next step in the development of the smart sensor system.
Wireless Monitoring of Cable Tension of Cable-Stayed Bridges Using PVDF Piezoelectric Films
Authors: Liao W. H. , Wang D. H. , Huang S. L.
Published: July 2008

For cable-stayed bridges, cable tension and its variation are two of the most important factors for judging whether the bridges are functional or not. Therefore, the in-situ monitoring of the stayed cables’ tension of the cable-stayed bridge is very important and necessary, from which we can determine the health of the bridge. However, how to acquire and retrieve the signal is the key problem to determine whether the method is suitable for in-situ monitoring of the cable tension of cable-stayed bridges. In this paper, polyvinylidene fluoride (PVDF) piezoelectric films are used as the sensors to acquire the dynamic responses of the stayed cables, from which the tension of the stayed cables can be determined. Signal retrieval from the PVDF film sensors via wireless transmission technology is developed, which could be used for the wireless in-situ monitoring of the cable tension. The principles, feasibility, and configuration of the wireless system for monitoring the stayed cable tension of cable-stayed bridges are investigated. Also the validating experiment is performed on a small-scale stayed cable model in the laboratory. Results show that the proposed wireless monitoring system is feasible for the in-situ monitoring of the stayed cable tension. The method and transmission system can be applied to wireless health monitoring of civil infrastructures with various sensors.
Deformation Measurement of Impulsed Viscoelastic Plate with Moire Method
Authors: Huimin Xie , Dietz Peter , Schmidt Axel , Kishimoto Satoshi , Shinya Norio , Fulong Dai
Published: July 2008

The dynamic deformations of impulsed viscoelastic plates measured with the moire method are discussed. A new method for producing visco-photoelastic material is proposed. The material was processed as plate type specimens with elliptical or circular holes, and utilized to investigate its dynamic deformation behavior at 42°C. The measuring method and procedures, as well as the experimental results are discussed in detail.
Adaptive Hysteresis Compensation for SMA Actuators with Stress-Induced Variations in Hysteresisa
Authors: Webb G. , Lagoudas D. , Kurdila A.
Published: July 2008

The strain-temperature hysteresis for shape memory alloy (SMA) actuators has been shown to undergo large changes according to the applied load. This paper provides an adaptive hysteresis model capable of accounting for a time-varying hysteresis, specifically SMA hysteresis under a varying applied stress. Previous research has established excellent performance, in both numerical and laboratory experiments, of the adaptive hysteresis model for actuators with fixed hysteresis. In this paper, the performance of the adaptive model when there are significant changes in the hysteresis characteristics is examined in a laboratory tracking experiment.
Decentralized Vibration Control and Coupled Aeroservoelastic Simulation of Helicopter Rotor Blades with Adaptive Airfoils
Authors: Konstanzer Peter , Grohmann Boris , Kroplin Bernd
Published: July 2008

In the present paper, helicopter rotor blades with adaptive airfoils are investigated considering discrete trailing edge flaps as well as continuous shape adaptation. First, a method for lagging mode stability augmentation is proposed and applied to a helicopter rotor with discrete trailing edge flaps located at the outer part of the rotor blades. Active damping enhancement of the aerodynamically weakly damped lagging modes defines the control objective subject to the requirement of robust performance with respect to the time-periodic system behaviour. A decentralized controller is proposed which is shown to be robust, conceptually simple and effectively provides damping enhancement. In the second part, we discuss continuous shape adaptation in order to overcome the disadvantages of discrete flaps. An Active Camber Rotor (ACR) with distributed active material components is proposed. Numerical simulations are presented demonstrating the aerodynamic effectiveness of shape adaptation.
Conjugate of Doxorubicin with a Thermosensitive Polymer Drug Carrier
Authors: Chtryt V. , Ulbrich K.
Published: July 2008

