The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Yu Zhao - One of the best experts on this subject based on the ideXlab platform.
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an elastic Stress Strain Relationship for porous rock under anisotropic Stress conditions
Rock Mechanics and Rock Engineering, 2012Co-Authors: Yu ZhaoAbstract:A Stress–Strain Relationship within porous rock under anisotropic Stress conditions is required for modeling coupled hydromechanical processes associated with a number of practical applications. In this study, a three-dimensional Stress–Strain Relationship is proposed for porous rock under elastic and anisotropic Stress conditions. This Relationship is a macroscopic-scale approximation that uses a natural-Strain-based Hooke’s law to describe deformation within a fraction of pores and an engineering-Strain-based Hooke’s law to describe deformation within the other part. This new Relationship is evaluated using data from a number of uniaxial and triaxial tests published in the literature. Based on this new Stress–Strain Relationship, we also develop constitutive Relationships among Stress, Strain, and related Stress-dependent hydraulic/mechanical properties (such as compressibility, shear modulus, and porosity). These Relationships are demonstrated to be consistent with experimental observations.
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An Elastic Stress–Strain Relationship for Porous Rock Under Anisotropic Stress Conditions
Rock Mechanics and Rock Engineering, 2011Co-Authors: Yu ZhaoAbstract:A Stress–Strain Relationship within porous rock under anisotropic Stress conditions is required for modeling coupled hydromechanical processes associated with a number of practical applications. In this study, a three-dimensional Stress–Strain Relationship is proposed for porous rock under elastic and anisotropic Stress conditions. This Relationship is a macroscopic-scale approximation that uses a natural-Strain-based Hooke’s law to describe deformation within a fraction of pores and an engineering-Strain-based Hooke’s law to describe deformation within the other part. This new Relationship is evaluated using data from a number of uniaxial and triaxial tests published in the literature. Based on this new Stress–Strain Relationship, we also develop constitutive Relationships among Stress, Strain, and related Stress-dependent hydraulic/mechanical properties (such as compressibility, shear modulus, and porosity). These Relationships are demonstrated to be consistent with experimental observations.
Keshan Zhu - One of the best experts on this subject based on the ideXlab platform.
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micromechanical modelling of the complete Stress Strain Relationship for crack weakened rock subjected to compressive loading
Rock Mechanics and Rock Engineering, 2008Co-Authors: Xiaoping Zhou, Yunhuai Zhang, Keshan ZhuAbstract:A micromechanics-based model, able to quantify the effect of various parameters on the complete Stress–Strain Relationship, is described. The closed-form explicit expression for the complete Stress–Strain Relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The complete Stress–Strain Relationship including the stages of linear elasticity, non-linear hardening and Strain softening is established. The results show that the complete Stress–Strain Relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the complete Stress–Strain Relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the complete Stress–Strain Relationship seem to be in good agreement with the measured values.
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Micromechanical Modelling of the Complete Stress–Strain Relationship for Crack Weakened Rock Subjected to Compressive Loading
Rock Mechanics and Rock Engineering, 2007Co-Authors: Xiaoping Zhou, Yunhuai Zhang, Keshan ZhuAbstract:A micromechanics-based model, able to quantify the effect of various parameters on the complete Stress–Strain Relationship, is described. The closed-form explicit expression for the complete Stress–Strain Relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The complete Stress–Strain Relationship including the stages of linear elasticity, non-linear hardening and Strain softening is established. The results show that the complete Stress–Strain Relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the complete Stress–Strain Relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the complete Stress–Strain Relationship seem to be in good agreement with the measured values.
Elisa E. Konofagou - One of the best experts on this subject based on the ideXlab platform.
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In vivo characterization of the aortic wall Stress-Strain Relationship.
Ultrasonics, 2010Co-Authors: Asawinee Danpinid, Jianwen Luo, Jonathan Vappou, Pradit Terdtoon, Elisa E. KonofagouAbstract:Abstract Arterial stiffness has been shown to be a good indicator of arterial wall disease. However, a single parameter is insufficient to describe the complex Stress–Strain Relationship of a multi-component, non-linear tissue such as the aorta. We therefore propose a new approach to measure the Stress–Strain Relationship locally in vivo noninvasively, and present a clinically relevant parameter describing the mechanical interaction between aortic wall constituents. The slope change of the circumferential Stress–Strain curve was hypothesized to be related to the contribution of elastin and collagen, and was defined as the transition Strain ( e θ T ). A two-parallel spring model was employed and three Young’s moduli were accordingly evaluated, i.e., corresponding to the: elastic lamellae (E1), elastin–collagen fibers (E2) and collagen fibers (E3). Our study was performed on normal and Angiotensin II (AngII)-treated mouse abdominal aortas using the aortic pressure after catheterization and the local aortic wall diameters change from a cross-correlation technique on the radio frequency (RF) ultrasound signal at 30 MHz and frame rate of 8 kHz. Using our technique, the transition Strain and three Young’s moduli in both normal and pathological aortas were mapped in 2D. The slope change of the circumferential Stress–Strain curve was first observed in vivo under physiologic conditions. The transition Strain was found at a lower Strain level in the AngII-treated case, i.e., 0.029 ± 0.006 for the normal and 0.012 ± 0.004 for the AngII-treated aortas. E1, E2 and E3 were equal to 69.7 ± 18.6, 214.5 ± 65.8 and 144.8 ± 55.2 kPa for the normal aortas, and 222.1 ± 114.8, 775.0 ± 586.4 and 552.9 ± 519.1 kPa for the AngII-treated aortas, respectively. This is because of the alteration of structures and content of the wall constituents, the degradation of elastic lamella and collagen formation due to AngII treatment. While such values illustrate the alteration of structure and content of the wall constituents related to AngII treatment, limitations regarding physical assumptions (isotropic, linear elastic) should be kept in mind. The transition Strain, however, was shown to be a pressure independent parameter that can be clinically relevant and noninvasively measured using ultrasound-based motion estimation techniques. In conclusion, our novel methodology can assess the Stress–Strain Relationship of the aortic wall locally in vivo and quantify important parameters for the detection and characterization of vascular disease.
