CAS Institute of Mechanics

Beijing, China

CAS Institute of Mechanics

Beijing, China
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The present invention discloses a root key type pressure bearing mechanism in an anchor hole, a root key type anchor cable and an anchor hole grouting method. The pressure bearing mechanism includes a carrier, root keys and a tapered plug, a through hole is formed in the center of the tapered plug, a taper hole is formed in the center of the carrier, key holes are formed along a radial direction of the carrier with an inner wall of the taper hole as a starting point, the number of the key holes is the same as that of the root keys, the root keys and the key holes constitute sliding pairs, an outer wall of the tapered plug is adapted to the taper hole, the sum of the length of the root key and the radius of a position corresponding to the tapered plug is larger than the radius of the anchor hole, and the length of the root key is less than the radius of the anchor hole; and when the tapered plug is plugged into the taper hole, the head of the root key stretches into a rock mass of the anchor hole. The pressure bearing mechanism assembled by the assembly method is applied to the anchor cable, and when the anchor cable is used for grouting, the anchoring effect of the anchor cable can be effectively improved.

Liu M.B.,CAS Institute of Mechanics | Liu G.R.,National University of Singapore
Archives of Computational Methods in Engineering | Year: 2010

Smoothed particle hydrodynamics (SPH) is a meshfree particle method based on Lagrangian formulation, and has been widely applied to different areas in engineering and science. This paper presents an overview on the SPH method and its recent developments, including (1) the need for meshfree particle methods, and advantages of SPH, (2) approximation schemes of the conventional SPH method and numerical techniques for deriving SPH formulations for partial differential equations such as the Navier-Stokes (N-S) equations, (3) the role of the smoothing kernel functions and a general approach to construct smoothing kernel functions, (4) kernel and particle consistency for the SPH method, and approaches for restoring particle consistency, (5) several important numerical aspects, and (6) some recent applications of SPH. The paper ends with some concluding remarks. © CIMNE, Barcelona, Spain 2010.

Yi X.,Brown University | Shi X.,CAS Institute of Mechanics | Gao H.,Brown University
Nano Letters | Year: 2014

Understanding cell interaction with one-dimensional nanomaterials, including nanotubes, nanowires, nanofibers, filamentous bacteria, and certain nanoparticle chains, has fundamental importance to many applications such as biomedical diagnostics, therapeutics, and nanotoxicity. Here we show that cell uptake of one-dimensional nanomaterials via receptor-mediated endocytosis is dominated by a single dimensionless parameter that scales with the membrane tension and radius of the nanomaterial and inversely with the membrane bending stiffness. It is shown that as cell membrane internalizes one-dimensional nanomaterials the uptake follows a near-perpendicular entry mode at small membrane tension but it switches to a near-parallel interaction mode at large membrane tension. © 2014 American Chemical Society.

Zhu Y.T.,North Carolina State University | Liao X.Z.,University of Sydney | Wu X.L.,CAS Institute of Mechanics
Progress in Materials Science | Year: 2012

Nanocrystalline (nc) materials can be defined as solids with grain sizes in the range of 1-100 nm. Contrary to coarse-grained metals, which become more difficult to twin with decreasing grain size, nanocrystalline face-centered-cubic (fcc) metals become easier to twin with decreasing grain size, reaching a maximum twinning probability, and then become more difficult to twin when the grain size decreases further, i.e. exhibiting an inverse grain-size effect on twinning. Molecular dynamics simulations and experimental observations have revealed that the mechanisms of deformation twinning in nanocrystalline metals are different from those in their coarse-grained counterparts. Consequently, there are several types of deformation twins that are observed in nanocrystalline materials, but not in coarse-grained metals. It has also been reported that deformation twinning can be utilized to enhance the strength and ductility of nanocrystalline materials. This paper reviews all aspects of deformation twinning in nanocrystalline metals, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformation twins, interactions between twins and dislocations, and the effects of twins on mechanical and other properties. It is the authors' intention for this review paper to serve not only as a valuable reference for researchers in the field of nanocrystalline metals and alloys, but also as a textbook for the education of graduate students. © 2011 Elsevier Ltd. All rights reserved.

Wei Y.,CAS Institute of Mechanics
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

When materials are deformed plastically via dislocations, a general finding is that samples with smaller dimensions exhibit higher strengths but with very limited amount of plasticity in tension. Here we report that one-dimensional coherent nanostructures with tilted internal twins exhibit anisotropic size effect: their strengths show no apparent change if only their thicknesses reduce, but become stronger as the sample sizes are reduced proportionally. Large-scale molecular dynamics simulations show that such nanowires deform primarily through twin migration mediated by partial dislocations in one active slip system, and a large amount of plasticity could be achieved in such nanowires via twin migration. The unique structure shown here is suitable to explore strengthening mechanisms in metals when plasticity is controlled by a single dislocation slip system. This study also suggests a novel approach to modulate strength and ductility in one-dimensional coherent nanostructures. © 2011 American Physical Society.

