Multi-scale parallel finite element analyses of LDH sheet formability tests based on crystallographic homogenization method

A multi-scale parallel finite element (FE) procedure based on the crystallographic homogenization method was applied to the LDH sheet formability test analysis. For the multi-scale structure, two scales are considered. One is a microscopic polycrystal structure and the other is a macroscopic elastic plastic continuum. The analysis code can predict the formability of sheet metal in macro-scale, simultaneously the crystal texture and hardening evolutions in the micro-scale (Nakamachi E et al. Int J Plasticity 2007;23:450-8). Since huge computation time is required for the nonlinear dynamic multi-scale FE analysis, parallel computing technique based on domain partitioning of FE model for macro-continuum is introduced into the multi-scale code using the message passing interface (MPI) library and PC cluster (Kuramae H et al. In: Proceedings of the eighth international conference on computational plasticity, Part 1, 2005. p. 622-5). The explicit time stepping solution scheme in the nonlinear multi-scale FE dynamic problem is well-suited for parallel computing on distributed memory environment such as PC cluster because solving simultaneous equation is not required. We measured crystal morphologies of four automotive sheet metals, aluminum alloy sheet metals A6022-T43 and A5182-O, an asymmetrically rolled aluminum alloy sheet metal A6022-ASR, and mild steel HC220YD, by using the scanning electron microscope (SEM) with electron back scattered diffraction (EBSD) analyses, and defined a three-dimensional representative volume element (RVE) of micro polycrystal structure, which satisfy the periodicity condition of crystal orientation distribution. We evaluate not only macroscopic formability of the automotive sheet metals by the multi-scale LDH test analysis, but also microcrystalline texture evolution during plastic deformation. Furthermore, a relationship between the macroscopic formability and the microcrystal texture evolution was discussed through looking at multi-scale FE results. It is concluded that the mild steel HC220YD was the highest formability than the aluminum alloy sheet metals because of remaining and generating the γ-fiber texture, such as {1 1 1}〈1 1 0〉-{1 1 1}〈1 1 2〉 orientations, during plastic deformation.     

Behavior of a mechanically anchored waterproofing membrane system under wind suction and uniform Pressure

A pressure and wind tunnel test was conducted to obtain the basic data for wind resistance design of a mechanically anchored waterproofing membrane system. The test specimen was a flat roof with the following dimensions: 2.4 m in width, 3 m in length and 0.29 m in height. The waterproofing material was polyvinyl chloride sheet reinforced with polyester fiber (PVC sheets). In the pressure test, because the applied pressure was equivalent to the pressure on the entire surface area of the roof, the billowing heights of the PVC sheet around the fastener had almost the same maximum values; therefore, the axial force at the fastener was also similar to the pressure induced by a compressor, and no lateral forces were measured. On the other hand, in the wind tunnel test, the strain of the PVC sheet around the fastener at windward side was larger than that of the leeward side. The lateral force was 70% of the axial force at a mean wind speed of 38.6 m/s. Therefore, it was clear that the characteristics of the mechanically anchored waterproofing membrane system in the pressure test and the wind tunnel test were different.     

Theory of electrostatics and electrokinetics of soft particles

We investigate theoretically the electrostatics and electrokinetics of a soft particle, i.e. a hard particle covered with an ion-penetrable surface layer of polyelectrolytes. The electric properties of soft particles in an electrolyte solution, which differ from those of hard particles, are essentially determined by the Donnan potential in the surface layer. In particular, the Donnan potential plays an essential role in the electrostatics and electrokinetics of soft particles. Furthermore, the concept of zeta potential, which is important in the electrokinetics of hard particles, loses its physical meaning in the electrokinetics of soft particles. In this review, we discuss the potential distribution around a soft particle, the electrostatic interaction between two soft particles, and the motion of a soft particle in an electric field.     

玻璃纤维/大麻纤维增强聚丙烯混杂复合材料的力学性能和断裂特征(英文)

目前在土木工程,建筑,汽车等领域里使用的复合材料中,玻璃纤维是用量最大的增强材料。由于保护地球环境的呼声日趋高涨,天然纤维被期待着代替源于石油而且再利用困难的玻璃纤维,成为绿色复合材料的必要材料之一。本文通过注射成型工艺制作了玻璃短纤维,大麻短纤维以及混杂型纤维增强复合材料,并在拉伸实验中应用两种不同频率的声发射技术检测了拉伸断裂特性。实验发现,随着大麻纤维的加入和混杂复合材料绿色度的增加,复合材料的拉伸弹性模量随之线性增大,而拉伸强度基本保持不变。当大麻纤维的含量超过20wt%的时候,拉伸强度开始降低。在不同频率的声发射实验中,混杂型复合材料的声发射事件的产生都比单一纤维增强型复合材料要来的晚,也就是说,纤维的混杂有助于推迟微裂纹的产生。     

Investigation report of geotechnical disaster on river area due to typhoon landfall three times on Okhotsk region,Hokkaido, Japan

