The numerical simulation of interface crack propagation without re-meshing

Based on the framework of the extended finite element method (XFEM), the enriched exponent discontinuous function is modified properly by introducing the rigidity ratio of two sides materials of interface crack, and the portion integral scheme is adopted for interface elements containing two materials. To embody the singularity of the crack tip, the triangle function is introduced directly. What’s more, the maximum loop stress fracture criterion is adopted to determine the extension direction in extended ma...     

Abnormality diagnosis of cracks in the concrete dam based on dynamical structure mutation

A method of the fuzzy cross-correlation factor exponent in dynamics is researched and proposed to diagnose abnormality of cracks in the concrete dam. Moreover, the Logistic time series changing from period-doubling bifurcation to chaos is tested first using this method. Results indicate that it can distinguish inherent dynamics of time series and can detect mutations. Considering that cracks in the concrete dam constitute an open, dissipative and complex nonlinear dynamical system, a typical crack on the do...     

Multi-pulse orbits dynamics of composite laminated piezoelectric rectangular plate

The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed that different layers are perfectly bonded to each other with piezoelectric actuator patches embedded. The nonlinear equations of motion for the laminated composite piezoelectric rectangular plate are derived from von Karman-type equation and third-order shear deformation plate theory of Reddy...     

A constitutive model for granular materials considering grain breakage

A particle breakage has a significant impact on the mechanical behavior of granular materials. In this paper, we present an elasto-plastic model with two yield surfaces to which the influence of particle breakage has been introduced. The main feature of this model is to incorporate the change in the critical state line (CSL) consequent to the grain breakage induced by isotropic and deviatoric stresses during loading. For this purpose we propose a breakage function which connects the evolution of the CSL to ...     

Necessary and sufficient conditions of the rendezvous between a single spacecraft and three non-coplanar Walker constellation satellites

The probability of the rendezvous between a single spacecraft and three non-coplanar constellation satellites is studied,and the necessary and sufficient conditions of the rendezvous without orbital maneuver are deduced.The rendezvous orbit design can be transformed into the patching of two spacecraft orbits,either of which can achieve the rendezvous with two satellites.Firstly,due to the precious quality of spherical geometry,the unique existence of the rendezvous orbit for two constellation satellites is ...     

Percolation transport and magnetic transitions in a phase-separated manganite La_(0.55)Ca_(0.45)MnO_3

The structural,electronic and magnetic properties of La0.55Ca0.45MnO3 were measured.A rapid change of lattice parameters appeared around 190 K associated with the d z2 orbital ordering and charge ordering (CO) states that were reflected by both magnetization and resistivity.Great difference of magnetizations between the field-cooling (FC) and zero-field-cooling (ZFC) modes below the charge ordering temperature TCO in high magnetic field (H > 4 T) was clearly seen.A field of 5 T (threshold field) is sufficie...     

Production of thick-walled hollow glass microspheres for inertial confinement fusion targets by sol-gel technology

To fabricate thick-walled hollow glass microspheres(HGMs)for inertial confinement fusion(ICF)targets by sol-gel technology,we investigated the effects of glass composition,blowing agent,refining temperature,pressure and composition of furnace atmosphere on the wall thickness of HGMs by numerical simulation and experiments.The results showed that the residence times of the thick-walled HGMs in the encapsulating and refining phases decreased with the increase of wall thickness of HGMs.As a response to this ch...     

Multi-level multi-area hybrid automatic voltage control system and its trial operation in Northeast China Grid

In order to coordinate automatic voltage control(AVC)systems of a large interconnected system,a multi-level multi-area hybrid automatic voltage control(MLMA-HAVC)system was constructed.This system began its trial operation in the Northeast China Grid in January 2010,and for the first time in China and abroad it realized automatic close-loop control of multi-area and multi-level interconnected power grid and multi-objective self-approaching optimization in aspects of security,high quality and economic operat...     

Influence of cooling rates on the precipitation behavior and microstructure of Nb-Ti microalloyed steel

Influence of different cooling rates on the microstructure and the precipitation behavior of Nb-Ti microalloyed steel was investigated by CSLM,OM,SEM and EDS. The results show that the precipitation process of carbonitrides can be in-situ observed by CSLM,and with the increase of the cooling rate,the distribution of precipitates changes from along the austenitic grain boundaries to within the grains. With the increase of the cooling rate,the proeutectoid ferritic film becomes smaller and smaller and then disappears,and the original austenitic grains become finer and finer. In order to obtain non-film like proeutectoid ferrites or non-chain like precipitates along the austenitic grain boundaries and finer austenitic grains,the cooling rate should be at least 5℃/s.     

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