超音波法於支撐鋼管材料受疲勞載重之安全評估

王奐欽(Huan-Chin Wang)

指導教授 ： 劉佩玲

國立臺灣大學/工學院/應用力學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00452

摘要

本研究是利用超音波的檢測方法來探求鋼管支撐架在反覆疲勞載重後有哪些超音波上的特性變化，經由這些變化試圖給定鋼管支撐架的疲勞安全評估的評估方法。
研究中發現當我們給予鋼管支撐架均勻的疲勞載重負載後，隨著疲勞載重的次數增加，鋼管支撐架的挫屈載重會有一開始塑性硬化過程此時強度增加，隨著疲勞次數再增加後強度則逐漸下降，實驗過程中我們使用超音波量測此鋼管支撐架的波速也有相對應的關係 ，並且將此波速時域圖做FFT轉換也得到一定特殊現象，由實驗的結果我們將試圖從波速改變及其時域圖的FFT轉換的特殊現象來給定鋼管支撐架的安全性評估，並且改善目前工安上無法評估已經施架在工地上的鋼管支撐架的安全性問題。

關鍵字

非破壞檢測 ； 超音波檢測法 ； 有限元素 ； 疲勞破壞 ； FFT轉換

並列摘要

This work makes use of ultrasound detection method to identify fatigue damage in steel tubes caused by cyclic loading. From characteristic changes in the ultrasonic wave, we attempt to determine the safety lifespan of steel tubes that are common used as support frame in construction sites. By analyzing the change in phase velocity, we found that with increasing uniform cyclic compressional loading, the critical buckling load of the tube undergoes plastic hardening and strength of the tube increases. If the loading continues, the tube starts to weaken. We start by using the theoretical analysis of wave propagation in tube to verify the results of our experiment, following this; we further verify our experimental results using simulation results obtained using finite element analysis software, ANSYS. From the experimental result, we devise a method to evaluate the safety of steel tube by analyzing the change in phase velocity, improving the safety standards of supporting frame.

並列關鍵字

Buckling load ； Fatigue damage ； Finite element ； Safety evaluation

參考文獻

779-792, 1982.

4. Christensen D.A., Ultrasonic Bioinstrumentation, Wiley, NewYork,1988.

5. Cheng, C. and Sansalone, M.,1993 “The Impact-Echo Response of Concrete Plates Containing Delaminations-Numerical, Experimental, and Field Studies,” RILEM: Materials and Structures, Vol. 26, pp.274-285.

8. Hancock, , J.R. and Grosskreutz ,1969. “ Mechanisms of fatigue hardening in copper single crystals. ”Acta Metall. 17, 77-97.

9. Hahner, P. ,1996. “A theory of dislocation cell formation based on stochastic dislocation dynamics. ”Acta Metall. 44, 2345-2352.