A new testing apparatus to evaluate creep lives is newly developed using very small disc specimens: Small Punch Creep (SPC). Creep rupture lives obtained at SPC tests have a good relationship with those from conventional creep tests. A series of interrupted SPC tests are performed to investigate the deformation and rupture process. The thickness at the center of the disc rapidly decreases at the loading, and gradually decreases till rupture due to the friction between the disc and a loading ball. Creep cracks which lead to rupture initiate around the last point of contact of the loading ball and disc. Observations at sections of discs in interrupted SPC tests show that the shear stress dominates the rupture of SPC specimens.

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Molecular dynamics simulations on the grain boundary behavior was simulated. This study is motivated to estimate the stability of grain boundaries and observe their motion based on the atomistic considerations, so that the results are able to be applied for multi-scale analyses such as one by using the phase field model. First, the grain-boundary energy is calculated as a function of misorientation angle, which revealed that several specific angles exhibit cusp-like low values. Secondly, change in morphology of a grain which is embedded in a bulk single crystal is simulated. Grains surrounded by stable grain boundaries are stable and do not show rotation or motion, while unstable grains change their shape or orientation. Finally the temperature dependence is simulated resulting in the grain contraction at high temperature even though the grain is stable at low temperature.

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In high-speed rotating turbine blades, tensile stresses are caused by centrifugal forces due to the rotation. In this case, the degree of foreign object damage is expected to be different from the case of stationary state blade. We make an attempt to simulate this problem by impact test of plastics under tensile preload. Three kinds of polymers (PC, HDPE and PMMA) are selected here for specimen. The Impact tests are carried out using a gas-gun type impact machine with an ultra-high speed digital imaging system. The effect of tensile preload on the ballistic impact properties of these plastics are evaluated from the test results.

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In order to evaluate a strain rate sensitivity of a dynamic flow stress "d σ/dlog ε" of SS400 at very high strain rates, constant strain rate tests and strain rate reduction tests are conducted in the strain rate range from about 2×10^3/s to 2×10^4/s. The flow stress depends strongly on the instantaneous strain rate and further, the "d σ/dlog ε" can be expressed by a thermally activated process of a formation of kink pairs. Alloying and impurity atoms contribute to the increase in an athermal component of flow stress.

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In order to study the microscopic deformation behavior of materials, numerical simulations such as the molecular dynamics (MD) method, Monte Carlo method and so forth have been developed. Empirical MD method is conducted by solving the movement of each particle, which constitutes the group of molecules or atoms, on the basis of the equation of motion and the potential function that represents the interaction among particles. This method enables us to trace respective particles, directly, while it also enables us to evaluate the dynamic behavior of the group of particles, statistically. It leads to understanding of macroscopic phenomena. In this study, we adopted the embedded atom method (EAM) potential for the investigation of the behavior of fcc metal (aluminum) subjected to impact loading.

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Shape memory alloys are quite fascinating materials characterized shape memory effect and superelasticity, which ordinary alloys have not. Many application using these alloys have been developed in several fields since 1981. Especially Ti-Ni alloys are now being as new key material for medical device. Arch wires and Guide wire were the starting point of the medical application. In particular, Guide wire formed the basics of today's IVR market application. Now Super elasticity of SMA became key material of stents. It is predicted that Medical Device and Diagnostics market spreads to 40,000,000,000,000 yen five years later.

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In this paper characteristics of corrosion fatigue failures of steam turbine blades learned from failure analysis are briefly summarized. Then influencing variables on corrosion fatigue crack initiation and propagation process of 12 pct chromium stainless steel are briefly reviewed. The emphasis is focused upon initiation and propagation of corrosion pit in corrosion fatigue crack initiation process. Recent investigation of early stage of corrosion pit initiation process by use of electrochemical noise method is demonstrated. Finally future problems should be solved in corrosion fatigue crack initiation and propagation process of 12 pct chromium stainless steel are touched on briefly.

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[in Japanese]

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The strain rate sensitivity in FCC metals is known to increase dramatically when the strain rate exceeds about 5×10^3/s. In order to evaluate the effect of a instantaneos strain rate upon the dynamic flow stress, strain rate reduction tests are conducted for high-purity aluminum. The instantaneous strain rate plays dominant role in the flow stress at very high strain rates where a steep increase in the strain rate sensitivity of the flow stress observed. A simplified model for the kinetics of dislocations is used to consider the transition mechanism. The flow stress calculated using the expression derived from the model shows fairly good agreement with the directly measured flow stress over the high strain rate range.

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