時間依存型材料モデルの改善による3Dプリント中の積層安定性評価解析の再検討
筆者らは，3Dプリント中の積層安定性の事前確認を効率化するために，FEMによる解析評価方法を開発してきた。従来の解析では，崩壊モードによって，積層可能高さを過小評価する場合があり，評価精度向上を目的とした検討を行った。高チキソ性である3Dプリント用材料の物性は，静置時の環境の影響を受けやすい。積層用材料は積層直後から気中静置されるが，従来法の材料試験では，材料が型枠内静置される時間が長く材料物性を過小評価している可能性を考えた。その確認のため要素試験を実施したところ，従来法の材料試験では，積層用材料を模擬して気中静置の時間を長くした材料試験よりも，ヤング係数や粘着力の時間依存変化が1/12～1/8程度小さくなることが明らかとなった。これを踏まえ材料試験方法を改善したところ，解析における積層可能高さの過小評価傾向が解消された。加えて，評価精度のさらなる向上に向け，時間依存型材料モデルや解析上の層要素の拘束方法に関する改善点を整理した。
キーワード：T-3DP®，3Dプリンティング，積層安定性，積層安定性評価解析，時間依存
＊１ 技術センター社会基盤技術研究部 先端構造研究室
Enhancement for Numerical Evaluation on Buildability of 3D Concrete Printing with Improved Time-dependent Material Model
The authors have been developing an FEM-based buildability analysis method for 3D concrete printing to make the process of pre-confirmation of buildability more efficient. The conventional analysis method tended to underestimate the collapse height in certain collapse modes, and this paper aims to improve the accuracy of the evaluation. Materials for 3D concrete printing have high thixotropy and the static environment of the materials is thought to affect time-dependent changes in material properties. Printed materials are left in the air immediately after extrusion, but in the conventional method of material testing, printed materials are left in the formwork for a longer period of time. The authors suspected that this difference may have led to an underestimation of material properties. Elemental tests were conducted to investigate this, and it was found that the time-dependent changes in Young's modulus and cohesion in the conventional material tests were about 1/12 to 1/8 smaller than those in the material tests in which materials were left in the air for a longer period of time. Based on this finding, the material testing method was improved, and the tendency to underestimate the collapse height in the analysis was eliminated. In addition, future issues regarding time-dependent material models and the method of constraining layer elements in the analysis were discussed for improving the evaluation accuracy of collapse height and out-of-plane displacement distribution.
Keywords: T-3DP, 3D printing, buildability, buildability analysis, time-dependent
*1 Advanced Structure Technology Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology