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Volume 25 (1997)
- Issue 5 Pages 243-
- Issue 4 Pages 187-
- Issue 3 Pages 113-
- Issue 2 Pages 55-
- Issue 1 Pages 7-
Volume 25, Issue 3
Displaying 1-9 of 9 articles from this issue
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Yoshio SHIRASAKI, Tetsuya TATEISHI, Masami AKAI, Mariko USUBA1997 Volume 25 Issue 3 Pages 113-117
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSIn this investigation, the effect of immobilization on the mechanical properties and bone density of the knee joint were evaluated for 32male 9wk old wistar rats. Mechanical tests were conducted for the tibial and the femoral bone. Dynamic stiffness and tan δ were measured with a viscoelastic spectrometer, and three-point bending test was performed with an Intron-type universal testing machine. Bone mineral content was measured by dual energy X-ray absorptiometry at the diaphysis of the tibial and femoral bone with tibial proximal and femoral distal portions. The results showed an early change of the mechanical properties and bone mineral density in periods of 2-3wks. Result also demonstrated that the bone mineral density of the peripheral site was significantly altered for the diaphysis of the bone.View full abstractDownload PDF (705K) -
Tsunemi MONMA, Masuo KUDO, Toru MASUKO1997 Volume 25 Issue 3 Pages 119-123
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSStatic and dynamic viscoelastic properties of synthetic saponite (Sumecton SA)/water dispersion systems have been investigated at 20°C. Solid concentrations of the system were changed in the range from 1 to 3wt%. At low concentrations less than 1.1wt% of solid content, the dispersions showed a typical Newtonian flow, however they exhibited a distinct shear thinning effect at concentrations exceeding 1.2wt%. This indicates that the coagulated structure of the saponite particles in the system begins to form at a concentration of 1.2wt%. Alternatively, at concentrations higher than 1.5wt%, the dispersions showed high storage moduli in the order of 10 Pa, due to formation of a gel structure. This structure was broken down by an applied weak strain, and later revealed rapid structural recovery. The scaling index calculated from the log-log plot of storage modulus against solid concentration was 5.3, larger than that of the commercial Namontmorillonite or the synthetic hectorite suspensions.View full abstractDownload PDF (623K) -
Takumi ARAKI, James L. WHITE1997 Volume 25 Issue 3 Pages 125-133
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSThe shear viscosity of carbon black filled and calcium carbonate filled polypropylene, PP-EPDM dynamically vulcanized thermoplastic elastomers (TPE) and ABS resins were investigated over a very wide shear rate and shear stress range. This was accomplished using (i) a constant shear stress creep instrument, (ii) a cone-plate rotational rheometer, (iii) a capillary extrusion rheometer. It was found that stresses exist for some of these compounds below which there are only finite deformations and no steady flow. These stresses define yield values. Much attention was given to measurements of creep at low stresses, especially in the neighborhood of the yield value. The magnitudes of yield stresses obtained from such creep measurements are significantly lower than those obtained from using standard extrapolation to zero shear rate of higher stresses from rotational instruments. The shear viscosity behavior near the yield value differs considerably depending upon the type of particle filler in the compound and the rubber content in TPE and ABS. We also observed a high shear viscosity (ca 109 Pas) plateau in many of our systems.View full abstractDownload PDF (954K) -
Khandker S. HOSSAIN, Norio NEMOTO, Katsuyoshi NISHINARI1997 Volume 25 Issue 3 Pages 135-142
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSA dynamic viscoelastic (DVE) and creep study has been made on five iota carrageenan gelling samples with polymer concentration C ranging from 1 to 3wt% over a wide range of temperature including the sol-gel transition point. All gel samples below and at room temperature show nearly ideal elastic behavior. The gel point is determined as temperature Tc at which the storage and the loss shear moduli, G′ and G″, follow the power law with the same exponent n, which is smaller than the universal value of 0.66 for chemical gels and decreases monotonously with increasing concentration. Superposition of dynamic and creep data reveals that the power law holds at least four decades at the gel point. DSC measurement on the same samples reveals a broad sol-gel transition. The transition temperature Tm determined as the peak temperature is found to be close to the gel point Tc, but always higher than Tc. At Tm, the samples are viscous solution at lower C and viscoelastic at higher C, clearly indicating that Tm can not be considered as the gel melting temperature.View full abstractDownload PDF (1091K) -
Sinichi TAKAHASHI, Kazuyoshi OGINO1997 Volume 25 Issue 3 Pages 143-148
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSViscoelastic properties of hyaluronic acid (HA) alkalinesalts in aqueous solution were studied in the concentration range of 1.0 to 0.25 wt% at 36°C. The viscoelastic behavior of the system was ex-pressed with simple mechanical models. Mechanical dispersion curve or Cole-Cole plot was approximately expressed with a four element model by adopting the adequate equilibrium compliance for each concentration. In the case of K-type HA solutions, in which Na+ was replaced with K+ by use of ion-exchange resin, viscosities decreased by two order from those in Na-type HA solutions, and rigidities became 1/2 to 1/3 of those observed in the Na-type HA solution.View full abstractDownload PDF (645K) -
