Nihon Kikai Gakkai ronbunshu (Nov 2020)
Optimization of mass properties of a rigid and small subsystem by comparison with a main system in conceptual design phase
Abstract
This paper addresses to clarify the contribution of a mass property of a rigid and small subsystem to low order resonance frequencies of a whole structure. Based on both a Frequency Response Function (FRF) based sub-structuring and a kernel compliance analysis, it is expected that the control of mass properties of a subsystem may dominates relatively low order resonance frequencies of a whole structure. Our proposed method decomposes, at first, a whole structure of interest into two different sizes of subsystems. In this decomposition, a small subsystem only is subjected to structural modification. Since the FRFs on interface DOFs of these two subsystems, based on the insight by the kernel compliance analysis, dominate the resonance frequencies of a whole structure, the FRFs on interface DOFs of the small subsystem have also a critical role. However, in the frequency range of low order resonances of a whole structure, the FRFs of a small subsystem is simply dominated by rigid body modes and have no resonance. The FRFs of a small subsystem in this frequency range are, therefore, dominated by a mass property of a rigid and small subsystem. The paper proposed that the effect of the mass properties of a rigid and small subsystem on the low order resonance frequencies can be visualized using a Gershgorin diagram, and the low order resonance response of interest can be reduced by optimizing the mass property based on the visualization by detuning the resonance frequencies from dominant excitation frequencies. Finally, this paper shows that it is possible to control low order resonance frequencies of a whole structure by changing the mass properties of a rigid and small subsystem using the visualization of Gershgorin circles through a concrete numerical example.
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