Generally speaking, it is difficult to obtain simulation results for a nonlinear quasi-static problem of a large-scale structure using the static implicit FEM. This is because not only the calculation cost such as necessary memory consumption becomes enormous but also iterative calculation does not often converge for a large-scale analysis model in consideration of the contact between the parts and material nonlinearity of the structure. Therefore, in this paper, we tried to perform a torsion deformation analysis of a multi-split type air-conditioning outdoor unit using the dynamic explicit FEM with the system damping method and mass scaling method. The torsion displacement based on the dynamic explicit method shows good agreement with the test result. It is found that the dynamic explicit method has an advantage in large-scale model analysis.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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In this study, three-dimensional acoustic absorbing due to membrane-type acoustic metamaterial with platelets is examined numerically by using finite-element analysis. In particular, the effects of platelets of semicircle and circular sector shape were investigated. It was found that membrane-type acoustic metamaterial works well for suppressing the exit acoustic sound level at low frequency around a few hundred Hz and its acoustic character is sensitive to the shape of platelets attached to the membrane. As a result of structural eigenfrequency analysis, it was found that circular sector shape could extend the range of eigenfrequency of the membrane and generate an equidistribution of eigenfrequency.

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In this study, three-dimensional thermal cloak for spherical domain is examined numerically based on transformed steady heat conduction equation and finite element analysis. It was found that both of ideal cloak and Han's cloak work well for cloaking a spherical domain within a rectangular conductive domain.

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The radiated sound from the impacted body must have the information with respect to the impact force and the impact location. We have proposed the method in order to identify the impact force and the impact location of the impacted plate by using the FEM analysis of the radiated sound. By this method, the impact location could be identified within 5mm using the sound pressure data from few microphones. In this paper, we construct the system to measure the sound pressure on the plane surface fictitiously by moving the microphones automatically. The accuracy of the identified impact location is increased within 1mm. Moreover, the identified time-dependence of the impact force is improved.

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[in Japanese]

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