Irreversible Bending Research Articles

Giant Bending Strain of Reversible Motion of Uni-Morph Soft Mover Composites Driven by Hydrogen Storage Alloy Powders Dispersed in Polyurethane Sheet

In order to generate the bending motion operated by pressure change in hydrogen gas, soft uni-morph composites were prepared, in which composites dispersed with not only driving particles of LaNi5 hydrogen storage alloy with Pd-Al2O3 catalyst powders to get high responsiveness, were piled up on a simple polyurethane sheet. Since the highest values of irreversible bending strain at the first hydrogenation ( 1 ) under 0.3 MPa H2 gas and the maximum irreversible bending strain during hydrogenation cycles ( m ) were remarkably obtained at the 35 vol% of LaNi5 powders dispersed in polyurethane composites, the bending strain of reversible motion was detected from the first to the 8th hydrogenation (r 1 and r 8 ) under 0.2 MPa H2 gas. The bending strain of reversible motion of polyurethane composites sheet is more than 2000 ppm, which was approximately equal to that of silicone rubber composites and is extremely larger than that (300 ppm) of ABS resin composites. Responsiveness (d=dt) of cyclic motion of elastic deformed mover composites, which were constructed with 35 vol%LaNi5 dispersed powder and matrix of polyurethane or silicone rubber, were more than 10 times higher than that of ABS composite. [doi:10.2320/matertrans.M2009178]

Estimation, variation and importance of leaf curvature in Zea mays hybrids

Maize leaves are curved but this curvature cannot be described by a single system of equations based on conic sections. We made comparisons of curvature between hybrids, leaf positions and planting density using measures of maximum leaf height and leaf tip:maximum leaf height ratio. With these measures a modern hybrid released in 1991 (Pioneer 3394) shows less curvature compared with hybrids released in 1963 (Pioneer 3306) and 1936 (Pioneer 307). The greater uprightness of 3394’s leaves was apparent for all leaves measured. Curvature is a plastic character. While all hybrids developed less curvature in higher density plantings the effect was greatest for 3394. 3394 had shorter, more lanceolate leaves with smaller leaf area, a lower estimated torque around the point of leaf attachment to the stem, and a significantly smaller auricle base and smaller angle between the leaf blade and auricle base. These results support suggestions that the pattern of curvature may be produced by the progression of irreversible bending during leaf development. We found no consistent relationships between differences in curvature and measurements of leaf midrib morphology or anatomy. A frequently used approach in modeling foliage area distribution by angle is to use an approximation provided by the angular distribution of an ellipsoid. We show that for leaves in this study this approach is biased and that a Richards function describes the cumulative frequency distribution of leaf area by inclination angle more effectively. The importance of an unbiased estimator is discussed in relation to the variation in photon flux density received by surfaces of different inclinations.

Modeling analysis of distribution of irreversible bending strain for critical current in Bi2223-composite tape

It was attempted to estimate the distribution of irreversible bending strain for critical current of the Bi2223 composite tape. In the modeling, the shape of the core composed of the current transporting Bi2223 filaments and Ag, and the damage strain parameter given by the difference between the intrinsic tensile damage strain and residual strain of the Bi2223 filaments, were incorporated to describe the damage evolution in the core and its relation to critical current. The application of the model to the experimental results of critical current-bending strain relation for many test specimens revealed that the distribution of the irreversible bending strain is described by the two parameter Weibull distribution function. Based on discussion about the influence of the core geometry on the irreversible strain and the result of analysis of the experimental data, a simple and practically useful method was proposed for estimation of the distribution of irreversible bending strain.

Statistical analysis of scatter in critical current of bent superconducting Bi2223 composite tape

The scatter of critical current of bent Bi2223 composite tape was analyzed from a statistical viewpoint. It was revealed that the increase in scatter of the critical current beyond the irreversible bending strain is attributed to the heterogeneous damage evolution. Further modeling analysis, based on the heterogeneous damage evolution, revealed that the distribution of the damage strain parameter-value, which refers to the difference between the intrinsic tensile damage strain and residual strain of the Bi2223 filaments, is described by the two parameter Weibull distribution function, from which the distribution of the normalized critical current value is described by the three parameter Weibull distribution function.

超伝導コア形状を組み込んだモデルによる曲げ変形された Bi2223 複合テープの臨界電流評価

The bending strain-dependence of critical current of Bi2223/Ag/Ag-Mg alloy superconducting composite tape was studied experimentally and analytically. The measured change of critical current with bending strain was described well by the superconducting core shape-incorporated model. The distribution of damage-inducing parameter (difference between the tensile fracture strain and thermally induced residual one) in the samples was described well by the Weibull distribution. By application of this result, the distributions of irreversible bending strain and critical current at various bending strain were discussed.

