A multiscale simulation is presented for polycrystalline multiferroic composite materials consisting of ferroelectric and ferromagnetic phases. The purpose of this study is to estimate the effect of off-axis electric and magnetic polarization on macroscopic magnetoelectric (ME) coupling constants. The asymptotic homogenization theory was employed for scale-bridging between macrostructure and microstructure. The crystal orientations and material types were randomly allocated into the microstructure. Especially the microstructural crystal orientations were controlled by the combination of off-axis electric and magnetic polarization treatments. Tetragonal perovskite BaTiO3 and hexagonal spinel CoFe2O4 were employed for ferroelectric and ferromagnetic phases, respectively. As the angle between electric and magnetic fields of polarization treatment was changed from 0 to 90 degree, the homogenized physical properties were calculated for the polycrystalline multiferroic composite material. The computation indicated the macroscopic ME constants and piezomagnetic constants vary more widely through off-axis polarization treatment than the other properties. It was confirmed that ME constants can be tailored by the combination between electric and magnetic polarization treatments.
In this study, high piezoelectric lead zirconate titanate (PZT) thin film was prepared with MPB (Morphotoropic Phase Boundary) composition and buffer layer. From our previous study, high piezoelectricity of PZT thin film was confirmed through MPB (Morphotoropic Phase Boundary) composition and also noted that the piezoelectricity becomes maximum when PZT (111) and PZT (110) thin films stacked evenly. MPB composition and buffer layer significantly reduces the lattice mismatch to attain maximum piezoelectricity. It has been already reported that Au (111) and Pt (111) take high priority to orient PZT thin film in (111) and (110) crystal planes respectively. Therefore, the purpose of this study is to create alternately oriented buffer layer of Au (111) and Pt (111) and its influence on crystal quality. Sputtering technique was used to deposit Au-Pt buffer layer on Si substrate. Due to natural oxidation of Si in air atmosphere, the growth orientation of the thin film may be affected. Hence, prior to deposition, Si substrate was washed with hydrofluoric acid to remove the natural oxidation film. Further using Au-Pt composite target, buffer later was deposited on Si substrate and consequently the film was annealed. As a result of Au-Pt buffer layer 127 % of increase in crystal quality was observed as compared with the film deposited without buffer layer.
The mechanical strength of composite functional films is investigated by numerical simulation in this paper. Such functional film is often required bending strength during assembly. It is calculated composites with method to calculate equivalent macroscopic properties such as equivalent inclusion method and homogenization method, but these methods cannot be considered size effect. Therefore, we developed method to evaluate bending strength of particulate composite film by bending calculation of RVE with relative periodic condition. From the results of DOE bending calculations by the developed method, filler size shows a high contribution rate, however the size under 0.1 um doesn't affects the contribution rate.
This paper describes an inverse stochastic homogenization analysis of a particle composite material considering correlated multiple microscopic random variations. Since a microscopic random variation will cause a random response of an equivalent material property or mechanical response of a composite structure, the analysis of its influence is important for reliability evaluation of the structure. On the other hand, in general, the probabilistic property of a microscopic quantity is unknown after manufacturing. From this reason, this study aims at development of the analysis method for the inverse stochastic homogenization problem, which identifies the microscopic probabilistic property from that of the macroscopic quantities. In particular, applicability of the polynomial-based approximation to the inverse stochastic homogenization analysis is investigated in this paper.
Due to the superior specific strength and stiffness, a fiber reinforced plastic (FRP) is applied to the various industrial fields such as aerospace, automobile and medical instruments. Especially, the FRP reinforced with textile architecture attracts an attention for its high performance and flexibility in material design. However, it is difficult to forecast the mechanical property of textile composites, because the stress distributions in textile structure under an applied loading is complicated. In this paper, the FE-modelling techniques for the numerical evaluation of 3D-woven composite is discussed. Firstly, a modelling method based on mesh super position FE analysis is proposed for several types of woven composites. Secondary, the effects of textile size and wave pattern of stress fields are investigated. As a result, stress concentration points, which are considered as failure initiation site of textile structure, can be controlled by changing weave patterns.
This paper presents the effectiveness of the error reduction methods for integrated dot centroid tracking method. Two important sources of error and noise are lens distortion and brightness intensity fluctuation on each pixel, which should be taken in account to achieve high accuracy of full-field strain measurement. The method can correct lens distortion at any focal distance between a digital camera and an object. Pixel based noise reduction method using Kalman filter and integrated image by multiple images was proposed. When we need very accurate strain field, the lens distortion should be removed as possible as we can. Due to the corrections, 0.1% strain accuracy is accomplished and total computation time is reduced in comparison with an arithmetic mean operations. The effectiveness of the idea is shown through experimental and numerical examples and the result of strain field measurement is presented and discussed.
The available piezoelectric vibration body in the artificial larynx has a vibration board in a frame. Therefore, the existing piezoelectric vibration body has oscillated at higher frequency than voice fundamental frequency. Moreover, it was unable to predict the sound pressure, because amplitude and area of the vibration board were small. Hence, we designed a new piezoelectric vibration body for the purpose to increase in vibration board amplitude and reduction of the oscillatory frequency. The designed piezoelectric vibration bodies consist of frame and vibration board which was supported by a diagonal beam. An actuator (PZT) is located on the both sides of the diagonal beam. PZT expands and contracts by adding AC voltage, it makes the vibration board vibrate. However, to know about the best dimensions of the beam and vibration board experimental design and piezoelectric analysis was performed. Furthermore, we have carried out dynamic analysis to evaluate the acoustic properties in the best condition model because acoustic properties of the resonance were unclear by the statics analysis. We have also confirmed frequency response characteristics and sound pressure distribution from dynamic analysis. From the analysis results, we confirmed that best condition model has low directional characteristics and it oscillated higher frequency than voice fundamental frequency. Moreover, we also confirmed that the sound pressure level is smaller than sound pressure of the human conversation.
