The present paper deals with a comparison of two noise control techniques developed separately; active and semi-passive approaches. A closed rigid box with a loudspeaker inside is designed so that sound pressure is transmitted through a smart board which consists in a clamped steel plate with piezo patches. The present active control technique uses the patches as actuators and a microphone as feedback. The semi-passive technique is a brand new control technique which uses a non-linear approach in which the voltage of piezoelectric patches is switched through an inductance for a very brief period of time when it reaches its maximum or minimum. They are compared and discussed in terms of efficiency on sweeping time response and robustness in non-linear regime. The results revealed that both techniques have different advantages and disadvantages.
Reducing the size of power supplies raises the problem of new elements which could be better candidates to integration. In this field, electromagnetic transformers may be replaced with significant profits by piezoelectric transformers (PT). In a piezoelectric transformer (PT), the input electrical energy is transferred to the output by a mechanical way, using the direct and converse effects of piezoelectric materials. Its main advantages over an electromagnetic transformer are no magnetic noise generation, small size, high power density and high efficiency. This paper presents an innovative non-linear processing technique. This technique is derived from the so-called “synchronized switch damping” technique that was developed to address structural vibration damping problems. Applied to PT, the vibration level of the structure is strongly reduced while keeping the transferred power practically constant. Vibration level is a critical parameter that determines the maximum power capability of a given PT. Thus the new processing reduces significantly losses of the PT for a given power. As a consequence, at vibration amplitude limit, the power capability is drastically enhanced. Theoretical predictions and experimental results both show that the increase of the power capability may reach 450% on a structure similar to a langevin transducer.
Piezoelectric hysteresis understanding is a key toward better displacement control of devices requiring high strain like micropositionners and adaptive optic systems. Large strain, in the non-resonant regime, requires high electric fields, which lead to an enhancement of the nonlinear/hysteresis effect and results in a lack of controllability. The modeling of the ferroïc hysteresis proposed here is based on a analogy with the dry friction concept used in mechanics. It is anticipated that the pinning/depinning domain wall motion is similar to a mass motion on a support presenting a dry friction dissipative force. From the model, a relationship showing the equivalence of the electric field and the stress by poling product is derived. It is shown that from the electric field influence on the polarization, the stress behavior is derived. Starting from the model, which is intrinsically hysteretic, the purely linear behaviors are eventually modeled, and the correlation between linear coefficients and the polarization states is presented. Rayleigh region behaviors are easily retrieved from the proposed model.
Coextrusion technologies are commonly used to produce multilayered composite sheets of films. Each layer of these composite materials provides a specific end-use characteristic, suc as optical, mechanical or barrier properties. Processing together polymers of different natures may have two consequences : on the one hand, the flow of two adjacent different liquids may give rise to interfacial instabilities which are detrimental to the quality of the final product. On the other hand, the difference of chemical natures of the polymers may lead to delamination of the multilayer film. In order to avoid the latter problem, polymers are compatibilized by introducing a binder between adjacent layers. As a consequence, a non-zero thickness interphase is created between the layers. In this paper, it is theoretically analysed how this interphase may influence the flow stability. As a matter of fact, it is experimentally known that flows of compatible polymers are more stable than those of incompatible systems. Next, a way to optimize the process is proposed.
This paper presents a study of active noise isolation using an advanced composite board with built-in piezoelectric elements, which are used as both sensors and actuators. An identification system, which estimates the radiated sound from the voltage signals of the built-in piezoelectric elements in the smart board, was constructed based on Rayleigh's integral formula so that no external microphone is needed for noise control. A FIR filter was used as the controller and its coefficients were updated adaptively using the Filtered-X LMS algorithm to minimize the estimated value of the sound pressure. The technique of self-sensing actuators was also used to reduce the number of needed piezoelectric elements in the control. Experiments were performed and the results showed that the transmitted noise level was successfully reduced at several resonant peaks.
