共查询到18条相似文献，搜索用时 313 毫秒
1.
Bearing Behaviors of Stiffened Deep Cement Mixed Pile 总被引：1，自引：0，他引：1
A series of investigations were conducted to study the bearing capacity and load transfer mechanism of stiffened deep cement mixed (SDCM) pile. Laboratory tests including six specimens were conducted to investigate the frictional resistance between the concrete core and the cement soil. Two model piles and twenty-four full-scale piles were tested to examine the bearing behavior of single pile. Laboratory and model tests results indicate that the cohesive strength is large enough to ensure the interaction between core pile and the outer cement-soil. The full-scale test results show that the SDCM piles exhibit similar bearing behavior to bored and cast-in-place concrete piles. In general, with the rational composite structure the SDCM piles can transmit the applied load effectively, and due to the addition of the stiffer core, the SDCM piles possess high bearing capacity. Based on the findings of these experimental investigations and theoretical analysis, a practical design method is developed to predict the vertical bearing capacity of SDCM pile. 相似文献
2.
Yan-yan Ma 《浙江大学学报(A卷英文版)》2008,9(7):916-921
To take into account the couple stress effects, a modified Reynolds equation is derived for dynamically loaded journal beatings with the consideration of the elasticity of the liner. The numerical results show that the influence of couple stresses on the bearing characteristics is significant. Compared with Newtonian lubricants, lubricants with couple stresses increase the fluid film pressure, as a result enhance the load-carrying capacity and reduce the friction coefficient. However, since the elasticity of the liner weakens the couple stress effect, elastic liners yield a reduction in the load-carrying capacity and an increase in the friction coefficient. The elastic deformation of the bearing liner should be considered in an accurate performance evaluation of the journal bearing. 相似文献
3.
The injury of gunners caused by muzzle shock-wave has always been a great problem when firing inside the protective cover. The distribution regularity and personnel injury from the muzzle blast-wave were investigated by both test and numerical simulation. Through the inside firing test, the changes of overpressure and noise have been measured at different measuring points in the thin-wall cover structure with different open widths and shallow covering thickness. The distribution regularity of muzzle shock-wave with different firing port widths is calculated by ANSYS/LSDYNA software. The overpressure distribution curves of muzzle shock-wave inside the structure can be obtained by comparing the test results with the numerical results. Then, the influence of open width and shallow covering thickness is proposed to give a reference to the protective design under the condition of the inside firing with the same cannon caliber. 相似文献
4.
The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive octree mesh system and multiple particle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of second-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison’s wave force formula with the coefficient values of the stable drag component and the inertial force component being set as 2.54. 相似文献
5.
To improve the static and dynamic performance of hydrodynamic journal beatings, a novel bearing is developed, which is a cone-shaped hydrodynamic bearing with spiral oil wedges. The major structural feature of this bearing is the three spiral circular recesses on the beating‘s surface, leading to improved characteristics. This paper aims to develop a model for design and calculation of the geometric parameters and the oil film thickness, and to provide a theoretical analysis to the static characteristics using a f‘mite element method. Some new features are introduced. 相似文献
6.
Model test and numerical analysis on long-term mechanical properties of stepped reinforced retaining wall 总被引：1，自引：0，他引：1
Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the structure.The geogrid tensions,soil pressures,wall deformations and foundation pressure were measured during model construction and loading.A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term loads.By comparing test data with numerical results,it is shown that the foundation pressure distribution is nonlinear,and the lateral constraint of geogrids for backfill can cause a redistribution of foundation pressure.The curve of soil pressure is outside convex at each step initially,and it is close to the distribution for the case of vertical wall subsequently.The variation trend of geogrid tensions at different heights is obtained.Moreover,the failure mechanism and development mode of potential slip surface in retaining wall are proposed. 相似文献
7.
This study provides a detailed report on the synthesis of spherical activated carbon with mesoporous structure using a soluble low molecular weight phenolic resol precursor through an ammonium alginate assisted sol–gel method. The effects of calcinating temperature and the addition of CaCO_3 as a pore-enlarging agent on texture structure and catalytic performance in isobutane dehydrogenation to isobutene were investigated. Characterization of N_2 sorption,mechanical strength tests,and optical photographs confirmed that the obtained carbon materials had high mechanical strength,a good degree of sphericity,and a large surface area. Introducing CaCO_3 as a pore-enlarging agent during the preparation process promoted the formation of a mesoporous structure of carbon spheres and evidently increased the surface area and oxygen content,which can improve isobutane conversion and isobutene selectivity of these carbon spheres. The conversion of isobutane reached up to 28% for this spherical activated carbon,and the selectivity of isobutene reached up to 96%. Isobutane conversion increased with an increase in calcination temperature due to an increase in the oxygen content,whereas the selectivity of isobutene decreased due to the slight decrease in the specific surface area. 相似文献
8.
A quasi-static wear model for helical gears is proposed based on finite element method and Archard’s formula to investigate the wear characteristics of tooth surface in real operation conditions. The numerical simulation reveals that the wear depth distributes unevenly along the tooth lead and varies along the tooth profile. The surface wear depth claims its minimal value at the pitch circle and reaches its maximal value near the tooth root of the pinion. The effects of misalignment on wear depth are further investigated to provide useful information for gear designers. The numerical simulation reveals that the vertical misalignment is more influential than the parallel misalignment on the gear wear depth. Therefore, to eliminate the negative effects of misalignment, the misalignment should be strictly controlled. 相似文献
9.
