Linear elastic properties of the rubber composites filled with nano- and micro-particles were discussed on the basis of the experimental results for the silicone rubbers filled with the silica particles and theoretical analysis. Because the nano-particles behaved in the composite as apparent particles composed of the nano-particles and interphase layers formed on the particles, it was validated that Lewis and Nielsen’s mixture law with the apparent volume fraction could evaluated Young’s modulus of the rubber composite in linear elastic region of the measured tensile stress-strain relations. The proportional limit strain of the composite was formulated theoretically using the model in which the particles were distributed three-dimensionally and randomly. The analyzed limit strain was clarified to be valid by comparing with the measured results of the composites filled with the nano- and micro-particles when the (apparent) volume fraction of the particles was less than the threshold of the particle percolation, 0.3. Finally, stress-strain relations in the linear elastic region were shown specifically by using the analytical Young’s moduli and proportional limit strains for the composites.
CCS (Carbon Dioxide Capture and Storage) is one of the technologies able to adequately displace CO2 from fossil fuel fired power plants and the only technology capable of reducing large-scale emissions. In particular, coal emits a lot of CO2, although it is an important energy resource in terms of energy security. To address this situation, IHI had developed oxyfuel combustion technology to capture CO2 from coal-fired power plants, and the demonstration using a 30MWe unit in Australia was successfully carried out. In order to commercialize the technology widely, how to configure the primary gas system is one of the important examination items. When adding oxygen into the primary gas system, depending on the type of mill, pulverized coal deposited in the mill may ignite spontaneously. To investigate the spontaneous combustion characteristics of the deposited pulverized coal under oxyfuel conditions, therefore, laboratory-scale experiments were carried out. The pulverized coal was deposited in a 100mm square mesh box, and it was installed in a thermostatic chamber. Then the mixed gas of N2/O2 or CO2/O2 was introduced into the chamber, and the temperature in the coal sample was measured. From the results, there was little temperature difference at which spontaneous combustion occurred between N2/O2 and CO2/O2 atmosphere, while there was a tendency that it might be relatively hard to occur under CO2/O2 atmosphere. The results also showed a tendency that the influence of temperature was stronger than the oxygen concentration.
Damping materials are sometimes employed to reduce vibrations. In vehicles, weight reduction and a high damping effect are required to reduce environmental impacts. Many studies have been conducted to determine an optimal topological layout with a high damping effect under a limited amount of damping material. However, many methods require finite element analysis to be performed several times owing to the nonlinearity of the objective function. In addition, if there exists a problem with the optimal shape, it is necessary to use a filter or change the penalty parameter and perform optimization again. Therefore, this study proposes a method to linearize optimization problems to reduce the number of finite element analysis procedures required, under the assumption that the layout of the damping material does not affect the eigenmode when the base structure is damped via unconstrained layer damping treatment. Several numerical examples are provided to demonstrate the effectiveness of proposed method. The verification results show that the optimal layout and loss factor of the proposed and conventional methods were similar for a large-scale finite element analysis model. Moreover, this study proposes an optimality evaluation method using the modal assurance criterion. As long as the assumption holds true, the proposed method can significantly improve the time efficiency when repeating optimization under different conditions.
In recent years, the use of earplugs with analog acoustic band pass filters has gained prominence. These earplugs can protect the ears of factory workers, who work in noisy environments, and simultaneously allow for necessary sounds such as colleagues' voices, danger alarms, and equipment-failure sounds to be heard. However, certain doubts still exist regarding the ability of these earplugs to protect the ears of the workers, particularly for low frequency ranges because of the relatively wide passing frequency ranges of sounds. From this standpoint, there exists a requirement for earplugs that can precisely control the passing amount and range of sounds in different working environments. Thus, we investigated an earplug with a simple lightweight structure, involving a filter consisting of a micro-orifice and flexible elastic plate. First, the frequency response of the proposed earplug was theoretically modeled using the transfer matrix method for each component. Second, the validity of the model was established experimentally, as confirmed by the results. Moreover, the proposed earplugs were confirmed to provide sufficient insulation against noise in a low frequency range and simultaneously allow for efficient passage of sounds in the range of 1–2 kHz. Further fine tuning can be expected by changing the detailed properties of the components.
