FEM-aided identification of gauge factors of unidirectional CFRP through multi-point potential measurements

Carbon fiber reinforced plastic (CFRP) has electrical conductivity in both the parallel and transverse directions of the fiber. Because an electrical network may be changed with the applied strain, the electrical conductivity of the CFRP will also be changed for the piezoresistivity. Strain monitoring of CFRP can therefore be conducted, not by using an additional sensor, but by measuring the change in electrical resistance. There have been many studies on the gauge factors of unidirectional CFRPs, although significant mutual differences have been determined in the results reported. It is thought that the differences may be caused by the strong electrical anisotropy and inhomogeneity of the unidirectional CFRP. In this study, a new concept was introduced to precisely measure the gauge factors of a unidirectional CFRP. A finite element analysis was utilized to take into consideration a non-uniform electrical potential field in a unidirectional CFRP. The gauge factors were obtained as a result of minimizing the error sum of the squares of the electrical potentials between the experimental and analytical results. The gauge factor in the fiber direction was affected by this factor in the thickness direction depending on the specimen configuration. The results of the finite element analysis showed the possibility of a unidirectional CFRP showing both positive and negative gauge factors in the fiber direction.     

Compression test of a single carbon fiber in a scanning electron microscope and its evaluation via finite element analysis

A longitudinal compression test for a single polyacrylonitrile-based carbon fiber (T300) was performed using a scanning electron microscope. The compressive stress/strain behavior was initially linear, but subsequently became nonlinear. The longitudinal tangent modulus decreased with increasing compressive strain. A cyclic compression test revealed that the T300 carbon fiber deformed elastically up to ~90% compressive strength. The variability in the compressive strength was evaluated using Weibull analysis. The representative compressive strength of the T300 carbon fiber was nearly the same as the tensile strength. The compressive strength of the T300 carbon fiber was almost same as that of the high-tensile strength T800S carbon fiber. Finite element analysis was performed to investigate the validity of the test method. The results showed that the longitudinal compressive stress on the carbon fiber varied during longitudinal compressive loading. The maximum longitudinal compressive stress in the carbon fiber was slightly higher than the average compressive strength applied at the end. However, the variability in the measured compressive strength was much higher than that in the longitudinal compressive stress on the carbon fiber, which does not affect the former.     

In situ pressure calibration for piston cylinder cells via ruby fluorescence with fiber optics

A fiber-optic measurement technique is developed for estimating the pressure inside a piston cylinder cell up to approximately 4 GPa, based on the pressure-induced R1 fluorescence line shift of ruby (ruby scale). Ruby scale and a conventional technique (calibration on phase transitions of bismuth) were simultaneously applied to the cell filled with a pressure transmitting medium of isopropyl alcohol. The pressure readings of the two methods were consistent with each other, and no pressure gradient was observed. The ruby scale has the advantages of real time estimation and easy installation in a small space. Because of these advantages, three fibers were simultaneously introduced in the sample space at the same time, and pressure distribution was measured for Fluorinert (FC70:FC77=1:1), Daphne oil 7373, and Fomblin oil (YHVAC 13014).     

Behavior emergence of a virtual creature living in complex environments

This study aimed at establishing a new computer-aided animation method using agent-based and physics modeling-based animation. The specific problem we addressed was to install adaptive behavior in a virtual creature placed in a complex environment, and to create its animated behavior automatically. The virtual creature is regarded as an autonomous agent who has sensors, actuators, and controllers. An artificial neural netword (ANN) and a central pattern generator (CPG) were adopted as the controllers. An optimization algorithm was introduced to train the controllers. Numerical experiments proved that the virtual creature acquires effective motions (walking, swimming) to move toward its destination, and to avoid obstacles and other creatures.     

Synthesis and characterization of three-branched star-like poly(γ-benzyl-l-glutamate)

Summary Three branched star-like poly(-benzyl-l-glutamate) was synthesized using three functional amine as an initiator, and characterized through light-scattering, ORD and intrinsic viscosity measurements. Experimental results suggest that the synthesized star-like poly(-benzyl-l-glutamate)s are composed of three branches of equal length.     