Surface engineering has been emerging as one of the most promising technologies to improve the tribological properties of biomaterials with a view to extending the life span of medical implants. For example, some novel surface engineering techniques including ion implantation of ultra-high molecular weight polyethylene (UHMWPE) and thermal oxidation (TO) treatment of titanium alloy have been developed. However, the full potential of improving the wear resistance of orthopaedic implants based on the UHMWPE/ Ti6A14V system will not be realized until the tribological performance of this surface engineered tribo-system is fully characterized and the acting wear mechanisms are well understood. In this paper, a pin-on-disc tribometer was employed to evaluate the tribological response of the following three tribo-systems: (1) untreated UHMWPE/untreated Ti6A14V. (2) untreated UHMWPE/TO-treated Ti6A14V and (3) ion implanted UHMWPE/TO treated Ti6A14V under water lubricated conditions. Experimental results show that the tribological properties of UHMWPE can be significantly increased by surface enghmering its surface and/or the counterface. Tiffs can be attributed to the hardened surface of UHMWPE via molecular structure modification induced by ion bean bombardment coupled with the surface oxide layer on Ti6A14V formed during TO treatment, which has favorable tribological compatibility with UHMWPE. 相似文献
10.
Misalignment analysis of journal bearing influenced by asymmetric deflection, based on a simple stepped shaft model 总被引：1，自引：0，他引：1
Zhen-peng He Jun-hong Zhang Wei-song Xie Zhou-yu Li Gui-chang Zhang 《浙江大学学报(A卷英文版)》2012,13(9):647-664
The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study.A new model considering the asymmetric deflection is applied.Also,the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis.Based on the structure stiffness equivalent characteristic,a simple stepped shaft can reflect the entire complex structure model.The existing lubrication model,which does not consider this angle component,is not very precise for journal bearings.Film pressure,misalignment angle,velocity field,oil leakage,and temperature field were calculated and compared in the journal bearing analysis.The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure.A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system. 相似文献
11.
杨清华 《邢台职业技术学院学报》2014,(5):80-83
本文中给出了由一对磁环轴向充磁组成的轴向永磁轴承,并采用等效电流法计算两磁环之间的轴向力,阐明了永磁轴承在某一方向不稳定的原因。根据特定的永磁轴承实体模型,给出了其动力学方程,并对轴向的非线性运动方程用迦辽金法求出了方程的解析解。通过利用matlab软件进行仿真,证明了特定的永磁轴承在小气隙内磁环可以获得小振幅的稳定模态。 相似文献
12.
Laser shock processing (LSP), also known as laser peening, is a novel surface treatment technique in the past few years. Compressive
residual stresses which imparted by LSP are very important for improving fatigue, corrosion and wear resistance of metals.
Finite element analysis (FEA) simulation using ABAQUS software has been applied to predict residual stresses induced by LSP
on Ti-6Al-4V titanium alloy with laser pulse duration 30 ns and water confined ablation mode. The residual stress field generated
by different shape laser spots was studied, and the square laser spot is shown the most suitability for avoiding stress lack
phenomenon and overlapping LSP. Surface residual stresses and plastically affected depth within single square spot both increased
with the increase of laser intensity and laser shock times. Furthermore, compared with circle and ellipse spot, the residual
stress distribution in overlapping square spots is very uniform only with small overlapping ratio. LSP with square spot can
process advantageous residual stress field, and this technique will be used widely. 相似文献
13.
T. Padmanabhan 《Resonance》1996,1(9):34-40
The orbits of planets, or any other bodies moving under an inverse square law force, can be understood with fresh insight using the idea of velocity space. Surprisingly, a particle moving on an ellipse or even a hyperbola still moves on a circle in this space. Other aspects of orbits such as conservation laws are discussed. 相似文献
14.
15.
对比有无磁场条件下铁磁性材料摩擦副的摩擦学性能,发现直流磁场的存在显著改善了铁磁性材料摩擦副的摩擦学性能。其主要原因是磁场的存在使磨屑保持摩擦副之间,从而铁磁性材料摩擦副的两体摩擦转变为摩擦副、磨屑之间的三体摩擦;同时,磁场的存在提高了氧化磨损在磨损中的比例。 相似文献
16.
椭圆曲线是计算机辅助几何设计中基本且重要的曲线.本文首先利用Tchebyshev多项式去逼近椭圆,再在此基础上得到插值椭圆首、末端点的n次Bézier多项式逼近.该算法可以逼近整椭圆,而且适合圆的逼近. 相似文献
17.
为研究滚动轴承套圈硬车削加工的特性,设计并研制了一种硬车削加工轴承内圈外圆表面、滚道、端面及倒角的夹具,文章介绍了该夹具的工作原理和结构特点。 相似文献
18.
冷轧薄板冲压性能的影响因素 总被引：2，自引：0，他引：2
闫志波 《石家庄职业技术学院学报》2006,18(2):14-16
概述了冷轧薄板的冲压性能的评价指标,详细介绍了冷轧薄板的化学成分、织构和晶粒尺寸、表面质量、厚度尺寸公差、冷轧工艺条件、拉伸试验值对冷轧薄板冲压性能的影响,并应用ANS YS/LS-DYNA软件对板材弯曲成形过程进行了模拟. 相似文献