Abstract Majority of minerals or rocks commonly display a positive Poisson’s ratio between 0.05 and 0.45. However, granites that experience high temperature treatment can exhibit negative Poisson’s ratio under low compressive stresses. The underlying mechanism responsible for the auxetic behavior of thermally-treated granites is poorly understood. Here we present experimental results of uniaxial compression tests on thermally-treated Beishan granite, which show auxetic behavior with increasing thermal treatment temperature and the Poisson’s ratio is as low as −0.18 for a maximum thermal treatment temperature of 650 °C. To reveal the thermally-induced change in the microstructures of Beishan granite, particle discrete element models are built and calibrated using the experimental data. The numerical results show that intensively distributed microcracks appear in the Beishan granite specimens after high temperature treatments. The number and the widths of microcracks increase with increasing thermal treatment temperature. A number of isolated block clusters consisting of mineral grains form due to the connection of thermally-induced microcracks under high temperature thermal treatment. The deformation behavior of these block clusters is primarily responsible for the observed negative Poisson’s ratio of the thermally-treated Beishan granite during compression.

中文翻译：

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热处理后北山花岗岩的拉胀行为：微裂纹视角

摘要 大多数矿物或岩石通常表现出介于 0.05 和 0.45 之间的正泊松比。然而，经过高温处理的花岗岩在低压缩应力下会表现出负泊松比。导致热处理花岗岩拉胀行为的潜在机制知之甚少。在这里，我们展示了热处理后的北山花岗岩单轴压缩试验的实验结果，随着热处理温度的升高，其表现出拉胀行为，泊松比低至 -0.18，最高热处理温度为 650 °C。为了揭示北山花岗岩微观结构的热致变化，使用实验数据建立和校准颗粒离散元模型。数值结果表明，经过高温处理的北山花岗岩试样出现了密集分布的微裂纹。微裂纹的数量和宽度随着热处理温度的升高而增加。由于高温热处理下热致微裂纹的连接，形成了许多由矿物颗粒组成的孤立块簇。这些块体簇的变形行为是在压缩过程中观察到的热处理北山花岗岩的负泊松比的主要原因。由于高温热处理下热致微裂纹的连接，形成了许多由矿物颗粒组成的孤立块簇。这些块体簇的变形行为是在压缩过程中观察到的热处理北山花岗岩的负泊松比的主要原因。由于高温热处理下热致微裂纹的连接，形成了许多由矿物颗粒组成的孤立块簇。这些块体簇的变形行为是在压缩过程中观察到的热处理北山花岗岩的负泊松比的主要原因。