An ultrahigh‐definition display using the pixel‐offset method

Abstract— An ultrahigh‐definition display system quadrupling the horizontal and vertical resolution of HDTV has been developed. In order to obtain the ultrahigh definition, four LCD panels (red, green 1, green 2, and blue) are combined using the spatial pixel‐offset method. Therefore, only green images have an ultrahigh resolution of 4096 × 7680 pixels, while red and blue images have 2048 × 3840 pixels. The ultrahigh resolution was confirmed by subjective assessment testing. The scores of the test have the same tendencies as the SQRI values. The necessary accuracy of the convergence correction is calculated to be within 0.3 pixels by the modified s‐CIELAB method.     

Heat transfer and pressure loss characteristics of very compact heat sinks

High-performance compact heat sinks have been developed for the effective cooling of high-density LSI packaging. Heat transfer and pressure loss characteristics of the heat sinks in both air-cross-flow and air-jet cooling have been experimentally studied. The present heat sinks were of plate-fin and pin-fin arrays with a fin pitch of 0.7 mm. The plate-fin heat sinks had higher cooling performance than the pin-fin heat sinks in the range of large airflow rates both in air-cross-flow and air-jet cooling. The thermal conductance in cross-flow cooling was 20 or 40% larger than that in jet cooling. The correlation of Colburn j-factor/Fanning friction factor versus the Reynolds number for the present heat sinks was found to be very close to that of a conventional large-size heat exchanger. © Scripta Technica, Heat Trans Asian Res, 28(8): 687-705, 1999     

Polypropylene-grafted nanoparticles as a promising strategy for boosting physical properties of polypropylene-based nanocomposites

SiO₂ nanoparticles grafted to terminally hydroxylated polypropylene (PP-g-SiO₂) with different molecular weights were melt mixed with PP to prepare a series of PP/PP-g-SiO₂ nanocomposites. PP/PP-g-SiO₂ offered several advantages over pristine PP and PP/unmodified SiO₂ such as highly uniform dispersion up to 10 wt.-%, +200–400% faster crystallization and +30% increments for both the Young's modulus and the tensile strength without largely sacrificing the melt viscosity of PP. We concluded that grafted chains act as crystallization nuclei and co-crystallize with matrix chains to make PP-g-SiO₂ nanoparticles as a physical cross-linker between lamellae, while the linkage disappears in melt and grafted chains minimize the cohesive attraction between nanoparticles.     

A design based on final-state control for residual vibrationless seeking in hard disk drives

A new design method - based on a final-state control (FSC) - for short-span seeking in a hard-disk drive (HDD) has been developed. The short-span seeking is performed by two-degree-of-freedom (2-DOF) control, which uses a feedforward (FF) control input along with a reference trajectory. The design method can directly generate the FF control input, whose derivative at a specified order is minimized and whose power spectrum amplitude is reduced at a specified frequency. The residual vibration caused by mechanical resonance can therefore be reduced by the generated FF control input. Test with a 2.5-in form-factor HDD experimentally confirmed that the developed seeking control significantly reduces the residual vibration in a HDD.     

Synthesis of a minute SiC product from polyvinylsilane with radiation curing: Part II—Ceramization process of radiation cured polyvinylsilane

We have synthesized minute SiC products from polyvinylsilane (PVS), which is a liquid organosilicon polymer, with radiation curing. Since there is a close relationship between the properties of obtained SiC products and pyrolysis condition, it is important to investigate the ceramization process of cured PVS in order to find out the optimum pyrolysis condition. In this paper, the ceramization process of the PVS cured by γ-ray irradiation at room temperature was investigated by gas analysis, thermogravimetric analysis (TGA), density measurement, and so on. It was found that the ceramization of γ-ray cured PVS starts above 500 K, and drastic organic–inorganic conversion occurs in the temperature range of 700–1100 K. According to the changes of mass and density, it was found that the volume shrinkage of PVS during the curing and pyrolysis processes is 80%. The SiC obtained by pyrolysis at 1573 K in argon gas atmosphere showed the density of 2500 kg/m³ and microvickers hardness of 31.6 GPa.