A temperature-responsive drug delivery system that is soluble in aqueous solutions below its phase transition temperature but hydrophobically collapsing and aggregating at higher temperatures was prepared. A ternary copolymer of N-isopropylmethacrylamide, N-propylmethacrylamide and 4-nitrophenyl N-methacryloylglycylglycinate was synthesized. The reaction of the 4-nitrophenyl ester groups with hydrazine resulted in a polymer hydrazide which enabled the attachment of doxorubicin (DOX) via a pH-sensitive hydrazone bond. The system exhibited phase separation in aqueous solutions at a temperature of about 41'C and released free DOX at pH 5.0 at a rate higher by one order of magnitude than at pH 7.4. In combination with local hyperthermia, the system is expected to be valuable for the delivery of chemotherapeutic agents in the treatment of solid tumors. The relation between the temperature of the phase transition of the system and the cloud point temperature (CPT) as well as the necessity to distinguish between the CPT and the lower critical solution temperature (LCST) is discussed and the factors influencing the results of determination of the CPT (its definition, concentration of the polymer solution, rate of heating, presence of cosolutes, chemical structure of polymer and its heterogeneity) are analysed in detail.
Mechanical Property of Metallic Closed Cellular Materials Containing Organic Material for Passive Damping and Energy-Absorbing Systems
Authors: Kishimoto S. , Shinya N.
Published: July 2008

A new material, which has a high energy-absorbing capacity and light weight, has been developed by cold isostatic pressing and sintering. Powder particles of a polymer coated with a nickel-phosphorus alloy layer using electroless plating were pressed into pellets and sintered in a vacuum at a high temperature. A metallic closed cellular material containing an organic material was then fabricated.

The physical, mechanical and ultrasonic properties of this material were measured. The density of this material is about 1.3-2.7 g/cm3. The compressive tests showed that the Young’s modulus of this material is very low and the stress-strain curves of this material have a linear elastic part, a plateau part and a wavy part. These results indicate that this material has a high energy absorbing capacity. The Young’s modulus of this material increases with an increase in the sintering temperature and the thickness of the cell walls. Ultrasonic measurements showed that the attenuation coefficient of this material is very large. These results also indicate that this metallic closed cellular material can be used for the materials in passive damping and energy-absorbing systems.
Antibiotic Releasing Urethane Polymers for Prevention of Catheter Related Infections
Authors: Marconi W. , Francolini I. , Piozzi A. , Rosa R. Di
Published: July 2008

In order to improve the resistance of catheters to microbial infections (particularly Staphylococci), a cephalosporin type antibiotic (cefamandole, CEF), and a glycopeptidic antibiotic (vancomycin), were adsorbed onto functionalized polyurethane films. The polymers were characterized by chemical, FT-IR and 'H-NMR analysis. The amounts of antibiotic adsorbed were higher than the ones reported in the literature. The kinetics of release, under standard conditions, was evaluated by in vitro tests; both the adsorption yield and the antibiotic release from the polymer surface depended on the type of the surface-antibiotic interactions. In particular, matrix hydrophilicity, formation of strong ionic bonds, existence of "spacing arms" between antibiotic and matrix bonding site play a role. The antimicrobial activity of the treated films was evaluated by optical microscopy and the Kirby-Bauer test. When exhausted polymer films, previously treated with CEF were submitted to a second adsorption, a superior antibacterial activity was observed.
Performance Comparison between Piezoelectric and Elastomeric Lag Dampers on Ground Resonance Stability of Helicopter
Authors: Kim Seung Jo , Yun Chul Yong
Published: July 2008

In this study, a piezoelectric lag damper using damping characteristics in piezoelectric ceramics is proposed to alleviate ground resonance instability. The piezoelectric passive damper consists of piezoelectric elements and electrical circuits such as resistors and inductors in a series. By bonding the piezoelectric ceramics to the rotor flexures, piezoelectric strain energy is converted to electrical energy and dissipated through an electrical network. To verify the effect of the piezoelectric damper on rotating blades, experiments for the aeroelastic stability of the rotor blades were carried out. The experiment results for rotor blades with the piezoelectric damper show that the piezoelectric damper has a strong stabilizing effect on the inherently weakly lag-mode damping of the blades. The performance of piezoelectric and elastomeric lag dampers on ground resonance instability are compared and modal frequency and modal damping with respect to rotating speed are shown.