The Experts below are selected from a list of 137085 Experts worldwide ranked by ideXlab platform
Viktor P. Efimov - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study on Loading Rate Effects on the Tensile Strength and Fracture Toughness of Rocks
Geotechnical and Geological Engineering, 2020Co-Authors: Viktor P. EfimovAbstract:The Brazilian method experiments were applied to investigate effects of Loading Rate on tensile strength of gabbro-diorite, marble, granite. The tensile strength was measured over a wide range of Loading Rate, $$\dot{\sigma } = 10^{ - 3} - 10^{2}$$ σ ˙ = 10 - 3 - 10 2 MPa s. Also the fracture toughness of marble, gabbro-diorite, dolerite were measured over a wide range of Loading Rate from 5 × 10^−4 to 25 MPa m^1/2/s by three-point bending of beams with a central narrow cut. The strength and fracture toughness of studied rocks are related to the Loading Rate by typical equations: $$\sigma = a + e\ln \dot{\sigma }$$ σ = a + e ln σ ˙ and $${\mathcal{K}}_{1c} = c + d\ln \dot{K}_{1}$$ K 1 c = c + d ln K ˙ 1 in the range of Loading Rates of 10^−3–10^2 MPa/s. A comparison of the characteristic fracture parameters for both types of tests showed the initial activation energy of fracture has the same values. The parameters of proportionality were compared on the basis of the integral strength criterion. The obtained parameters of the studied rocks allow extrapolating the results of measurements of strength and fracture toughness for longer periods, it is important for estimating the long-term stability of rock structures. The methodology for determining the characteristics of rock fracture from the Loading Rate in static fracture of rocks can be easily applied to other brittle materials.
Jilei Zhang - One of the best experts on this subject based on the ideXlab platform.
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temperature and Loading Rate effects on tensile properties of kenaf bast fiber bundles and composites
Composites Part B-engineering, 2008Co-Authors: Yicheng Du, Steve Elder, Kunpeng Wang, Jilei ZhangAbstract:Abstract This paper presents extensive experiments and micromechanics-based modeling to evaluate systematically the tensile properties of kenaf bast fibers bundle (KBFB) and kenaf bast fiber-reinforced epoxy strands. Uniaxial tension behaviors of KBFBs and KBFB-reinforced epoxy strands were evaluated statistically using large sample sets. The elastic modulus, tensile strength, as well as failure strains of KBFBs, displayed large scatter statistically ranging from 10% to 30%. The Loading Rate-dependency was evaluated at three strain Rates ranging from approximately 10−4 ∼ 10−2/s. The tensile strength increases gradually as the Loading Rate increases, while the tensile modulus almost remains the same as the Loading Rate increases until the Loading Rate reaches 10−2/s, at which a much higher modulus was presented. The high temperatures (170–180 °C), possibly subjected during fiber processing and composite fabrication, do not impose significant effects on the tensile properties of KBFBs if the duration is less than 1-h. The tensile properties of KBFB were not affected by the conditioning at 130 °C for 24-h, which mimics the severe service temperature of automotive front-end components. KBFB-epoxy composite strands were further evaluated at various Loading Rates. A micromechanics-based Mori–Tanaka model was implemented to predict the anisotropic elastic moduli of KBFB and KBFB-epoxy composite strands based on the microstructural compositions.
Patrick Kanopolous - One of the best experts on this subject based on the ideXlab platform.
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Dependence of Dynamic Tensile Strength of Longyou Sandstone on Heat-Treatment Temperature and Loading Rate
Rock Mechanics and Rock Engineering, 2016Co-Authors: Wei Yao, W X Wang, Ying Xu, Patrick KanopolousAbstract:As a material for famous historical underground rock caverns, Longyou sandstone (LS) may fail under the combination of high Loading Rate and high temperature. The thermal damage induced by various heat-treatment temperatures (150, 250, 350, 450, 600 and 850 °C) is first characterized by X-ray Micro-computed tomography (CT) method. The damage variable derived from the average CT value for heat-treated LS specimen and reference specimen without heat treatment was used to quantify the thermal damage. The dynamic tensile strengths of these LS samples under different dynamic Loading Rates (ranging from 24 to 540 GPa/s) were then obtained using the split Hopkinson pressure bar (SHPB) system. The dynamic tensile strength of LS increases with the Loading Rate at a given heat-treatment temperature, and the tensile strength at the same Loading Rate decreases with the heat-treatment temperature except for 450 °C. Based on the experimental data, an empirical equation was established to relate the dynamic tensile strength of LS to the Loading Rate and the heat-treatment temperature.
Jian Zhao - One of the best experts on this subject based on the ideXlab platform.
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Loading Rate dependency of dynamic responses of rock joints at low Loading Rate
Rock Mechanics and Rock Engineering, 2012Co-Authors: Wei Wu, Jianchun Li, Jian ZhaoAbstract:Keywords: Split Hopkinson rock bar ; Loading Rate ; Stress wave ; Rock joints Reference EPFL-ARTICLE-176969doi:10.1007/s00603-011-0212-zView record in Web of Science URL: http://www.springerlink.com/content/6368x8x2v2533u63/ Record created on 2012-05-11, modified on 2017-12-10
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Loading Rate dependency of dynamic responses of rock joints at low Loading Rate
Rock Mechanics and Rock Engineering, 2011Co-Authors: Jian ZhaoAbstract:Keywords: Split Hopkinson rock bar ; Loading Rate ; Stress wave ; Rock joints Reference EPFL-ARTICLE-176969doi:10.1007/s00603-011-0212-zView record in Web of Science URL: http://www.springerlink.com/content/6368x8x2v2533u63/ Record created on 2012-05-11, modified on 2017-12-10
Yicheng Du - One of the best experts on this subject based on the ideXlab platform.
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temperature and Loading Rate effects on tensile properties of kenaf bast fiber bundles and composites
Composites Part B-engineering, 2008Co-Authors: Yicheng Du, Steve Elder, Kunpeng Wang, Jilei ZhangAbstract:Abstract This paper presents extensive experiments and micromechanics-based modeling to evaluate systematically the tensile properties of kenaf bast fibers bundle (KBFB) and kenaf bast fiber-reinforced epoxy strands. Uniaxial tension behaviors of KBFBs and KBFB-reinforced epoxy strands were evaluated statistically using large sample sets. The elastic modulus, tensile strength, as well as failure strains of KBFBs, displayed large scatter statistically ranging from 10% to 30%. The Loading Rate-dependency was evaluated at three strain Rates ranging from approximately 10−4 ∼ 10−2/s. The tensile strength increases gradually as the Loading Rate increases, while the tensile modulus almost remains the same as the Loading Rate increases until the Loading Rate reaches 10−2/s, at which a much higher modulus was presented. The high temperatures (170–180 °C), possibly subjected during fiber processing and composite fabrication, do not impose significant effects on the tensile properties of KBFBs if the duration is less than 1-h. The tensile properties of KBFB were not affected by the conditioning at 130 °C for 24-h, which mimics the severe service temperature of automotive front-end components. KBFB-epoxy composite strands were further evaluated at various Loading Rates. A micromechanics-based Mori–Tanaka model was implemented to predict the anisotropic elastic moduli of KBFB and KBFB-epoxy composite strands based on the microstructural compositions.
