When solid materials break under external forces, fast propagating cracks often appear and propagate at a speed more than several hundred meters per second. The fast propagating crack often bifurcates into two cracks, and it is necessary to measure the energy release rate of the bifurcating crack to figure out the mechanism of crack bifurcation. The present paper describes the Moire interferometiy used to develop the measurement method and high-speed holographic microscopy to measure the energy release rate of rapidly bifurcating cracks.

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ITER is a world collaborative project being undertaken jointly by EU, Japan, Russia, US, China, Korea and India with the objective of demonstrating the scientific and technological feasibility of fusion energy by producing a reactor-relevant burning plasma in Tokarnak type fusion machine. ITER Organization was established in 2007 to construct the ITER in Cadarache, south France. A platfonn with 1km in length, 400m in width is ready for building construction. Fabrication of the super conduction magnets and other components have been started in Japan. The Broader Approach (BA) project has been launched also in 2007 under the framework of collaboration between Japan and EU. The BA project aims at complementing the ITER project and at an early realization of fusion energy by carring out R&D and developing some advanced technologies for the future demonstration power reactor (DEMO). A new research site named "International Fusion Energy Research Center" has been established in Rokkasho, Aomori as a center of the BA project.

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This paper describes recent advances in experimental techniques for fatigue and fracture of materials. First, ultrasonic fatigue experiment is introduced and the example of the results of very high-cycle fatigue is demonstrated. In order to investigate the fracture mechanism, conventional technique of plastic replica is still a powerful tool when it is observed by atomic force microscope (AFM). Also shown is an example of this technique for fatigue crack initiation under low cycle fatigue. Second, recent development of indentation technique is introduced including the measurement of elasto-plastic stress-strain response, creep deformation and strength of thin film.

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The ZrNiAl bulk metallic glass with different glass forming ability (GFA) was used to establish relationship between mechanical properties with GFA. The distance to the highest GFA alloy in ternary diagram decreases with an increase in glass transition temperature, hardness, compressive strength and Young's modulus. The size of vein on fracture surface decreases with an increase in the glass forming ability.

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Various methods have been proposed for fabricating nanocoils in order to extend the range of elements for building nanodevices. Most of these methods are based on self-assembly technique. We have previously demonstrated an alternative method in which a straight nanowire is bent by depositing a thin film on the nanowire. The bending is due to the misfit strain of the coated film. However, nanocoil formation using this method is highly inefficient. In this study, we developed an advanced method in which the helical formation of coated nanowires takes place because of the viscous flow of the core material, i.e., the nanowires, and the misfit strain of the coating film. When the melting temperature of the nanowire material is lower than that of the coating, elevating the temperature induces a viscous flow, i.e., creep, which only occurs in the nanowire. The creep releases the constraint of the nanowire on elastic bending due to film strain.

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An optimal condition of thermal stress cleaving was investigated by assuming the element-by-element temperature rise situation using fmite element method. The obtained thermal stress cleaving condition is found to be optimal for the symmetrical cleaving of a rectangular plate.

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This study estimates the displacement of the bolster and slider having a few kinds of the adjustment methods at press forming by several EEM analysis and experiments, respectably. The methods of the adjustment have as follows, 1)Curved surface at the die and mold bottoms, 2) Lay with the shim plates, 3)With T- Blocks in T groove on the bolster. First and Second methods are adjusted according to the curvatures of the bolster in order to elastic deformation of the bolster at press that having it curvature or used various shim plates between the die and the bolster. In this report, a T-block method hardens the bolster or slider used to bury the part of the T grooves. As the results by several experiments and FEM simulations, development method could adjust the elastic deformation at the press forming.

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ZrO_2/SiC composite was hot-pressed in order to investigate the crack-healing behavior. A semi-circular surface crack of 100μn surface length was made on each specimen. The specimens were heat-treated in air or N_2 gas at 800℃. After heat-treatment, the bending strengths were measured by three-point bending test at room temperature. The main conclusions are as follows. (1)Crack-healing occurred by the heat-treatment in air. However, the crack-healing didn't occur by the heat-treatment in N2 gas. (2)A phase Iransformation occuffed if the specimens were heat-treated in air. (3)The fracture resistance Kc increased by the heat-treatment in air because of the phase transformation.

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The generation strength, the length and the feature of the ring crack were investigated in several contact angle under static and impact tests. The generation strengths of the ring crack were decreased with increasing contact angles. Shape parameters of Weibull distribution were also decreased with increasing contact angles.

