| Summary: | 碩士 === 國立成功大學 === 機械工程研究所 === 81 === The dynamic behavior of a vertical machining center is
investigated by modal testing. We use polyreference time domain
technique to estimate the system dynamic parameters. Complex
mode indication function (CMIF) and multivariate mode indicator
function (MMIF) are employed to check the natural frequencies
and are compared with each other. The results indicate that
MMIF is a better indicator than CMIF in this study. In the
experiment, the impulse hammer and the magnetic shaker are used
to measure the natural frequencies. From the measured dynamic
receptance, we estimate the static receptance and compare it
with that from static stiffness test. The results show good
agreement. From the mode shapes we discover that the area
located between the column and the table base appears weak, and
needs improvements. In addition, the modal filter technique is
studied and is employed as a monitor to diagnose if any
variation of the structural property occurs. It is found that
it works well for low-mode-density structures, but it is not so
reliable for high-mode-density and high damping structures.
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