Single fiber pull-out tests under static and fatigue loading were carried out to investigate the influence of wet environment on the interfacial strength and on the propagation properties of interfacial debonding of an aramid/epoxy system using the specially designed model composites. The fiber/matrix interfacial strength was decreased by 26% after 7 week immersion in deionized water at 80℃. In dry air, interfacial debonding under fatigue loading propagated faster than in laboratory air, whereas it hardly propagated in wet air. When the length of interfacial debonding became longer, the fatigue propagation rate of interfacial debonding slowed down and retarded irrespective of the environment although a constant fatigue load was applied to the sample. This behavior was considered to be owing to the friction stress on the debonded wakes.

抄録全体を表示

Mechanical characteristics and Fracture phenomena of dismantlable adhesive including thermally expansive particles were investigated experimentally and analytically. The adhesive could swell due to the expansion of the microcapsules by heating and internal stress occurred in the adhesive layer confined in joints. By the stress, interfacial cracks or the pits of partial debonding along the interfaces were caused and led to the total dismantlement. The expansive properties of the microcapsules were measured experimentally using PVT apparatus under the condition of particular pressure and temperature. The stress intensity factors near the tips of the carcks or the pits along the interface of the adhesive and adherend were calculated based on the data obtained in the experiments. The failure condition of the joint, which consisted of glass adherends, was observed using a microscope to verify the calculated results.

抄録全体を表示

Ceramic coatings are widely used for high temperature applications such as thermal barrier coatings on power generation turbine and aircraft engine. This paper describes recent researches on nano-structure control in ceramics coating technology by using electron beam physical vapor deposition (EB-PVD) process.

抄録全体を表示

The newly developed Three-cathode Plasma Spray Gun can produce plasma jet flame that has desired temperature and velocity distribution in a concentric circle, and it is expected to make homogeneous coatings with faster speed. We observed and tested the characteristics of the sprayed coating with this system such as structure, hardness, density, adhesion strength, thickness, etc to examine the applicability for industrial parts.

抄録全体を表示

It is quite difficult to spray fine powders with particle size of -5 micrometers, using conventional HVOF or plasma spraying. A new type of HVOF, referred to as θ-gun, has recently made it possible to spray fine powders of ceramics, as well as metals and cermets without clogging or spitting troubles. The ceramic coatings indicate phenomenally unique microstructures and mechanical properties, such as much higher wear resistance, due to higher cohesive strength between particles and less thermal deterioration during spraying, compared with those of the coatings prepared by conventional plasma spraying.

抄録全体を表示

Thermal barrier coating (TBC) have been used in advanced gas turbine hot parts for improved performance. The failer TBC is induced by thermal stresses and shock due to the large formation of thermally grown oxide (TGO) at the interface between the YSZ top coat and MCrAlY bond coat. TGO is the mixed oxides layer consisting of the MCrAlY bond coat components such as Co, Ni, Cr and Al, formed by oxidation of bond coat and unmelted particles of the MCrAlY powders deposited in the plasma spraying. Thin film Cr2O3 overlay coating on MCrAlY bond coat is prepared using chromate treatment with chromic acid solution for control of oxidation growth rate of TGO at high temperature. TGO formed on chromate treated bond coat is composed of Al2O3 rich layer continuously and much more thermally stable. Chromate treatment process can be expected as an environmental barrier and oxidation rate control of MCrAly bond coat.

抄録全体を表示

Effects of process variables and the long term thermal exposure on adhesion strength of top coat in a APS-TBC were studied. The experiments indicated the adhesion strength was significantly changed, under the influences of many factors; e.g., pore ratio, elastic moduli, TGO formation, intersplats microcracks. Some discussions were made on the the physical meanings of the JIS test.