Ryo SAKURAI, Howard SEE, Tasuku SAITO1997 Volume 25 Issue 3 Pages 149-154
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSWe have carried out a set of experiments to determine the effect of adding small amounts of conductive carbon black fragments to an electrorheological fluid consisting of a dispersion of anhydrous carbonaceous particles. We find that there is a large reduction in the shear stress under an electric field as the concentration of conductive fragments is increased, and an accompanying increase in the electric current. This decrease in shear stress is different to that caused by a broad distribution of particulate conductivity, investigated in a previous work. We explain this behavior by a simple model based on the “bouncing motion” of the conductive fragments, where there is a transfer of charge by the fragments oscillating across the electrode gap.View full abstractDownload PDF (827K) -
Kiichiro MUKAI, Fumihiko KISHI, Takeshi AMARI1997 Volume 25 Issue 3 Pages 155-160
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSFor liquid crystals, 4-cyano-4′-pentylbiphenyl (5CB) and 4-cyano-4′-octylbiphenyl (8CB), flow behavior was investigated with a slit viscometer composed of sliding glass plates. Three types of plates, bare glass plates and polyimide (PI)-coated plates rubbed in directions parallel or perpendicular to the flow direction, were used. The gap between the plates was 5 μ m, and the measurements were carried out in a shear rate range between 5 and 300 sec-1 at various temperatures ranging from 25 to 43°C. For 5CB and 8CB in the nematic phase, an apparent viscosity was higher in the PI-coated slit channel rubbed in a direction perpendicular to the flow than in the channel rubbed in the parallel direction. Shear thinning was observed in the former channel while Newtonian behavior was found in the latter. This difference was related to the alignment of the 5CB and/or 8CB molecules: They were aligned to the rubbing direction near the slit surface but to the flow direction near the center of the slit. Thus, the flow in the perpendicularly rubbed channel induced twist of molecular alignment in the slit thereby being associated with the high viscosity of shear-thinning nature. For 8CB in the smectic phase, the apparent viscosity was lower in the PI-coated slit channel rubbed in the perpendicular direction than in the channel rubbed in the parallel direction. This result was related to the smectic layer structure: For the former case the flow was achieved by motion of 8CB molecules in each layer and thus the layer structure was preserved to give the low viscosity, while for the latter case this structure was disrupted under flow to give the high viscosity.View full abstractDownload PDF (1060K) -
Hiromi YANASE, Keiko KATSUTA1997 Volume 25 Issue 3 Pages 161-163
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSSalad oil was sheared with specially designed bob and cup type rheometer at room temperature.The flow curve consists of two regions;shear thinning at lower shear rates and Newtonian at higher shear rates. The results was compatible with those by the measurement of the same material using conventional Weissenberg Rheogoniometer R-18with different geometry of cone and plate. The shear thinning behavior was tentatively attributed to the ambiguous structure of locally oriented or(and)aligned molecules by virtue of the amphiphilic nature of the glycerides, the main components of salad oil.View full abstractDownload PDF (501K) -
Akiko KAWAI, Kunio KAMIYA, Kunio UCHIDA, Satoshi YODA, Kei URABE, Akih ...1997 Volume 25 Issue 3 Pages 165-169
Published: August 15, 1997
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSThe degradation mechanism of the electrorheological (ER) effect in hydrous ER systems was studied by using two kinds of ER fluids. One contained titania and the other microcrystalline cellulose as dispersoids in silicon oil. The ER effect of the fluids with different water content was measured for several samples during a time interval of several months. The interval of several months degraded the ER effect in all the fluids. After the degradation, the water content of the dispersoid was found to decrease. The electric current density decreased and the dielectric properties changed. The relation between the ER effect and the electric current density and the relation between the ER effect and the dielectric properties were investigated before and after the degradation. The amount of water in the silicon oil was measured using TG (thermogravimetry) to detect the amount of water in the silicon oil after removal of particles from an aged fluid. There was no detectable water in as-received silicon oil, but water was detected in the silicon oil after the degradation. It was suggested that the water diffused from the surface of the dispersoid to the silicon oil. Finally, a suspension made up of a used silicon oil and a dispersoid was subject to the evaluation of ER effect. No degradation was found for the fluid.View full abstractDownload PDF (554K)
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