Role of Boundary Strengthening on Prevention of Type IV Failure in High Cr Ferritic Heat-Resistant Steels

Microstructure evolution of newly developed 9Cr-3W-3Co-V, Nb steel with boron addition (B steel) has been analyzed during HAZ thermal cycle at the peak temperature of around A_c3 (A_c3 HAZ) and post-weld heat treatment (PWHT) to elucidate the prevention mechanism of type IV failure by boron addition. It was found that enhancement of the boundary strengthening by precipitates is the main reason for prevention of type IV failure by boron addition. In B steel HAZ, original austenite is reconstituted through martensitic α to γ reverse transformation during the heating and original martensite is reconstituted through martensitic transformation during cooling of the A_c3 HAZ thermal cycle. This process allows M₂₃C₆ carbides to precipitate at the prior austenite grain (PAG) and block boundaries during PWHT even if the chemical segregation of carbide forming elements exists. The effect of boundary strengthening on the creep property has also been investigated. Microstructure evolution during creep was compared among Gr.92 with different A_c3 HAZ microstructures prepared by three kinds of heat treatments and B steel. The results revealed that both the boundary length and kernel average misorientation value decreased in all samples during creep. However, this process occurred very rapidly in A_c3 HAZ simulated Gr.92, whereas it was significantly retarded in the other samples with sufficient boundary strengthening by precipitates. This result confirms that the precipitates formed at PAG and block boundaries play the most important role to stabilize the microstructure of A_c3 HAZ simulated samples during creep and prolong the creep life.     

Phase Diagram of the Li4GeS4–Li3PS4 Quasi‐Binary System Containing the Superionic Conductor Li10GeP2S12

A phase diagram is constructed for the quasi‐binary Li₄GeS₄–Li₃PS₄ system containing the lithium superionic conductor Li₁₀GeP₂S₁₂ (LGPS), having an LGPS‐type structure, and the β‐Li₃PS₄‐type phase, having a thio‐LISICON structure. The LGPS and thio‐LISICON intermediate compounds are found to exhibit solid solution ranges and show incongruent melting at 650°C and 560°C, respectively. The end‐member Li₄GeS₄ has a compositional range of 0 < k < 0.3 in [(1?k) Li₄GeS₄ + k Li₃PS₄], while the other end‐member γ‐Li₃PS₄ has no solid solution range. The crystal structures appearing in the binary systems are the α‐, β‐, and γ‐type Li₃PS₄ structures and the LGPS‐type structure, and these are formed by PS₄ tetrahedra with different arrangements in each structure. The phase and structural relationships between the compounds appearing in the Li₄GeS₄–Li₃PS₄ system are thus clarified.     

Influence on the propulsive performance due to the difference in the fin shape of a robotic manta

This paper experimentally investigates the influence on the propulsive performance by the difference in the fin shape of a robotic manta. Five kinds of fin shapes, i.e., a rectangle, a triangle, a trapezoid, and two right triangles, are used in experiment to measure the forward speed of the robot, where two types of right triangle are discriminated, depending on the arrangement of the right angle part and each fin area is assumed to be approximately equal, and the number of fin rays is the same at all the fins. It is proved that a significant difference in propulsive speed arises depending on the difference in the fin shape. Some experiments are additionally conducted to examine the influence on the propulsive speed and its efficiency, due to the parameter change of a progressive wave in the fin.     

Tongue-Movement Communication and Control Concept for Hands-Free Human–Machine Interfaces

A new communication and control concept using tongue movements is introduced to generate, detect, and classify signals that can be used in novel hands-free human-machine interface applications such as communicating with a computer and controlling devices. The signals that are caused by tongue movements are the changes in the airflow pressure that occur in the ear canal. The goal is to demonstrate that the ear pressure signals that are acquired using a microphone that is inserted into the ear canal, due to specific tongue movements, are distinct and that the signals can be detected and classified very accurately. The strategy that is developed for demonstrating the concept includes energy-based signal detection and segmentation to extract ear pressure signals due to tongue movements, signal normalization to decrease the trial-to-trial variations in the signals, and pairwise cross-correlation signal averaging to obtain accurate estimates from ensembles of pressure signals. A new decision fusion classification algorithm is formulated to assign the pressure signals to their respective tongue-movement classes. The complete strategy of signal detection and segmentation, estimation, and classification is tested on four tongue movements of eight subjects. Through extensive experiments, it is demonstrated that the ear pressure signals due to the tongue movements are distinct and that the four pressure signals can be classified with an accuracy of more than 97% averaged across the eight subjects using the decision fusion classification algorithm. Thus, it is concluded that, through the unique concept that is introduced in this paper, human-computer interfaces that use tongue movements can be designed for hands-free communication and control applications.     

Frequency domain analyses of a thin liquid film surface by repetitively applied stress (dynamic response analyses by the long wave equation)

Numerical results were calculated for the dynamic behavior of an ultrathin liquid (lubricant) surface resulting from repetitively applied pressure and shear stress using the frequency domain equation and compared with those obtained using the time domain equation. Frequency domain analyses of the dynamic behavior of the ultrathin liquid (lubricant) surface produced by sinusoidally applied pressure and shear stress clarified the dependence of the liquid surface deformation on the frequency of the stresses and the disk speed. The dynamic behavior resulting from sinusoidally applied pressure and shear stress calculated using the time domain equation were found to gradually coincide with those obtained using the frequency domain equation.