薄殼生物材料機械性質研究與應用

Investigation and Application of Mechanical Properties of Thin-Shell Biomaterials

楊達璋(Da-Chang Yang)

指導教授 ： 莊嘉揚

國立臺灣大學/工學院/機械工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201703044

摘要

生物薄殼材料是自然界中最常見的結構之一，本研究以鳥類蛋殼做為研究對象。地球上的鳥類表現出非凡的生物多樣性，以及卓越的環境適應性，而蛋殼的設計，在鳥類繁衍中扮演關鍵角色。本研究結合壓縮實驗、薄殼理論以及有限元素模擬，探討所有鳥類蛋殼背後是否存在一個通用的設計準則。
在鳥類蛋殼的研究中，大部分的研究團隊花了許多時間在蛋殼化學組成、生物演化、氣體交換機制等生物特徵上的討論，卻鮮少有研究團隊以工程的角度，針對蛋殼在作為承重結構上做深入的探討。特別是在鳥類的演化上，蛋殼的設計為因應不同環境條件、生殖策略，所造成幾何形狀、大小上的差異。因此，本研究定義與蛋重、形狀和整體蛋殼剛度相關的無因次參數C，綜合不同因素，消弭不同形狀、大小所帶來的影響，以單一度量化的方式來進行鳥類蛋殼種間和種內的比較。
本研究通過實驗和有限元素模擬，分析體形重量上差異超過五個數量級的四百六十種鳥類蛋殼樣本，並顯示無因次參數C對大多數物種具有一定不變量。而這種不變性，或稱之為設計準則，規範了蛋殼厚度和彈性性質的變化上受到蛋重的限制。除此之外，本研究藉由結合有限元素模擬與挫曲效應所造成的局部扁平效果，定義蛋殼可承受親鳥進行接觸孵化的臨界值以及安全係數，並分析在自然界中具有獨特生殖策略的物種（奇異鳥、塚雉、信天翁、杜鵑），量化並分析人擇或環境毒素對鳥類生態系統的影響。本研究以工程觀點來討論生物薄殼材料，對蛋殼背後的設計機制進行探討與分析，並為卵生動物的演化起源提供線索。利用本研究所建立之分析方法，希望為研究生物材料領域，提出創新的見解與貢獻。

關鍵字

壓縮試驗 ； 薄殼理論 ； 有限元素法 ； 鳥類蛋殼 ； 接觸孵化

並列摘要

The thin shell biomaterial is one of the most common structures in nature. This study takes avian eggshells as the main research object. In this world, birds exhibit extraordinary diversity in biological characteristics, and the design of eggshell plays a key role in avian adaptive radiations. In this study, we utilize the thin shell theory, finite element method (FEM), and compression test, attempting to explore whether there is a common design criterion behind the avian eggs.
In the previous study, most of the research team spent much time on the composition of the eggshell, pattern, gas exchange mechanism and other biological characteristics. However, our understanding of the underlying principles that guide the “design” of the egg as a load-bearing structure remains incomplete, especially over broad taxonomic scales. The function of the eggshell depends on different environmental conditions and reproductive strategies. Here we define a dimensionless number C, a function of egg weight, rigidity, and dimensions, to quantify how rigid an eggshell is concerning the egg weight after removing the shape-induced rigidity. The dimensionless number is the quantification of eggshell rigidity in a way that allows meaningful intraspecific and interspecific comparisons.
In this study, we experimentally and numerically analyze eggs of 450 bird species across four orders of magnitude in body mass and reveal that C is nearly invariant for most species, including tiny hummingbirds and giant elephant birds. This invariance or “design guideline” dictates that the evolutionary changes in shell thickness and elastic properties be constrained by changes in egg weight. In addition, we utilize the FEM and local flattening of the eggshells, caused by buckling, to define the critical values and the factor of safety during the contact incubation. Our analyses illuminate the unique reproductive strategies of brood parasites, kiwi, and megapodes, and quantify the reduction in a safety margin for contact incubation due to artificial selection and environmental toxins. In this study, we work on the thin shell biomaterial from the engineering point of view, provide a mechanistic framework for better understanding the mechanical design of the avian eggs, and may provide clues to the evolutionary origin of amniote eggs. Using the numerical method established in this study, we hope to make innovative insights and contributions in the field of biomaterials.

並列關鍵字

compression test ； thin shell theory ； finite element method ； avian eggs ； contact incubation

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