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On the compressive response of open-cell aluminum foams.

機譯：關于開孔鋁泡沫的壓縮響應。

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摘要

This study is concerned with the mechanical behavior of open-cell aluminum foams. In particular the compressive response of aluminum foams is analyzed through careful experiments and analyses. The microstructure of foams of three different cell sizes was first analyzed using X-ray tomography. This included characterization of the polyhedral geometry of cells, establishment of the cell anisotropy and statistical distribution of ligament lengths, and measurement of the ligament cross sectional area distribution. Crushing experiments were performed on various specimen sizes in the principal directions of anisotropy. The compressive response of aluminum foams is similar to that of many other cellular materials. It starts with a linearly elastic regime that terminates into a limit load followed by an extensive stress plateau. During the plateau, the deformation localizes in the form of inclined but disorganized bands. The evolution of such localization patterns was monitored using X-ray tomography. At the end of the plateau, the response turns into a second stable branch as most cells collapse and the foam is densified.;The crushing experiments are simulated numerically using several levels of modeling. The ligaments are modeled as shear-deformable beam elements and the cellular microstructure is mainly represented using the 14-sided Kelvin cell in periodic domains of various sizes. Other geometries considered include the perturbed Kelvin cell, and foams with random microstructures generated by the Surface Evolver software. All microstructures are assigned geometric characteristics that derive directly from the measurements. Unlike elastic foams, for elastic-plastic foams the prevalent instability is a limit load. The limit load can be captured using one fully periodic characteristic cell. The predicted limit stresses agree with the measured initiation stresses very well. This very good performance coupled with its simplicity make the characteristic cell model a powerful tool in metal foam mechanics. The subsequent crushing events, the stress plateau and desification were successfully reproduced using models with larger, finite size domains involving several characteristic cells. Results indicate that accurate representation of the ligament bending rigidity and the base material inelastic properties are essential whereas the randomness of the actual foam microstructure appears to play a secondary role.
機譯：這項研究與開孔鋁泡沫的力學性能有關。特別是通過仔細的實驗??和分析來分析泡沫鋁的壓縮響應。首先使用X射線斷層掃描技術分析了三種不同泡孔尺寸的泡沫的微觀結構。這包括表征細胞的多面體幾何形狀，確定細胞的各向異性以及韌帶長度的統(tǒng)計分布以及測量韌帶橫截面積。在各向異性的主要方向上對各種尺寸的試樣進行了壓碎實驗。泡沫鋁的壓縮響應類似于許多其他多孔材料的壓縮響應。它以線性彈性狀態(tài)開始，該狀態(tài)終止于極限載荷，隨后是較大的應力平穩(wěn)狀態(tài)。在高原時期，變形以傾斜但雜亂的條帶形式出現(xiàn)。使用X射線斷層掃描監(jiān)測這種定位模式的演變。在高原結束時，隨著大多數(shù)細胞的塌陷和泡沫的致密化，響應變成第二個穩(wěn)定分支。破碎實驗是使用幾個層次的建模數(shù)值模擬的。韌帶被建模為可剪切變形的梁單元，并且在各種尺寸的周期域中，主要使用14面的開爾文單元表示細胞的微結構?？紤]的其他幾何形狀包括受擾動的Kelvin孔，以及由Surface Evolver軟件生成的具有隨機微觀結構的泡沫。為所有微結構分配了直接從測量得出的幾何特征。與彈性泡沫不同，對于彈塑性泡沫，普遍的不穩(wěn)定性是極限載荷?？梢允褂靡粋€完全周期性的特征單元來捕獲極限載荷。預測的極限應力與測得的初始應力非常吻合。這種非常好的性能加上其簡單性，使特征性的單元模型成為金屬泡沫力學中的強大工具。隨后的壓碎事件，應力平穩(wěn)期和降落現(xiàn)象已使用包含多個特征單元的較大，有限尺寸域的模型成功復制。結果表明，韌帶彎曲剛度和基礎材料的非彈性性能的準確表示至關重要，而實際泡沫微觀結構的隨機性似乎起次要作用。

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  • 作者

    Jang, Wen-Yea.;

  • 作者單位

    The University of Texas at Austin.;

  • 授予單位 The University of Texas at Austin.;
  • 學科 Applied Mechanics.;Engineering Mechanical.;Engineering General.
  • 學位 Ph.D.
  • 年度 2008
  • 頁碼 280 p.
  • 總頁數(shù) 280
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 應用力學;工程基礎科學;機械、儀表工業(yè);
  • 關鍵詞

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