This paper presents a vibration analysis using the substructure elimination and binding method for vibration systems governed by a one-dimensional wave equation. Coupled vibration analysis has been developed, and the component mode synthesis method is commonly used for dynamic analysis. In the component mode synthesis method, each substructure is formulated, and then coupling between substructures is considered. The component mode synthesis method is a type of modal analysis, and the coupled vibration between vibration systems with different governing equations can be easily formulated. The component mode synthesis method has the problem of increasing the degrees of freedom when the entire structure is complicated and needs to be divided into many substructures. Therefore, the first author proposed methods to analyze the entire vibration system without dividing it into substructures, for example, when a structure is installed inside an acoustic field or when acoustic fields with different media are in contact. These methods have the advantage that only the eigenmodes of the entire acoustic field are used. However, the calculation accuracy has been found to deteriorate because of the discontinuities or non-smooth points in sound pressure and particle displacement at the interface between air and a structure or between two acoustic fields. This study proposed a method to set a virtual elimination region at the interface and then bind the two ends of the virtual elimination region to solve this problem. The analytical model for this method was presented, and a wave equation was derived in this study. Modal analysis was applied to the wave equation. The simulations revealed that the density and bulk modulus of the virtual elimination region should be zero and that its length should be set at 2.5–3.5 times the wavelength of the highest eigenmode of the entire vibration system. To investigate the advantage of low DOFs, the simulation results obtained using the proposed method were compared with those obtained using the component mode synthesis method based on the exact solutions.

We developed a technique which can increase the yield of one-to-one particle encapsulation by applying the dielectrophoretic particle alignment technique using boxcar-type electrodes. Dielectrophoretic force generated by the boxcar-type electrodes accelerate and decelerate the particles periodically as they flow in the electrode region. Further, the dielectrophoretic force is turned on and off at constant frequency. The force exerted on the particle periodically over space and time can align them in the streamwise direction with even interval. In this study, the boxcar-type electrodes were installed in the microchannel in the region upstream of the flow-focusing channel in which the water-in-oil droplets were generated. By adjusting the on-off period of the applied voltage generating the dielectrophoretic force to the period of the droplet generation, each particle could be separately encapsulated in the droplets. The principle of particle alignment using periodic force was first described based on a one-dimensional model. The flow structure and the characteristics of the droplet generation in the flow-focusing channel was then discussed in relation to the surface tension of the fluids and the wettability of the wall. We measured the velocity distribution of the particles flowing in the boxcar-type electrode region to evaluate the effects of the droplet generation on the motion of the particles and the alignment performance. The results showed that the particle could be aligned in the fluctuating flow caused by the droplet generation, and each particle can be encapsulated in different droplets. This was further demonstrated by measuring the probability function of the droplets containing specific number of particles, which showed that 100% yield of one-to-one particle encapsulation can be achieved under the investigated condition of particle number density of 0.4. Moreover, the throughput increased 46% compared to the case of having the particles supplied randomly.

This paper presents a case study of the design, fabrication, and evaluation of an automotive rear-frame model made of variable axial composites (VAC), using a tailored fiber placement (TFP) technique. Conventionally, the design of a three-dimensional complex VAC structure places significant demands on mechanical engineering expertise (for anisotropic structural design) and on man-hours (for fiber-path CAD). The proposed methods facilitate the design of complex VAC structures with significantly reduced manpower requirements. A computational design method, anisotropic topology optimization, was used to create the base design. The fiber paths on the preform surfaces were generated using a Turing pattern algorithm (based on optimized fiber orientation distributions) subsequent to designing developable three-dimensional surfaces to fill the interior of the target structure. The preforms were fabricated using a computer numerical control (CNC) embroidery machine by stitching the raw fiber tow onto the base fabric in accordance with the generated fiber path data. After stacking the preforms in the mold, they were formed using vacuum-assisted resin-transfer molding (VaRTM). The static stiffness of the prototype was evaluated experimentally, and the results were compared with numerical simulations. This study demonstrates the potential for achieving further weight reduction in large-scale 3D structures by combining innovative computational design techniques with advanced fabrication methods.

In the wire and arc additive manufacturing technology, which involves melting and depositing metal wire materials by arc discharge, it is possible to use a wide variety of wire materials and change the composition locally. However, CuSn alloys with a high Sn content have poor ductility and are difficult to process into wires. In this study, we propose an accumulation method in which Sn wire is fed from the outside to the molten pool during the deposition process using a CuSn alloy wire with a low Sn content. This study investigated the relationship between wire feed rate and actual Sn content rate. Tensile and acoustic tests were conducted. Sn content of the additively manufactured materials was changed by varying the Sn wire feed rate. It was verified that Sn content influences the mechanical and acoustic characteristics of CuSn alloys.