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Characterization of the Stress-Strain Relationship of the abdominal aortic wall in vivo
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Asawinee Danpinid, Jianwen Luo, Jonathan Vappou, Pradit Terdtoon, Elisa E. KonofagouAbstract:We hereby propose a new method to determine the regionally passive, elastic, Stress-Strain Relationship of the normal murine abdominal aorta in vivo. The circumferential Stress-Strain Relationship was assessed through Laplace's law, a small deformation framework and a Relationship between luminal pressure and diameter variation. The regional diameter variation of the murine abdominal aortas was obtained using a cross-correlation technique on radio-frequency (RF) signals at the extremely high frame rate of 8 kHz. The luminal pressure variation was measured by an ultra-miniature pressure catheter over one cardiac cycle. The change of slope of the Stress-Strain curve was noticed, which was the contribution of elastin and engaged collagen fibers. The Stress-Strain Relationships before and after this transition was assumed to be linear. Three Young's moduli of the aortic wall were characterized in six mice in vivo: (1) elastin, (2) elastin-collagen and (3) engaged collagen fibers, which were equal to 91.6plusmn26.5, 229.0plusmn80.4 and 137.5plusmn65.6 kPa, respectively. The proposed methodology thus allowed for noninvasive mapping of the mechanical properties of its constituents in vivo.
Xiaoping Zhou - One of the best experts on this subject based on the ideXlab platform.
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micromechanical modelling of the complete Stress Strain Relationship for crack weakened rock subjected to compressive loading
Rock Mechanics and Rock Engineering, 2008Co-Authors: Xiaoping Zhou, Yunhuai Zhang, Keshan ZhuAbstract:A micromechanics-based model, able to quantify the effect of various parameters on the complete Stress–Strain Relationship, is described. The closed-form explicit expression for the complete Stress–Strain Relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The complete Stress–Strain Relationship including the stages of linear elasticity, non-linear hardening and Strain softening is established. The results show that the complete Stress–Strain Relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the complete Stress–Strain Relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the complete Stress–Strain Relationship seem to be in good agreement with the measured values.
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Micromechanical Modelling of the Complete Stress–Strain Relationship for Crack Weakened Rock Subjected to Compressive Loading
Rock Mechanics and Rock Engineering, 2007Co-Authors: Xiaoping Zhou, Yunhuai Zhang, Keshan ZhuAbstract:A micromechanics-based model, able to quantify the effect of various parameters on the complete Stress–Strain Relationship, is described. The closed-form explicit expression for the complete Stress–Strain Relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The complete Stress–Strain Relationship including the stages of linear elasticity, non-linear hardening and Strain softening is established. The results show that the complete Stress–Strain Relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the complete Stress–Strain Relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the complete Stress–Strain Relationship seem to be in good agreement with the measured values.
Wenzhong Zheng - One of the best experts on this subject based on the ideXlab platform.
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effects of steel fiber and Strain rate on the dynamic compressive Stress Strain Relationship in reactive powder concrete
Construction and Building Materials, 2018Co-Authors: Xiaomeng Hou, Shaojun Cao, Qin Rong, Wenzhong ZhengAbstract:Abstract Three types of steel fiber-reinforced reactive powder concrete (SFRPC) with steel fiber contents of 0%, 2%, and 5% by volume are tested under dynamic compression by using a 40-mm-diameter split Hopkinson pressure bar (SHPB) apparatus. Data from SHPB experiments are employed to analyze the influence of critical parameters on the dynamic compressive Stress-Strain Relationship of SFRPC at high Strain rates. Test results show that steel fiber has a significant effect on the Stress-Strain Relationship and energy absorption of RPC. Peak Strain and peak Stress increase with the increasing steel fiber content at the identical Strain rates. A dynamic compressive damage-softening model for SFRPC at high Strain rates is put forward on the basis of the Weibull distribution of SFRPC strength. A theoretical formula for Ed was established in order to ascertain Ed for the proposed constitutive model. The ratio of Ed to static elastic modulus Es increases with increasing Strain rate and decreasing steel fiber content. The proposed constitutive model captures the dynamic compressive Stress-Strain Relationship of SFRPC, and theoretical results are in agreement with measured data.