- 學位論文
超穎材料單元於低速衝擊下之動態反應
Low-Velocity Impact Response of Metamaterial Units
摘要
本文延伸具內質量共振結構球之理論研究，以兩種實驗探討具內質量共振結構球於低速衝擊下之反應。實驗試體是以三維成型機製作而成，並改良模型的外球殼構造，於外球殼上挖鑿數個孔洞，除了可降低外球殼的重量外，也易於觀察試體內部的現象。實驗先藉由高速攝影機比較均質球與具內質量共振結構球反彈高度的差異，結果顯示具內質量共振結構球的反彈高度明顯低於均質球，由此可知具內質量共振結構球能抑制衝擊外力。接著進一步探討具內質量共振結構球之自然頻率與反彈高度的關係，並根據實驗結果建立恢復係數相對自然頻率之趨勢線，藉由趨勢線預測具不同自然頻率之內質量共振結構球的恢復係數。除此之外，也根據牛頓擺之概念懸掛不同試體，觀察尺寸相近的不同試體相互撞擊之情形，可以發現撞擊後內質量共振器會產生振盪，由此可知撞擊後內質量共振器會吸收部分的衝擊能。 本文也參考多孔結構的相關研究，並以三維成型機製作具挫曲特性結構，再利用自行設計與製作的落摔衝擊試驗機進行實驗探討。最後，結合內質量共振特性與結構的挫曲特性，提出具內質量共振與挫曲特性結構，實驗結果顯示該結構具有較佳的抑制衝擊能力。
並列摘要
This thesis extends the theoretical study of the mass-in-mass structure. Low-velocity impact response of mass-in-mass unit cell is investigated by two experimental methods. The mass-in-mass unit cell is manufactured by 3D printing technology. Modification is made by drilling holes on the shell for easiness of observation of the internal motion, and for decreasing the mass of the shell. In the first step of experiment, the bounce height of mass-in-mass ball and equivalent ball is recorded by high-speed camera for comparison. The result shows that the bounce height of mass-in-mass ball is lower than equivalent ball which means the mass-in-mass ball has impact-mitigation capability. Second, the relation between resonance frequency of mass-in-mass ball and bounce height is investigated. To predict the COR (coefficient of restitution) of mass-in-mass ball with different resonance frequency, trend line is built according to the experimental results. In addition, the impact response of two different specimens are observed. According to the research of cellular solids, structure with buckling property is fabricated by 3D printing technology. The self-designed drop impact tester is used to perform impact test, and the deformation of structure is recorded. Finally, a structure combining local resonance and buckling property is introduced. The experimental results show that the structure has a better impact-mitigation capacity.