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Discrete element modeling on nanoindentation creep behavior of C-S-H under berkovich and flat-tip indenters
Cement and Concrete Research ( IF 10.9 ) Pub Date : 2025-01-28 , DOI: 10.1016/j.cemconres.2025.107808
Weiqiang Guo, Ya Wei

This paper employs the discrete element method (DEM) to simulate the nanoindentation creep of calcium-silicate-hydrate (C-S-H), focusing on indentation deformation, particle interactions, and stress transmission paths. The Rate Process Theory (RPT), previously utilized in the creep modeling of cohesive soils and other granular materials, is proposed to simulate C-S-H creep. Due to the nanometer size of C-S-H particles, the critical time step in DEM simulations is very small. Therefore, a time-scaling algorithm is used to match the DEM simulation time with the physical time in laboratory tests, accelerating the simulation time by a factor of 1 × 108. C-S-H particle assemblies with specific packing densities are generated using Particle Flow Code (PFC3D, version 5.0), with coordination numbers and cohesion forces controlled by the stress-servo of PFC walls. Virtual nanoindentations using a Berkovich indenter are conducted on C-S-H particle assemblies with three different packing densities (0.74, 0.64, and 0.58), followed by parameters calibration. Results show that the DEM + RPT method can capture the scaling relations between the indentation modulus, hardness, and contact creep modulus of C-S-H particle assemblies and the packing density. Furthermore, DEM simulations reveal particle rearrangement under Berkovich and flat-tip indenters, highlighting that different indenter types lead to distinct creep kinetics in C-S-H, with the Berkovich indenters experimentally capturing long-term creep and flat-tip indenters measuring short-term creep.

中文翻译:


Berkovich 和平尖压头下 C-S-H 纳米压痕蠕变行为的离散元建模



本文采用离散元法 (DEM) 模拟钙-硅酸盐-水合物 (CS-H) 的纳米压痕蠕变,重点关注压痕变形、颗粒相互作用和应力传递路径。以前用于粘性土壤和其他颗粒材料的蠕变建模的速率过程理论 (RPT) 用于模拟 C-S-H 蠕变。由于 C-S-H 颗粒的纳米尺寸,DEM 模拟中的关键时间步长非常小。因此,使用时间缩放算法将 DEM 模拟时间与实验室测试中的物理时间相匹配,从而将模拟时间加快 1 × 10 8 倍。具有特定堆积密度的 C-S-H 颗粒组件是使用粒子流代码(PFC3D 版本 5.0)生成的,配位数和内聚力由 PFC 壁的应力伺服控制。使用 Berkovich 压头对具有三种不同堆积密度(0.74、0.64 和 0.58)的 CSH 颗粒组件进行虚拟纳米压痕,然后进行参数校准。结果表明,DEM + RPT 方法可以捕获 C-S-H 颗粒组装体的压痕模量、硬度和接触蠕变模量与堆积密度之间的缩放关系。此外,DEM 仿真揭示了 Berkovich 和平尖压头下的颗粒重排,突出了不同的压头类型导致 CSH 中不同的蠕变动力学,Berkovich 压头实验捕获长期蠕变,平尖压头测量短期蠕变。
更新日期:2025-01-28
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