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The crack bridging behavior of multi-walled carbon nanotube-reinforced alumina matrix composites has been investigated using a single fiber pullout testing method. Contradictory to the conventional understanding (which have reported that pullout phenomena evidently occurred in the bulk nanotube-reinforced alumina composites), the pullout experiments using an in situ SEM method with a nanomanipulator system demonstrated that strong load transfer was revealed, and no pullout behavior was observed for all 15 MWCNTs. The MWCNTs, rather than puffing out from the alumina matrix broke in the outer-shells and the inner section pulled away, leaving the outer-shells of the fragment in the matrix. This implies that tougher ceramics with MWCNT can be obtained by creating the appropriate interaction between the matrix and MWCNT: not too week but also not too strong to permit an adequate load transfer between the two parts and thus a consequent pulling out without breakage of MWCNT. Our finding suggests important implications for design of tougher ceramic with MWCNTs. The important factor for such tougher ceramics will thus be the use of 'strong' NWCNTs having higher mechanical performance (as well as a good dispersion in the matrix).

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We report the mechanical properties and microstructures of multi-walled carbon nanotube (MWCNT)/alumina composites made with MWCNTs that have nanoscale defects on their surfaces from an acid treatment We conducted the fracture surface observations of the composites, in order to evaluate the effects of the acid treatment conditions of MWCNTs on the mechanical properties of the composites and the microstructures such as dispersibility and pullout length of MWCNTs. It was found that the dispersibiity of MWCNTs affected the mechanical properties of the composites. The composites with 0.9 vol.% MWCNTs that were acid-treated for 2 hours showed a higher mechanical properties than those of the composites with identical MWCNTs content that were acid-treated for 0, 0.5, 1, 3 and 4 hours. According to the SEM observations, the pullout length of MWCNTs decreased with increasing of acid treatment time of MWCNTs, and the diameter changed at the tip of some MWCNTs.

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Crack propagation tests of lead-free solder were conducted using center-notched plates under cyclic tension-compression of five strain waveforms: pp waveform having fast loading and unloading, cc waveform with slow loading and unloading, cp waveform having slow loading and fast unloading, and pa waveform with fast loading and slow unloading, also th waveform with tension hold, and thch waveform with tension and compression holds. Fatigue and creep components of J integrals were evaluated from the load displacements relations using simple estimates. For fatigue loading of pp wavefonn, the crack propagation rate was expressed as a power function of the fatigue I integral. The creep component due to the hold time greatly accelerates the crack propagation rate. The creep crack propagation rate was expressed as a power function of the creep J integral for each case of cp and cc waveforms. The crack propagation rate for cp waveform is higher than that for cc waveform.

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To develop a life prolongation technology, we investigated a restraint technology of fatigue crack growth (FCG). Though it was reported that paste including fine aluminum particles decelerates FCG via wedge effect, the production condition for making effective paste for the deceleration had been not clear. As the result of this study, it was appeared that the appropriate condition ranges of the paste viscosity and the aluminum diameter are 5〜50 Pa sec and 0.1〜10 μm, respectively. Also, the effect of FCG deceleration due to wedge effect was confirmed for high carbon steel, in high temperature and under random stress condition.

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Fatigue tests were carried out using extruded Mg alloy AZ61 to study the distribution of fatigue lives under constant stress amplitudes. Cracks initiated from the inclusions existing on the specimen surface during the fatigue process of the alloy, and then propagated prior to final failure of the specimen. The probabilistic distributions of both the inclusion's densities, and their sizes (areas) were investigated experimentally in detail. The distributions of the fatigue lives of the extruded Mg alloys under the constant stress amplitudes were evaluated using the Monte-Carlo simulation, in which the Weibull random numbers coffesponding to the above probabilistic distributions of the inclusions are utilized. A good agreement between the evaluated distribution of the fatigue lives and the experimental one was obtained.

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The hydrogen diffuses and accumulates at the stress concentration area like a crack tip and it causes hydrogen embrittlement. To clarify the mechanism of hydrogen embrifflement, it is important to obtain the hydrogen concentration behavior. However, experimental detection of hydrogen distribution is not feasible due to the high diffusivity of hydrogen in materials and the numerical analyses have been proceeded. In this paper, by using Finite Element Method (FEM) and Finite Difference Method (FDM) coupled method which is the diffusion analysis by FDM coupled the stress analysis by FEM, the analyses of hydrogen diffusion were conducted under cyclic loading conditions. The hydrogen diffusion behavior and its influence for hydrogen embrittlement were obtained.

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Cavitation peening (CP) is one of the surface modification techniques for metallic materials to introduce an equibiaxial compressive residual stress on their surface and it was demonstrated that the CP significantly decreases the fatigue crack growth rate on the modified surface during a plate bending fatigue test. To understand the mechanism underlying the peening effect, the present study presented a numerical model to address the crack retardation using a fatigue cohesive zone model. The present cohesive zone model incorporates the static fracture based on fracture mechanics and the fatigue damage accumulation based on damage mechanics. Using the finite element model, we investigated the effect of the surface residual stress introduced by CP for austenite stainless steel SUS316L, which was reported by our previous literature, on the retardation of crack growth. The simulated results demonstrated that the equibiaxial compressive residual stress is a main factor causing the crack retardation

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