自行車結構在動態與靜態負載下之力學探究

A Study on the Mechanics of Bicycle Frame under Dynamic and Static Loadings

林俊印(Chun-Yin Lin)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2008年)

摘要

本研究主要透過實驗及有限元素分析，針對自行車結構在動態及靜態負載下之力學行為進行探討。在實驗部分，以應變規配合動態訊號擷取系統，即時擷取自行車於不同騎乘狀況下各測點之應變值，據以做為判斷自行車結構強度不足處。而所規劃之騎乘條件分別為(1) 騎乘者乘坐於靜止之自行車上，評估自行車於靜態下之受力狀態，(2) 100Kg與50Kg騎乘者於滾輪式練習台上，模擬騎乘於平坦道路上，並比較不同負載下自行車之變形狀況，(3) 騎乘於高低落差為15公分之階差，探討自行車於衝擊狀況下之受力。此外，為進一步了解自行車整體受力變形狀況，因此，本研究以有限元素分析，計算自行車於受力狀態下之變形，並與實驗數據做比對以驗証其正確性。

由研究中發現，自行車座桿部位之應變值最大，因此，研判該處為支撐人體重量之主要結構。此外，不論在靜態負載或於滾輪式練習台上，當騎乘者由50Kg到100Kg，自行車座桿的結構應變增加約2.6倍。另一方面，當騎乘於階差時，登山車座桿之應變量為在靜態負載之1.46倍，而折疊式自行車則為2.20倍；由此可知，自行車行經階差時，受力狀態更為嚴苛，而登山車由於有避震器，因此具較佳之抗振效果。經由本研究，將自行車結構強度較不足處，在不同負載及騎乘條件下之變形狀態數據化，據此自行車研發人員可於設計階段，針對該處結構進行設計改善，以提高自行車騎乘之安全性。

關鍵字

自行車 ； 車架 ； 座桿 ； 結構變形 ； 應變 ； 動態負荷

並列摘要

In this study, the mechanics of bike under dynamic and static loadings is investigated with experiments and finite element analysis. As for the experiment, strain gage and real time data acquisition system are used to obtain strain data at measured points under specified riding conditions. Thus, the weakness of bike structure can then be check out via the test results. The riding conditions include (1) rider sits on the bike to estimate the static stress conditions of the bike, (2) 100 and 50 kg riders on the bike running on a rolling platform to simulate the ride on a flat road. This test can check the deformation of bike frame under different loading conditions, (3) riding through a step with 15 cm gap to check the stress conditions of the bike when passing the step. In addition, finite element analysis is also conducted for getting the stress distribution of the whole bike frame. The simulated results are also compared with the experimental data for validation purposes.

It is found that the seat post has the maximum strain throughout all the test conditions. The deformation of seat post with 100 kg rider is about 2.6 times higher than that with 50 kg rider both for riding on the rolling platform or static riding condition. Besides, while riding through a step, the strain of the seat post for the mountain bike was 1.46 times to that of the static riding condition. Likewise, the folding bike has a 2.20 times difference for the same two riding conditions. It is concluded that the resulted strain is more severe when riding through a step, and the mountain bike has better anti-shock capability because it has shock absorbers installed. Through the study, the weakness of the bike frame under different loading conditions is obtained. It is believed that these quantized data can help the engineer to improve the bike structure at the design stage and thus improve both the reliability of bike and the safety of the riders.

並列關鍵字

bike frame ； deformation ； dynamic loading ； seat post ； strain

參考文獻

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