Solid-state particle deposition is expected to be a novel material process for producing micrometer-order coatings to centimeter-order thick components by collisional stacking of particles without melting. This research project aims to examine such processes as a series of nano-mechanochemical phenomena, such as the ultrafast deformation of materials occurring in the nanoregion of a solid-state bonding interface. The corresponding chemical changes and the physicochemical phenomena associated with bonding have been analyzed. This research project challenges the practice of extending the mechanics of the materials to explain nano-mechanochemical phenomena that integrate deformation and chemical reactions in micromaterials. In this article, we review the current progress in the solid-state particle deposition process and introduce a direction for this direction.

This paper presents an experimental approach to estimate reproductive condition of failure event of steel pipe open sabo dam by hitting debris flow at Nagiso river in 2014. Based on estimated damage process, some skeleton models, in which some members of structure have been removed, are used. And moment strength at bolt connection is also modeled and its effects on structural failure is evaluated. Debris flow is modeled by mixture of gravels and water in straight channel. Similarlity of failure between experiment and real structure is categorized in terms of experimental model condi-tions. The real failure mechanism reproduced by the structural model which has 70 % strength re-duction at bolt connection and loss of diagonal support member. From the comparison of experiments it was found that preceding damage of member has a significant effect on the robusutness of the structure.

In our previous studies, heat treatment of cedar (Cryptomeria japonica D. Don) sapwood was carried out with a diluted NH₄Cl aqueous solution impregnated. As a result, it was clarified that the decomposition of wood is promoted even by heat treatment at 150°C, and the decay resistance was improved. In addition, the heat-treated wood had an increased amount of acid insoluble components that contributed to the improvement of decay resistance. Therefore, we aimed to investigate the involvement of ammonium in the increased acid-insoluble components of wood in the heat treatment of NH₄Cl impregnated wood. After impregnating wood with some ammonium salts and carried out heat treatment, the acid-insoluble components and nitrogen content of the heat-treated wood were quantified. In addition, we measured the thermogravimetric analysis of salt alone and cedar sapwood impregnated with salt aqueous solution and investigated the mechanism by which salt acts on wood components. The following became clear as that result. 1) When the heat treatment was carried out by impregnating with an ammonium salt, the acid-insoluble component increased when all the salts were used. 2) Heat treatment of NH₄Cl impregnated wood resulted in a darker color up to the interior of the wood. However, the NH₄H₂PO₄ and (NH₄)₂SO₄ impregnated woods had a darker color near the surface, but the color inside did not become so dark. 3) When the ammonium salt was heated at 170°C, NH₄Cl disappeared by decomposition in about 4.5 hours, but other salts hardly decomposed at 170°C. 4) Only the NH₄Cl impregnated wood had a significantly increased nitrogen content compared to the untreated wood. In the heat treatment of NH₄Cl impregnated wood, it was clarified that the gas generated by sublimation and decomposition of NH₄Cl salt by heating acted in a wide range and was reformed to the inside of the wood. In addition, ammonium or ammonia in the generated gas may react with wood components to form substances that are insoluble in acid, contributing to the improvement of decay resistance.

In the present work, smooth and notched rectangular cross-sectional specimens machined from two distinct heat-treated SCM435 steels were employed to carry out fatigue testing in air or in 70 MPa high-pressure hydrogen gas environment. Fracture surfaces of the specimens exposed to hydrogen have revealed intergranular and quasi-cleavage fracture mechanisms, which is a typical effect of the hydrogen embrittlement phenomenon. Evaluation of the hydrostatic stress in notched specimens by an elastoplastic finite element analysis was carried out. A correlation between high hydrostatic stress at the notch vicinity and large fraction of intergranular fracture was found, regardless of the stress concentration factor value induced by the notch. Smooth specimens have highlighted a slight hydrogen gas effect on the fatigue life limited to the high stress region only for low temperature tempered steel. The hydrogen sensitivity for notched specimens tempered at low temperature was also emphasized by a distinct decrease in the fatigue limit, caused by the high triaxial stress state around the notch which enhances the hydrogen accumulation.

Rotating bending fatigue tests were conducted to investigate the fatigue property of age hardening treated maraging steel made by direct metal laser sintering process which was one of additive manufacturing processes. In this study, fatigue properties were evaluated firstly using the as-additive manufactured specimen with the surface shape remaining in the additive manufacturing process. After that, the effects of additional treatments such as mechanical polishing, hot isostatic press (HIP) treatment and shot peening (SP) treatment on fatigue properties were investigated. The main results obtained are as follows. The effect of surface roughness produced during manufacturing process on fatigue strength is significant, and is greater than the effect of initial defects. If HIP treatment is performed with the surface shape remaining, the fatigue life will be shortened. On the other hand, the fatigue strength of the maraging material which was made by additive manufacturing process can be dramatically improved by SP treatment and fatigue fracture from surface can be suppressed. The fatigue fracture mode shifts by SP treatment from surface origin type where fatigue cracks initiate from dents on the surface to the internal origin type where fatigue cracks initiate from cleavage crack of martensite block or initial defect. To further improve fatigue property, it is necessary to suppress the occurrence of cleavage crack.