應用奈米材料之多功能阻尼器研發

The Development of Nanomaterial Based Multi-parameter Viscous Damper

游忠翰(Chung-Han Yu)

指導教授 ： 張國鎮

國立臺灣大學/工學院/土木工程學研究所/博士(2018年)

https://doi.org/10.6342/NTU201800310

摘要

被動型奈米流體阻尼器具有雙指數之力學特性，於小速度下力量與速度呈現 之關係，而於一般運作速度下則呈現 之關係。應用於橋梁，可以降低平時溫差或行車作用下阻尼器之內壓與油封之磨耗，大幅提升阻尼器之耐久性；應用於隔震結構，可以使隔震系統於小地震下充分發揮隔震效果，並且不影響大地震下的消能行為。奈米流體阻尼器物理機構簡單，相較於傳統液態黏性阻尼器製作成本低廉，且可以因應結構設計需求直接進行製造，而非市面上必須配合傳統黏性阻尼器產品型號進行結構設計，因此更一步地提高了結構控制之精度。同時奈米流體阻尼器不須透過內部加壓的方式進行力學行為調整，因此於常時靜止裝態下，不會有額外力量作用於阻尼器油封，可大幅提升油封壽命。另一方面，奈米流體阻尼器安裝於結構物上時，可以直接更換內部奈米流體，以達到即時改變阻尼器的力學行為之目的。奈米流體阻尼器之研發共可分為三大部分：第一為奈米流體流變特性之研究，其中包含奈米流體的配製、以及流體流變特性之試驗，並且透過演算法將奈米流體的黏度曲線，回歸成三組Cross Model組合之數學模型，進一部透過參數分析建立公式化的奈米流體流變資料庫。第二部分為奈米流體阻尼器力學公式之推導與驗證，該公式自流體力學理論出發，將奈米流體的流變行為，導入具有簡單環形間隙之阻尼器構造中，推導出詳解以及誤差極小之簡化公式。同時，藉由實尺寸奈米流體阻尼器之性能試驗，推測理論公式可能的誤差來源，並且進一步透過辦經驗之方式修正材料特性，以擬合試驗結果。最後，第三部分則探討奈米流體尼器之工程特性，藉由參數研究進一步了解各阻尼器物理機構對於其力學行為之影響；最後參考歐盟規範，驗證奈米流體阻尼器符合其消能元件中STU之性能規定，並且透過實際橋梁試驗之量測資料，驗證阻尼器於橋梁車行振動下，相較於傳統黏性阻尼器，具備有極低出力以及累積阻尼能。

關鍵字

奈米材料 ； 流變學 ； 阻尼器性能試驗 ； 阻尼器設計 ； 結構被動控制

並列摘要

This Study aims to perform a methodology study and design method for nanofluid dampers. The development of nanofluid dampers comprises three parts, such as material properties, damper behaviors, and engineering applications, in brief. In the first part, 90 nanofluid samples are fabricated with various combinations of different types of fumed silica particles, PPGs, and fluid concentrations. The viscous curves and fluid curves of nanofluids are obtained from rheology tests and also simulated by a triple-Cross model with eleven parameters. Through observing from the results, it could be summarized that the initial viscosity and maximum viscosity are proportional to the fluid concentrations and the polymer chain lengths, but the shear rates corresponding to the maximum viscosities are inversely proportional to these two variations; in addition, the shear thickening and shear thinning effects become more obvious when the concentrations of fluid rise
The second part aims to apply the fluid properties into damper devices by means of theoretical derivations and full-scale damper performance tests. First, an exact solution for the force curves of nanofluid dampers is deduced based on the viscous curve of the fluid triple-Cross model and the theory of equilibrium of fluid momentum. However, owing to the complex viscous model of materials and many unknown parameters in the equations of damper force curve, it is time-consuming for obtaining the force curves by iterations, and is not applicable for further observations on the damper properties. Hence, a simplified solution is deduced according to the simplified bi-linear model of stress curve (in logarithm coordinates) as well as the mass conservation theory of fluid mechanics; several comparisons between the exact solution and simplified solution are made, and the results show only slightly difference between such solutions. Nevertheless, the numerical derivations are fail to predict the force behaviors of the full-scale damper performance tests, which are conducted with two identical dampers filled with nanofluids PPG3000-R972-10% and PPG1000-R972-10% respectively. The major reason is supposed to be the measurement errors caused from the rheology test. Therefore, the fluid stress curves of these two types of nanofluids are modified corresponding to the results of performance tests.
In the last part, several properties of nanofluid dampers are discovered by transforming the simplified solution into the combination of two continuous curves with typical forms of viscous dampers, ; for example, the exponents of the force equations are directly equal to the exponents of the simplified fluid bi-linear stress curve and independent to the damper dimensions. On the other hand, the critical velocity, which is corresponding to the intersection point of the two force curves, is independent to the length of piston head but could be enlarged by reducing the radius of piston head and increasing the width of annular gap.
Furthermore, the same nanofluid dampers, used in the full-scale damper performance tests, are adopted to verify that the nanofluid dampers meet the requirements listed in the European Standard (EN15129) for the shock-transmission units (STU). Through inputting the recorded data from a practical bridge experiment, which is conducted by driving trucks moving at constant velocities, the energy dissipated by nanofluid dampers is merely 2% to 11% of conventional dampers. Although no former study confirms that the accumulative damping energy will directly affect the durability of one damper (or the seal system), the less energy implies that the seal system will receive smaller pressure and wear.

並列關鍵字

Nano-material ； Rheology ； damper performance test ； damper design ； structural passive control

參考文獻

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