以動力模態變形進行(線桿)斷面變化評估之可行性研究

Preliminary Study on Evaluation of Sectional Variation of Linear Members with Dynamic Mode Shape

林巧玲(Ciao-Ling Lin)

指導教授 ： 余志鵬

朝陽科技大學/理工學院/營建工程系碩士在職專班/碩士(2011年)

摘要

近年來工程界對於結構之損傷檢測與評估逐漸成為國內外工程研究發展中最受重視的議題，且損傷檢測方面之研究也有不錯的成果。本研究以單一結構為主，針對均勻及漸變斷面進行局部缺陷之變化探討，藉由有限元素程式模擬驗證，將靜力變形與動力模態相關連，以動力模態變形進行斷面性質變異之估算。本文首先採用了漸變斷面懸臂梁的變形解析解對應SAP2000及ANSYS分析結果進行比較，其次為了驗證數值模擬之模型無誤，先以簡支梁之自然頻率進行檢覈，再以不同的斷面與邊界條件進行完整與缺陷梁分析及曲率變化之探討。結果顯示利用靜力及動力模態變化之變形曲線皆可以二次微分求得變化較為明顯的曲率曲線圖。
實驗方面則是進行互易定理之理論應用於實驗上之驗證，以敲擊式非破壞性檢測法，得到真實的動態分析結果進行探討。初步驗證結果顯示，實驗過程中儀器造成之訊號差異，使得互易定理於現場試驗之適用性受限。本研究嘗試將所取得之尖峰值以鄰近資料利用梯形公式去修正，雖使互易定理現象較易由實驗資料中觀察到但效果並不顯著，相關議題值得進行後續研究。

關鍵字

互易定理 ； 動力模態變形

並列摘要

In recent years, people gradually pay much attention to topics related to the assessment and detection of structural damages and there are already quite amount of related research outcomes. The work aims at evaluating the feasibility of using modal shape obtained from direct impacting tests to assess the variation of stiffness along beam-like members. The proposed methodology requires the use of Reciprocity theory to simplify the derivation of the modal shape due to impact excitation. Finite element simulations using ANSYS and SAP2000 were employed to numerically verify the proposed methodology. Realistic impact tests on an arbitrarily selected reinforced beam were carried out to provide an insight into the possible scenario one might face when applying such methodology to the practice.
The preliminary results indicate that the modal shape obtained from impacting tests can be used to correctly assess the damage designated in the simulation models while there are still difficulties in applying the methodology to analyze realistic test signals. One major problem is the difficulty to obtain repeatable stable values associated with the frequency peaks. Test results can be improved by numerous repeated tests yet more efficient ways to improve the analysis outcomes are still in demand.

並列關鍵字

Reciprocity theory ； Dynamic Mode Shape

參考文獻

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