This paper mainly describes that surface density changes in dangling bonds caused the multi-properties of polymers irradiated by electron beam (EB). The irradiated polymers with high wettability, mist resistance, sterilization and high hardness have been successfully developed. EB irradiation decreases the water contact angle of polymers, because dangling bond formation generally attracts the poling of water molecules. Scattering of light reflection of fine sessile drops of water usually causes the misting. The extreamely thin film of water is formed by wettability enhancement induced by EB irradiation. Thus, the electron beam irradiation prevents the misting. On the other hand, the hardening has been generated by EB irradiation
This paper examines the switching process occuring in ferroelectric and ferroelastic relaxor single crystals under electro-mechanical loadings. Relaxors undergoing a cubic to tetragonal phase transition are considered. The single crystal energy has three origins: elastic, electric and the incompatibilities of the spontaneous strain and electric displacement fieds between domains. The stress and the electric field fluctuate and present jumps at the domain walls. As a consequence, they induce electro-elastic interaction energy. Thus, it involves dissipation that the present work aims to capture through an electro-micromechanical approach.
Influence of fatigue on shape memory effect in Ni-Ti-Cu wires was quantitatively evaluated. Strain and variation of transformation points was measured under constant tensile load. Transformation points depending on cycle numbers of SMA wire specimen decrease until 1000 thermal cycles and length of the sample at high and low temperature increases when the number of thermal cycles increases.
This paper is a study on the development of a tactile sensor system for reading Braille. The tactile sensor uses a PVDF (Polyvinylidene Fluoride) film as the sensory material. The sensor is attached onto a mechanical slider and is slid over Braille to obtain the output. The effects of the speed and the contact depth are focused on, and the measurements are discussed. Subsequently, the method that can recognize Braille regardless of the effects is proposed. In an experimental verification, the sensor system is examined whether it has performance to recognize Braille appropriately. The obtained result shows that the proposed system is effective to recognize Braille regardless of the speed and the contact depth.
This article proposes a novel concept of hemostatic forceps for less invasive surgical operation. Hemostatic forceps has more than 400-year's history but remain an instrument with a potential of over-pressure induced lesion. The proposed hemostatic forceps allows a possibility to limit the clamping pressure within a safe range. This is to be realized by employing the constant stress property of superelastic shape memory alloys to limit the pressure applied on biological tissues. It is expected that the development of safe hemostatic forcepses based on this concept would reduce medical accidents.
This paper is a study on the optimum design of a palpation sensor for detecting prostatic cancer and hypertrophy. The recepter of the sensor is a polyvinylidene fluoride (PVDF) film placed on the surface of the matrix rubber base. The sensor is pressed against the prostate gland and driven sinusoidally, with a constant amplitude. The voltage signal from the PVDF film is integrated over the sampling period and is used as the output of the sensor for evaluating the stiffness of the pressed prostate gland. The output strength of the sensor is dependent on the relative stiffness of the sensor base rubber to the stiffness of the object prostate gland. Thus, the stiffness of the base rubber is of great importance to make the sensor output maximum and achieve the best discrimination of the normality and abnormality of the organ. The FEM analysis is introduced for the optimum design of sensor, and the best fit stiffness of the matrix rubber base is determined.
The advent of electronic noses opened a new kind of analytical approach, which offers an easy, quick, and cheap measurement comparing to conventional analytical approaches. It has potential applications on many different fields, such as assessment of various foodstuffs and beverages, environmental contamination monitoring and medical diagnostics etc. In this study, we used odorant binding protein (OBP) as odor-sensing material for developing such kind of artificial odorant biosensor. And biological films of OBP-1F (rat OBP) were deposited by Langmuir-Blodgett (LB) technique on gold electrode previously functionalised with 1-octadecanethiol (ODT) by self-assembled monolayers (SAMs). It is known that successful immobilization of the Langmuir-Blodgett films depends strongly on the characteristics, particularly stability, of the corresponding Langmuir films at the air/water interface. Hence the characteristics of monolayer of amphiphile octadecylamine (ODA) and the mixed monolayer of ODA/OBP were studied. Electrochemical impedance spectroscopy (EIS) was used to monitor the response of the system to a specific odorant molecule, isoamyl acetate.
