The Experts below are selected from a list of 7776 Experts worldwide ranked by ideXlab platform
Aibing Yu - One of the best experts on this subject based on the ideXlab platform.
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prediction of mass discharge rate in conical hoppers using elastoplastic model
Powder Technology, 2017Co-Authors: Qijun Zheng, Aibing YuAbstract:Abstract Precise evaluation of mass discharge rate (MDR) in hoppers is an important topic in many industries. Facilitated by an Eulerian-formulation finite element method (FEM), this paper uses an elastoplastic model to investigate the MDR in conical hoppers and evaluates its applicability in various cases of hopper geometries and material properties. The obtained flow field complies with the scaling of outlet velocity V y ~ gD 0 and that of the discharge rate MDR ~ g D 0 5 / 2 universally. The MDR is basically independent of the fill height and silo width, but a strong height dependency may emerge for very small Internal Friction Angle of granular material, similar to the fluid-like discharging observed in previous DEM simulation. As for the material properties, the MDR is mainly controlled by the plastic parameters such as Internal Friction Angle and dilation but is insensitive to the elastic modulus. The quantitative accuracy of the model is verified by comparing experimental measurements and discrete simulation over a wide range of hopper half Angles. The existing correlations are often conditionally applicable in describing MDR – some for steep hoppers while others mainly suitable for shallow ones. An empirical correlation is formulated based on the FEM results to achieve a general applicability, which may help to improve the hopper design in practical applications. The needs for future research are also discussed.
Shuwei Zhou - One of the best experts on this subject based on the ideXlab platform.
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phase field modeling of brittle compressive shear fractures in rock like materials a new driving force and a hybrid formulation
Computer Methods in Applied Mechanics and Engineering, 2019Co-Authors: Shuwei Zhou, Xiaoying Zhuang, Timon RabczukAbstract:Abstract Compressive-shear fracture is commonly observed in rock-like materials. However, this fracture type cannot be captured by current phase field models (PFMs), which have been proven an effective tool for modeling fracture initiation, propagation, coalescence, and branching in solids. The existing PFMs also cannot describe the influence of cohesion and Internal Friction Angle on load–displacement curve during compression tests. Therefore, to develop a new phase field model that can simulate well compressive-shear fractures in rock-like materials, we construct a new driving force in the evolution equation of phase field. Strain spectral decomposition is applied and only the compressive part of the strain is used in the new driving force with consideration of the influence of cohesion and Internal Friction Angle. For ease of implementation, a hybrid formulation is established for the phase field modeling. Then, we test the brittle compressive-shear fractures in uniaxial compression tests on intact rock-like specimens as well as those with a single or two parallel inclined flaws. All numerical results are in good agreement with the experimental observation, validating the feasibility and practicability of the proposed PFM for simulating brittle compressive-shear fractures.
Du L Nguye - One of the best experts on this subject based on the ideXlab platform.
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discussion on size effect of footing in ultimate bearing capacity of sandy soil using rigid plastic finite element method
Soils and Foundations, 2016Co-Authors: Du L Nguye, Satoru Ohtsuka, Takashi Hoshina, Koichi IsobeAbstract:Abstract Currently, many formulas are used to calculate the ultimate bearing capacity. However, these formulas have disadvantages when being applied in practice since they can only be applied for calculating simple footing shapes and uniform grounds. Most formulas do not take into account the size effect of the footing on the ultimate bearing capacity, except for the formula by the Architectural Institute of Japan. The advantage of using the finite element method (FEM) is its applicability to non-uniform grounds, for example, multi-layered and improved grounds, and to complicated footing shapes under three-dimensional conditions. FEM greatly improves the accuracy in estimating the ultimate bearing capacity. The objective of this study is to propose a rigid plastic constitutive equation using the non-linear shear strength property against the confining pressure. The constitutive equation was built based on experiments for the non-linear shear strength property against the confining pressure reported by Tatsuoka and other researchers. The results from tests on Toyoura sand and various other kinds of sand indicated that, although the Internal Friction Angle differs among sandy soils, the normalized Internal Friction Angle decreases with an increase in the normalized first stress invariant for various sands despite dispersion in the data. This property always holds irrespective of the reference value of the confining pressure in the normalization of the Internal Friction Angle. The applicability of the proposed rigid plastic equation was proved by comparing it to the ultimate bearing capacity formula by the Architectural Institute of Japan, which is an experimental formula that takes into account the size effect of the footing. The results of rigid plastic finite element method (RPFEM) with the proposed constitutive equation were found to be similar to those obtained with the Architectural Institute of Japan’s formula. It is clear that RPFEM, with the use of the non-linear shear strength against the confining pressure, provides good estimations of the ultimate bearing capacity of the footing by taking account of the size effect of the footing.
Tomoyoshi Nishimura - One of the best experts on this subject based on the ideXlab platform.
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influences of degree of saturation and strain rate on strength characteristics of unsaturated granular subbase course material
Transportation geotechnics, 2014Co-Authors: Yuan Zhang, Tatsuya Ishikawa, Tetsuya Tokoro, Tomoyoshi NishimuraAbstract:The aim of this study is to clarify strength characteristics of a subbase course material changed due to the degree of saturation and the strain rate. A series of monotonic triaxial compression tests was carried out under desired unsaturated and strain rate conditions using a medium-size triaxial compression apparatus. The test results indicate that the degree of saturation can significantly affect shear behaviors of the subbase course material in terms of the shear strength and deformability. On the other hand, the triaxial compression tests with the strain rate of 0.5%/min were conducted as well as those with 0.05%/min, which has been usually employed. The experimental results show that the mechanical behavior of the subbase course material is susceptible to the strain rate, and such relations can vary depending on the degree of saturation in shear. Furthermore, change in the strength parameters such as the total Internal Friction Angle and the total cohesion resulting from the degree of saturation and the strain rate effects will be discussed. The calculation results show that the effects of degree of saturation and strain rate on the total Internal Friction Angle appear to be negligible, while the total cohesion can be affected by the degree of saturation and the strain rate. More specifically, the failure envelope for the subbase course material is nonlinear under the low suction ranges. Therefore, the failure surface drawn through the failure envelope with respect to the matric suction is curved surface. The failure surface for unsaturated specimens with higher strain rate is located above that with lower strain rate.
Timon Rabczuk - One of the best experts on this subject based on the ideXlab platform.
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phase field modeling of brittle compressive shear fractures in rock like materials a new driving force and a hybrid formulation
Computer Methods in Applied Mechanics and Engineering, 2019Co-Authors: Shuwei Zhou, Xiaoying Zhuang, Timon RabczukAbstract:Abstract Compressive-shear fracture is commonly observed in rock-like materials. However, this fracture type cannot be captured by current phase field models (PFMs), which have been proven an effective tool for modeling fracture initiation, propagation, coalescence, and branching in solids. The existing PFMs also cannot describe the influence of cohesion and Internal Friction Angle on load–displacement curve during compression tests. Therefore, to develop a new phase field model that can simulate well compressive-shear fractures in rock-like materials, we construct a new driving force in the evolution equation of phase field. Strain spectral decomposition is applied and only the compressive part of the strain is used in the new driving force with consideration of the influence of cohesion and Internal Friction Angle. For ease of implementation, a hybrid formulation is established for the phase field modeling. Then, we test the brittle compressive-shear fractures in uniaxial compression tests on intact rock-like specimens as well as those with a single or two parallel inclined flaws. All numerical results are in good agreement with the experimental observation, validating the feasibility and practicability of the proposed PFM for simulating brittle compressive-shear fractures.