AbstractJapan is prone to natural disasters such as earthquakes and torrential rains. Since those disasters have become more severe, extending the life of infrastructure is an urgent issue. Modern sewer system in Japan have been constructed since 1884, and regular inspection, cleaning, and repair are essential to prolonging the life of sewage pipes. Manholes, which are entrances to sewage systems, can be regarded to be one of the important structures that support our safe, secure, and comfortable lives.In this paper, two main parts composed of a manhole, a cover and its bottom, are introduced. The cover made of spheroidal graphite cast iron (cast iron cover) and the manhole bottom made of resin concrete have been developed to extend the life and performance of manholes. The cast iron cover has been made lighter by optimizing the material and structure, does not rattle even when automobiles pass through it at high speed, and automatically releases pressure when the pressure in pipe rises. In addition, the introduction of resin concrete compensates for the shortcomings of cement concrete, such as low curing speed, salt damage, and freezethaw characteristics. Finally, examples of implementations and achievements with the developed materials and structures are presented and discussed.

AbstractIn general, a web of the steel box girder is designed as an independent. However, in actual behaviour, since the web and the flange behave in couple, the web is considered to have a higher bending buckling strength than the designed standard due to the restraint by the flanges. Therefore, horizontal stiffeners for the web of the steel box girder might be omitted. In this study, focusing on the effect of the coupled behaviour of the web and flange on the bending buckling strength of the web of a box girder, FE analyses were carried out of steel box girder model with different structural configuration and of a panel model under identical boundary conditions as the design. From these results, it was found that the web of box girders without horizontal stiffeners have a higher bending buckling strength than the panel model due to restraint by the top of end of the web by the flange. In the case that buckling parameters of the flange are smaller than those critical buckling parameters, the influence of the bending buckling of the web of the box girder on the buckling strength of the flange is slight.

In recent years, the technique of scanning electron microscopy (SEM) observation with low landing energy of a few keV or less has become common. We have especially focused on the drastic contrast change at near 0 eV. Using a patterned sample consisting of Si, Ni and Pt, threshold energies where total reflection of incident electrons occur was investigated by SEM at near 0 eV. In both the cases of in-situ and ex-situ sample cleaning, drastic changes in the brightness of each material were observed at near 0 eV, with threshold energies in the order Si < Ni < Pt. This order agreed with the order of the literature values of the work functions and the surface potentials measured by Kelvin force probe microscopy. This result suggests that the difference of the threshold energy is caused by the difference in surface potential due to the work function difference of each material. Although the order of the threshold energies also agreed with those of work functions reported in literatures, the work functions of air exposed surfaces should be rather considered as "modified work functions", since they could be significantly altered by the adsorbates etc. Nevertheless, the difference of threshold energy for each material was observed with commercial SEM at landing energy near 0 eV, which opens new possibility to distinguish materials, although the difference should be rather recognized as "fingerprints", since surface potentials are sensitive to conditions of surface treatments and atmospheric exposure. Mini-abstract In this study, we utilized a commercial SEM with near 0 eV landing energy to explore threshold energies where total reflection occurs for various materials in air-exposed model samples. Our results demonstrate the potential of threshold energy as a distinctive fingerprint for material differentiation.

A Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal boule was grown by the continuous-feeding Bridgman method to investigate the relationship between the MnO content and the properties such as piezoelectric coefficient and mechanical quality factor. Using high MnO content ceramics as an initially loaded material and low MnO content ceramics as a continuous-feeding material, a suitable composition distribution was achieved for the investigation (i.e. MnO content monotonically decreases from 0.45 to 0.29 wt% while the content of other elements are stable along the growth direction). The evaluation of the boule revealed that the MnO content greatly affects the properties despite the small variation in MnO content (0.16 wt%). The highest mechanical quality factor Qm31 of 900 along with a high piezoelectric constant d 33 of 840 pC/N was obtained at 0.35 wt% MnO. The data obtained during this investigation will be beneficial to determine a suitbable MnO content for building a practical piezoelectric device.

Abstract Hydrogen is one of the promising energy carriers for achieving a carbon neutral society. The pipeline system is positioned as a major type of infrastructure which will be indispensable for mass transportation of gaseous hydrogen. It is acknowledged that existing natural gas pipelines can be used safely to transport hydrogen blends up to 10 or 20 %. However, it is also known that the mechanical properties of steels are significantly degraded by hydrogen embrittlement, even under small partial pressures of hydrogen. Material degradation is considered in the hydrogen pipeline code ASME B31.12. This code requires evaluation of the fracture and fatigue properties of linepipe materials used under hydrogen, and a critical assessment is conducted so that fracture of the pipeline can be avoided during its service life. In the present study, the hydrogen absorption properties, fracture toughness and fatigue crack growth properties under a 25 MPa hydrogen gas environment were investigated by using 3 kinds of linepipe steels manufactured by different methods. The materials were API X65 linepipe steel, which were manufactured as ERW, LSAW and seamless (SMLS) linepipes. Although all the materials showed a bainitic ferrite generally called, each microstructure had distinctive characteristics attributable to the manufacturing process. While all the linepipe steels showed better fracture toughness and fatigue crack growth rates than the ASME B. 31.12 design curve, their hydrogen absorption properties, fracture toughness in hydrogen gas and fatigue crack growth properties in hydrogen gas differed due to their crystal structures, even though the strength grade of the materials. In the steels used in this study, the fracture toughness and fatigue crack growth characteristics under a hydrogen atmosphere were insensitive to the influence of absorbed hydrogen, and were considered to be influenced by the material factors that determine the fracture toughness and fatigue crack growth characteristics in the atmosphere.

Work-hardening behavior of a lath martensitic Fe–18Ni alloy during tensile deformation is discussed based on the Taylor's equation. The dislocation characteristics are monitored using in situ neutron diffraction. In the specimens of as-quenched (AQ) and tempered at 573 K (T573), the dislocations are extremely dense and randomly arranged. The dislocations in AQ and T573 form dislocation cells as deformation progresses. Consequently, a composite condition comprising cell walls and cell interiors is formed, and the coefficient α in the Taylor's equation increases. Cells are already present in the specimen tempered at 773 K (T773), which has a low dislocation density and a large fraction of edge-type dislocations. As deformation continues, the dislocation density of T773 increases, its cell size decreases, and its composite condition become stronger. Simultaneously, the edge-type dislocation fraction decreases, keeping α unchanged. Thus, both the dislocation arrangement and character affected α, thereby affecting the work-hardening behavior.