This paper describes an investigation into the vibration characteristics resulting from lateral track irregularities that are transferred and become lateral vehicle vibrations when a railway car transits a curved section of track. These transfer characteristics are derived via vehicle dynamics simulations that take into consideration nonlinear characteristics such as flange contact between the wheels and rail. The derived results revealed that the transmissibility of wheel-set lateral movement from lateral track irregularity is larger on a curved section of track than that on a straight section due to restrictions between the wheel flange and rail. Consequently, the mechanism of vibration transfer that occurs when a railway vehicle is transiting a curved section of track can be theoretically explained.
Accurately and reliably measuring the gross weight and static load of the axles of moving vehicles, especially trucks, is important for preventing road damage and improving traffic safety and monitoring efficiency. This type of vehicle weight measurement is called “weigh-in-motion” (WIM). The conventional purpose of WIM is solely the estimation of the vehicle gross weight. However, WIM is also valuable for estimating the static axle load and the height of the vehicle’s center of gravity, and possibly additional measurements. In this study, a method based on the averaging principle is proposed for signal processing in WIM systems. A preliminary experimental investigation, which involved two types of motorbikes and a light truck as test vehicles, and miniature plate-type measurement devices built by the authors, is presented. The gross weight and the static load of each axle of the vehicles, which traveled at various speeds up to approximately 40 km/h, are estimated with high accuracy.
Topology optimization is the most flexible structural optimization method that allows the topological modification as well as the shape changes. Topology optimization techniques have recently been utilized in engineering applications regarding multi-physics or multi-disciplinary optimization. The manufacturing evaluation is an important factor for the practical application to the field of industry. For example, conventional manufacturing processes such as molding and casting, require fulfillment of specific geometric conditions due to the path of the tools. To obtain the optimal structures satisfying such conditions, a new level set-based topology optimization method, based on the convection-diffusion equations with fictions fluxes, are utilized to impose the geometric constrains regarding manufacturability, has been developed. In this method, handling geometric constraints for the manufacturability depends on the fictitious heat fluxes. The propagation of the fictitious fluxes distinguishes the non-manufacturable domain. However, in previous approaches, the manufacturing directions are regarded as design parameters where the values are fixed before the optimization procedure. As the non-manufacturable domain is dominated by the path of the manufacturing tools, the appropriate selection of these parameter values is necessary to obtain the optimal design with the best manufacturability constraints. Thus, these parameters should be appropriately set during the optimization process. In this method, we develop a new topology optimization method where the manufacturing directions are also considered as design variables. A sensitivity analysis based on the adjoint equation is introduced to obtain optimized manufacturing directions. Several engineering applications are introduced and optimized through the new method and the previous methods to confirm the availability of the proposed method.
The objective of this research is to assess aerodynamic noise sources and the wind velocity conversion of the similarity law in an increasing wind velocity. We measured the aerodynamic noise that radiates from cylinders with and without periodic holes and a pantograph model with and without a sound insulating plate in a low-noise high-speed wind tunnel. The noise level of the cylinders was in proportion to the sixth power of wind velocity because the cylinders acted as a dipole sound source. The effect of noise reduction caused by the change in flow structure, that is, the periodic holes, also continued. However, the second peak noise radiating from the cylinder was in proportion to the sum of the sixth power and the eighth power of wind velocity and was underestimated by wind velocity conversion based on a dipole sound source. The noise level of the pantograph model with the sound insulating plate was in proportion to lower than the sixth power of wind velocity in contrast to the pantograph model itself. This is because the noise reduction effect of the sound insulating plate had a frequency characteristic. In this research, when increasing the wind velocity, the dominant pantograph noise frequency region shifted to a higher level, and the dominant noise level began to be affected by the noise reduction of the sound insulating plate. This caused the reduction effect of the sound insulating plate to be underestimated by 2.5 dB due to the noise level conversion of wind velocity. To solve this problem, the plate’s theoretical reduced noise level, which was calculated by using the Fresnel number, was subtracted from the estimated noise level of the pantograph itself. This lead to pantograph noise with the sound insulating plate being estimated within a 0.8-dB difference.