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张文清, 穆朝民, 李重情. 冲击荷载下煤的动态力学性质研究[J]. 煤炭科学技术, 2019, (10).
引用本文: 张文清, 穆朝民, 李重情. 冲击荷载下煤的动态力学性质研究[J]. 煤炭科学技术, 2019, (10).
ZHANG Wenqing, MU Chaomin, LI Zhongqing. Study on dynamic mechanical properties of coal under impact loading[J]. COAL SCIENCE AND TECHNOLOGY, 2019, (10).
Citation: ZHANG Wenqing, MU Chaomin, LI Zhongqing. Study on dynamic mechanical properties of coal under impact loading[J]. COAL SCIENCE AND TECHNOLOGY, 2019, (10).

冲击荷载下煤的动态力学性质研究

Study on dynamic mechanical properties of coal under impact loading

  • 摘要: 为了研究不同软硬程度煤在冲击荷载作用下的力学特性,分别制取了型煤与原煤2种不同煤样,采用分离式霍普金森压杆试验装置对其进行了不同应变率条件下的单轴冲击破坏试验,获得了2种煤的动态应力应变曲线和相关动态力学参数,并分析得到2种煤的破坏变形特征及能量耗散规律。试验结果表明:2种煤在冲击荷载下的变形在初始阶段即表现出非线性;总体上,其破坏变形过程均可概括为:初始非线性阶段、屈服阶段、应变强化阶段和卸载破坏阶段。在试验应变率70~280 s-1内,2种煤的动态抗压强度和峰值应变均具有应变率强化的特性,随应变率呈指数增加,且原煤的应变率硬化特性更为显著,说明原煤比型煤具有更好的抵抗冲击载荷的能力。由于材料受热活化机制和惯性效应所起的作用不相同,2种煤的动态应力增长因子DIF随应变率呈2种不同的变化趋势,存在一个转折应变率(130 s-1);在高应变率下,型煤比原煤体现出更高的应变率硬化和动态增韧效应。2种煤的破碎功密度随应变率均呈指数增长,体现出显著的率相关性,但在相同荷载下,原煤破碎功密度高于型煤,破坏需要耗散更多的能量。原煤和型煤的能量吸收率均无明显的应变率相关性,平均分别为10.1%和19.3%,说明型煤的能量吸收能力更强,体现出更为显著的率敏感性。研究结论表明,2种煤均是率敏感材料,在高应变率下,型煤比原煤体现出更高的应变率硬化、动态增韧效应和能量吸收能力。2种煤在更高应变率条件下的力学特性如何,有待进一步试验研究。

     

    Abstract: In order to study the mechanical properties of coal samples with different hardness under impact loading, two different coal samples of briquette and raw coal samples were prepared, and they were subjected to different strain rate conditions using a separate Hopkinson pressure bar experimental device.. The uniaxial impact failure experiments were carried out, and the dynamic stress-strain curves and related dynamic mechanical parameters of two kinds of coal were obtained. The failure deformation characteristics and energy dissipation laws of the two coals were analyzed. The experimental results show that, the two kinds of coal show non-linear deformation at the initial stage under impact loading, which is different from that under quasi-static loading obviously. In general, the failure and deformation process can be summarized as follows: initial non-linear stage, yield stage, strain strengthening stage and unloading failure stage. In the range of strain rate 70~280 s-1, the dynamic compressive strength and peak strain of both coals have the characteristics of strain rate strengthening, which increases exponentially with strain rate, and the strain rate hardening characteristics of the raw coal are more significant. Since the material is affected by the heat activation mechanism and the inertia effect, the dynamic stress increasing factor (DIF) of two kinds of coal shows two different trends with strain rate, and there is a transition strain rate (130 s-1). At the rate, the briquette exhibits higher strain rate hardening and dynamic toughening effects than the raw coal. The dissipation energy density of both coals increas-es exponentially with strain rate, showing a significant rate correlation. However, under the same load, the dissipation energy density of raw coal is higher than that of briquette coal, which requires more energy to be destroyed. The average energy dissipation rates of raw and briquette coal have no obvious strain rate correlation, with an average of 10.1% and 19.3%, respectively. It shows that briquette coal has stronger energy absorption capacity and more significant rate sensitivity than raw coal. The results show that the two kinds of coals are both rate-sensitive materials. At high strain rates, briquette exhibits higher strain rate hardening, dynamic toughening effect and energy absorption capacity than raw coal. The mechanical properties of the two coals at higher strain rates are subject to further experimental research.

     

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