In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmosph...In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmospheres. In this paper, we have analyzed the effect of slenderness ratio on the mechanical properties and energy dissipation characteristics of red sandstone under high strain rates. The processes of compaction, elastic deformation and stress softening deformation of specimens contract with an increase in slenderness ratio, whilst the nonlinear deformation process extends correspondingly. In addition, degrees of damage of specimens reduced gradually and the type of destruction showed a transformation trend from stretching failure towards shear failure when the slenderness ratio increased. A model of dynamic damage evolution in red sandstone was established and the parameters of the constitutive model at different ratios of length to diameter were determined. By comparison with the experimental curve, the accuracy of the model, which could reflect the stress–strain dynamic characteristics of red sandstone, was verified. From the view of energy dissipation, an increase in slenderness ratio of a specimen decreased the proportion of energy dissipation and caused a gradual fall in the capability of energy dissipation during the specimen failure process. To some extent, the study indicated the effects of slenderness ratios on the mechanical properties and energy dissipation characteristics of red sandstone under the high strain rate, which provides valuable references to related engineering designs and academic researches.展开更多
为了探究茶树精油的研究热点,本文对近年来茶树精油研究成果进行了系统分析。文章基于Web of Science核心数据库、中国知网(CNKI)、万方数据库和维普数据库所收录期刊文献,利用VOSviewer软件对2016-2022年茶树精油研究的关键词进行共现...为了探究茶树精油的研究热点,本文对近年来茶树精油研究成果进行了系统分析。文章基于Web of Science核心数据库、中国知网(CNKI)、万方数据库和维普数据库所收录期刊文献,利用VOSviewer软件对2016-2022年茶树精油研究的关键词进行共现和可视化图谱绘制,共纳入759篇文献。研究结果显示,茶树精油的近年研究热点可归纳为3个主要方面,即茶树精油制备与质量评价、猪产业和蠕形螨睑缘炎治疗中的应用、药理与毒理研究。展开更多
The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysi...The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor. The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS. Our results show that each order of the system frequency varied with an increase in preload forces. A single order frequency decreased with an increase in the preload force. A preload force affected low-order frequencies more than high-order frequencies. We obtained a functional relationship by fitting preload forces and fundamental frequencies, which was in agreement with our theretical considerations. This study provides theoretical support for the detection of preload forces.展开更多
The mechanical properties of marble, limestone, and sandstone as well as the stress-strain curve, the varying characteristics of the peak strength, the peak strain and elastic modulus were studied by using the MTS810 ...The mechanical properties of marble, limestone, and sandstone as well as the stress-strain curve, the varying characteristics of the peak strength, the peak strain and elastic modulus were studied by using the MTS810 Rock Mechanics Servo-controlled Testing System under the action of temperatures rang- ing from room temperature to 800℃ . Results show that (1) the peak strength and elastic modulus of marble fluctuate at the temperature from normal to 400 ℃ ; and they decrease gradually over 400℃ . (2) With the rise of the temperature, the peak strength and elastic modulus of limestone show downward trend from normal temperature to 200 ℃ ; have little change from 200 ℃ to 600 ℃; and decrease sharply over 600 ℃ . (3) The peak strength of sandstone shows a downward trend while a little change for elastic modulus at normal temperature to 200 ℃ ; and from 200 ℃ to 600 ℃ , the peak strength of sandstone in- creases while a little change for elastic modulus; the peak strength and elastic modulus decrease rap- idly at the temperature over 600 ℃ . (4) The peak strain of limestone shows little change at normal tem- perature to 600 ℃ , however, the peak strain increases rapidly over 600 ℃; and for marble and sandstone, the peak strain decreases with the rise of the temperature from normal temperature to 200℃ , the peak strain increases rapidly over 200℃. The result can provide valuable references for the rock engineering design at high temperature.展开更多
基金Financial support for this work, provided by the National Basic Research Program of China (No. 2013CB227900)the National Natural Science Foundation of China (No. 51074166), the National Natural Science Foundation for Young (Nos. 51304200, 51304201 and 51104128)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120095110013)the Open Fund of the State Key Laboratory of Coal Resource and Safe Mining (No. 10F08)the Colleges and Universities in Jiangsu Province Plans to Graduate Research and Innovation (No. CXLX13_935)the College Students’ Innovative Entrepreneurial Foundation of China University of Mining and Technology (No. 2013DXS03)
