Rotating bending fatigue tests were conducted to investigate the effect of shot peening on fatigue properties of maraging steels made by direct metal laser sintering process which was one of additive manufacturing processes. In order to investigate the effect of lamination direction of material, two types of specimen changed modeling pattern as horizontal modeling and vertical modeling were prepared. As the result of the fatigue test, non peened specimen was fractured from initial defect near the specimen surface, but the shot peened specimen was fractured from initial defect inside specimen where located 600µm deeper from surface of specimen. The size of initial defect differs according to the difference in modeling pattern and its size of the vertical modeling material was larger than the horizontal modeling material ones. However, threshold stress intensity factor at which specimen fracture of both materials were the same levels. The cause of this, fatigue limits of the vertical modeling material was slightly smaller than the horizontal modeling material ones. And then, since the final dimensions of the fish eye of both materials become the same, fatigue life of vertical modeling material shorter than horizontal modeling material.
The adsorption capacity of cesium and strontium in the aqueous solution of rice hull charcoal was examined. Rice husk which was carbonized at various temperatures was added to each of cesium aqueous solution and strontium aqueous solution and stirred. As a result, rice hull charcoal carbonized at 400°C adsorbed the cesium. Rice hull charcoal carbonized at 800°C adsorbed the strontium. From this result, it was considered that the adsorption mechanism of rice hull charcoal cesium and strontium are different. From the analysis results by FTIR and Boehm method, charcoal carbonized at 400°C had acidic functional group. There was a tendency that the pH of the rice hull charcoal carbonized at high temperature became higher. It is considered to be due to precipitation of inorganic substances such as potassium on the surface of rice hull charcoal. As a result of pore distribution measurement, it was found that many mesopores were formed in rice hull charcoal carbonized at 800°C. It is assumed that cesium adsorbs primarily on acidic functional groups on the surface of rice hull charcoal, strontium undergoes ion exchange with potassium, or adsorbs to mesopores.
Post-installed anchors are used in many existing concrete structures to construct additional members. The purposes of this study are to investigate the bond strength, pull-out bearing capacity, and torque of a post-installed screw anchor with the epoxy resin adhesion. In this study, the single anchor was installed into concrete slabs. The test parameter was the embedment depth. From the results of the pull-out tests, firstly, the bond strength was obtained. Secondary, the pull-out bearing capacity failed in the cone failure mode was estimated based on the empirical equation proposed by Fuchs et al. Furthermore, from the relationship between the pull-out bearing capacity and bond strength curves, the pull-out bearing capacity in the combined failure mode was safely estimated applying the intersection value at the depth of the bond failure. Finally, the correlation between the pull-out bearing capacity and the torque was revealed to be the linear trend in the relatively short embedment depth of anchor.
Hyperthermia has been reported to be an effective cancer treatment, and magnetic nanofibers are expected to be used for it. As a material of the nanofiber for this purpose, poly lactic acid (PLA) and magnetite (Fe3O4) are used. Aligned fabrics and nonwoven fabrics are usually used for evaluation of mechanical properties on nanofibers containing nano-particles. Since their detailed fracture mechanisms have not been clarified yet, mechanical properties of single nanofiber which is the element of these aligned and nonwoven fabrics must be evaluated. In this study, PLA single nanofibers, magnetite/PLA single nanofibers and their aligned and nonwoven fabrics were fabricated by the electrospinning method and their mechanical properties were evaluated by tensile test. Aligned fabrics having the largest distribution of orientation angle from 80° to 90° can be fabricated by the rotation speed of the drum collector at more than 2000 rpm. By applying oleic acid treatment to the magnetite, which is added to the PLA nanofiber, the formation of clusters and the decrease of tensile strength of the PLA nanofibers is suppressed. In the nonwoven fabric, not only the tensile strength of the single nanofiber but also the bond at the intersection of their nanofibers greatly affects the tensile strength.
