Poly(vinylidene fluoride) (PVDF) has four crystalline structures (α, β, γ and δ phase structures) in solid state. The extraordinary PVDF electrical properties are directly attributable to its crystalline structure. Only α-phase structure shows no crystal dipole, but this phase structure is converted easily into other phase structures according to some schemes. Generally, PVDF is given uniaxial stretch and polarization processes in order to convert into β-phase or γ- phase structure before sensor and actuator film use. However, we recently found a novel method in which PVDF film structure became β-phase or γ-phase without mechanical deformation processes. Furthermore, this technique enables us to apply printing technology, and realize the creation of free-form 3D sensor and actuators.
In the development of printed PVDF film, the integration of material fabrication technique, its crystalline structure state, forming technology and macroscopic electrical properties will be important research topics. Up to the present, authors have constructed PVDF film fabrication techniques. As a result, PVDF crystalline structure was changeable using the techniques. In addition, some in-house PVDF property measurement systems have been constructed for the sensor and actuator applications. Furthermore, a novel PVDF printer, which can draw freeform 2D PVDF film, has been developed on the basis of PVDF film fabrication results. In present paper, we would introduce our PVDF film fabrication techniques, in-house PVDF property measurement systems and P-p printer.
We used a new method to fabricate salami-type porous metal from glass microcapsules and liquid metal. Each pore of its
salami-like structure behaves as a micro-bell. This metal, which is more than 20% lighter than bulk material, also shows
a unique characteristic: high-frequency oscillation is greatly attenuated when propagated in its medium. This method
offers great potential for size, shape, and conformation control, with changed attenuation characteristics of its salami-like
pore structure achieved merely by changing the mixing technique. This study was conducted to measure compressive
deformation behavior and attenuation characteristic of salami-type porous SnSbCu. To begin with, we fabricated two
salami-type porous metals using 16um or 60um diameter microcapsule, which have different salami structures in its
body. Next, compressive loading test was conducted for the metals. Then, the attenuation characteristic was investigated
using laser ultrasonic measurement. Thereby, compressive deformation behavior was same between fabricated two
salami-type porous metals. In contrast, the attenuation characteristic was different at low frequency range between them.
Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In general, it is necessary to give large stretch to PVDF film when PVDF film is used as sensor or actuator element. However, we recently found that PVDF shows piezoelectricity without large stretch if nano-clays are uniformly dispersed into it.
The aim of present study is to investigate the possibilities of nano-clay/PVDF composite film as sensor and actuator element. Firstly, PVDF films and nano-clay/PVDF composite film are fabricated by solvent casting. Also, commercial PVDF film is prepared as comparative material. Secondarily, we investigate the change of electrical displacement according to the input voltage of triangle wave by using Sawyer-tower bridge circuit for PVDF films and nano-clay/PVDF composite film. Then, the change of impedance is also measured at broad frequency by using impedance analyzer. Thirdly, we apply the voltage of sine wave to fabricated films, and measure the output oscillation generated from films. Finally, we discuss the possibilities of nano-clay/PVDF composite film as sensor and actuator element.
The aim of present study is to investigate the local strain band behavior and the influence of it on macroscopic deformation behavior, of NiTi plates under mechanical loading. Firstly, we evaluate the transformation temperature by Differential Scanning Calorimetry (DSC) and investigate the initial phase for two NiTi thin plates with different texture. Next, we investigate the texture by X-ray diffraction method. Then, we measure local strain distribution arising in NiTi thin plates under uniaxial tensile loading, by using in-house measurement system on the basis of digital image correlation. Finally, we discuss about the "Mechanism of angle, nucleation and propagation for local strain band" and "Relationship between macroscopic stress-strain curve and local strain band behavior" on the basis of results in present study.
Bone is a smart, self-adaptive and also partly self-repairing tissue. In recent years, many researchers seek to find
how to give the effective mechanical stimulation to bone, because it is the predominant loading that determines
the bone shape and macroscopic structure. However, the trial of regeneration of bone is still under way. On the
other hand, it has been known that electrical potential generates from bone by mechanical stimulation (Yasuda,
1977; Williams, 1982; Starkebaum, 1979; Cochran, 1968; Lanyon, 1977; Salzstein, 1987a,b; Friedenberg, 1966).
This is called "stress-generated potential (SGP)". The process of information transfer between "strain" and
"cells" is not still clear. But, there is some possibility that SGP has something to do with the process of
information transfer. If the electrical potential is more clear under some mechanical loadings, we will be able to
regenerate bone artificially and freely. Therefore, it is important to investigate SGP in detail.
The aim of present study is to investigate the electric reaction arising in dry bone subjected to mechanical
loadings at high amplitude and low frequency strain. Firstly, specimen is fabricated from femur of cow. Next,
the speeds of wave propagation in bone are tried to measure by laser ultra sonic technique and wavelet transform,
because these have relationship with bone density. Secondary, 4-point bending test is conducted up to fracture.
Then, electric reaction arising in bone is measured during loading. Finally, cyclic 4-point bending tests are
conducted to investigate the electric reaction arising in bone at low frequency strain.
The aim of present study is the investigation of the electric reaction arising in bone subjected to mechanical loadings. Firstly, specimen was fabricated from femur of cow, and ultrasonic propagation in bone was measured by ultrasonic technique. Secondary, 4-point bending test was conducted up to fracture, and electric reaction arising in bone was measured during loading. Thirdly, cyclic 4-point bending test was conducted to investigate the effect of applied displacement speed on electric reaction.
Composites containing Shape Memory Alloy (SMA) fiber and polymer (or metal) matrix are expected as smart materials and structural materials. For example, Shape Memory Alloy Composite (SMAC) exhibits creating of compressive residual stress (Creating of internal stress) in matrix and deformation of composite under thermo-loading.
In the present study, firstly, the experimental model of SMAC (NiTi/Epoxy) were fabricated, and internal stress, deformation and temperature distribution of SMAC were measured under thermo-loading by using photoelasticity, digital image corelation and infrared radiation thermometry. As a result, some assumptions were obtained to construct analytical model of SMAC.
Secondaly, the analytical model considering distribution of stress and strain in SMAC was constructed based on shear lag model. Closed solutions, such as shear stress in matrix and so on, were obtained from this analytical model. Then, some analyses were conducted for predicting internal stress and deformation of SMAC during thermo-mechanical loadings by using present closed solution.