The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Zibo Du - One of the best experts on this subject based on the ideXlab platform.
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effects of principal stress rotation on stress strain behaviors of saturated clay under traffic load induced stress path
Soils and Foundations, 2019Co-Authors: Jiangu Qian, Zibo Du, Xiaoqiang Gu, Xilin Lu, Maosong HuangAbstract:Abstract A series of cyclic torsional shear tests using hollow cylinder apparatus (HCA) were performed to investigate the effect of principal stress rotation (PSR) on the stress–strain behaviors of saturated soft clay. The traffic–load–induced shear stress path was used in the cyclic test and the investigation mainly concerned the influence of PSR on the shear stiffness and non-Coaxiality. It indicated that the effects of PSR substantially depends on the magnitude of deviatoric stress (q = {[(σ1 − σ2)2 + (σ2 − σ3)2 + (σ1 − σ3)2]/2}1/2) as well as the intermediate principal stress ratio (b = (σ2 − σ3)/(σ1 − σ3)). At low deviatoric stress, the trajectory envelope of deviatoric strain path translates with a nearly constant size, showing constant shear stiffness and strong non-Coaxiality. However, at high deviatoric stress, the trajectory envelope of deviatoric strain rapidly expands towards instability, showing degenerating shear stiffness and weak non-Coaxiality. Moreover, the excess pore water pressure increases and the shear stiffness decreases more rapidly as b value increases. The results can provide an experimental basis for constitutive modelling of clays under traffic–induced loadings.
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cyclic degradation and non Coaxiality of soft clay subjected to pure rotation of principal stress directions
Acta Geotechnica, 2018Co-Authors: Jiangu Qian, Zibo DuAbstract:Foundation soils are often under non-proportional cyclic loadings. The deformation behaviour and the mechanism of non-Coaxiality under continuous pure principal stress rotation for clays are not clearly investigated up to now. In order to study the effect of pure principal stress rotation, a series of cyclic undrained tests on Shanghai soft clay subjected to cyclic rotation of principal stress directions keeping the deviatoric stress constant under the pure rotation condition were conducted using hollow cylinder apparatus. Based on this, the evolutions of excess pore pressure and strains during cyclic loading were investigated, together with the effects of the intermediate principal stress parameter and the deviatoric stress level on stress–strain stiffness and non-Coaxiality. The result can provide an experimental basis for constitutive modelling of clays describing the behaviour under non-proportional loadings.
Jiangu Qian - One of the best experts on this subject based on the ideXlab platform.
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effects of principal stress rotation on stress strain behaviors of saturated clay under traffic load induced stress path
Soils and Foundations, 2019Co-Authors: Jiangu Qian, Zibo Du, Xiaoqiang Gu, Xilin Lu, Maosong HuangAbstract:Abstract A series of cyclic torsional shear tests using hollow cylinder apparatus (HCA) were performed to investigate the effect of principal stress rotation (PSR) on the stress–strain behaviors of saturated soft clay. The traffic–load–induced shear stress path was used in the cyclic test and the investigation mainly concerned the influence of PSR on the shear stiffness and non-Coaxiality. It indicated that the effects of PSR substantially depends on the magnitude of deviatoric stress (q = {[(σ1 − σ2)2 + (σ2 − σ3)2 + (σ1 − σ3)2]/2}1/2) as well as the intermediate principal stress ratio (b = (σ2 − σ3)/(σ1 − σ3)). At low deviatoric stress, the trajectory envelope of deviatoric strain path translates with a nearly constant size, showing constant shear stiffness and strong non-Coaxiality. However, at high deviatoric stress, the trajectory envelope of deviatoric strain rapidly expands towards instability, showing degenerating shear stiffness and weak non-Coaxiality. Moreover, the excess pore water pressure increases and the shear stiffness decreases more rapidly as b value increases. The results can provide an experimental basis for constitutive modelling of clays under traffic–induced loadings.
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cyclic degradation and non Coaxiality of soft clay subjected to pure rotation of principal stress directions
Acta Geotechnica, 2018Co-Authors: Jiangu Qian, Zibo DuAbstract:Foundation soils are often under non-proportional cyclic loadings. The deformation behaviour and the mechanism of non-Coaxiality under continuous pure principal stress rotation for clays are not clearly investigated up to now. In order to study the effect of pure principal stress rotation, a series of cyclic undrained tests on Shanghai soft clay subjected to cyclic rotation of principal stress directions keeping the deviatoric stress constant under the pure rotation condition were conducted using hollow cylinder apparatus. Based on this, the evolutions of excess pore pressure and strains during cyclic loading were investigated, together with the effects of the intermediate principal stress parameter and the deviatoric stress level on stress–strain stiffness and non-Coaxiality. The result can provide an experimental basis for constitutive modelling of clays describing the behaviour under non-proportional loadings.
Marte Gutierrez - One of the best experts on this subject based on the ideXlab platform.
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Modeling of the simple shear deformation of sand: effects of principal stress rotation
Acta Geotechnica, 2009Co-Authors: Marte Gutierrez, J. Wang, M. YoshimineAbstract:The paper presents a simple constitutive model for the behavior of sands during monotonic simple shear loading. The model is developed specifically to account for the effects of principal stress rotation on the simple shear response of sands. The main feature of the model is the incorporation of two important effects of principal stress on stress–strain response: anisotropy and non-Coaxiality. In particular, an anisotropic failure criterion, cross-anisotropic elasticity, and a plastic flow rule and a stress–dilatancy relationship that incorporate the effects of non-Coaxiality are adopted in the model. Simulations of published experimental results from direct simple shear and hollow cylindrical torsional simple shear tests on sands show the satisfactory performance of the model. It is envisioned that the model can be valuable in modeling in situ simple shear response of sands and in interpreting simple shear test results.
