查看更多>>摘要：Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete (SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.
查看更多>>摘要：In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq. (19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.
查看更多>>摘要：Ten studied steels including different carbon content, silicon content, and manganese content were deformed in compression over a temperature range of 600 °C to 1 000 °C at the strain rate of 1 s-1. The curves of the mean flow stress-deformation temperature were drawn up. The mean flow stresses of higher carbon content steels decreased continuously as the applied deformation temperature increased in the whole temperature range, while the mean flow stress of lowest carbon steel displayed an abrupt drop near the two phases region. The reason for the abrupt drop phenomena was explained as the result of phase transformation. The mean flow stresses of steels with high silicon content and low manganese content also have this phenomena.
查看更多>>摘要：In this research, the changing rules of billet forged Ti-22Al-24Nb alloy with various solution time were studied, and the mechanical properties of different microstructure were tested at the room temperature. The results indicate that the (α2+O+B2) three- phase microstructure with equiaxed grains was acquired by Ti-22Al-24Nb alloy billet forging, and the average size of the grains was about 300 μm. With the increase of solution time, the primary lath-shaped O phase began to dissolve, and then the equiaxial α2phase started to dissolve, but the undissolved α2/O phase began to be equiaxial and grow. The grains of original B2 phase recrystallized and grew. After the 2 h solution treatment, the recrystallization of grains was completed basically and the average size of the grains was about 100 μm. After the 2.5 h solution treatment, the strength of the alloy decreased, and the plasticity increased. However, when the solution treatment increased to 3 h, the plasticity decreased but the strength increased. The optimal solution parameters of Ti-22Al-24Nb alloy were the holding time of 2 h, the solution temperature of 1 000 °C, and water cooling. Excellent comprehensive mechanical properties can be accquired under these parameters. The tensile strength, the yield strength, the elasticity modulus, the elongation, and the section shrinkage were 950 MPa, 915 MPa, 90 GPa, 15.69% and 42.28%, respectively.
查看更多>>摘要：It is explored that the line integral is a path independent in two or three arbitrary dimensional orthogonal curvilinear coordinate systems, which is based on the integral condition with the path independent in two or three dimensional rectangular coordinate systems. Firstly, according to the coordinate transformation, the condition that the line integral is the path independent in the polar coordinate system is obtained easily from the Green’s theorem in two-dimensional rectangular coordinate system and the condition is extended to arbitrary two-dimension orthogonal curvilinear coordinates. Secondly, through the coordinate transformation relationship and the area projection method, the Stokes formula in three-dimensional rectangular coordinate system is promoted to the spherical coordinate system and cylindrical coordinate system, and the condition that the line integral is a path independent is obtained. Furthermore, the condition is extended to arbitrary three-dimension orthogonal curvilinear coordinates. Lastly, the conclusions are made.
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