数値粒状体モデルの一般的増分挙動 General incremental behavior of idealized granular media

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Abstract

粒状体の弾塑性増分挙動が従来の塑性論からどのように異なるかを調べるために,粒状要素法を用いた数値実験を行った.粒状体モデルは幾つかの粒径をもつ球形粒子を球状の領域に等方圧でランダムパッキングしたもので,パイ平面上で数方向に比例載荷して得られた状態に対して,多方向の応力プローブ試験を行った.その結果,応力空間において原点と現在の応力点を結ぶ線および等方圧からの載荷経路を含む面が重要な基準面となることを見出した.この基準面内の応力プローブに対しては,ほぼ,非関連流動則が成立するが,その他の場合,一般に塑性ひずみの方向が応力増分の方向に依存すること,唯一の降伏条件を仮定できないことが分かった.

To investigate how the incremental behavior of granular media deviates from the conventional plasticity theory, a series of numerical tests were carried out in terms of Granular Element Method. The model specimen used for the numerical tests was a random assembly of spherical particles with different radii; the particles were packed with an isotropic pressure in a spherical region. The numerical tests were the combination of several proportional loadings in the pi-plane to get sheared stress states and subsequent series of stress-probe tests to investigate plastic responses at these sheared stress states. The important features of plastic responses were found to be characterized in terms of a reference plane in stress space that includes the loading path and the line that connects the origin of stress space and the current stress point. As far as stress probes within this reference plane concerned, the plastic response seemed to be predicted almost by the non-associated flow rule. On the other hand, the incremental behavior for other stress-probe directions were totally different. The direction of incremental plastic strain was apparently dependent on the direction of incremental stress, and the existence of unique yield surface could never be assumed.

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  • NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan

    NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan 54(0), 217-217, 2005

    National Committee for IUTAM

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