文摘In this experiment, red sandstone specimens, having slenderness ratios of 0.5, 0.7, 0.9 and 1.1 respectively, were subjected to blow tests using a Split Hopkinson Pressure Bar(SHPB) system at a pressure of 0.4 atmospheres. In this paper, we have analyzed the effect of slenderness ratio on the mechanical properties and energy dissipation characteristics of red sandstone under high strain rates. The processes of compaction, elastic deformation and stress softening deformation of specimens contract with an increase in slenderness ratio, whilst the nonlinear deformation process extends correspondingly. In addition, degrees of damage of specimens reduced gradually and the type of destruction showed a transformation trend from stretching failure towards shear failure when the slenderness ratio increased. A model of dynamic damage evolution in red sandstone was established and the parameters of the constitutive model at different ratios of length to diameter were determined. By comparison with the experimental curve, the accuracy of the model, which could reflect the stress–strain dynamic characteristics of red sandstone, was verified. From the view of energy dissipation, an increase in slenderness ratio of a specimen decreased the proportion of energy dissipation and caused a gradual fall in the capability of energy dissipation during the specimen failure process. To some extent, the study indicated the effects of slenderness ratios on the mechanical properties and energy dissipation characteristics of red sandstone under the high strain rate, which provides valuable references to related engineering designs and academic researches.
文摘为了探究茶树精油的研究热点,本文对近年来茶树精油研究成果进行了系统分析。文章基于Web of Science核心数据库、中国知网(CNKI)、万方数据库和维普数据库所收录期刊文献,利用VOSviewer软件对2016-2022年茶树精油研究的关键词进行共现和可视化图谱绘制,共纳入759篇文献。研究结果显示,茶树精油的近年研究热点可归纳为3个主要方面,即茶树精油制备与质量评价、猪产业和蠕形螨睑缘炎治疗中的应用、药理与毒理研究。
基金the financial support from the National Basic Research Program of China (No. 2013CB227900)the China Postdoctoral Science Foundation (No. 20110491483)the State Key Laboratory of Coal Resources and Mine Safety(No. 10F08)
文摘The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor. The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS. Our results show that each order of the system frequency varied with an increase in preload forces. A single order frequency decreased with an increase in the preload force. A preload force affected low-order frequencies more than high-order frequencies. We obtained a functional relationship by fitting preload forces and fundamental frequencies, which was in agreement with our theretical considerations. This study provides theoretical support for the detection of preload forces.
基金Supported by the National Natural Science Foundation of China (Grant No. 50490273)the National Key Basic Research and Development Program of China (973 Project) (Grant No. 2007CB209400)Xuzhou Institute of Technology (Grant No. XKY2007219)
文摘The mechanical properties of marble, limestone, and sandstone as well as the stress-strain curve, the varying characteristics of the peak strength, the peak strain and elastic modulus were studied by using the MTS810 Rock Mechanics Servo-controlled Testing System under the action of temperatures rang- ing from room temperature to 800℃ . Results show that (1) the peak strength and elastic modulus of marble fluctuate at the temperature from normal to 400 ℃ ; and they decrease gradually over 400℃ . (2) With the rise of the temperature, the peak strength and elastic modulus of limestone show downward trend from normal temperature to 200 ℃ ; have little change from 200 ℃ to 600 ℃; and decrease sharply over 600 ℃ . (3) The peak strength of sandstone shows a downward trend while a little change for elastic modulus at normal temperature to 200 ℃ ; and from 200 ℃ to 600 ℃ , the peak strength of sandstone in- creases while a little change for elastic modulus; the peak strength and elastic modulus decrease rap- idly at the temperature over 600 ℃ . (4) The peak strain of limestone shows little change at normal tem- perature to 600 ℃ , however, the peak strain increases rapidly over 600 ℃; and for marble and sandstone, the peak strain decreases with the rise of the temperature from normal temperature to 200℃ , the peak strain increases rapidly over 200℃. The result can provide valuable references for the rock engineering design at high temperature.