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non Coaxiality and energy dissipation in granular materials
Soils and Foundations, 2000Co-Authors: Marte Gutierrez, Kenji IshiharaAbstract:ABSTRACT The paper presents a theoretical and experimental study of the effects of non-Coaxiality or non-coincidence of the principal stress and the principal plastic strain increment directions on the behaviour of granular materials. Experimental results from hollow cylindrical tests on sand involving principal stress rotation which support previously published results on non-Coaxiality are presented. These results imply that constitutive relations cannot be sufficiently formulated in the principal stress space unless the deviations between the principal stress and plastic strain increment directions are taken into consideration. It is shown that plasticity formulations with plastic potentials that are scalar functions of the stress invariants alone implicitly assume Coaxiality and cannot be used for loading involving principal stress rotation. The paper presents a comprehensive analysis of the effects of non-Coaxiality on the energy dissipation of sand. The paper shows that energy dissipation calculated from the principal stresses and the principal plastic strain increments or from the stress and plastic strain increment invariants, would be erroneous and would over-estimate the amount of dissipated energy during loading in the case of non-coaxial flow. A non-Coaxiality factor is introduced in order to account for the effects of non-Coaxiality on the energy dissipation equation and in a stress-dilatancy relation for granular materials. Explicit expressions of the non-Coaxiality factor for two-and three-dimensional loading conditions are given at the end of the paper. Experimental results are presented to show the validity of the proposed energy dissipation and stress-dilatancy equations.
M. Yoshimine - One of the best experts on this subject based on the ideXlab platform.
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Modeling of the simple shear deformation of sand: effects of principal stress rotation
Acta Geotechnica, 2009Co-Authors: Marte Gutierrez, J. Wang, M. YoshimineAbstract:The paper presents a simple constitutive model for the behavior of sands during monotonic simple shear loading. The model is developed specifically to account for the effects of principal stress rotation on the simple shear response of sands. The main feature of the model is the incorporation of two important effects of principal stress on stress–strain response: anisotropy and non-Coaxiality. In particular, an anisotropic failure criterion, cross-anisotropic elasticity, and a plastic flow rule and a stress–dilatancy relationship that incorporate the effects of non-Coaxiality are adopted in the model. Simulations of published experimental results from direct simple shear and hollow cylindrical torsional simple shear tests on sands show the satisfactory performance of the model. It is envisioned that the model can be valuable in modeling in situ simple shear response of sands and in interpreting simple shear test results.
Ken Chen - One of the best experts on this subject based on the ideXlab platform.
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investigation on the non Coaxiality in the drilling of carbon fibre reinforced plastic and aluminium stacks
International Journal of Machine Tools & Manufacture, 2018Co-Authors: Xiong Liang, Dan Wu, Ken ChenAbstract:Abstract The non-coaxial stacked holes caused by cutting deformation is a common problem in stack drilling, particularly for low-rigidity structure, and the non-Coaxiality in carbon-fibre-reinforced plastic and aluminium (CFRP/Al) stack drilling has not been studied. Because of the non-homogeneous behaviour and poor machinability of CFRP, the non-Coaxiality in CFRP/Al stack drilling is significantly different from previous studies on Al/Al stack drilling. Focusing on the non-Coaxiality in CFRP/Al stack drilling, this paper proposed the mechanism of the non-Coaxiality through both experiments and numerical study. Severe non-Coaxiality occurrences were observed in the CFRP/Al stack drilling experiments. To explain the observation, the macroscopic mechanics theory of composite was applied to obtain the engineering constants of composite laminates, which are necessary for the numerical model. This application leads to the development of an optimized simulation model to predict the interlayer gaps and non-Coaxiality. The numerical results that predict the non-Coaxiality are consistent with the experiments, which verified the rationality of simulation model. Furthermore, the effect of the thrust force and clamping force on both interlayer gaps and non-Coaxiality were studied. The interlayer gaps gradually increase with the increase in thrust force but decrease with the clamping force. Moreover, the thrust force has a complicated effect on the non-Coaxiality. The non-Coaxiality first decreases and subsequently increases with the increase in thrust force, which can be attributed to the “tilt effect” in the lower layer. In addition, the non-Coaxiality increases with the clamping force in the simulation experiment range. The work in this paper enables us to understand the particularity of the non-Coaxiality in CFRP/Al stack drilling and select the appropriate cutting parameters for CFRP/Al stack drilling.
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the interlayer gap and non Coaxiality in stack drilling
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Dan Wu, Yunfei Dong, Ken ChenAbstract:Abstract Interlayer gap formation during through-hole drilling in stacked structures is a common problem in large assembly operations. The resulting interfacial burrs and non-coaxial stacked holes deteriorate the machining quality and increase the overall assembly time and costs. This study presents both experimental work and theoretical analysis to understand the interlayer gap formations and non-Coaxiality occurrences in the drilling of stacked structures of broad skins and narrow stringers, which imitate typical structures of large assemblies. First, some stack drilling experiments are specially designed and are performed to observe that the stacked holes are non-coaxial in a regular fashion by measuring the hole diameters of the upper layer, lower layer and interface. Then, a simplified mechanical model of the stacks is built in 2-D to study how the interlayer gaps and non-Coaxiality are formed during stack drilling. Through quantitative analysis based on the simplified model, it is noted that the stack stiffness, drilling thrust force and pressing force have important impact on the interlayer gaps and non-Coaxiality. Finally, finite element methods are adopted to present the deformations in 3-D. The calculation results agree with the theoretical explanations for non-Coaxiality given by the analytical simplified model. In addition, the beneficial effects of the fasteners and ribs are discussed based on the calculation results, and thus, they could contribute to proposals for better designs for stack drilling.