In recent years, wound management based on moist healing is getting popular because moist healing is to induce the ability of natural healing by keeping moist that contain many kinds of substances from the biological fluid. A suitable material for moist healing is hydrogel dressing, however it can’t adsorb a therapeutic agent in general. In this study, a wound healing dressing providing sustained release of fradiomycin sulfate was prepared using chitosan nanofiber and sodium alginate composite. Gauze coated with chitosan nanofiber and sodium alginate (CAG) forms polyion complex by calcium cross-linkage which has a hemostatic effect. The resultant CAG demonstrated sufficient mechanical properties, water absorption, and biocompatibility as for wound healing dressing, and the optimum weight mixing ratio of chitosan and alginate was set to 6:4. The chitosan nanofiber and CAG adsorbed fradiomycin sulfate in a manner of monolayer. The fradiomycin sulfate adsorbed to CAG was gradually released at a constant rate in PBS (phosphate buffer solution).
The target of this study is that the electrically conductive and light transmissive CNTs/polymer composite film is made by applying traveling electric field. In the previous study, it was found that the CNTs in the uncured polymer suspension can be aligned by applying traveling electric field from the underside to the suspension in the whole coated area on the cover glass (18 mm×18 mm). In this study, to improve the dispersibility of the CNTs in the suspension, the CNTs are treated with a surfactant. Moreover, to expand the applicability of the technique of the traveling electric field application, the multiple electrode is located over the suspension coated on the slide glass, and the traveling electric field is applied from the upper side to the suspension. If this technique is established, the composite film in which the CNTs are aligned can be easily coated on the thick object. The electrical resistivity and light transmittance of the produced composite film are measured. The dispersibility of the CNTs in the composite by the surfactant treatment is improved, although the surfactant treatment does not necessarily reduce the electrical resistivity. In addition, the CNTs in the suspension coated on the thick object can be aligned by applying the traveling electric field from the upper side to the suspension.
It is important for industry products to keep enough adhesive strength between inorganic and organic materials. Therefore silane coupling agents are employed for various applications. Silane coupling agent consists of the hydrolyzable group which reacts to inorganic materials, and the organic functional group which reacts to organic materials. The molecular structure of silane coupling agents must be optimally designed. In this paper, the first principles calculation based on density functional theory was introduced into the interface between metal layer and silane coupling agent, and then two different numerical approaches were examined to evaluate the adhesive strength. One is based on cohesion energy, the other is a tensile test on the molecular level. Two typical silane coupling agents, 3-mercaptopropyltrimethoxy silane and 3-aminopropyltriethoxy silane, were selected, and chromium was used for metal layer. Cohesion energy and stress-strain curve were compared, then the difference of adhesive strength and the availability of the two approaches were discussed.
Glass Fiber Reinforced Plastics (GFRP) have been used for various applications such as automobiles, motorboats and so on. Since GFRP in which thermosetting resins are used as a matrix is difficult to recycle, thermoplastic resins superior in recyclability have been receiving attention. Especially, polylactic acid (PLA), which is plant-derived and biodegradable resin, has been receiving attention as an environmentally friendly material. When PLA is used as a matrix of FRP, it is necessary to suppress hydrolysis at the time of use as in ordinary petroleum-based plastics. Recently, a method to decrease the rate of decomposition of PLA has been developed by combining a decomposition inhibitor (Poly Methyl Methacrylate: PMMA) with PLA and annealing treatment. For a decomposition inhibitor PMMA, in which the methyl ester group protects the ester group of PLA, suppress the hydrolysis during use. By performing an annealing treatment, the degree of crystallization of PLA is increased and the progress of hydrolysis can be delayed. As described above, although PLA with higher resistance to hydrolysis have been developed, the mechanical properties of GFRP using PLA decomposition inhibitor as a matrix have not been clarified yet. In this study, single fiber pull-out tests were conducted by using GF/PLA model composites to clarify the influence of decomposition inhibitor and annealing treatment. Though the fiber/matrix interfacial shear strength was decreased by water absorption, the decomposition rate for GF/PLA with a decomposition inhibitor and annealing treatment was the lowest and showed excellent water resistance.