Among diamond-like carbon coatings, hydrogenated amorphous carbon films are of peculiar interest, since some of them exhibit under vacuum coefficient of friction in the millirange, so-called “superlow friction”. This paper will review some key requirements for achieving this peculiar friction regime. Firstly, not all hydrogenated amorphous carbon films lead to superlow friction. Hydrogen content is known to be critical, but it appears to be strongly dependent on deposition process. Some mechanical properties of the films can also be correlated with friction reduction, like viscoplasticity. Secondly, formation and evolution of a transfer film on sliding counterface seems to control frictional behavior. By performing tribological experiments under controlled environment, combined with the use of “Triboscopy”, it is possible to have some clues on the evolution of the transfer film and on its relation with the friction level observed.
Metal-carbon nanocomposites are characterized by a number of unique properties, perspective for the various-type sensor applications. Presented experimental data of the conductivity of amorphous tungsten- and niobium-containing carbon-silicon nanocomposite films show the possibility to design the advanced wide-range temperature sensors, which are expected to possess the chemical stability, biocompatibility, mechanical, and other properties typical for this class of materials. The investigated films were deposited onto polycrystalline substrates using combination of Plasma Enhanced Chemical Vapor Deposition (PECVD) of siloxane vapors and DC magnetron co-sputtering of metal target. The conductivity σ of the films, measured using standard 4-probe technique in the temperature range 80-400K, is characterized by the gradual decrease with temperature. The experimental σ(T) dependences are well fitted by the power-law expression, σ(T) = σ0+aTn, where σ0, a, and n are the fitting parameters dependent on the type of metal and the value of metal concentration. The electron transport mechanism in the investigated amorphous metal-containing carbon-silicon nanocomposite films is discussed in the framework of the model of inelastic tunneling of electrons in amorphous insulators in the presence of the structural transformation in the carbon-silicon host matrix. The evolution of the structure of the carbon phase by metal concentration increase was studied by Raman spectroscopy.
This paper discusses the feasibility of Eddy Current Monitoring (ECM) system as a in-situ evaluation method of crack propagation in a Boiling Water Reactor (BWR) environment. For the purpose, we review an ECM experiment conducted at a System Safety Benchmark Facility (SSBF) with a large-scale austenitic stainless steel pipe specimen. Several slits were prepared at the Heat Affected Zones (HAZs) and weld lines from the inner surface. After exerting the load, Eddy Current Testing (ECT) probes attached on the outer surface of the specimen provide the crack propagation signal. Numerical simulation of eddy current signals based on the experimental conditions indicate that this system is capable of monitoring the crack growth in BWR environments.
The monitoring of the nonlinear acoustic properties of high performance structural materials during damaging mechanical tests is presented. The samples were instrumented using piezoelectric sensors, which were hardly glued to the surface of the samples constituting a smart structure allowing the in situ health monitoring of the material. Fast dynamics experiments have allowed the monitoring of damage through the changes of the frequency and the quality factor under the effect of the excitation amplitude. With the help of slow dynamics we used the relaxation time as a damage indicator and could differentiate damaged and undamaged concrete samples. After that, we used slow dynamics relaxation time as a tool to monitor the damage induced gradually with three points bending tests in a polymer composite sample. Slow dynamics, which is a new and very sensitive damage indicator, is qualified for future applications in health monitoring of smart or instrumented structures.
Multipass welds made in 316-L stainless steel are specific welds of the primary circuit in nuclear power plants. Their complex structure complicates ultrasonic assessment of their structural integrity : they present a heterogeneous anisotropy that modifies wave propagation (deviation and division of the beam, high attenuation, high grain noise…). In order to understand ultrasonic propagation in such media, a finite-element model called Athena was developed (INRIA-EDF). Athena predicts ultrasonic beam and particle's velocity in heterogeneous and anisotropic materials, but attenuation has still to be integrated to the code. Our work aims at providing realistic input data of attenuation compatible with the existing model by studying mechanisms leading to attenuation in anisotropic structures. Experimental measurements are made with two immersion techniques using longitudinal waves. Results are presented and compared with theoretical predictions of the literature.
In this paper, for composite structures, an identification method of impact force is proposed. Based on the finite element method (FEM), the relation between force histories and strain responses is first formulated. From this relation, an error vector indicating the force location is defined and used for the force location identification. Next, the identification of force history is performed with the modified least-squares method that imposes the penalty on the first derivative of the force history. The validity of the present method has been verified through the impact experiment of CFRP laminated plates embedded with PZT piezoelectric sensors. Based on a FEM model, the possibility of employment of the obtained impact force history and impact force location for the prediction of material internal damages is discussed, which illustrates that this method can be used for the real-time health monitoring of composite structures.
