Understanding the dynamic tensile response of microwave damaged rock is of great significance to promote the development of microwave-assisted hard rock breakage technology. However, most of the current research on this issue is limited to static loading conditions, which is inconsistent with the dynamic stress circumstances encountered in real rock-breaking operations. The objective of this work is to investigate the effects of microwave irradiation on the dynamic tensile strength, full-field displacement distribution and average fracture energy of a granitic rock. The split Hopkinson pressure bar (SHPB) system combined with digital image correlation (DIC) technique is adopted to conduct the experiments. The overload phenomenon, which refers to the strength over-estimation phenomenon in the Brazilian test, is validated using the conventional strain gauge method. Based on the DIC analysis, a new approach for calculating the average fracture energy is proposed. Experimental results show that both the apparent and true tensile strengths increase with the loading rate while decreasing with the increase of the irradiation duration; and the true tensile strength after overload correction is lower than the apparent strength. Besides, the overload ratio and fracture energy also show the loading rate and irradiation duration dependency. Our findings prove clearly that microwave irradiation significantly weakens the dynamic tensile properties of granitic rock.

中文翻译：

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微波损伤花岗岩的动态拉伸响应

了解微波破碎岩石的动态拉伸响应对推动微波辅助硬岩破碎技术的发展具有重要意义。然而，目前对这个问题的研究大多仅限于静态加载条件，这与实际破岩作业中遇到的动态应力情况不一致。这项工作的目的是研究微波辐射对花岗岩的动态抗拉强度、全场位移分布和平均断裂能的影响。采用分体式霍普金森压力棒（SHPB）系统结合数字图像相关（DIC）技术进行实验。过载现象，指的是巴西测试中的强度高估现象，使用传统的应变计方法进行验证。基于DIC分析，提出了一种计算平均断裂能的新方法。实验结果表明，表观抗拉强度和真抗拉强度均随着加载速率的增加而增加，随着辐照时间的增加而降低；过载校正后的真实抗拉强度低于表观强度。此外，过载率和断裂能也表现出加载速率和辐照持续时间的依赖性。我们的研究结果清楚地证明，微波辐射显着削弱了花岗岩的动态拉伸性能。实验结果表明，表观抗拉强度和真抗拉强度均随着加载速率的增加而增加，随着辐照时间的增加而降低；过载校正后的真实抗拉强度低于表观强度。此外，过载率和断裂能也表现出加载速率和辐照持续时间的依赖性。我们的研究结果清楚地证明，微波辐射显着削弱了花岗岩的动态拉伸性能。实验结果表明，表观抗拉强度和真抗拉强度均随着加载速率的增加而增加，随着辐照时间的增加而降低；过载校正后的真实抗拉强度低于表观强度。此外，过载率和断裂能也表现出加载速率和辐照持续时间的依赖性。我们的研究结果清楚地证明，微波辐射显着削弱了花岗岩的动态拉伸性能。