衝擊載重不連續之補救方法在擬動態實驗的應用

在進行擬動態試驗時，為了減少或去除衝擊載重作用結束時之不連續所引起的額外振幅誤差，常選用遠小於一般需求的時間步長。當使用極小的時間步長時，逐步積分法所算得的每一步位移增量也會變的極小，當位移增量小於或接近於量測儀器的解析度時，就可能會發生位移增量被雜訊所掩蓋而造成不正確的試驗結果。同時極小的積分時間步長也會增加實驗所需的時間。本研究提出了一個可以克服此困難的擬動態實驗技術，只需調整衝擊載重不連續點的輸入值即可，亦即輸入不連續點的平均值就可以消除衝擊載重不連續所引起的振幅誤差。此時可選用較大的積分時間步長來進行實驗以防止誤差掩蓋正確的位移增量，除了可以減少實驗的時間，也不會增加任何計算程式。透過數值模擬與擬動態實驗的驗證，可以更確定此補救方法能夠消除衝擊載重作用結束時之不連續所引起的額外振幅誤差。

關鍵字

擬動態實驗；時間步長；脈衝不連續

並列摘要

In order to reduce or eliminate the extra amplitude distortion due to a load discontinuity at the end of an impulse, a very small time step, which may be much smaller than that required by general considerations, is often used. The use of small time step will lead to a small displacement increment and this small increment might be contaminated by experimental errors as its amount is close to or smaller than the resolution of displacement transducer. As a result, an inaccurate test result is obtained. A remedy is proposed to overcome the difficulty in performing a pseudodynamic test. The remedy is simply to adjust the input value at the end of an impulse. In fact, the average of the load discontinuity values is adopted as an alternative. This will significantly reduce the extra amplitude distortion since the total impulse is exactly inputted into the system. Consequently, a large time step can be used to obtain a reliable pseudodynamic result and hence the test duration can be drastically reduced. In addition, this remedy will not complicate coding. Both numerical simulations and actual verification tests attest to the feasibility of the proposed remedy for pseudodynamic testing.

並列關鍵字

pseudodynamic testing ； time step ； impact discontinuity

國際替代計量

衝擊載重不連續之補救方法在擬動態實驗的應用

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