Two examples of in situ monitoring of ageing of materials with optical fibres are shown in this paper: thermal degradation of polyethylene and corrosion in aeronautic structures (aluminium) with an optical fibre corrosion sensor (OFCS). The thermal degradation of polyethylene is monitored by inclusion of an uncladded optical fibre in the polymer. Through modelling of the angle distribution of the normalized light power transmitted with geometric optics, the refractive index of the polymer is determined at different temperatures (n=1.4594 - i0.0007 at 28°C and n=1.5162 - i0.0007 at 120°C). The variation of the refractive index is related to a variation of crystallinity of the polymer. The kinetics of degradation was directly followed at different temperatures. The OFCS is tested by two methods: optical and electrochemical methods for different aluminum thickness deposited on the sensitive part of the optical fibre, in different acid concentration. The mechanisms of corrosion (uniform or in preferential places) can be deduced from the optical signal. The sensitivity of the OFCS is good for the low thickness. Corrosion rates for aluminum and copper are quite different, the effect of oxide layer on aluminum is important and induces corrosion in several stages.
Pulsed eddy current imaging non-destructive technique was used for detection of subsurface defects in ferromagnetic materials. In this work, an excitation probe coil is wounded around two small pickup coils arranged in a differential measurement set up. In order to avoid the non-linear behavior of the ferromagnetic material a static magnetic field is applied. The magnetically saturated metal behaves then like a non-magnetic one. This set up improves the performance of eddy current testing for detecting the defects, cracks, mass loss, and the corrosion defects in the ferrous materials. The results are very good since defects up to 10mm in depth are detected and observed in the c-scan image.
An alcohol oxidase (AOD) enzyme immobilized gas-sensor (bio-sniffer) with stick-type configuration was developed for convenient analysis of ethanol vapor. The stick-type sniffer device was constructed in a sandwich configuration with a filter paper placed between carbon- and Ag/AgCl electrodes. The electrode-coated paper was shaped by knife into 2mm-wide stick. In order to isolate a sensitive- (length: 5 mm) and terminal-areas, an epoxy-resin adhesive was applied to the middle part of the narrow stick paper. AOD was immobilized to the sensitive area with photocrosslinkable polymer. The characteristics of the stick-type sniffer moistened with phosphate buffer were assessed using standard ethanol vapor supplied from a gas generator. The oxidation current of hydrogen peroxide, produced by the AOD enzymatic reaction by applying ethanol vapor, was detected a computer-controlled potentiostat at a fixed voltage of +900 mV. The calibration range of the ethanol sniffer covered the concentration range encountered in breath after alcohol consumption including the permissible legal limit (130 ppm) for driving, and the sensing range of smell in humans. As the physiological application, the bio-sniffer was used to monitor the concentration change of breath ethanol after drinking.
Where is a place to be assisted for the patients with congestive heart failure? It is contraction of myocardium. We do not need to exchange the whole hearts. We started the ARTIFICIAL MYOCARDIUM development project. In the first step, pneumatic drive type artificial myocardium was developed. Next, development of an implantable type device was started. The animal experiment which studies the direct ventricle supporting effect by this motor was conducted. Although cardiac assistance of the right ventricle was enough as a result of repeating an animal experiment, the left ventricle supporting effect was inadequate. By such reason, we planned the development of an electrohydraulic driving system with grass fiber belt for fixation. The drive system with which it equipped between ribs controls silicon oil in our plan. Energy is supplied by transcutaneous energy transmission system from the outside of the body. As the results, this device is easily attached to the ventricle and the left ventricle and the right ventricle were able to be assisted as a result of the animal experiment. The cardiac output increased and blood pressure rose in the time series data during artificial myocardium support. Since this device is not a pump, it does not have a valve and does not have the risk of a thrombus, either. Therefore, it is also possible to implant in prevention to a slight heart failure patient. It is expected that it becomes an important artificial organ with a big market.
