本文主要針對1.5 GHz雙腔型共振腔體在雙線性曲線之材料模型下進行彈塑性調頻分析歷程對於結構振動頻率之影響。本文運用商用軟體ANSYS建立全模型,探討先拉伸後壓縮之彈塑性調頻歷程、先壓縮後拉伸之反向調頻歷程與拉伸或壓縮至最大位移量値下,各個狀態對於模態頻率之影響,並討論其振型順序;由結果得知其第一模態頻率遠高於步進馬達之工作頻率,在正向調頻歷程後前六模態因軸向永久變形量為負値,故結構頻率皆略為下降,而反向調頻軸向之永久變形量為正,故結構頻率上升;而受軸向拉伸或壓縮至最大位移量値時,因塑性行為之影響,改變材料之楊氏模數,故兩者結構頻率皆為下降。
Modal analysis of a 1.5-GHz two-cell radiofrequency (RF) cavity is carried out by the commercial code ANSYS. In this study a full structure model is established to include the asymmetrical modes. Since the cavity is longitudinally stretched or squeezed to plastic deformation in order to adjust its electromagnetic characteristics, a bilinear fit of the material's stress-strain curve is adopted in the FEM model to account its plastic behavior. Effects of the elastoplastic deformation on the resonant modes are studied. The stress and the residual displacement of the tuning progress at every step are recorded and then applied to the modal analysis. The states of the maximum and minimum axial displacement are particularly discussed. It is found that the first modal frequency of the 1.5-GHz two-cell RF cavity is far higher than the operating frequency of the stepping motor of tuning mechanism. A stretch-first tuning progress causes a negative longitudinal residual displacement, whereas a squeeze-first tuning progress has a positive one. The residual deformation dominates the modal frequency. The case of longitudinally stretching the cavity to 4 mm is illustrated to demonstrate the effects on modal frequency and modal shape. It is found that the plastic behavior of the cavity material could decrease the resonant frequencies of first three modes up to 25 %.
為了持續優化網站功能與使用者體驗,本網站將Cookies分析技術用於網站營運、分析和個人化服務之目的。
若您繼續瀏覽本網站,即表示您同意本網站使用Cookies。