Ti-6Al-4V alloy exhibits a good combination of excellent properties, such as high specific strength, high fatigue strength, good ductility and weldability. However, Ti-6Al-4V alloy shows low stiffness and poor wear resistance. To further increase the strength properties and improve the stiffness and wear resistance, TiB reinforced Ti-6Al-4V alloy matrix (TiB/Ti-6Al-4V) composites were fabricated by a spark plasma sintering (SPS) process. The TiB/Ti-6Al-4V alloy composites with 4.2 vol.% TiB, which were fabricated at a sintering temperature of 900 °C and for a holding time of 30 min, had the highest tensile strength of 1174 MPa. The Young’s modulus and Vickers microhardness of the composites increased with increasing TiB volume fraction, and the composite with 16.7 vol.% TiB exhibited values of 159 GPa and 517 HV, respectively. The tensile strength of the composite with 4.2 vol.% TiB at 400 °C was higher than that of the mild annealed Ti-6Al-4V alloy. The fatigue limits (over 107 cycles) at room temperature and 600 °C of the composites with 4.2 vol.% TiB were 350 MPa and 200 MPa, respectively. The creep strains at room temperature of the composites with 1.4 and 4.2 vol.% TiB did not increase with increasing creep time.
Wave-shaped vanes are widely used in various power and energy systems for improved efficiency and prevention of droplet erosion. The vanes consist of wave-shaped parallel plates with pockets. As wet steam flows through the wave-shaped path, heavier droplets are thrown to the outside and captured in the pockets while frequently changing direction. However, microscale droplets are difficult to completely catch since they flow straight with the steam and are carried over through the wave-shaped vanes. Accordingly, we previously investigated installing a wire mesh at the inlet of the wave-shaped vanes to enhance the droplet capture efficiency by enlarging the microdroplets. In the present study, we examined the effect of the wire mesh configuration on enlarging the microdroplet size through air-water experiments. Droplet diameters were measured by a real-time image processing system consisting of a CCD camera and pulsed laser light source. The results showed that the droplet diameter distribution largely depended on the wire mesh configuration. We evaluated the mass flow ratio for droplets with a diameter smaller than the threshold diameter. The ratio was smallest in the case of the six-layer configuration of 0.65 mm diameter compared with two other cases, 0.19 and 0.80 mm, whereas the pressure loss was largest in the case of 0.19 mm. We conducted flow visualization at the outlet of the wire mesh using a high-speed camera. The visualization results showed that a liquid film had formed over the layered wire mesh and the surface wave of the liquid film on the last layer induced the detachment of enlarged droplets from the liquid film.
After the Fukushima Daiichi nuclear power plant accident due to the pacific coast of Tohoku earthquake and Tsunami, we have been developing an analysis method considering creep damage mechanisms based on three-dimensional analysis in order to estimate condition of the fuel debris and failure behavior of the reactor due to severe accidents for the early completion of the decommissioning of nuclear power plants. We have also been obtaining material properties that are not provided in existing databases or literature for the analysis. In this study, we measure the tensile and creep properties of low alloy steel, Ni-based alloy, and stainless steel at high temperatures near the melting points. Using experimental data, some parameters for the creep constitutive law and creep failure evaluation method are determined. It is confirmed that the estimated rupture time by the failure evaluation method agree well with the experimental one.
In automobile-exhaust systems, catalytic converters are the main components to produce substantial pressure drops, which induce engine-power loss and fuel-consumption rise. In addition to the need to reduce the pressure loss, the flow passing through the catalytic substrate should be as uniform as possible, which provides a uniform thermal distribution and high catalytic-conversion efficiency. The authors have reported that a flow deflector placed inside a catalytic-converter diffuser part can drastically reduce the pressure loss and improve the velocity-profile uniformity in comparison with the no-flow-deflector case (Hirata et al., 2006 & 2008). In those reports, the authors' concern is restricted only to steady flow, due to the authors' intention to reveal fundamental features precisely under a simple and general condition. On the other hand, actual exhaust flows often include various pulsative components. So, the authors investigate the effects of flow pulsation upon the flow-deflector performances such as the pressure-loss reduction and the flow-uniformity improvement. As a result, the authors reveal that the flow deflector can reduce the pressure loss and improve the velocity-profile uniformity in comparison with the no-flow-deflector case, even for pulsating flow as well as steady flow.
As is well known, a sub-domain method is often used in computational mechanics. The conforming sub-domains, where the sub-domains are not separated nor overlapped each other, are often used, while the nonconforming sub-domains could be employed if needed. In the latter cases, the integrations of the sub-domains may be performed easily by choosing a simple configuration. Then, the meshless method with nonconforming sub-domains is considered one of the reasonable choices for the large-scale computational mechanics without the troublesome integration. We have proposed the sub-domain meshless method (SDMM). It is noted that, since the method can employ both the conforming and the nonconforming sub-domains, the integration for the weak form is necessarily accurate and easy by selecting the nonconforming sub-domains with simple configuration. In this paper, in order to solve more difficult issues, the linear elastic cantilever beam problem and the nonlinear problem are analyzed by using the proposed SDMM. The numerical solutions are compared with the exact solutions and the solutions of the collocation method, showing that the relative errors by using the SDMM are smaller than those by using the collocation method and that the proposed method possesses a good convergence.
Folding method of structures which are composed of hinges and panels are studied in origami engineering. There is an open issue in the origami engineering that folding method of cylindrical structure with base is unknown. In this study, author had elucidated the folding method of a cylindrical structure with a flat bottom from combination and modification of the folding method proposed in previous research. Two types of foldable cylinder with flat base has developed. One is a combination of the Sogame fold and modified Guest fold (structure A), and the other is a combination of the modified stent fold and Guest fold (structure B). Here, modification has been done in order to coincide their trajectories at their juncture. Then we evaluate the dissimilarity of trajectories at the juncture of base and side, transition of strain value during folding process, and the shrink ratio which is the ratio which is the ratio of deployed volume to folded volume. From evaluation of those element, we clarified that structure A can shrink about twice smaller than structure B in its volume, and the dissimilarity of trajectories and magnitude of strain are smaller for structure A than structure B. So it can be said that structure A has an advantage over practicality. Shape of the base is expandable to dome type by combing the Sogame dome or dome type Guest fold with Sogame fold. In addition, Sogame dome's top flat surface can be replaced by the modified Guest fold. Note that these proposed foldable structures are not rigidly foldable, but elastically foldable. These results will cause the expansion of the application range of origami engineering.