圓柱形共振腔在軸向負載下之彈塑性變形對其高頻電磁場共振頻率之影響研究

Resonance Frequency Shift of the Electromagnetic Field of a Circular Cylindrical Cavity as Being Elastoplastic Deformed by Axial Loading

許周叡(Hsu, Chou Jui)

指導教授 ： 葉孟考

國立清華大學/工學院/動力機械工程學系/碩士(2015年)

摘要

隨著科技不斷的研究與創新，各個領域都已經有許多的科學研究與應用，因此將不同領域進行結合也成為了相當有趣的議題。其中一項應用是粒子加速器中的超導共振腔，當此薄殼結構在受到不同負載下的結構變形行為對電磁場共振頻率飄移的影響是近年來被關注的一項重要議題。本研究在於探討當薄殼圓柱形腔體受彈塑性變形時所影響到的第一個橫向電磁場模態的共振頻率。在採用雙線性曲線擬合及Ramberg-Osgood曲線擬合以描述材料的彈塑性行為的基礎下，不僅可導出結構變形的理論解，並且可成功地與高頻電磁場的理論解連結。之後並對各材料常數如降伏強度、正切模數、硬化指數等對結構變形與共振頻率的影響等進行探討。另外也輔以商用套裝有限單元分析軟體ANSYS進行數值模擬分析，以真實不銹鋼腔體為模型，模擬腔體受軸向壓力的分析，並與理論解進行相互驗證進一步驗證理論解之正確性。目前已初步建構出一套理論計算方法，可推估腔體材料特性各個參數改變對腔體進入彈塑性變形與高頻電磁場共振頻率變化的影響。

關鍵字

圓柱形腔體 ； 彈塑性變形 ； 結構-電磁場研究

並列摘要

The couple-field research becomes interested and important in science and application researches in the recent decades. The superconducting cavity is made of thin-walled niobium and thus its electromagnetic resonance frequencies relate to its structural deformation. This structure-electromagnetic research becomes one of the coupled-filed topics, with a main application on superconducting radio-frequency cavity for particle accelerators. This study investigates the effects of the elastoplastic behavior of a thin-walled circular cylindrical cavity on its resonance frequency of first transverse magnetic mode, TM010 mode. Both the bilinear fit and Ramberg-Osgood fit are used to approach the material’s elastoplastic behavior in the theoretical analysis for structural deformation, which is then successfully linked to the electromagnetic resonance frequency of the circular cylindrical cavity. Effects of the related parameters such as yielding stress and tangent modulus are examined. The commercial available finite element code ANSYS is used for multi-physics computation.

並列關鍵字

Cylindrical cavity ； Elastoplastic behavior ； Structure-electromagnetic research

參考文獻

2. N. Akdogan, Origin of Ferromagnetism in Oxide-Based Diluted Magnetic Semiconductors, Ruhr-Universitat Bochum, Germany, 2008.

4. H. Padamsee, ”The Science and Technology of Superconducting Cavity for Accelerators,” Superconducting Science and Technology, Vol. 14, pp.28-51, 2001.

7. S. Belomestnykh, “The High Luminosity Performance of CESR with the New Generation Superconducting Cavity,” Report SRF 990407-03, Laboratory of Nuclear Studies, Cornell University, Ithaca, New York, 1999.

11. M. Meidlinger, T. L. Grimm and W. Hartung, “Design of Half-Reentrant SRF Cavities,” Physica C, Vol. 441, pp. 155-158, 2006.

13. M. G. Rao and P. Kneisel, “Thermal and Mechanical Properties of Electron Beam Welded and Heated-Treated Niobium for TESLA,” Continuous Electron Beam Accelerator Facility Newport News, pp. 1-7, 1993.