This study has developed a novel method to estimate the creep deformation and rupture of electrode materials for lithium-ion batteries by simplified calculations using mechanical models which approximate the microscopic structure of the electrode materials. In order to verify the basic validity of the estimation method, a series of static tensile and creep tests was performed on carbon-based anode and binder materials, and the creep deformation and rupture of the anode material were estimated by the estimation method. In this verification experiment, considering applications to aqueous batteries and all-solid-state batteries, polyvinylidene fluoride (PVDF) that is a solvent-based binder with greater water resistance than aqueous binders was used for the specimens. The test results showed that both the anode and binder materials exhibited a transition creep region, in which the creep rate, that is the increase in the amount of tensile strain with respect to time, gradually decreases after reaching the holding stress, and a steady-state creep region, in which the creep rate remains constant after the transition creep region. Due to the binder material softening, the creep transition region became longer, and the creep strain was larger in water than in air. Using the mechanical properties of the binder material, the proposed method successfully estimated the creep deformation and rupture of the anode material.

This study applied a method of estimating the singular stress field at the bonded edge interface of dissimilar materials through inverse analysis on the deformed shape of the adherend. The inverse analysis used a mathematical model of the bonded member based on the free body diagram concept. Tikhonov regularization was applied in the inverse analysis to reduce the influence of displacement measurement errors on the estimated values. The Tikhonov regularization parameter was selected based on the behavior of the estimated singular stress field and singularity index. In order to verify the validity of the estimation method for adhesive joints combining dissimilar materials, peel tests were performed in numerical simulation, and the singular stress field at the bonded edge was estimated by the estimation method. The verification examined the influence of regulation parameters in the inverse analysis based on results obtained by introducing artificial measurement errors into the deformation shape data. The numerical simulation results showed that the stress distribution obtained from the inverse analysis was close to the correct value for all material combinations. Furthermore, the inverse analysis results remained close to the correct values even when measurement errors were introduced. These results demonstrate the effectiveness of the estimation method for predicting singular stress fields at bonded interfaces involving dissimilar materials. Additionally, the regularization parameter was shown to be effective in handling measurement errors.

Biomass is considered as one of the most promising alternatives to fossil fuels, and is commonly burned in circulating fluidized bed (CFB) due to the broad fuel flexibility like shape, moisture content, heating value, and other properties. However, at relatively high temperatures, reactions between the silica sand used as a bed material and biomass ash can lead to ash agglomeration within the fluidized bed. While several indices have been developed to evaluate and predict the agglomeration behaviors of coal, these are not necessarily applicable to the actual biomass fuels. This study proposed a method for evaluating the agglomeration tendency of biomass ash based on its reaction with silica sand in a small-scale packed bed setup. To theoretically explain the fundamental mechanisms of agglomeration, chemical equilibrium calculations were also performed. The results show that, for five types of biomass ash, the observed agglomeration behavior closely correlates with the calculated fraction of molten slag. Notably, when the molten slag fraction exceeds 40%, the sinter ratio increases significantly, suggesting that this threshold could serve as a useful screening criterion for evaluating the potential for sintering and agglomeration.

A temperature measurement method utilizing wedge waves is proposed and demonstrated experimentally. The method is based on the principle that the propagation velocity of wedge waves depends on the temperature of the medium. First, the temperature dependence of the wedge wave velocity is quantified by measuring the round-trip propagation time. Next, the temperature distribution along the longitudinal direction of the wedge is reconstructed using the one-dimensional heat conduction equation in the form of a finite difference method. In the experiment, an aluminum wedge with a length of 120 mm, thickness of 15 mm, and apex angle of 30° was heated from one end while wedge waves were transmitted and received from the opposite end. The temperature at the heated end, where no temperature sensor was installed, was estimated from the measured propagation time of the wedge wave. The temperature resolution of the method at room temperature is obtained as approximately 0.7 °C. The obtained temperature distributions were compared with the reference temperatures measured by thermocouples installed at multiple positions along the wedge. The maximum errors between the proposed method and the thermocouple measurements were 2.46, 0.802, and 1.31 °C at three positions, confirming high measurement accuracy. The results indicate that the proposed method enables remote temperature sensing without requiring multiple sensors or optical access. This study demonstrates the feasibility of wedge-wave-based thermometry for practical use in environments where direct temperature measurement is difficult or unsafe.

The viscoelastic material constitutive law based on the anisotropic generalized Maxwell model, which assumes a three-dimensional (3D) stress state, is reduced to a plane-stress state to efficiently analyze thin plate-like laminated structures. When the method used to derive the elasticity coefficient matrix for purely elastic problems is applied to viscoelastic problems under a plane-stress assumption, the rheological model breaks down. Therefore, the time-evolution equation for the out-of-plane strain is formulated so that the parallel Maxwell elements share a common strain. To enhance compatibility with existing constitutive laws, an algorithm is also proposed to convert material constants for a 3D stress state into those applicable to a plane-stress state. A virtual stress relaxation test based on homogenization theory under a 3D stress state is applied to an unidirectionally reinforced thermoplastic epoxy resin with glass fibers. From these results, both the raw material constants for the 3D stress state and the corresponding converted constants for plane-stress conditions are obtained. Furthermore, the validity of the derived constitutive law and the proposed approach for reducing the material constants is verified by comparing the out-of-plane strain predicted by the law with the results of virtual material tests. By combining the anisotropic viscoelastic constitutive law proposed in this study for plane-stress states with layer theory, laminated composites can be efficiently analyzed using shell elements.

Legged robots offer superior terrain traversability compared to wheeled robots, making them a focus of extensive research. The performance of legged robots depends on their leg mechanisms. Among the various options, leg mechanisms utilizing link mechanism provide advantages in energy efficiency and load capability. However, the design of link leg mechanisms is nontrivial because the analytical design of the link mechanisms is challenging due to their nonlinear nature. Thus, our preliminary research developed a new design method for one-degree-of-freedom link leg mechanisms, one of the simplest link mechanisms, as a foundational step toward a comprehensive design method of link leg mechanisms. While this method could design functional link leg mechanisms, their performance was insufficient for properly walking because they were designed through single-objective optimization to maximize walking distance. In this study, we extend the method incorporating multi-objective optimization, Nondominated Sorting Genetic Algorithm II (NSGA-II). This approach includes two additional objectives: maximizing foot lift height and minimizing body rocking. We also refined the decoding technique to address the problem identified in our preliminary research. The improved method can design link leg mechanisms with the performance required for effective locomotion, and a fabricated link leg mechanism based on a resulting design demonstrates this capability in real-world environments.

Measurement of contact pressure and shear stress is crucial in fields like sports engineering and bioengineering. Conventional sensors used for these measurements are often thick and rigid, making them unsuitable for accurate measurements on the contact interface. While sensors for shear stress distribution have been developed, they are typically too bulky to place on the contact surface. Furthermore, few sensors are both thin and flexible enough to measure shear stress distribution without disturbing the interaction between the contacting objects. Recent advances have been led to the development of a thin and flexible sensor using printable conductive materials, enabling simultaneous measurement of contact pressure and shear stress. However, these sensors face limitations in integrating measurement points due to increased complexity of lead wiring. To address the challenges, a novel thin and flexible sensor system has been developed to measure both contact pressure and shear stress distributions. This system is designed to offer flexibility while maintaining accuracy. Its effectiveness is demonstrated through experimental validation, highlighting its potential for practical applications.