For one week from August 17 to 23, 2016, three consecutive typhoons made landfall in Hokkaido for the first time on record. These typhoons and the front they stimulated brought record-breaking torrential rain over the eastern part of Hokkaido. To investigate the damage to grounds and rivers resulting from this rainfall, the Japan Society of Civil Engineers (JSCE) and the Japanese Geotechnical Society (JGS) formed a disaster research group to conduct an investigation. This report provides the results of the investigation into damage to the grounds of areas along the Tokoro River of the Okhotsk region, Hokkaido, that suffered from this tremendous and diverse disaster. Specifically, the report describes the situation of the levees which were broken and eroded by the overflowing water, the shape of the levee bodies, the levee body soil properties examined by observation of the sections, as well as the occurrence of sand boiling and air blows. The washout of road embankments as well as damage to road bridge mounting fills and abutment backfills were also investigated. The investigation has demonstrated the need to clarify the resistance of the abutment backfills and levee bodies to flowing water as well as the geotechnical predominant factors in order to clarify the mechanisms behind erosion and washout, the need to review new measures that allow for the scale of sand boiling and resultant changes in levee body stability, and the fact that the existing embankments were able to temporarily suppress the flooding water which had spilled over from the river. Furthermore, although it has been identified that the findings of a study on an embankment washout associated with a tsunami can be applied to measures taken against the overflowing water, it has also been found necessary to clarify the predominant geotechnical factors using model tests and to use a more sophisticated analytical approach to establish a geotechnical stability review as soon as possible in order to prevent the levees and embankments from being eroded and washed out due to overflowing water.     

Poly(p‐phenylene sulfide) nanofibers prepared by CO2 laser supersonic drawing

Poly(p‐phenylene sulfide) (PPS) nanofibers are prepared by irradiating a PPS fiber with a carbon dioxide (CO₂) laser while drawing it at supersonic speeds. A supersonic jet is generated by blowing air into a vacuum chamber through the fiber injection orifice. Nanofibers obtained at a laser power of 30 W and chamber pressure of 10 kPa exhibit an average diameter of 600 nm and a draw ratio of 110,000. Scanning electron microscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction analyses are employed to investigate the relationships among the chamber pressure, fiber morphology, and crystallization behavior. The nanofibers exhibit two melting temperatures (T_m): approximately 280°C and 320°C. The endothermic peak at T_m = 280°C is ascribable to lamellar crystals and that at T_m = 320°C to the highly complete crystals, since the polymer molecular chain is highly oriented. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40922.     

Role of interfacial potential in coagulation of cuprammonium cellulose solution

The electric potential, copper ion flux, and ammonia flux across the interface of cuprammonium cellulose solution (CCS) and various 1.0 equiv/Lelectrolyte solutions (ES) at 25°C were measured. The interfacial potentials were strongly negative (–10 to –35 mV) with H₂SO_4, HCI, and (NH₄)₂SO₄ as ES, weakly positive (6 to 8 mV) with NaCl, KCl, LiCl, CsCL, and RbCl as ES, and strongly positive (19 to 34 mV) with KOH and NaOH as ES, generally showing values similar to the diffusion potentials for electrolyte solutions comprising ions of the same absolute charge. The ammonia flux (about 1 X 10^-4 mol/cm₂/s) was relatively unaffected by the interfacial potential, but the copper ion flux was clearly dependent on it. These results, together with the observed rates of CCS coagulation, indicate that the mechanism of the coagulation was largely determined by the interfacial potential, with strongly negative potential gradients accelerating the Cu²⁺ flux into the ES and CCS coagulation proceeding rapidly by Cu²⁺ removal, strongly positive potential gradients accelerating the Na⁺ flux into the CCS and coagulation proceeding rapidly via the formation of cellulose-Na⁺ complex, and the absence of a strong potential gradient capable of accelerating the ion flux resulting in slow coagulation by ammonia removal. It may therefore be possible to control the interfacial potential and the ion flux by the ES composition, and thus to influence the structure of regenerated cellulosic fibers and membranes. © 1996 John Wiley & Sons, Inc.     

The terminal protein of the linear DNA plasmid pGKL2 shares an N-terminal domain of the plasmid-encoded DNA polymerase

The 36K protein attached at the 5′ end of the linear DNA plasmid pGKL2 from the yeast Kluyveromyces lactis was first purified and characterized. The terminal protein was purified from cells (1 kg wet weight) by ammonium sulphate precipitation and two rounds of centrifugation to equilibrium in CsCl gradients. The pGKL2 was present only in the post-microsomal supernatant. Approximately 10 mg of the purified pGKL2 was recovered and digested with DNase I. The terminal protein (final ca. 0·8 mg) was homogeneous by electrophoresis and we determined the N-terminal amino acid sequence up to ten residues, showing that it existed in the cryptic N-terminal domain of pGKL2-ORF2 (DNA polymerase) sequence.