抄録全体を表示

CFRP (Carbon Fiber Reinforced Plastic) has been used for space structures generally because of its high strength, stiffness, light weight and low thermal expansion. Especially, CTE (Coefficient of Thermal Expansion) of CFRP is much lower than that of metals so CFRP has been used for precision like space telescopes. But recently, accuracy demands for high precision space structures have become increasingly stringent. To meet these requirements, not only thermal expansion but moisture expansion of CFRP has to be considered. Measuring moisture expansion requires long term experiments, and state of the art measurement systems were unable to provide sufficient stability and accuracy. A new method for measuring the moisture expansion of CFRP using optical interferometry was developed. Using this method, CFRP moisture expansion was evaluated stably at high accuracy.

抄録全体を表示

This paper shows results of fatigue properties and design fatigue curves for Cr-Mo steels. Reactors of gas facilities of oil refinery and chemical plants are constructed with the Cr-Mo steels due to better properties in the conditions of elevated temperature and hydrogen. To take advantage of plant design at low cost, the design fatigue curves are required. However, fatigue data are not so many, in particular, at high temperature. Results of fatigue properties and design fatigue curves of the Cr-Mo Steels (SCMV4-2 steel, modified 2.25Cr-1Mo steel and modified 3Cr-1Mo steel) by testing at room temperature and high temperatures (400℃-500℃) are shown. The fatigue strength is decreased with increasing of test temperature. In high cycle region at high temperature, the fish-eye type interior fracture is found, and the S-N curve shows no fatigue limit. The design fatigue curves are constructed in accordance with ASME (Section VIII Division 2).

抄録全体を表示

This paper shows results of fatigue properties and design fatigue curves of dual phase stainless steels. The dual phase stainless steels are often used in chemical plants because of advantageous properties of corrosion resistance for seawater, weldability and workability. To take advantage of plant design at low cost, the design fatigue curves are required. However, fatigue data of the dual phase stainless steels are not so many. Results of fatigue properties and design fatigue curves of the dual phase stainless steels (SUS329J4L and DP-3) by testing at room temperature are shown. In ultra high cycle region, the fish-eye type interior fracture is found. The design fatigue curves are constructed in accordance with ASME (Section VIII Division 2).

抄録全体を表示

Material database can play an important roll in engineering fields, such as material science, mechanical engineering and civil engineering. Many material databases were built, however, each database has its own database format. XML (eXtensible Markup Language) is very useful and strong language to describe database and define the structure using DTD, XML Schema, Relax, etc. Therefore, database definition by XML is suitable for a template of databases having different formats. The research project about the XML material database on commission of NIMS has been progressed from 1997 to discuss interpretation and interoperability of the databases, establish the basic format of the database and build new fact database about amorphous materials. In this paper, we (XML database WG of the project) show the result of the project about design concept of the basic database structure and show the comparison with MatML developed by NIST.

抄録全体を表示

In order to investigate the influence of radical nitriding on the fatigue strength of high strength steels, rotating bending fatigue tests were carried out for a high chromium bearing steel SUJ2 and a low alloy steel SNCM439 which were radical nitrided to the quenched and tempered specimens. By nitriding, fatigue strengths were decreased in SUJ2 and increased in SNCM439,though surface hardening, compressive residual stress and softening of matrix were yield in the same degree in both steels. The difference in the influence of nitriding on the fatigue strength was mainly caused by the difference in the ductility of material. By removing the compound layer from the specimen surface, the fracture origin was changed from the specimen subsurface to the surface, meaning the suppression of initiation of a surface crack by the compound layer.

抄録全体を表示

Rotating bending fatigue tests were carried out for a high silicon stainless steel in order to clarify the fatigue properties through the successive observation of the crack initiation and its propagation behavior. The fatigue strength of high silicon stainless steel was increased by aging, which was caused by the increase in both of resistances for a crack initiation and its propagation. The effect of aging condition on the fatigue life was not or little, while the crack initiation and its propagation behavior was markedly influenced by aging condition. Aging condition is better for fatigue properties in under one, though it is better for static strength in peak or over one.

抄録全体を表示