Bending strain effect on critical current of Bi-2223 superconductor tapes—report of international round-robin-test

An inter-comparison program (round-robin-test) aimed at the establishment of a standard test method for the bending strain effect on the critical current in Ag alloy-sheathed Bi-2223 tapes was implemented with participation of 12 laboratories around the world. Samples were bent at room temperature using bending devices that were specially designed for this RRT. The critical current was measured at 77 K and in the self-field. After critical current measurement of an unbent sample, bending of the sample and subsequent critical current measurements were done from 0.2% to 1.0% in 0.2% steps of strains on a single sample. Reported data from participants showed that the critical current values start to decrease from 0.4% strain and continue to decrease to 1.0% strain. Moreover, the data scatter starts to increase stepwise at 0.4% strain, being correspondent to the variation in the critical current values with bending strain, and it continues to increase gradually to 1.0% strain. The coefficient of variation values are 2.5%, 5.1% and 6.4% for 0%, 0.4% and 1.0% bending strain, respectively. Results were also compared in terms of the irreversible bending strain. Possible sources of error are discussed.

Encapsulation of cesium inside single-walled carbon nanotubes by plasma-ion irradiation method

Positive Cs ions are irradiated to a negatively biased substrate, which is covered with the dispersed single-walled carbon nanotubes (SWNTs) and immersed in the Cs plasma. Field emission type transmission electron microscopy (FE-TEM) and Z-contrast technique by scanning TEM (STEM) are used for the precise observation. FE-TEM gives high resolved images of structurally modified SWNTs such as irreversible bending of tube bundles, tube dislocation, and cutting due to the positive Cs ion irradiation. Moreover, this structural modification becomes severe with an increase in the acceleration energy of irradiating Cs ions. Especially, the Cs encapsulation inside SWNTs is directly observed, the configuration of which is confirmed to comprise three varieties by FEG-TEM and STEM. In addition to these experimental results, ab initio study is used to investigate the static stable configurations due to Cs ion irradiation.

Electromagnetic properties of bronze processed Nb/sub 3/Sn superconducting wires and multi-strand cables for AC use with a Cu-Sn-X(X; Ge,Ni,Mn,Si) matrix and a Nb-Ta core

A bronze processed 0.275 mm-dia. Nb/sub 3/Sn strand composed of Nb-0.5at%Ta cores and a Cu-2.7at%Sn-1.0at%Ge matrix was fabricated into cables of 6 and 36 strands. Each strand contained 75990 filaments 0.28 /spl mu/m in diameter. The AC quench current for the 36-strand cable reached 2500 A/sub peak/ at 50 Hz and 0.5 T DC field. The 6-strand cable showed a significantly improved irreversible bending strain limit of over 10% due to the fine filament size. This result enabled building of a magnet through the react and wind method. A 50 mm-bore 2T-class magnet wound by the 6 strand cable was successfully operated at 52.7 Hz and 4.2 K. In order to reduce AC losses another bronze processed 0.218 mm-dia. Nb/sub 3/Sn strand with 147510 0.15 /spl mu/m-dia. filaments was fabricated from Nb05%Ta/Cu-4.9%Sn-2.0%Ge/Cu-2.7%Sn-2%Ni-1%Mn double matrix composite. The strand showed a hysteresis loss of 447J/m/sup 3/ at /spl plusmn/0.5 T/cycle and /spl lambda/J/sub c/ of 857A/mm/sup 2/ at 0.5 T after the heat treatment at 500/spl deg/C for 100 h.

Evolution of the elastoplastic bending of whisker crystals of NaCl due to nanosecond exposure to a high-density electron beam

High-speed photography is used to study the evolution of the plastic bending of whisker crystals (WCs) of NaCL caused by nanosecond exposure to a pulsed high-density electron beam. The total time of irreversible bending of a WC, reckoned from the radiation pulse to attainment of the quasisteady state, is equal to 1.5–2.5 msec and nearly coincides with the characteristic relaxation time of the quasistatic thermoelastic mechanical stresses that develop due to the nonuniform distribution of the dose and the corresponding temperature through the thickness of the specimen. These stresses relax when the temperature distribution is equalized by heat conduction. There is an induction period of 0.3–0.6 msec between the radiation pulse and the beginning of intensive bending, this period being much longer than the period of the thermoelastic bending vibrations. One interesting result of the study is that the bending is nonmonotonic.

Photoemission Study of the Physical Nature of the InP Near-Surface Defect States

ABSTRACTThe physical nature of the InP near-surface defect acceptor and donor states are studied by using photoemission spectroscopy. It is found that the In/n-InP(110) interface band bending does not start until the In coverage reaches about 0.3 monolayer (ML), while the In/p-InP(110) band bending is almost saturated at 0.3 ML. The annealing effect on the band bending of clean cleaved n-and p-type InP(llO) surfaces is also studied. It is found that annealing of the clean surface creates an irreversible band bending effect on the p-InP(110), but the n-InP(110) almost does not show any band bending after low temperature annealing. Based on these two striking differences in the band bending behavior of n- and p-type InP, it is proposed that the physical nature of InP near-surface defect acceptor and donor levels may be different and that phosphorus vacancies are the cause of p-InP surface Fermi level pinning.