Wood particle-polypropylene composites were prepared and the effect of wood particle size on mechanical properties was investigated. The target of this study was micro-order wood particles which reside in transition area from industrial wood composites to nano cellulose composites. Wood particles were fabricated from thinned wood such as cedars and cypresses through ball mill wet crushing. The average size of wood particles, which was controlled by changing the crushing time, was set to three different levels, 30 μm, 50 μm and 150 μm. Then their wood particles were kneaded with polypropylene at the condition that the weight fraction of wood was 10% and maleic anhydride grafted polypropylene (MAPP) was employed for sufficient interfacial adhesion. The specimens were prepared through injection molding and the uni-axial tensile and three-point bending tests were performed. The experimental results indicated elastic modulus and strength decrease almost linearly in both tests as the particle size becomes smaller. This phenomenon was discussed at the view point of crystallinity of matrix polymer to understand the mechanism of wood particle size dependence.
Failure probability model of unidirectional fiber-reinforced plastic was constructed based on P-S-N curve using the S-N data set collected from database and published papers. Firstly, S-N curves for each data set were obtained by using a regression method based on fatigue strength distribution. To merge each S-N data set with various test conditions, maximum stress of their data set was normalized by tensile strength. As the result, each data set could be gathered into narrow region. However, some data sets still existed out of common region. Secondly, statistical test for differentiating between S-N data sets was carried out by using analysis of variance, and then merged data set was obtained. Finally, failure probability model was constructed based on P-S-N curve using the merged data set and a regression method based on fatigue strength distribution. The model could be applied to Reliability design.
This paper describes a torque measurement method using integrated dot centroid tracking method which is a full-field measurement technique. Since torque makes torsional displacement of a shaft in three dimension, two dimensional displacement measurement cannot be directly applied. The measurement of torque requires a precise conversion from two dimensional displacement to three dimensional rotational displacement. The mapping, which represents relationship between two dimensional displacement and three dimensional torsional angle, is precisely calculated by high resolution computer graphics images. At first, the integrated dot centroid tracking method using the mapping is applied to static torsional measurement. After the experiment, the method is applied to dynamic torque measurement in a large milling machine. Those measurement results are compared with the result of a torque meter. The accuracy of static torque measurement is accepted. We evaluate measurement result and how to improve the accuracy of the measurement.
A flame combustion method enables the synthesis of diamond using acetylene-oxygen gas in ambient atmosphere. It has various advantages over other methods. We previously synthesized diamond films on a Mo substrate surface by the flame combustion method. In this method, most diamond films delaminate as a result of thermal stress during cooling. To prevent diamond film delamination for the synthesis of good diamond films, a three-step synthesis method was proposed. However, the surface roughness of synthesized diamond films by this method became large. In this study, to reduce the surface roughness of synthesized diamond films by flame combustion and to achieve good adhesion on the Mo substrate, the flow ratio of oxygen flow rate to acetylene flow rate and synthesis time of the three-step synthesis method were varied during the synthesis of diamond. We previously determined optimal ratio of oxygen flow rate (Fo = 63.8 cm3/s) to acetylene flow rate (Fa = 70.9 cm3/s) which was set to Rf = Fo/Fa = 0.90, because delamination free good crystalline growth could be obtained at Rf = 0.90. The acetylene flow rate was carefully varied in the range of 63.8-75.1 cm3/s (Rf = 0.85-1.00) of each synthesis time (10 min) of the three-step synthesis method. The oxygen flow rate was not varied, and it was 63.8 cm3/s. To investigate the surface morphology and the surface roughness of synthesized diamond films, synthesized films were observed. The flow ratio and synthesis time of the three-step synthesis method affected the surface morphology and the surface roughness of synthesized diamond films. The surface roughness of the synthesized film was reduced by the proposed method in this study. The surface roughness in the Case 3 condition was the smallest in this experiment.
Weld metal derived from titania-based flux cored wire, which was used in the past for gas shielded arc welding, was not applicable for low-temperature service. In recent years, a new titania-based flux cored wire which can be applicable for the use until low temperature has been developed by improving the toughness of the weld metal. In this study the improvement of the toughness in the weld metal by titania-based flux cored wires is described. It was found that ,not only adding Mn,Ni,and Ti-B, but also lowering oxygen content and impurities of P,Nb,and V are effective to improve the toughness in the weld metal by titania-based flux cored wire.
In recent years, gas shielded arc welding processes with flux cored wire have been widely used in many industrial sectors because of various advantages in fabrication: weldability, productivity, etc. In this study, MAG welding phenomena with titania-based flux cored wire were experimentally investigated in comparison with those with solid wire. In the vertical upward position, feasible operation range of welding current and welding speed was examined for both wires of flux cored wire and solid wire. Through the observation of high speed photography, dynamic behaviors of droplet transfer and molten pool were clarified and discussed in MAG welding with titania-based flux cored wire. Melting temperature of the titania- based slag was confirmed to be higher than that of mild steel by using differential thermal analysis (DTA). It is found that the molten metal at the wire tip is transferred along the flux pillar to weld pool in flux cored wire welding. The slag of higher melting temperature solidifies ahead of metal and supports liquid metal in the weld pool in the vertical upward position.