Based on the train-track coupling dynamics and high-speed train aerodynamics, this paper deals with an improved algorithm for fluid-structure interaction of high-speed trains. In the algorithm, the data communication between fluid solver and structure solver is avoided by inserting the program of train-track coupling dynamics into fluid dynamics program, and the relaxation factor concerning the load boundary of the fluid-structure interface is introduced to improve the fluctuation and convergence of aerodynamic forces. With this method, the fluid-structure dynamics of a high-speed train are simulated under the condition that the velocity of crosswind is 13.8 m/s and the train speed is 350 km/h. When the relaxation factor equals 0.5, the fluctuation of aerodynamic forces is lower and its convergence is faster than in other cases. The side force and lateral displacement of the head train are compared between off-line simulation and co-simulation. Simulation results show that the fluid-structure interaction has a significant influence on the aerodynamics and attitude of the head train under crosswind conditions. In addition, the security indexes of the head train worsen after the fluid-structure interaction calculation. Therefore, the fluid-structure interaction calculation is necessary for high-speed trains.
The shrinkage of the cement paste with low water-cement ratio at different relative humidity was observed and analyzed with
ESEM and deformation map technique. The crack morphology was observed with different magnification with SEM and FESEM, and
the formation of the crack was observed with AFM between two C-S-H nano particles. The observation by multi technique at multi
scale indicated that the shrinkage was increase with the decrease of the humidity due to the increase of the pressure of the
capillary pressure, the morphology of the crack in smaller scale was similar to that in the bigger scale, the smaller crack
distributed in the latticework of the bigger ones, and the crack propagated along the gap between two nano particles of C-S-H
with weaker bonding. 相似文献
CuS pineal microspheres congregated from interleaving nanoflakes with thickness of 40 to 200 nm were synthesized by a pyridine-solvothermal process via the reaction between cupric chloride(CuCl2·2H2O) and thioacetamide(TAA,CH3CSNH2).The products were characterized by X-ray diffraction and scanning electron microscopy.UV-Vis absorption spectrum,excitation and photoluminescence spectra of CuS pineal microspheres were obtained at room temperature to investigate their optical properties.A possible growth mechanism on the formation of CuS pineal microspheres is proposed.The factors influencing the evolution of morphologies of CuS crystals including the dosage of the reactants,surfactant,and sulphur-source were also analyzed. 相似文献
Poly(vinyl alcohol)/Hydroxylapatite (PVA/HA) composite hydrogel was prepared with poly(vinyl alcohol) and hydroxylapatite
as raw materials, using the method of repeated freezing and thawing. The morphologies of PVA/HA composite hydrogel were observed
by means of high-accuracy 3D profiler and scanning electron microscope (SEM). The compressive elastic modulus and the stress
relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter. The friction
and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer.
The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope (ESEM). The
results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural
bovine knee articular cartilages. With the increase of freezing-thawing cycles and the HA content, the degree of cross-link
and the crystallization of PVA/HA composite hydrogel both increase, the elastic modulus increases evidently, the rate of stress
relaxation is improved and the value of balance stress decreases. The friction coefficient decreases with the increase of
the freezing-thawing cycles and the HA content. The more the freezing-thawing cycles are, the earlier the friction coefficient
reaches the stable balance value. The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular
cartilage is inversely proportional to freezing-thawing cycles and the HA content. The main wear mechanisms of PVA/HA composite
hydrogel are plastic flowing and adhesive flaking. The wear severity degree decreases with the increase of freezing-thawing
cycles and the HA content.
Supported by Key Program of the National Natural Science Foundation of China (Grant No. 50535050), Program for New Century
Excellent Talents in University (Grant No. NCET-06-0479) and Natural Science Foundation of Jiangsu Province (Grant No. BK2005403) 相似文献
Electrochemical deposition method was employed to prepare CNx thin film from methanol-urea solution,and it was shown that adding a little acetic acid in the solution significantly affected the deposition process.After optimizing the experiment conditions,we obtained polycrystalline grains with sizes of about 3―7μm on the faces of single crystal silicon.X-ray diffraction spectrua indicate that the grains are mainly composed of cubic phase mixed with a small amount of β and α phases. 相似文献