This paper is a study on the development of a sensor for measuring tactile sensation. The sensor using the pyroelectric effect of a PVDF (Polyvinylidene Fluoride) film is fabricated for measuring the human warm feeling. The base of the sensor is an aluminum block, around which a synthetic rubber layer overlaid with Nichrome wire, a PVDF film and a protective layer of acetate film are stacked in sequence. Furthermore a thermistor is attached on the side of the sensor. The sensor is heated and kept at a constant temperature by PID control. The heated sensor is contacted with the object to obtain the pyroelectric output from the PVDF film. Through experiments on several fabrics, the results show that the PVDF sensor using the pyroelectric effect is available to obtain information on the warm feeling.
In this paper, the mechanical constitutive relation of Shape Memory Alloys (SMAs) during stress-induced transitions is discussed based on mixture theories. The twinned martensite variants and austenite parents are taken as two constituents with their own reorientation or transformation behavior when subjected to external loading. Corresponding internal variables for describing these transitions are newly defined. This model enables the numerical prediction of the overall mechanical behavior of SMA materials in the temperature range form Ms to Mf. The approach of mixture theory; series models are applied in the formulation of the constitutive behavior of SMAs with isostress conditions. Tensile tests have been carried out with Ti-Ni specimens in a temperature range including martensite transformation temperatures. Numerical simulation based on the proposed model accurately predicted the mechanical behavior of stress-induced transitions in the concerned temperature range.
Magnetorheological elastomers consist in a dispersion of micron size (typically 1-5μm) magnetic particles inside an elastomer. During curing, the suspension is subjected to a strong magnetic field that creates an attractive force between particles in a direction parallel to the magnetic field, thus arranging the homogeneous dispersion in a chain-like structure. Once the polymer is cured, this unidirectional structure is kept. We shall present some results showing that the adaptive character of the material does not depend on the fact that particles are grafted to the matrix or not, but rather on the volume fraction of particles and above all on their organisation inside the matrix. In particular we shall see that, in addition to the change of modulus in the presence of a field, some very important magnetostrictive effect can also be observed in such composite. We explain this behaviour by the existence of a small layer of elastomer between the magnetic particles. In an other situation, with the use of nickel particles inside the elastomer, the gap between particles is much thinner and a small compression can change the resistivity of the sample by many orders of magnitude making it a very sensitive pressure sensor.
Thermoforming is a very popular method of plastics processing, because it is simple and inexpensive. There is a growing interest for thermoforming in the case of applications which are more and more technical, i.e. for automotive industry. This implies to better control and optimize the process. One key step is the heating of the plate in order to reach the viscoelastic state of the material, the heat required for this change of state being mainly transferred in a radiative form. Therefore the energy distribution in the plate should be carefully optimized. Classical methods based on the “view factors concept” are known to be difficult to operate in the case of complex geometries and/or spectral diffusion sources. In this study, an approach using the “ray tracing method” is used. The principle of this method consists in discretizing the heating source surface and associating to each element several rays which carry a given amount of energy. Each ray interferes with the plate, directly or after reflection on the reflectors, and transfers its energy to the plate. The energy distribution on the plate surface is easily deduced and the temperature field can be calculated, providing the bases for the inverse problem which is more interesting from the process point of view : starting from a required temperature distribution on the plate, the adequate sources (emissivity, shape…) and their relative locations with respect to the heated plate will be predicted.
The possibility of detecting the phase transformation of stress-induced martensite in a ferromagnetic shape memory alloy Fe-30.2at%Pd thin foil was investigated by using the Barkhausen noise (BHN) method. Stress-induced martensite twining was observed by laser microscopy above a stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twining in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to the austenite phase at weak magnetic fields. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field levels. The BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.
This paper describes research developments of smart materials and processing for mover engineering. Smart materials and processing related to high power and high responsiveness successfully developed in 2004 were developed for giant magnetostrictive Tb-Fe and Sm-Fe and movable film device with hydrogen storage alloy. To obtain reliability related to elasticity, fracture resistance and fatigue resistance, we developed processing of joining of metal and carbon fiber and electron beam irradiation treatment to obtain high fracture toughness of carbon fiber (CF), CFRP, C/C composite materials and PZT for movable technology.