Wei Y.,CAS Institute of Mechanics
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Engineers usually face the difficulty of making careful choices between one good and another in terms of strength, ductility, and electrical conductance in nanostructured metals. The emergence of polycrystalline Cu with ultrafine grains and the included nanotwins supplies an ideal solution because such materials owe high strength, high electrical conductance, and intermediate ductility. We answer in this Brief Report where the strength of such materials maximizes and how it depends on grain size. Based on the competitive plastic deformation mechanisms-the strengthening mechanism by inclined dislocations (with respect to twin planes) and detwinning-induced softening-we find that the critical twin thickness where the strength maximizes is proportional to d1 /2 and the maximum strength is proportional to d-1 /2. © 2011 American Physical Society.

Yuan Q.,CAS Institute of Mechanics | Zhao Y.-P.,CAS Institute of Mechanics
Physical Review Letters | Year: 2010

Dynamic wetting and electrowetting are explored using molecular dynamics simulations. The propagation of the precursor film (PF) is fast and obeys the power law with respect to time. Against the former studies, we find the PF is no slip and solidlike. As an important application of the PF, the electro-elasto-capillarity, which is a good candidate for drug delivery at the micro- or nanoscale, is simulated and realized for the first time. Our findings may be one of the answers to the Huh-Scriven paradox and expand our knowledge of dynamic wetting and electrowetting. © 2010 The American Physical Society.

Liu Y.,CAS Institute of Mechanics | Wei Y.,CAS Institute of Mechanics
International Journal of Plasticity | Year: 2014

Low thermoplastic formability is a key factor limiting the usage of magnesium alloys, which otherwise can have broad application in automotive industry for their competitive strength to density ratio. Combining with experimental calibration and validation, we report a systematic numerical investigation about the plastic deformation of magnesium alloy AZ31B at different temperatures and subjected to different boundary conditions. By employing 3D Voronoi grains based microstructure and the crystal plasticity constitutive model developed by Staroselsky and Anand (2003), which accounts for both dislocation slip and deformation twinning in polycrystalline magnesium, we estimate the dependence of critical resolved shear stresses (CRSS) of different slip/twinning systems on temperature. We further obtain the fractional plastic strains contributed by individual slip/twinning systems at different loading conditions. Grain level deformation analysis indicates that there exists significant stress and plasticity inhomogeneity among grains. © 2013 Elsevier Ltd. All rights reserved.

CAS Institute of Mechanics | Date: 2012-02-22

The present invention discloses a cyclone generator for a pipeline type oil-water separator which separates oil from water using the principle of cyclone. The cyclone generator comprises: flow deflectors which are fixedly arranged along the circumferential direction of a pipe to generate, when an oil-water mixture flows through the flow deflectors, a centrosymmetric cyclone field to centrifugally separate oil from water. The present invention further discloses an oil-water separation device which uses the aforementioned principle, the mixture of oil and water flowing through the device forms a centrosymmetric cyclone field in which an oil core is distributed in the central area of a pipe without shifting significantly so as to achieve an excellent oil-water separation effect.

Zhao J.-f.,CAS Institute of Mechanics
International Journal of Multiphase Flow | Year: 2010

Researches on two-phase flow and pool boiling heat transfer in microgravity, which included ground-based tests, flight experiments, and theoretical analyses, were conducted in the National Microgravity Laboratory/CAS. A semi-theoretical Weber number model was proposed to predict the slug-to-annular flow transition of two-phase gas-liquid flows in microgravity, while the influence of the initial bubble size on the bubble-to-slug flow transition was investigated numerically using the Monte Carlo method. Two-phase flow pattern maps in microgravity were obtained in the experiments both aboard the Russian space station Mir and aboard IL-76 reduced gravity airplane. Mini-scale modeling was also used to simulate the behavior of microgravity two-phase flow on the ground. Pressure drops of two-phase flow in microgravity were also measured experimentally and correlated successfully based on its characteristics. Two space experiments on pool boiling phenomena in microgravity were performed aboard the Chinese recoverable satellites. Steady pool boiling of R113 on a thin wire with a temperature-controlled heating method was studied aboard RS-22, while quasi-steady pool boiling of FC-72 on a plate was studied aboard SJ-8. Ground-based experiments were also performed both in normal gravity and in short-term microgravity in the drop tower Beijing. Only slight enhancement of heat transfer was observed in the wire case, while enhancement in low heat flux and deterioration in high heat flux were observed in the plate case. Lateral motions of vapor bubbles were observed before their departure in microgravity. The relationship between bubble behavior and heat transfer on plate was analyzed. A semi-theoretical model was also proposed for predicting the bubble departure diameter during pool boiling on wires. The results obtained here are intended to become a powerful aid for further investigation in the present discipline and development of two-phase systems for space applications. © 2009 Elsevier Ltd. All rights reserved.

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