水化硅酸钙纳米压痕分子动力学模拟方法优化

针对水化硅酸钙纳米压痕模型忽视了压头与基底之间相互作用的问题，由尺寸差异引起的金刚石压头难以计算的问题，以及Wittmann模型无法得到实际接触面积的问题，提出了新的模型与计算方法．结合分子动力学方法，采用金刚石压头-Wittmann模型基底的组合方式构建无定形态水化硅酸钙纳米压痕试验模型．在建模阶段，考虑到压头模型与基底模型粒子间尺寸差异，提出了等比例替换模型，通过公式推导并就不同尺寸模拟结果验证了等比例替换模型的可行性．在计算阶段，提出了局部前处理的弛豫方法进行模拟．确定最大荷载位置处的接触面积为546 nm2，进而求出水化硅酸钙模型硬度H为0.84 GPa、折合模量Er为30.52 GPa．并通过纳米压痕试验，验证了模拟结果的准确性，证明了模型的科学性，对今后水化硅酸钙(C-S-H)纳米层面的模拟具有重要借鉴意义．

Optimization of Molecular Dynamics Simulation Method for Nanoindentation of Calcium Silicate Hydrate

Aiming at addressing the problems in nanoindentation modeling of the calcium silicate hydrate including ignoring the interaction between the indenter and the substrate, the difficulty of calculating the diamond indenter due to the size difference, and the difficulty in obtaining the actual contact area using the Wittmann model, in this paper new models and calculation methods are proposed. Based on the molecular dynamics method, a nanoindentation model of calcium silicate hydrate (C-S-H) gel was developed by the combination of diamond indenter model and Wittmann model. For creating the model, an equal-proportional replacement method is proposed considering the size difference between the indenter model and the Wittmann model. The feasibility of the equal-proportional replacement method is verified through formula derivations and simulations with different sizes. During the simulation, a relaxation method of local pretreatment is proposed. The contact area at the maximum load is determined to be 546 nm2. Then, the hardness H of the hydration calcium silicate model is obtained as 0.84 GPa, corresponding to an equivalent modulus Er of 30.52 GPa. Finally, compared with the experimental data of nanoindentation, the accuracy of the simulation data is verified, and the scientificity of the model is proven. This work is of considerable significance for the nano-scale simulation of calcium silicate hydrate in future research.